Add support for the latest 1G/10G Chelsio adapter, T3.

[safe/jmp/linux-2.6] / drivers / net / cxgb3 / sge.c

/*
 * This file is part of the Chelsio T3 Ethernet driver.
 *
 * Copyright (C) 2005-2006 Chelsio Communications.  All rights reserved.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the LICENSE file included in this
 * release for licensing terms and conditions.
 */

#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_vlan.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/dma-mapping.h>
#include "common.h"
#include "regs.h"
#include "sge_defs.h"
#include "t3_cpl.h"
#include "firmware_exports.h"

#define USE_GTS 0

#define SGE_RX_SM_BUF_SIZE 1536
#define SGE_RX_COPY_THRES  256

# define SGE_RX_DROP_THRES 16

/*
 * Period of the Tx buffer reclaim timer.  This timer does not need to run
 * frequently as Tx buffers are usually reclaimed by new Tx packets.
 */
#define TX_RECLAIM_PERIOD (HZ / 4)

/* WR size in bytes */
#define WR_LEN (WR_FLITS * 8)

/*
 * Types of Tx queues in each queue set.  Order here matters, do not change.
 */
enum { TXQ_ETH, TXQ_OFLD, TXQ_CTRL };

/* Values for sge_txq.flags */
enum {
        TXQ_RUNNING = 1 << 0,   /* fetch engine is running */
        TXQ_LAST_PKT_DB = 1 << 1,       /* last packet rang the doorbell */
};

struct tx_desc {
        u64 flit[TX_DESC_FLITS];
};

struct rx_desc {
        __be32 addr_lo;
        __be32 len_gen;
        __be32 gen2;
        __be32 addr_hi;
};

struct tx_sw_desc {             /* SW state per Tx descriptor */
        struct sk_buff *skb;
};

struct rx_sw_desc {             /* SW state per Rx descriptor */
        struct sk_buff *skb;
         DECLARE_PCI_UNMAP_ADDR(dma_addr);
};

struct rsp_desc {               /* response queue descriptor */
        struct rss_header rss_hdr;
        __be32 flags;
        __be32 len_cq;
        u8 imm_data[47];
        u8 intr_gen;
};

struct unmap_info {             /* packet unmapping info, overlays skb->cb */
        int sflit;              /* start flit of first SGL entry in Tx descriptor */
        u16 fragidx;            /* first page fragment in current Tx descriptor */
        u16 addr_idx;           /* buffer index of first SGL entry in descriptor */
        u32 len;                /* mapped length of skb main body */
};

/*
 * Maps a number of flits to the number of Tx descriptors that can hold them.
 * The formula is
 *
 * desc = 1 + (flits - 2) / (WR_FLITS - 1).
 *
 * HW allows up to 4 descriptors to be combined into a WR.
 */
static u8 flit_desc_map[] = {
        0,
#if SGE_NUM_GENBITS == 1
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
        4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4
#elif SGE_NUM_GENBITS == 2
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
        4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
#else
# error "SGE_NUM_GENBITS must be 1 or 2"
#endif
};

static inline struct sge_qset *fl_to_qset(const struct sge_fl *q, int qidx)
{
        return container_of(q, struct sge_qset, fl[qidx]);
}

static inline struct sge_qset *rspq_to_qset(const struct sge_rspq *q)
{
        return container_of(q, struct sge_qset, rspq);
}

static inline struct sge_qset *txq_to_qset(const struct sge_txq *q, int qidx)
{
        return container_of(q, struct sge_qset, txq[qidx]);
}

/**
 *      refill_rspq - replenish an SGE response queue
 *      @adapter: the adapter
 *      @q: the response queue to replenish
 *      @credits: how many new responses to make available
 *
 *      Replenishes a response queue by making the supplied number of responses
 *      available to HW.
 */
static inline void refill_rspq(struct adapter *adapter,
                               const struct sge_rspq *q, unsigned int credits)
{
        t3_write_reg(adapter, A_SG_RSPQ_CREDIT_RETURN,
                     V_RSPQ(q->cntxt_id) | V_CREDITS(credits));
}

/**
 *      need_skb_unmap - does the platform need unmapping of sk_buffs?
 *
 *      Returns true if the platfrom needs sk_buff unmapping.  The compiler
 *      optimizes away unecessary code if this returns true.
 */
static inline int need_skb_unmap(void)
{
        /*
         * This structure is used to tell if the platfrom needs buffer
         * unmapping by checking if DECLARE_PCI_UNMAP_ADDR defines anything.
         */
        struct dummy {
                DECLARE_PCI_UNMAP_ADDR(addr);
        };

        return sizeof(struct dummy) != 0;
}

/**
 *      unmap_skb - unmap a packet main body and its page fragments
 *      @skb: the packet
 *      @q: the Tx queue containing Tx descriptors for the packet
 *      @cidx: index of Tx descriptor
 *      @pdev: the PCI device
 *
 *      Unmap the main body of an sk_buff and its page fragments, if any.
 *      Because of the fairly complicated structure of our SGLs and the desire
 *      to conserve space for metadata, we keep the information necessary to
 *      unmap an sk_buff partly in the sk_buff itself (in its cb), and partly
 *      in the Tx descriptors (the physical addresses of the various data
 *      buffers).  The send functions initialize the state in skb->cb so we
 *      can unmap the buffers held in the first Tx descriptor here, and we
 *      have enough information at this point to update the state for the next
 *      Tx descriptor.
 */
static inline void unmap_skb(struct sk_buff *skb, struct sge_txq *q,
                             unsigned int cidx, struct pci_dev *pdev)
{
        const struct sg_ent *sgp;
        struct unmap_info *ui = (struct unmap_info *)skb->cb;
        int nfrags, frag_idx, curflit, j = ui->addr_idx;

        sgp = (struct sg_ent *)&q->desc[cidx].flit[ui->sflit];

        if (ui->len) {
                pci_unmap_single(pdev, be64_to_cpu(sgp->addr[0]), ui->len,
                                 PCI_DMA_TODEVICE);
                ui->len = 0;    /* so we know for next descriptor for this skb */
                j = 1;
        }

        frag_idx = ui->fragidx;
        curflit = ui->sflit + 1 + j;
        nfrags = skb_shinfo(skb)->nr_frags;

        while (frag_idx < nfrags && curflit < WR_FLITS) {
                pci_unmap_page(pdev, be64_to_cpu(sgp->addr[j]),
                               skb_shinfo(skb)->frags[frag_idx].size,
                               PCI_DMA_TODEVICE);
                j ^= 1;
                if (j == 0) {
                        sgp++;
                        curflit++;
                }
                curflit++;
                frag_idx++;
        }

        if (frag_idx < nfrags) {        /* SGL continues into next Tx descriptor */
                ui->fragidx = frag_idx;
                ui->addr_idx = j;
                ui->sflit = curflit - WR_FLITS - j;     /* sflit can be -1 */
        }
}

/**
 *      free_tx_desc - reclaims Tx descriptors and their buffers
 *      @adapter: the adapter
 *      @q: the Tx queue to reclaim descriptors from
 *      @n: the number of descriptors to reclaim
 *
 *      Reclaims Tx descriptors from an SGE Tx queue and frees the associated
 *      Tx buffers.  Called with the Tx queue lock held.
 */
static void free_tx_desc(struct adapter *adapter, struct sge_txq *q,
                         unsigned int n)
{
        struct tx_sw_desc *d;
        struct pci_dev *pdev = adapter->pdev;
        unsigned int cidx = q->cidx;

        d = &q->sdesc[cidx];
        while (n--) {
                if (d->skb) {   /* an SGL is present */
                        if (need_skb_unmap())
                                unmap_skb(d->skb, q, cidx, pdev);
                        if (d->skb->priority == cidx)
                                kfree_skb(d->skb);
                }
                ++d;
                if (++cidx == q->size) {
                        cidx = 0;
                        d = q->sdesc;
                }
        }
        q->cidx = cidx;
}

/**
 *      reclaim_completed_tx - reclaims completed Tx descriptors
 *      @adapter: the adapter
 *      @q: the Tx queue to reclaim completed descriptors from
 *
 *      Reclaims Tx descriptors that the SGE has indicated it has processed,
 *      and frees the associated buffers if possible.  Called with the Tx
 *      queue's lock held.
 */
static inline void reclaim_completed_tx(struct adapter *adapter,
                                        struct sge_txq *q)
{
        unsigned int reclaim = q->processed - q->cleaned;

        if (reclaim) {
                free_tx_desc(adapter, q, reclaim);
                q->cleaned += reclaim;
                q->in_use -= reclaim;
        }
}

/**
 *      should_restart_tx - are there enough resources to restart a Tx queue?
 *      @q: the Tx queue
 *
 *      Checks if there are enough descriptors to restart a suspended Tx queue.
 */
static inline int should_restart_tx(const struct sge_txq *q)
{
        unsigned int r = q->processed - q->cleaned;

        return q->in_use - r < (q->size >> 1);
}

/**
 *      free_rx_bufs - free the Rx buffers on an SGE free list
 *      @pdev: the PCI device associated with the adapter
 *      @rxq: the SGE free list to clean up
 *
 *      Release the buffers on an SGE free-buffer Rx queue.  HW fetching from
 *      this queue should be stopped before calling this function.
 */
static void free_rx_bufs(struct pci_dev *pdev, struct sge_fl *q)
{
        unsigned int cidx = q->cidx;

        while (q->credits--) {
                struct rx_sw_desc *d = &q->sdesc[cidx];

                pci_unmap_single(pdev, pci_unmap_addr(d, dma_addr),
                                 q->buf_size, PCI_DMA_FROMDEVICE);
                kfree_skb(d->skb);
                d->skb = NULL;
                if (++cidx == q->size)
                        cidx = 0;
        }
}

/**
 *      add_one_rx_buf - add a packet buffer to a free-buffer list
 *      @skb: the buffer to add
 *      @len: the buffer length
 *      @d: the HW Rx descriptor to write
 *      @sd: the SW Rx descriptor to write
 *      @gen: the generation bit value
 *      @pdev: the PCI device associated with the adapter
 *
 *      Add a buffer of the given length to the supplied HW and SW Rx
 *      descriptors.
 */
static inline void add_one_rx_buf(struct sk_buff *skb, unsigned int len,
                                  struct rx_desc *d, struct rx_sw_desc *sd,
                                  unsigned int gen, struct pci_dev *pdev)
{
        dma_addr_t mapping;

        sd->skb = skb;
        mapping = pci_map_single(pdev, skb->data, len, PCI_DMA_FROMDEVICE);
        pci_unmap_addr_set(sd, dma_addr, mapping);

        d->addr_lo = cpu_to_be32(mapping);
        d->addr_hi = cpu_to_be32((u64) mapping >> 32);
        wmb();
        d->len_gen = cpu_to_be32(V_FLD_GEN1(gen));
        d->gen2 = cpu_to_be32(V_FLD_GEN2(gen));
}

/**
 *      refill_fl - refill an SGE free-buffer list
 *      @adapter: the adapter
 *      @q: the free-list to refill
 *      @n: the number of new buffers to allocate
 *      @gfp: the gfp flags for allocating new buffers
 *
 *      (Re)populate an SGE free-buffer list with up to @n new packet buffers,
 *      allocated with the supplied gfp flags.  The caller must assure that
 *      @n does not exceed the queue's capacity.
 */
static void refill_fl(struct adapter *adap, struct sge_fl *q, int n, gfp_t gfp)
{
        struct rx_sw_desc *sd = &q->sdesc[q->pidx];
        struct rx_desc *d = &q->desc[q->pidx];

        while (n--) {
                struct sk_buff *skb = alloc_skb(q->buf_size, gfp);

                if (!skb)
                        break;

                add_one_rx_buf(skb, q->buf_size, d, sd, q->gen, adap->pdev);
                d++;
                sd++;
                if (++q->pidx == q->size) {
                        q->pidx = 0;
                        q->gen ^= 1;
                        sd = q->sdesc;
                        d = q->desc;
                }
                q->credits++;
        }

        t3_write_reg(adap, A_SG_KDOORBELL, V_EGRCNTX(q->cntxt_id));
}

static inline void __refill_fl(struct adapter *adap, struct sge_fl *fl)
{
        refill_fl(adap, fl, min(16U, fl->size - fl->credits), GFP_ATOMIC);
}

/**
 *      recycle_rx_buf - recycle a receive buffer
 *      @adapter: the adapter
 *      @q: the SGE free list
 *      @idx: index of buffer to recycle
 *
 *      Recycles the specified buffer on the given free list by adding it at
 *      the next available slot on the list.
 */
static void recycle_rx_buf(struct adapter *adap, struct sge_fl *q,
                           unsigned int idx)
{
        struct rx_desc *from = &q->desc[idx];
        struct rx_desc *to = &q->desc[q->pidx];

        q->sdesc[q->pidx] = q->sdesc[idx];
        to->addr_lo = from->addr_lo;    /* already big endian */
        to->addr_hi = from->addr_hi;    /* likewise */
        wmb();
        to->len_gen = cpu_to_be32(V_FLD_GEN1(q->gen));
        to->gen2 = cpu_to_be32(V_FLD_GEN2(q->gen));
        q->credits++;

        if (++q->pidx == q->size) {
                q->pidx = 0;
                q->gen ^= 1;
        }
        t3_write_reg(adap, A_SG_KDOORBELL, V_EGRCNTX(q->cntxt_id));
}

/**
 *      alloc_ring - allocate resources for an SGE descriptor ring
 *      @pdev: the PCI device
 *      @nelem: the number of descriptors
 *      @elem_size: the size of each descriptor
 *      @sw_size: the size of the SW state associated with each ring element
 *      @phys: the physical address of the allocated ring
 *      @metadata: address of the array holding the SW state for the ring
 *
 *      Allocates resources for an SGE descriptor ring, such as Tx queues,
 *      free buffer lists, or response queues.  Each SGE ring requires
 *      space for its HW descriptors plus, optionally, space for the SW state
 *      associated with each HW entry (the metadata).  The function returns
 *      three values: the virtual address for the HW ring (the return value
 *      of the function), the physical address of the HW ring, and the address
 *      of the SW ring.
 */
static void *alloc_ring(struct pci_dev *pdev, size_t nelem, size_t elem_size,
                        size_t sw_size, dma_addr_t *phys, void *metadata)
{
        size_t len = nelem * elem_size;
        void *s = NULL;
        void *p = dma_alloc_coherent(&pdev->dev, len, phys, GFP_KERNEL);

        if (!p)
                return NULL;
        if (sw_size) {
                s = kcalloc(nelem, sw_size, GFP_KERNEL);

                if (!s) {
                        dma_free_coherent(&pdev->dev, len, p, *phys);
                        return NULL;
                }
        }
        if (metadata)
                *(void **)metadata = s;
        memset(p, 0, len);
        return p;
}

/**
 *      free_qset - free the resources of an SGE queue set
 *      @adapter: the adapter owning the queue set
 *      @q: the queue set
 *
 *      Release the HW and SW resources associated with an SGE queue set, such
 *      as HW contexts, packet buffers, and descriptor rings.  Traffic to the
 *      queue set must be quiesced prior to calling this.
 */
void t3_free_qset(struct adapter *adapter, struct sge_qset *q)
{
        int i;
        struct pci_dev *pdev = adapter->pdev;

        if (q->tx_reclaim_timer.function)
                del_timer_sync(&q->tx_reclaim_timer);

        for (i = 0; i < SGE_RXQ_PER_SET; ++i)
                if (q->fl[i].desc) {
                        spin_lock(&adapter->sge.reg_lock);
                        t3_sge_disable_fl(adapter, q->fl[i].cntxt_id);
                        spin_unlock(&adapter->sge.reg_lock);
                        free_rx_bufs(pdev, &q->fl[i]);
                        kfree(q->fl[i].sdesc);
                        dma_free_coherent(&pdev->dev,
                                          q->fl[i].size *
                                          sizeof(struct rx_desc), q->fl[i].desc,
                                          q->fl[i].phys_addr);
                }

        for (i = 0; i < SGE_TXQ_PER_SET; ++i)
                if (q->txq[i].desc) {
                        spin_lock(&adapter->sge.reg_lock);
                        t3_sge_enable_ecntxt(adapter, q->txq[i].cntxt_id, 0);
                        spin_unlock(&adapter->sge.reg_lock);
                        if (q->txq[i].sdesc) {
                                free_tx_desc(adapter, &q->txq[i],
                                             q->txq[i].in_use);
                                kfree(q->txq[i].sdesc);
                        }
                        dma_free_coherent(&pdev->dev,
                                          q->txq[i].size *
                                          sizeof(struct tx_desc),
                                          q->txq[i].desc, q->txq[i].phys_addr);
                        __skb_queue_purge(&q->txq[i].sendq);
                }

        if (q->rspq.desc) {
                spin_lock(&adapter->sge.reg_lock);
                t3_sge_disable_rspcntxt(adapter, q->rspq.cntxt_id);
                spin_unlock(&adapter->sge.reg_lock);
                dma_free_coherent(&pdev->dev,
                                  q->rspq.size * sizeof(struct rsp_desc),
                                  q->rspq.desc, q->rspq.phys_addr);
        }

        if (q->netdev)
                q->netdev->atalk_ptr = NULL;

        memset(q, 0, sizeof(*q));
}

/**
 *      init_qset_cntxt - initialize an SGE queue set context info
 *      @qs: the queue set
 *      @id: the queue set id
 *
 *      Initializes the TIDs and context ids for the queues of a queue set.
 */
static void init_qset_cntxt(struct sge_qset *qs, unsigned int id)
{
        qs->rspq.cntxt_id = id;
        qs->fl[0].cntxt_id = 2 * id;
        qs->fl[1].cntxt_id = 2 * id + 1;
        qs->txq[TXQ_ETH].cntxt_id = FW_TUNNEL_SGEEC_START + id;
        qs->txq[TXQ_ETH].token = FW_TUNNEL_TID_START + id;
        qs->txq[TXQ_OFLD].cntxt_id = FW_OFLD_SGEEC_START + id;
        qs->txq[TXQ_CTRL].cntxt_id = FW_CTRL_SGEEC_START + id;
        qs->txq[TXQ_CTRL].token = FW_CTRL_TID_START + id;
}

/**
 *      sgl_len - calculates the size of an SGL of the given capacity
 *      @n: the number of SGL entries
 *
 *      Calculates the number of flits needed for a scatter/gather list that
 *      can hold the given number of entries.
 */
static inline unsigned int sgl_len(unsigned int n)
{
        /* alternatively: 3 * (n / 2) + 2 * (n & 1) */
        return (3 * n) / 2 + (n & 1);
}

/**
 *      flits_to_desc - returns the num of Tx descriptors for the given flits
 *      @n: the number of flits
 *
 *      Calculates the number of Tx descriptors needed for the supplied number
 *      of flits.
 */
static inline unsigned int flits_to_desc(unsigned int n)
{
        BUG_ON(n >= ARRAY_SIZE(flit_desc_map));
        return flit_desc_map[n];
}

/**
 *      get_packet - return the next ingress packet buffer from a free list
 *      @adap: the adapter that received the packet
 *      @fl: the SGE free list holding the packet
 *      @len: the packet length including any SGE padding
 *      @drop_thres: # of remaining buffers before we start dropping packets
 *
 *      Get the next packet from a free list and complete setup of the
 *      sk_buff.  If the packet is small we make a copy and recycle the
 *      original buffer, otherwise we use the original buffer itself.  If a
 *      positive drop threshold is supplied packets are dropped and their
 *      buffers recycled if (a) the number of remaining buffers is under the
 *      threshold and the packet is too big to copy, or (b) the packet should
 *      be copied but there is no memory for the copy.
 */
static struct sk_buff *get_packet(struct adapter *adap, struct sge_fl *fl,
                                  unsigned int len, unsigned int drop_thres)
{
        struct sk_buff *skb = NULL;
        struct rx_sw_desc *sd = &fl->sdesc[fl->cidx];

        prefetch(sd->skb->data);

        if (len <= SGE_RX_COPY_THRES) {
                skb = alloc_skb(len, GFP_ATOMIC);
                if (likely(skb != NULL)) {
                        __skb_put(skb, len);
                        pci_dma_sync_single_for_cpu(adap->pdev,
                                                    pci_unmap_addr(sd,
                                                                   dma_addr),
                                                    len, PCI_DMA_FROMDEVICE);
                        memcpy(skb->data, sd->skb->data, len);
                        pci_dma_sync_single_for_device(adap->pdev,
                                                       pci_unmap_addr(sd,
                                                                      dma_addr),
                                                       len, PCI_DMA_FROMDEVICE);
                } else if (!drop_thres)
                        goto use_orig_buf;
              recycle:
                recycle_rx_buf(adap, fl, fl->cidx);
                return skb;
        }

        if (unlikely(fl->credits < drop_thres))
                goto recycle;

      use_orig_buf:
        pci_unmap_single(adap->pdev, pci_unmap_addr(sd, dma_addr),
                         fl->buf_size, PCI_DMA_FROMDEVICE);
        skb = sd->skb;
        skb_put(skb, len);
        __refill_fl(adap, fl);
        return skb;
}

/**
 *      get_imm_packet - return the next ingress packet buffer from a response
 *      @resp: the response descriptor containing the packet data
 *
 *      Return a packet containing the immediate data of the given response.
 */
static inline struct sk_buff *get_imm_packet(const struct rsp_desc *resp)
{
        struct sk_buff *skb = alloc_skb(IMMED_PKT_SIZE, GFP_ATOMIC);

        if (skb) {
                __skb_put(skb, IMMED_PKT_SIZE);
                memcpy(skb->data, resp->imm_data, IMMED_PKT_SIZE);
        }
        return skb;
}

/**
 *      calc_tx_descs - calculate the number of Tx descriptors for a packet
 *      @skb: the packet
 *
 *      Returns the number of Tx descriptors needed for the given Ethernet
 *      packet.  Ethernet packets require addition of WR and CPL headers.
 */
static inline unsigned int calc_tx_descs(const struct sk_buff *skb)
{
        unsigned int flits;

        if (skb->len <= WR_LEN - sizeof(struct cpl_tx_pkt))
                return 1;

        flits = sgl_len(skb_shinfo(skb)->nr_frags + 1) + 2;
        if (skb_shinfo(skb)->gso_size)
                flits++;
        return flits_to_desc(flits);
}

/**
 *      make_sgl - populate a scatter/gather list for a packet
 *      @skb: the packet
 *      @sgp: the SGL to populate
 *      @start: start address of skb main body data to include in the SGL
 *      @len: length of skb main body data to include in the SGL
 *      @pdev: the PCI device
 *
 *      Generates a scatter/gather list for the buffers that make up a packet
 *      and returns the SGL size in 8-byte words.  The caller must size the SGL
 *      appropriately.
 */
static inline unsigned int make_sgl(const struct sk_buff *skb,
                                    struct sg_ent *sgp, unsigned char *start,
                                    unsigned int len, struct pci_dev *pdev)
{
        dma_addr_t mapping;
        unsigned int i, j = 0, nfrags;

        if (len) {
                mapping = pci_map_single(pdev, start, len, PCI_DMA_TODEVICE);
                sgp->len[0] = cpu_to_be32(len);
                sgp->addr[0] = cpu_to_be64(mapping);
                j = 1;
        }

        nfrags = skb_shinfo(skb)->nr_frags;
        for (i = 0; i < nfrags; i++) {
                skb_frag_t *frag = &skb_shinfo(skb)->frags[i];

                mapping = pci_map_page(pdev, frag->page, frag->page_offset,
                                       frag->size, PCI_DMA_TODEVICE);
                sgp->len[j] = cpu_to_be32(frag->size);
                sgp->addr[j] = cpu_to_be64(mapping);
                j ^= 1;
                if (j == 0)
                        ++sgp;
        }
        if (j)
                sgp->len[j] = 0;
        return ((nfrags + (len != 0)) * 3) / 2 + j;
}

/**
 *      check_ring_tx_db - check and potentially ring a Tx queue's doorbell
 *      @adap: the adapter
 *      @q: the Tx queue
 *
 *      Ring the doorbel if a Tx queue is asleep.  There is a natural race,
 *      where the HW is going to sleep just after we checked, however,
 *      then the interrupt handler will detect the outstanding TX packet
 *      and ring the doorbell for us.
 *
 *      When GTS is disabled we unconditionally ring the doorbell.
 */
static inline void check_ring_tx_db(struct adapter *adap, struct sge_txq *q)
{
#if USE_GTS
        clear_bit(TXQ_LAST_PKT_DB, &q->flags);
        if (test_and_set_bit(TXQ_RUNNING, &q->flags) == 0) {
                set_bit(TXQ_LAST_PKT_DB, &q->flags);
                t3_write_reg(adap, A_SG_KDOORBELL,
                             F_SELEGRCNTX | V_EGRCNTX(q->cntxt_id));
        }
#else
        wmb();                  /* write descriptors before telling HW */
        t3_write_reg(adap, A_SG_KDOORBELL,
                     F_SELEGRCNTX | V_EGRCNTX(q->cntxt_id));
#endif
}

static inline void wr_gen2(struct tx_desc *d, unsigned int gen)
{
#if SGE_NUM_GENBITS == 2
        d->flit[TX_DESC_FLITS - 1] = cpu_to_be64(gen);
#endif
}

/**
 *      write_wr_hdr_sgl - write a WR header and, optionally, SGL
 *      @ndesc: number of Tx descriptors spanned by the SGL
 *      @skb: the packet corresponding to the WR
 *      @d: first Tx descriptor to be written
 *      @pidx: index of above descriptors
 *      @q: the SGE Tx queue
 *      @sgl: the SGL
 *      @flits: number of flits to the start of the SGL in the first descriptor
 *      @sgl_flits: the SGL size in flits
 *      @gen: the Tx descriptor generation
 *      @wr_hi: top 32 bits of WR header based on WR type (big endian)
 *      @wr_lo: low 32 bits of WR header based on WR type (big endian)
 *
 *      Write a work request header and an associated SGL.  If the SGL is
 *      small enough to fit into one Tx descriptor it has already been written
 *      and we just need to write the WR header.  Otherwise we distribute the
 *      SGL across the number of descriptors it spans.
 */
static void write_wr_hdr_sgl(unsigned int ndesc, struct sk_buff *skb,
                             struct tx_desc *d, unsigned int pidx,
                             const struct sge_txq *q,
                             const struct sg_ent *sgl,
                             unsigned int flits, unsigned int sgl_flits,
                             unsigned int gen, unsigned int wr_hi,
                             unsigned int wr_lo)
{
        struct work_request_hdr *wrp = (struct work_request_hdr *)d;
        struct tx_sw_desc *sd = &q->sdesc[pidx];

        sd->skb = skb;
        if (need_skb_unmap()) {
                struct unmap_info *ui = (struct unmap_info *)skb->cb;

                ui->fragidx = 0;
                ui->addr_idx = 0;
                ui->sflit = flits;
        }

        if (likely(ndesc == 1)) {
                skb->priority = pidx;
                wrp->wr_hi = htonl(F_WR_SOP | F_WR_EOP | V_WR_DATATYPE(1) |
                                   V_WR_SGLSFLT(flits)) | wr_hi;
                wmb();
                wrp->wr_lo = htonl(V_WR_LEN(flits + sgl_flits) |
                                   V_WR_GEN(gen)) | wr_lo;
                wr_gen2(d, gen);
        } else {
                unsigned int ogen = gen;
                const u64 *fp = (const u64 *)sgl;
                struct work_request_hdr *wp = wrp;

                wrp->wr_hi = htonl(F_WR_SOP | V_WR_DATATYPE(1) |
                                   V_WR_SGLSFLT(flits)) | wr_hi;

                while (sgl_flits) {
                        unsigned int avail = WR_FLITS - flits;

                        if (avail > sgl_flits)
                                avail = sgl_flits;
                        memcpy(&d->flit[flits], fp, avail * sizeof(*fp));
                        sgl_flits -= avail;
                        ndesc--;
                        if (!sgl_flits)
                                break;

                        fp += avail;
                        d++;
                        sd++;
                        if (++pidx == q->size) {
                                pidx = 0;
                                gen ^= 1;
                                d = q->desc;
                                sd = q->sdesc;
                        }

                        sd->skb = skb;
                        wrp = (struct work_request_hdr *)d;
                        wrp->wr_hi = htonl(V_WR_DATATYPE(1) |
                                           V_WR_SGLSFLT(1)) | wr_hi;
                        wrp->wr_lo = htonl(V_WR_LEN(min(WR_FLITS,
                                                        sgl_flits + 1)) |
                                           V_WR_GEN(gen)) | wr_lo;
                        wr_gen2(d, gen);
                        flits = 1;
                }
                skb->priority = pidx;
                wrp->wr_hi |= htonl(F_WR_EOP);
                wmb();
                wp->wr_lo = htonl(V_WR_LEN(WR_FLITS) | V_WR_GEN(ogen)) | wr_lo;
                wr_gen2((struct tx_desc *)wp, ogen);
                WARN_ON(ndesc != 0);
        }
}

/**
 *      write_tx_pkt_wr - write a TX_PKT work request
 *      @adap: the adapter
 *      @skb: the packet to send
 *      @pi: the egress interface
 *      @pidx: index of the first Tx descriptor to write
 *      @gen: the generation value to use
 *      @q: the Tx queue
 *      @ndesc: number of descriptors the packet will occupy
 *      @compl: the value of the COMPL bit to use
 *
 *      Generate a TX_PKT work request to send the supplied packet.
 */
static void write_tx_pkt_wr(struct adapter *adap, struct sk_buff *skb,
                            const struct port_info *pi,
                            unsigned int pidx, unsigned int gen,
                            struct sge_txq *q, unsigned int ndesc,
                            unsigned int compl)
{
        unsigned int flits, sgl_flits, cntrl, tso_info;
        struct sg_ent *sgp, sgl[MAX_SKB_FRAGS / 2 + 1];
        struct tx_desc *d = &q->desc[pidx];
        struct cpl_tx_pkt *cpl = (struct cpl_tx_pkt *)d;

        cpl->len = htonl(skb->len | 0x80000000);
        cntrl = V_TXPKT_INTF(pi->port_id);

        if (vlan_tx_tag_present(skb) && pi->vlan_grp)
                cntrl |= F_TXPKT_VLAN_VLD | V_TXPKT_VLAN(vlan_tx_tag_get(skb));

        tso_info = V_LSO_MSS(skb_shinfo(skb)->gso_size);
        if (tso_info) {
                int eth_type;
                struct cpl_tx_pkt_lso *hdr = (struct cpl_tx_pkt_lso *)cpl;

                d->flit[2] = 0;
                cntrl |= V_TXPKT_OPCODE(CPL_TX_PKT_LSO);
                hdr->cntrl = htonl(cntrl);
                eth_type = skb->nh.raw - skb->data == ETH_HLEN ?
                    CPL_ETH_II : CPL_ETH_II_VLAN;
                tso_info |= V_LSO_ETH_TYPE(eth_type) |
                    V_LSO_IPHDR_WORDS(skb->nh.iph->ihl) |
                    V_LSO_TCPHDR_WORDS(skb->h.th->doff);
                hdr->lso_info = htonl(tso_info);
                flits = 3;
        } else {
                cntrl |= V_TXPKT_OPCODE(CPL_TX_PKT);
                cntrl |= F_TXPKT_IPCSUM_DIS;    /* SW calculates IP csum */
                cntrl |= V_TXPKT_L4CSUM_DIS(skb->ip_summed != CHECKSUM_PARTIAL);
                cpl->cntrl = htonl(cntrl);

                if (skb->len <= WR_LEN - sizeof(*cpl)) {
                        q->sdesc[pidx].skb = NULL;
                        if (!skb->data_len)
                                memcpy(&d->flit[2], skb->data, skb->len);
                        else
                                skb_copy_bits(skb, 0, &d->flit[2], skb->len);

                        flits = (skb->len + 7) / 8 + 2;
                        cpl->wr.wr_hi = htonl(V_WR_BCNTLFLT(skb->len & 7) |
                                              V_WR_OP(FW_WROPCODE_TUNNEL_TX_PKT)
                                              | F_WR_SOP | F_WR_EOP | compl);
                        wmb();
                        cpl->wr.wr_lo = htonl(V_WR_LEN(flits) | V_WR_GEN(gen) |
                                              V_WR_TID(q->token));
                        wr_gen2(d, gen);
                        kfree_skb(skb);
                        return;
                }

                flits = 2;
        }

        sgp = ndesc == 1 ? (struct sg_ent *)&d->flit[flits] : sgl;
        sgl_flits = make_sgl(skb, sgp, skb->data, skb_headlen(skb), adap->pdev);
        if (need_skb_unmap())
                ((struct unmap_info *)skb->cb)->len = skb_headlen(skb);

        write_wr_hdr_sgl(ndesc, skb, d, pidx, q, sgl, flits, sgl_flits, gen,
                         htonl(V_WR_OP(FW_WROPCODE_TUNNEL_TX_PKT) | compl),
                         htonl(V_WR_TID(q->token)));
}

/**
 *      eth_xmit - add a packet to the Ethernet Tx queue
 *      @skb: the packet
 *      @dev: the egress net device
 *
 *      Add a packet to an SGE Tx queue.  Runs with softirqs disabled.
 */
int t3_eth_xmit(struct sk_buff *skb, struct net_device *dev)
{
        unsigned int ndesc, pidx, credits, gen, compl;
        const struct port_info *pi = netdev_priv(dev);
        struct adapter *adap = dev->priv;
        struct sge_qset *qs = dev2qset(dev);
        struct sge_txq *q = &qs->txq[TXQ_ETH];

        /*
         * The chip min packet length is 9 octets but play safe and reject
         * anything shorter than an Ethernet header.
         */
        if (unlikely(skb->len < ETH_HLEN)) {
                dev_kfree_skb(skb);
                return NETDEV_TX_OK;
        }

        spin_lock(&q->lock);
        reclaim_completed_tx(adap, q);

        credits = q->size - q->in_use;
        ndesc = calc_tx_descs(skb);

        if (unlikely(credits < ndesc)) {
                if (!netif_queue_stopped(dev)) {
                        netif_stop_queue(dev);
                        set_bit(TXQ_ETH, &qs->txq_stopped);
                        q->stops++;
                        dev_err(&adap->pdev->dev,
                                "%s: Tx ring %u full while queue awake!\n",
                                dev->name, q->cntxt_id & 7);
                }
                spin_unlock(&q->lock);
                return NETDEV_TX_BUSY;
        }

        q->in_use += ndesc;
        if (unlikely(credits - ndesc < q->stop_thres)) {
                q->stops++;
                netif_stop_queue(dev);
                set_bit(TXQ_ETH, &qs->txq_stopped);
#if !USE_GTS
                if (should_restart_tx(q) &&
                    test_and_clear_bit(TXQ_ETH, &qs->txq_stopped)) {
                        q->restarts++;
                        netif_wake_queue(dev);
                }
#endif
        }

        gen = q->gen;
        q->unacked += ndesc;
        compl = (q->unacked & 8) << (S_WR_COMPL - 3);
        q->unacked &= 7;
        pidx = q->pidx;
        q->pidx += ndesc;
        if (q->pidx >= q->size) {
                q->pidx -= q->size;
                q->gen ^= 1;
        }

        /* update port statistics */
        if (skb->ip_summed == CHECKSUM_COMPLETE)
                qs->port_stats[SGE_PSTAT_TX_CSUM]++;
        if (skb_shinfo(skb)->gso_size)
                qs->port_stats[SGE_PSTAT_TSO]++;
        if (vlan_tx_tag_present(skb) && pi->vlan_grp)
                qs->port_stats[SGE_PSTAT_VLANINS]++;

        dev->trans_start = jiffies;
        spin_unlock(&q->lock);

        /*
         * We do not use Tx completion interrupts to free DMAd Tx packets.
         * This is good for performamce but means that we rely on new Tx
         * packets arriving to run the destructors of completed packets,
         * which open up space in their sockets' send queues.  Sometimes
         * we do not get such new packets causing Tx to stall.  A single
         * UDP transmitter is a good example of this situation.  We have
         * a clean up timer that periodically reclaims completed packets
         * but it doesn't run often enough (nor do we want it to) to prevent
         * lengthy stalls.  A solution to this problem is to run the
         * destructor early, after the packet is queued but before it's DMAd.
         * A cons is that we lie to socket memory accounting, but the amount
         * of extra memory is reasonable (limited by the number of Tx
         * descriptors), the packets do actually get freed quickly by new
         * packets almost always, and for protocols like TCP that wait for
         * acks to really free up the data the extra memory is even less.
         * On the positive side we run the destructors on the sending CPU
         * rather than on a potentially different completing CPU, usually a
         * good thing.  We also run them without holding our Tx queue lock,
         * unlike what reclaim_completed_tx() would otherwise do.
         *
         * Run the destructor before telling the DMA engine about the packet
         * to make sure it doesn't complete and get freed prematurely.
         */
        if (likely(!skb_shared(skb)))
                skb_orphan(skb);

        write_tx_pkt_wr(adap, skb, pi, pidx, gen, q, ndesc, compl);
        check_ring_tx_db(adap, q);
        return NETDEV_TX_OK;
}

/**
 *      write_imm - write a packet into a Tx descriptor as immediate data
 *      @d: the Tx descriptor to write
 *      @skb: the packet
 *      @len: the length of packet data to write as immediate data
 *      @gen: the generation bit value to write
 *
 *      Writes a packet as immediate data into a Tx descriptor.  The packet
 *      contains a work request at its beginning.  We must write the packet
 *      carefully so the SGE doesn't read accidentally before it's written in
 *      its entirety.
 */
static inline void write_imm(struct tx_desc *d, struct sk_buff *skb,
                             unsigned int len, unsigned int gen)
{
        struct work_request_hdr *from = (struct work_request_hdr *)skb->data;
        struct work_request_hdr *to = (struct work_request_hdr *)d;

        memcpy(&to[1], &from[1], len - sizeof(*from));
        to->wr_hi = from->wr_hi | htonl(F_WR_SOP | F_WR_EOP |
                                        V_WR_BCNTLFLT(len & 7));
        wmb();
        to->wr_lo = from->wr_lo | htonl(V_WR_GEN(gen) |
                                        V_WR_LEN((len + 7) / 8));
        wr_gen2(d, gen);
        kfree_skb(skb);
}

/**
 *      check_desc_avail - check descriptor availability on a send queue
 *      @adap: the adapter
 *      @q: the send queue
 *      @skb: the packet needing the descriptors
 *      @ndesc: the number of Tx descriptors needed
 *      @qid: the Tx queue number in its queue set (TXQ_OFLD or TXQ_CTRL)
 *
 *      Checks if the requested number of Tx descriptors is available on an
 *      SGE send queue.  If the queue is already suspended or not enough
 *      descriptors are available the packet is queued for later transmission.
 *      Must be called with the Tx queue locked.
 *
 *      Returns 0 if enough descriptors are available, 1 if there aren't
 *      enough descriptors and the packet has been queued, and 2 if the caller
 *      needs to retry because there weren't enough descriptors at the
 *      beginning of the call but some freed up in the mean time.
 */
static inline int check_desc_avail(struct adapter *adap, struct sge_txq *q,
                                   struct sk_buff *skb, unsigned int ndesc,
                                   unsigned int qid)
{
        if (unlikely(!skb_queue_empty(&q->sendq))) {
              addq_exit:__skb_queue_tail(&q->sendq, skb);
                return 1;
        }
        if (unlikely(q->size - q->in_use < ndesc)) {
                struct sge_qset *qs = txq_to_qset(q, qid);

                set_bit(qid, &qs->txq_stopped);
                smp_mb__after_clear_bit();

                if (should_restart_tx(q) &&
                    test_and_clear_bit(qid, &qs->txq_stopped))
                        return 2;

                q->stops++;
                goto addq_exit;
        }
        return 0;
}

/**
 *      reclaim_completed_tx_imm - reclaim completed control-queue Tx descs
 *      @q: the SGE control Tx queue
 *
 *      This is a variant of reclaim_completed_tx() that is used for Tx queues
 *      that send only immediate data (presently just the control queues) and
 *      thus do not have any sk_buffs to release.
 */
static inline void reclaim_completed_tx_imm(struct sge_txq *q)
{
        unsigned int reclaim = q->processed - q->cleaned;

        q->in_use -= reclaim;
        q->cleaned += reclaim;
}

static inline int immediate(const struct sk_buff *skb)
{
        return skb->len <= WR_LEN && !skb->data_len;
}

/**
 *      ctrl_xmit - send a packet through an SGE control Tx queue
 *      @adap: the adapter
 *      @q: the control queue
 *      @skb: the packet
 *
 *      Send a packet through an SGE control Tx queue.  Packets sent through
 *      a control queue must fit entirely as immediate data in a single Tx
 *      descriptor and have no page fragments.
 */
static int ctrl_xmit(struct adapter *adap, struct sge_txq *q,
                     struct sk_buff *skb)
{
        int ret;
        struct work_request_hdr *wrp = (struct work_request_hdr *)skb->data;

        if (unlikely(!immediate(skb))) {
                WARN_ON(1);
                dev_kfree_skb(skb);
                return NET_XMIT_SUCCESS;
        }

        wrp->wr_hi |= htonl(F_WR_SOP | F_WR_EOP);
        wrp->wr_lo = htonl(V_WR_TID(q->token));

        spin_lock(&q->lock);
      again:reclaim_completed_tx_imm(q);

        ret = check_desc_avail(adap, q, skb, 1, TXQ_CTRL);
        if (unlikely(ret)) {
                if (ret == 1) {
                        spin_unlock(&q->lock);
                        return NET_XMIT_CN;
                }
                goto again;
        }

        write_imm(&q->desc[q->pidx], skb, skb->len, q->gen);

        q->in_use++;
        if (++q->pidx >= q->size) {
                q->pidx = 0;
                q->gen ^= 1;
        }
        spin_unlock(&q->lock);
        wmb();
        t3_write_reg(adap, A_SG_KDOORBELL,
                     F_SELEGRCNTX | V_EGRCNTX(q->cntxt_id));
        return NET_XMIT_SUCCESS;
}

/**
 *      restart_ctrlq - restart a suspended control queue
 *      @qs: the queue set cotaining the control queue
 *
 *      Resumes transmission on a suspended Tx control queue.
 */
static void restart_ctrlq(unsigned long data)
{
        struct sk_buff *skb;
        struct sge_qset *qs = (struct sge_qset *)data;
        struct sge_txq *q = &qs->txq[TXQ_CTRL];
        struct adapter *adap = qs->netdev->priv;

        spin_lock(&q->lock);
      again:reclaim_completed_tx_imm(q);

        while (q->in_use < q->size && (skb = __skb_dequeue(&q->sendq)) != NULL) {

                write_imm(&q->desc[q->pidx], skb, skb->len, q->gen);

                if (++q->pidx >= q->size) {
                        q->pidx = 0;
                        q->gen ^= 1;
                }
                q->in_use++;
        }

        if (!skb_queue_empty(&q->sendq)) {
                set_bit(TXQ_CTRL, &qs->txq_stopped);
                smp_mb__after_clear_bit();

                if (should_restart_tx(q) &&
                    test_and_clear_bit(TXQ_CTRL, &qs->txq_stopped))
                        goto again;
                q->stops++;
        }

        spin_unlock(&q->lock);
        t3_write_reg(adap, A_SG_KDOORBELL,
                     F_SELEGRCNTX | V_EGRCNTX(q->cntxt_id));
}

/**
 *      write_ofld_wr - write an offload work request
 *      @adap: the adapter
 *      @skb: the packet to send
 *      @q: the Tx queue
 *      @pidx: index of the first Tx descriptor to write
 *      @gen: the generation value to use
 *      @ndesc: number of descriptors the packet will occupy
 *
 *      Write an offload work request to send the supplied packet.  The packet
 *      data already carry the work request with most fields populated.
 */
static void write_ofld_wr(struct adapter *adap, struct sk_buff *skb,
                          struct sge_txq *q, unsigned int pidx,
                          unsigned int gen, unsigned int ndesc)
{
        unsigned int sgl_flits, flits;
        struct work_request_hdr *from;
        struct sg_ent *sgp, sgl[MAX_SKB_FRAGS / 2 + 1];
        struct tx_desc *d = &q->desc[pidx];

        if (immediate(skb)) {
                q->sdesc[pidx].skb = NULL;
                write_imm(d, skb, skb->len, gen);
                return;
        }

        /* Only TX_DATA builds SGLs */

        from = (struct work_request_hdr *)skb->data;
        memcpy(&d->flit[1], &from[1], skb->h.raw - skb->data - sizeof(*from));

        flits = (skb->h.raw - skb->data) / 8;
        sgp = ndesc == 1 ? (struct sg_ent *)&d->flit[flits] : sgl;
        sgl_flits = make_sgl(skb, sgp, skb->h.raw, skb->tail - skb->h.raw,
                             adap->pdev);
        if (need_skb_unmap())
                ((struct unmap_info *)skb->cb)->len = skb->tail - skb->h.raw;

        write_wr_hdr_sgl(ndesc, skb, d, pidx, q, sgl, flits, sgl_flits,
                         gen, from->wr_hi, from->wr_lo);
}

/**
 *      calc_tx_descs_ofld - calculate # of Tx descriptors for an offload packet
 *      @skb: the packet
 *
 *      Returns the number of Tx descriptors needed for the given offload
 *      packet.  These packets are already fully constructed.
 */
static inline unsigned int calc_tx_descs_ofld(const struct sk_buff *skb)
{
        unsigned int flits, cnt = skb_shinfo(skb)->nr_frags;

        if (skb->len <= WR_LEN && cnt == 0)
                return 1;       /* packet fits as immediate data */

        flits = (skb->h.raw - skb->data) / 8;   /* headers */
        if (skb->tail != skb->h.raw)
                cnt++;
        return flits_to_desc(flits + sgl_len(cnt));
}

/**
 *      ofld_xmit - send a packet through an offload queue
 *      @adap: the adapter
 *      @q: the Tx offload queue
 *      @skb: the packet
 *
 *      Send an offload packet through an SGE offload queue.
 */
static int ofld_xmit(struct adapter *adap, struct sge_txq *q,
                     struct sk_buff *skb)
{
        int ret;
        unsigned int ndesc = calc_tx_descs_ofld(skb), pidx, gen;

        spin_lock(&q->lock);
      again:reclaim_completed_tx(adap, q);

        ret = check_desc_avail(adap, q, skb, ndesc, TXQ_OFLD);
        if (unlikely(ret)) {
                if (ret == 1) {
                        skb->priority = ndesc;  /* save for restart */
                        spin_unlock(&q->lock);
                        return NET_XMIT_CN;
                }
                goto again;
        }

        gen = q->gen;
        q->in_use += ndesc;
        pidx = q->pidx;
        q->pidx += ndesc;
        if (q->pidx >= q->size) {
                q->pidx -= q->size;
                q->gen ^= 1;
        }
        spin_unlock(&q->lock);

        write_ofld_wr(adap, skb, q, pidx, gen, ndesc);
        check_ring_tx_db(adap, q);
        return NET_XMIT_SUCCESS;
}

/**
 *      restart_offloadq - restart a suspended offload queue
 *      @qs: the queue set cotaining the offload queue
 *
 *      Resumes transmission on a suspended Tx offload queue.
 */
static void restart_offloadq(unsigned long data)
{
        struct sk_buff *skb;
        struct sge_qset *qs = (struct sge_qset *)data;
        struct sge_txq *q = &qs->txq[TXQ_OFLD];
        struct adapter *adap = qs->netdev->priv;

        spin_lock(&q->lock);
      again:reclaim_completed_tx(adap, q);

        while ((skb = skb_peek(&q->sendq)) != NULL) {
                unsigned int gen, pidx;
                unsigned int ndesc = skb->priority;

                if (unlikely(q->size - q->in_use < ndesc)) {
                        set_bit(TXQ_OFLD, &qs->txq_stopped);
                        smp_mb__after_clear_bit();

                        if (should_restart_tx(q) &&
                            test_and_clear_bit(TXQ_OFLD, &qs->txq_stopped))
                                goto again;
                        q->stops++;
                        break;
                }

                gen = q->gen;
                q->in_use += ndesc;
                pidx = q->pidx;
                q->pidx += ndesc;
                if (q->pidx >= q->size) {
                        q->pidx -= q->size;
                        q->gen ^= 1;
                }
                __skb_unlink(skb, &q->sendq);
                spin_unlock(&q->lock);

                write_ofld_wr(adap, skb, q, pidx, gen, ndesc);
                spin_lock(&q->lock);
        }
        spin_unlock(&q->lock);

#if USE_GTS
        set_bit(TXQ_RUNNING, &q->flags);
        set_bit(TXQ_LAST_PKT_DB, &q->flags);
#endif
        t3_write_reg(adap, A_SG_KDOORBELL,
                     F_SELEGRCNTX | V_EGRCNTX(q->cntxt_id));
}

/**
 *      queue_set - return the queue set a packet should use
 *      @skb: the packet
 *
 *      Maps a packet to the SGE queue set it should use.  The desired queue
 *      set is carried in bits 1-3 in the packet's priority.
 */
static inline int queue_set(const struct sk_buff *skb)
{
        return skb->priority >> 1;
}

/**
 *      is_ctrl_pkt - return whether an offload packet is a control packet
 *      @skb: the packet
 *
 *      Determines whether an offload packet should use an OFLD or a CTRL
 *      Tx queue.  This is indicated by bit 0 in the packet's priority.
 */
static inline int is_ctrl_pkt(const struct sk_buff *skb)
{
        return skb->priority & 1;
}

/**
 *      t3_offload_tx - send an offload packet
 *      @tdev: the offload device to send to
 *      @skb: the packet
 *
 *      Sends an offload packet.  We use the packet priority to select the
 *      appropriate Tx queue as follows: bit 0 indicates whether the packet
 *      should be sent as regular or control, bits 1-3 select the queue set.
 */
int t3_offload_tx(struct t3cdev *tdev, struct sk_buff *skb)
{
        struct adapter *adap = tdev2adap(tdev);
        struct sge_qset *qs = &adap->sge.qs[queue_set(skb)];

        if (unlikely(is_ctrl_pkt(skb)))
                return ctrl_xmit(adap, &qs->txq[TXQ_CTRL], skb);

        return ofld_xmit(adap, &qs->txq[TXQ_OFLD], skb);
}

/**
 *      offload_enqueue - add an offload packet to an SGE offload receive queue
 *      @q: the SGE response queue
 *      @skb: the packet
 *
 *      Add a new offload packet to an SGE response queue's offload packet
 *      queue.  If the packet is the first on the queue it schedules the RX
 *      softirq to process the queue.
 */
static inline void offload_enqueue(struct sge_rspq *q, struct sk_buff *skb)
{
        skb->next = skb->prev = NULL;
        if (q->rx_tail)
                q->rx_tail->next = skb;
        else {
                struct sge_qset *qs = rspq_to_qset(q);

                if (__netif_rx_schedule_prep(qs->netdev))
                        __netif_rx_schedule(qs->netdev);
                q->rx_head = skb;
        }
        q->rx_tail = skb;
}

/**
 *      deliver_partial_bundle - deliver a (partial) bundle of Rx offload pkts
 *      @tdev: the offload device that will be receiving the packets
 *      @q: the SGE response queue that assembled the bundle
 *      @skbs: the partial bundle
 *      @n: the number of packets in the bundle
 *
 *      Delivers a (partial) bundle of Rx offload packets to an offload device.
 */
static inline void deliver_partial_bundle(struct t3cdev *tdev,
                                          struct sge_rspq *q,
                                          struct sk_buff *skbs[], int n)
{
        if (n) {
                q->offload_bundles++;
                tdev->recv(tdev, skbs, n);
        }
}

/**
 *      ofld_poll - NAPI handler for offload packets in interrupt mode
 *      @dev: the network device doing the polling
 *      @budget: polling budget
 *
 *      The NAPI handler for offload packets when a response queue is serviced
 *      by the hard interrupt handler, i.e., when it's operating in non-polling
 *      mode.  Creates small packet batches and sends them through the offload
 *      receive handler.  Batches need to be of modest size as we do prefetches
 *      on the packets in each.
 */
static int ofld_poll(struct net_device *dev, int *budget)
{
        struct adapter *adapter = dev->priv;
        struct sge_qset *qs = dev2qset(dev);
        struct sge_rspq *q = &qs->rspq;
        int work_done, limit = min(*budget, dev->quota), avail = limit;

        while (avail) {
                struct sk_buff *head, *tail, *skbs[RX_BUNDLE_SIZE];
                int ngathered;

                spin_lock_irq(&q->lock);
                head = q->rx_head;
                if (!head) {
                        work_done = limit - avail;
                        *budget -= work_done;
                        dev->quota -= work_done;
                        __netif_rx_complete(dev);
                        spin_unlock_irq(&q->lock);
                        return 0;
                }

                tail = q->rx_tail;
                q->rx_head = q->rx_tail = NULL;
                spin_unlock_irq(&q->lock);

                for (ngathered = 0; avail && head; avail--) {
                        prefetch(head->data);
                        skbs[ngathered] = head;
                        head = head->next;
                        skbs[ngathered]->next = NULL;
                        if (++ngathered == RX_BUNDLE_SIZE) {
                                q->offload_bundles++;
                                adapter->tdev.recv(&adapter->tdev, skbs,
                                                   ngathered);
                                ngathered = 0;
                        }
                }
                if (head) {     /* splice remaining packets back onto Rx queue */
                        spin_lock_irq(&q->lock);
                        tail->next = q->rx_head;
                        if (!q->rx_head)
                                q->rx_tail = tail;
                        q->rx_head = head;
                        spin_unlock_irq(&q->lock);
                }
                deliver_partial_bundle(&adapter->tdev, q, skbs, ngathered);
        }
        work_done = limit - avail;
        *budget -= work_done;
        dev->quota -= work_done;
        return 1;
}

/**
 *      rx_offload - process a received offload packet
 *      @tdev: the offload device receiving the packet
 *      @rq: the response queue that received the packet
 *      @skb: the packet
 *      @rx_gather: a gather list of packets if we are building a bundle
 *      @gather_idx: index of the next available slot in the bundle
 *
 *      Process an ingress offload pakcet and add it to the offload ingress
 *      queue.  Returns the index of the next available slot in the bundle.
 */
static inline int rx_offload(struct t3cdev *tdev, struct sge_rspq *rq,
                             struct sk_buff *skb, struct sk_buff *rx_gather[],
                             unsigned int gather_idx)
{
        rq->offload_pkts++;
        skb->mac.raw = skb->nh.raw = skb->h.raw = skb->data;

        if (rq->polling) {
                rx_gather[gather_idx++] = skb;
                if (gather_idx == RX_BUNDLE_SIZE) {
                        tdev->recv(tdev, rx_gather, RX_BUNDLE_SIZE);
                        gather_idx = 0;
                        rq->offload_bundles++;
                }
        } else
                offload_enqueue(rq, skb);

        return gather_idx;
}

/**
 *      update_tx_completed - update the number of processed Tx descriptors
 *      @qs: the queue set to update
 *      @idx: which Tx queue within the set to update
 *      @credits: number of new processed descriptors
 *      @tx_completed: accumulates credits for the queues
 *
 *      Updates the number of completed Tx descriptors for a queue set's Tx
 *      queue.  On UP systems we updated the information immediately but on
 *      MP we accumulate the credits locally and update the Tx queue when we
 *      reach a threshold to avoid cache-line bouncing.
 */
static inline void update_tx_completed(struct sge_qset *qs, int idx,
                                       unsigned int credits,
                                       unsigned int tx_completed[])
{
#ifdef CONFIG_SMP
        tx_completed[idx] += credits;
        if (tx_completed[idx] > 32) {
                qs->txq[idx].processed += tx_completed[idx];
                tx_completed[idx] = 0;
        }
#else
        qs->txq[idx].processed += credits;
#endif
}

/**
 *      restart_tx - check whether to restart suspended Tx queues
 *      @qs: the queue set to resume
 *
 *      Restarts suspended Tx queues of an SGE queue set if they have enough
 *      free resources to resume operation.
 */
static void restart_tx(struct sge_qset *qs)
{
        if (test_bit(TXQ_ETH, &qs->txq_stopped) &&
            should_restart_tx(&qs->txq[TXQ_ETH]) &&
            test_and_clear_bit(TXQ_ETH, &qs->txq_stopped)) {
                qs->txq[TXQ_ETH].restarts++;
                if (netif_running(qs->netdev))
                        netif_wake_queue(qs->netdev);
        }

        if (test_bit(TXQ_OFLD, &qs->txq_stopped) &&
            should_restart_tx(&qs->txq[TXQ_OFLD]) &&
            test_and_clear_bit(TXQ_OFLD, &qs->txq_stopped)) {
                qs->txq[TXQ_OFLD].restarts++;
                tasklet_schedule(&qs->txq[TXQ_OFLD].qresume_tsk);
        }
        if (test_bit(TXQ_CTRL, &qs->txq_stopped) &&
            should_restart_tx(&qs->txq[TXQ_CTRL]) &&
            test_and_clear_bit(TXQ_CTRL, &qs->txq_stopped)) {
                qs->txq[TXQ_CTRL].restarts++;
                tasklet_schedule(&qs->txq[TXQ_CTRL].qresume_tsk);
        }
}

/**
 *      rx_eth - process an ingress ethernet packet
 *      @adap: the adapter
 *      @rq: the response queue that received the packet
 *      @skb: the packet
 *      @pad: amount of padding at the start of the buffer
 *
 *      Process an ingress ethernet pakcet and deliver it to the stack.
 *      The padding is 2 if the packet was delivered in an Rx buffer and 0
 *      if it was immediate data in a response.
 */
static void rx_eth(struct adapter *adap, struct sge_rspq *rq,
                   struct sk_buff *skb, int pad)
{
        struct cpl_rx_pkt *p = (struct cpl_rx_pkt *)(skb->data + pad);
        struct port_info *pi;

        rq->eth_pkts++;
        skb_pull(skb, sizeof(*p) + pad);
        skb->dev = adap->port[p->iff];
        skb->dev->last_rx = jiffies;
        skb->protocol = eth_type_trans(skb, skb->dev);
        pi = netdev_priv(skb->dev);
        if (pi->rx_csum_offload && p->csum_valid && p->csum == 0xffff &&
            !p->fragment) {
                rspq_to_qset(rq)->port_stats[SGE_PSTAT_RX_CSUM_GOOD]++;
                skb->ip_summed = CHECKSUM_UNNECESSARY;
        } else
                skb->ip_summed = CHECKSUM_NONE;

        if (unlikely(p->vlan_valid)) {
                struct vlan_group *grp = pi->vlan_grp;

                rspq_to_qset(rq)->port_stats[SGE_PSTAT_VLANEX]++;
                if (likely(grp))
                        __vlan_hwaccel_rx(skb, grp, ntohs(p->vlan),
                                          rq->polling);
                else
                        dev_kfree_skb_any(skb);
        } else if (rq->polling)
                netif_receive_skb(skb);
        else
                netif_rx(skb);
}

/**
 *      handle_rsp_cntrl_info - handles control information in a response
 *      @qs: the queue set corresponding to the response
 *      @flags: the response control flags
 *      @tx_completed: accumulates completion credits for the Tx queues
 *
 *      Handles the control information of an SGE response, such as GTS
 *      indications and completion credits for the queue set's Tx queues.
 */
static inline void handle_rsp_cntrl_info(struct sge_qset *qs, u32 flags,
                                         unsigned int tx_completed[])
{
        unsigned int credits;

#if USE_GTS
        if (flags & F_RSPD_TXQ0_GTS)
                clear_bit(TXQ_RUNNING, &qs->txq[TXQ_ETH].flags);
#endif

        /* ETH credits are already coalesced, return them immediately. */
        credits = G_RSPD_TXQ0_CR(flags);
        if (credits)
                qs->txq[TXQ_ETH].processed += credits;

# if USE_GTS
        if (flags & F_RSPD_TXQ1_GTS)
                clear_bit(TXQ_RUNNING, &qs->txq[TXQ_OFLD].flags);
# endif
        update_tx_completed(qs, TXQ_OFLD, G_RSPD_TXQ1_CR(flags), tx_completed);
        update_tx_completed(qs, TXQ_CTRL, G_RSPD_TXQ2_CR(flags), tx_completed);
}

/**
 *      flush_tx_completed - returns accumulated Tx completions to Tx queues
 *      @qs: the queue set to update
 *      @tx_completed: pending completion credits to return to Tx queues
 *
 *      Updates the number of completed Tx descriptors for a queue set's Tx
 *      queues with the credits pending in @tx_completed.  This does something
 *      only on MP systems as on UP systems we return the credits immediately.
 */
static inline void flush_tx_completed(struct sge_qset *qs,
                                      unsigned int tx_completed[])
{
#if defined(CONFIG_SMP)
        if (tx_completed[TXQ_OFLD])
                qs->txq[TXQ_OFLD].processed += tx_completed[TXQ_OFLD];
        if (tx_completed[TXQ_CTRL])
                qs->txq[TXQ_CTRL].processed += tx_completed[TXQ_CTRL];
#endif
}

/**
 *      check_ring_db - check if we need to ring any doorbells
 *      @adapter: the adapter
 *      @qs: the queue set whose Tx queues are to be examined
 *      @sleeping: indicates which Tx queue sent GTS
 *
 *      Checks if some of a queue set's Tx queues need to ring their doorbells
 *      to resume transmission after idling while they still have unprocessed
 *      descriptors.
 */
static void check_ring_db(struct adapter *adap, struct sge_qset *qs,
                          unsigned int sleeping)
{
        if (sleeping & F_RSPD_TXQ0_GTS) {
                struct sge_txq *txq = &qs->txq[TXQ_ETH];

                if (txq->cleaned + txq->in_use != txq->processed &&
                    !test_and_set_bit(TXQ_LAST_PKT_DB, &txq->flags)) {
                        set_bit(TXQ_RUNNING, &txq->flags);
                        t3_write_reg(adap, A_SG_KDOORBELL, F_SELEGRCNTX |
                                     V_EGRCNTX(txq->cntxt_id));
                }
        }

        if (sleeping & F_RSPD_TXQ1_GTS) {
                struct sge_txq *txq = &qs->txq[TXQ_OFLD];

                if (txq->cleaned + txq->in_use != txq->processed &&
                    !test_and_set_bit(TXQ_LAST_PKT_DB, &txq->flags)) {
                        set_bit(TXQ_RUNNING, &txq->flags);
                        t3_write_reg(adap, A_SG_KDOORBELL, F_SELEGRCNTX |
                                     V_EGRCNTX(txq->cntxt_id));
                }
        }
}

/**
 *      is_new_response - check if a response is newly written
 *      @r: the response descriptor
 *      @q: the response queue
 *
 *      Returns true if a response descriptor contains a yet unprocessed
 *      response.
 */
static inline int is_new_response(const struct rsp_desc *r,
                                  const struct sge_rspq *q)
{
        return (r->intr_gen & F_RSPD_GEN2) == q->gen;
}

#define RSPD_GTS_MASK  (F_RSPD_TXQ0_GTS | F_RSPD_TXQ1_GTS)
#define RSPD_CTRL_MASK (RSPD_GTS_MASK | \
                        V_RSPD_TXQ0_CR(M_RSPD_TXQ0_CR) | \
                        V_RSPD_TXQ1_CR(M_RSPD_TXQ1_CR) | \
                        V_RSPD_TXQ2_CR(M_RSPD_TXQ2_CR))

/* How long to delay the next interrupt in case of memory shortage, in 0.1us. */
#define NOMEM_INTR_DELAY 2500

/**
 *      process_responses - process responses from an SGE response queue
 *      @adap: the adapter
 *      @qs: the queue set to which the response queue belongs
 *      @budget: how many responses can be processed in this round
 *
 *      Process responses from an SGE response queue up to the supplied budget.
 *      Responses include received packets as well as credits and other events
 *      for the queues that belong to the response queue's queue set.
 *      A negative budget is effectively unlimited.
 *
 *      Additionally choose the interrupt holdoff time for the next interrupt
 *      on this queue.  If the system is under memory shortage use a fairly
 *      long delay to help recovery.
 */
static int process_responses(struct adapter *adap, struct sge_qset *qs,
                             int budget)
{
        struct sge_rspq *q = &qs->rspq;
        struct rsp_desc *r = &q->desc[q->cidx];
        int budget_left = budget;
        unsigned int sleeping = 0, tx_completed[3] = { 0, 0, 0 };
        struct sk_buff *offload_skbs[RX_BUNDLE_SIZE];
        int ngathered = 0;

        q->next_holdoff = q->holdoff_tmr;

        while (likely(budget_left && is_new_response(r, q))) {
                int eth, ethpad = 0;
                struct sk_buff *skb = NULL;
                u32 len, flags = ntohl(r->flags);
                u32 rss_hi = *(const u32 *)r, rss_lo = r->rss_hdr.rss_hash_val;

                eth = r->rss_hdr.opcode == CPL_RX_PKT;

                if (unlikely(flags & F_RSPD_ASYNC_NOTIF)) {
                        skb = alloc_skb(AN_PKT_SIZE, GFP_ATOMIC);
                        if (!skb)
                                goto no_mem;

                        memcpy(__skb_put(skb, AN_PKT_SIZE), r, AN_PKT_SIZE);
                        skb->data[0] = CPL_ASYNC_NOTIF;
                        rss_hi = htonl(CPL_ASYNC_NOTIF << 24);
                        q->async_notif++;
                } else if (flags & F_RSPD_IMM_DATA_VALID) {
                        skb = get_imm_packet(r);
                        if (unlikely(!skb)) {
                              no_mem:
                                q->next_holdoff = NOMEM_INTR_DELAY;
                                q->nomem++;
                                /* consume one credit since we tried */
                                budget_left--;
                                break;
                        }
                        q->imm_data++;
                } else if ((len = ntohl(r->len_cq)) != 0) {
                        struct sge_fl *fl;

                        fl = (len & F_RSPD_FLQ) ? &qs->fl[1] : &qs->fl[0];
                        fl->credits--;
                        skb = get_packet(adap, fl, G_RSPD_LEN(len),
                                         eth ? SGE_RX_DROP_THRES : 0);
                        if (!skb)
                                q->rx_drops++;
                        else if (r->rss_hdr.opcode == CPL_TRACE_PKT)
                                __skb_pull(skb, 2);
                        ethpad = 2;
                        if (++fl->cidx == fl->size)
                                fl->cidx = 0;
                } else
                        q->pure_rsps++;

                if (flags & RSPD_CTRL_MASK) {
                        sleeping |= flags & RSPD_GTS_MASK;
                        handle_rsp_cntrl_info(qs, flags, tx_completed);
                }

                r++;
                if (unlikely(++q->cidx == q->size)) {
                        q->cidx = 0;
                        q->gen ^= 1;
                        r = q->desc;
                }
                prefetch(r);

                if (++q->credits >= (q->size / 4)) {
                        refill_rspq(adap, q, q->credits);
                        q->credits = 0;
                }

                if (likely(skb != NULL)) {
                        if (eth)
                                rx_eth(adap, q, skb, ethpad);
                        else {
                                /* Preserve the RSS info in csum & priority */
                                skb->csum = rss_hi;
                                skb->priority = rss_lo;
                                ngathered = rx_offload(&adap->tdev, q, skb,
                                                       offload_skbs, ngathered);
                        }
                }

                --budget_left;
        }

        flush_tx_completed(qs, tx_completed);
        deliver_partial_bundle(&adap->tdev, q, offload_skbs, ngathered);
        if (sleeping)
                check_ring_db(adap, qs, sleeping);

        smp_mb();               /* commit Tx queue .processed updates */
        if (unlikely(qs->txq_stopped != 0))
                restart_tx(qs);

        budget -= budget_left;
        return budget;
}

static inline int is_pure_response(const struct rsp_desc *r)
{
        u32 n = ntohl(r->flags) & (F_RSPD_ASYNC_NOTIF | F_RSPD_IMM_DATA_VALID);

        return (n | r->len_cq) == 0;
}

/**
 *      napi_rx_handler - the NAPI handler for Rx processing
 *      @dev: the net device
 *      @budget: how many packets we can process in this round
 *
 *      Handler for new data events when using NAPI.
 */
static int napi_rx_handler(struct net_device *dev, int *budget)
{
        struct adapter *adap = dev->priv;
        struct sge_qset *qs = dev2qset(dev);
        int effective_budget = min(*budget, dev->quota);

        int work_done = process_responses(adap, qs, effective_budget);
        *budget -= work_done;
        dev->quota -= work_done;

        if (work_done >= effective_budget)
                return 1;

        netif_rx_complete(dev);

        /*
         * Because we don't atomically flush the following write it is
         * possible that in very rare cases it can reach the device in a way
         * that races with a new response being written plus an error interrupt
         * causing the NAPI interrupt handler below to return unhandled status
         * to the OS.  To protect against this would require flushing the write
         * and doing both the write and the flush with interrupts off.  Way too
         * expensive and unjustifiable given the rarity of the race.
         *
         * The race cannot happen at all with MSI-X.
         */
        t3_write_reg(adap, A_SG_GTS, V_RSPQ(qs->rspq.cntxt_id) |
                     V_NEWTIMER(qs->rspq.next_holdoff) |
                     V_NEWINDEX(qs->rspq.cidx));
        return 0;
}

/*
 * Returns true if the device is already scheduled for polling.
 */
static inline int napi_is_scheduled(struct net_device *dev)
{
        return test_bit(__LINK_STATE_RX_SCHED, &dev->state);
}

/**
 *      process_pure_responses - process pure responses from a response queue
 *      @adap: the adapter
 *      @qs: the queue set owning the response queue
 *      @r: the first pure response to process
 *
 *      A simpler version of process_responses() that handles only pure (i.e.,
 *      non data-carrying) responses.  Such respones are too light-weight to
 *      justify calling a softirq under NAPI, so we handle them specially in
 *      the interrupt handler.  The function is called with a pointer to a
 *      response, which the caller must ensure is a valid pure response.
 *
 *      Returns 1 if it encounters a valid data-carrying response, 0 otherwise.
 */
static int process_pure_responses(struct adapter *adap, struct sge_qset *qs,
                                  struct rsp_desc *r)
{
        struct sge_rspq *q = &qs->rspq;
        unsigned int sleeping = 0, tx_completed[3] = { 0, 0, 0 };

        do {
                u32 flags = ntohl(r->flags);

                r++;
                if (unlikely(++q->cidx == q->size)) {
                        q->cidx = 0;
                        q->gen ^= 1;
                        r = q->desc;
                }
                prefetch(r);

                if (flags & RSPD_CTRL_MASK) {
                        sleeping |= flags & RSPD_GTS_MASK;
                        handle_rsp_cntrl_info(qs, flags, tx_completed);
                }

                q->pure_rsps++;
                if (++q->credits >= (q->size / 4)) {
                        refill_rspq(adap, q, q->credits);
                        q->credits = 0;
                }
        } while (is_new_response(r, q) && is_pure_response(r));

        flush_tx_completed(qs, tx_completed);

        if (sleeping)
                check_ring_db(adap, qs, sleeping);

        smp_mb();               /* commit Tx queue .processed updates */
        if (unlikely(qs->txq_stopped != 0))
                restart_tx(qs);

        return is_new_response(r, q);
}

/**
 *      handle_responses - decide what to do with new responses in NAPI mode
 *      @adap: the adapter
 *      @q: the response queue
 *
 *      This is used by the NAPI interrupt handlers to decide what to do with
 *      new SGE responses.  If there are no new responses it returns -1.  If
 *      there are new responses and they are pure (i.e., non-data carrying)
 *      it handles them straight in hard interrupt context as they are very
 *      cheap and don't deliver any packets.  Finally, if there are any data
 *      signaling responses it schedules the NAPI handler.  Returns 1 if it
 *      schedules NAPI, 0 if all new responses were pure.
 *
 *      The caller must ascertain NAPI is not already running.
 */
static inline int handle_responses(struct adapter *adap, struct sge_rspq *q)
{
        struct sge_qset *qs = rspq_to_qset(q);
        struct rsp_desc *r = &q->desc[q->cidx];

        if (!is_new_response(r, q))
                return -1;
        if (is_pure_response(r) && process_pure_responses(adap, qs, r) == 0) {
                t3_write_reg(adap, A_SG_GTS, V_RSPQ(q->cntxt_id) |
                             V_NEWTIMER(q->holdoff_tmr) | V_NEWINDEX(q->cidx));
                return 0;
        }
        if (likely(__netif_rx_schedule_prep(qs->netdev)))
                __netif_rx_schedule(qs->netdev);
        return 1;
}

/*
 * The MSI-X interrupt handler for an SGE response queue for the non-NAPI case
 * (i.e., response queue serviced in hard interrupt).
 */
irqreturn_t t3_sge_intr_msix(int irq, void *cookie)
{
        struct sge_qset *qs = cookie;
        struct adapter *adap = qs->netdev->priv;
        struct sge_rspq *q = &qs->rspq;

        spin_lock(&q->lock);
        if (process_responses(adap, qs, -1) == 0)
                q->unhandled_irqs++;
        t3_write_reg(adap, A_SG_GTS, V_RSPQ(q->cntxt_id) |
                     V_NEWTIMER(q->next_holdoff) | V_NEWINDEX(q->cidx));
        spin_unlock(&q->lock);
        return IRQ_HANDLED;
}

/*
 * The MSI-X interrupt handler for an SGE response queue for the NAPI case
 * (i.e., response queue serviced by NAPI polling).
 */
irqreturn_t t3_sge_intr_msix_napi(int irq, void *cookie)
{
        struct sge_qset *qs = cookie;
        struct adapter *adap = qs->netdev->priv;
        struct sge_rspq *q = &qs->rspq;

        spin_lock(&q->lock);
        BUG_ON(napi_is_scheduled(qs->netdev));

        if (handle_responses(adap, q) < 0)
                q->unhandled_irqs++;
        spin_unlock(&q->lock);
        return IRQ_HANDLED;
}

/*
 * The non-NAPI MSI interrupt handler.  This needs to handle data events from
 * SGE response queues as well as error and other async events as they all use
 * the same MSI vector.  We use one SGE response queue per port in this mode
 * and protect all response queues with queue 0's lock.
 */
static irqreturn_t t3_intr_msi(int irq, void *cookie)
{
        int new_packets = 0;
        struct adapter *adap = cookie;
        struct sge_rspq *q = &adap->sge.qs[0].rspq;

        spin_lock(&q->lock);

        if (process_responses(adap, &adap->sge.qs[0], -1)) {
                t3_write_reg(adap, A_SG_GTS, V_RSPQ(q->cntxt_id) |
                             V_NEWTIMER(q->next_holdoff) | V_NEWINDEX(q->cidx));
                new_packets = 1;
        }

        if (adap->params.nports == 2 &&
            process_responses(adap, &adap->sge.qs[1], -1)) {
                struct sge_rspq *q1 = &adap->sge.qs[1].rspq;

                t3_write_reg(adap, A_SG_GTS, V_RSPQ(q1->cntxt_id) |
                             V_NEWTIMER(q1->next_holdoff) |
                             V_NEWINDEX(q1->cidx));
                new_packets = 1;
        }

        if (!new_packets && t3_slow_intr_handler(adap) == 0)
                q->unhandled_irqs++;

        spin_unlock(&q->lock);
        return IRQ_HANDLED;
}

static int rspq_check_napi(struct net_device *dev, struct sge_rspq *q)
{
        if (!napi_is_scheduled(dev) && is_new_response(&q->desc[q->cidx], q)) {
                if (likely(__netif_rx_schedule_prep(dev)))
                        __netif_rx_schedule(dev);
                return 1;
        }
        return 0;
}

/*
 * The MSI interrupt handler for the NAPI case (i.e., response queues serviced
 * by NAPI polling).  Handles data events from SGE response queues as well as
 * error and other async events as they all use the same MSI vector.  We use
 * one SGE response queue per port in this mode and protect all response
 * queues with queue 0's lock.
 */
irqreturn_t t3_intr_msi_napi(int irq, void *cookie)
{
        int new_packets;
        struct adapter *adap = cookie;
        struct sge_rspq *q = &adap->sge.qs[0].rspq;

        spin_lock(&q->lock);

        new_packets = rspq_check_napi(adap->sge.qs[0].netdev, q);
        if (adap->params.nports == 2)
                new_packets += rspq_check_napi(adap->sge.qs[1].netdev,
                                               &adap->sge.qs[1].rspq);
        if (!new_packets && t3_slow_intr_handler(adap) == 0)
                q->unhandled_irqs++;

        spin_unlock(&q->lock);
        return IRQ_HANDLED;
}

/*
 * A helper function that processes responses and issues GTS.
 */
static inline int process_responses_gts(struct adapter *adap,
                                        struct sge_rspq *rq)
{
        int work;

        work = process_responses(adap, rspq_to_qset(rq), -1);
        t3_write_reg(adap, A_SG_GTS, V_RSPQ(rq->cntxt_id) |
                     V_NEWTIMER(rq->next_holdoff) | V_NEWINDEX(rq->cidx));
        return work;
}

/*
 * The legacy INTx interrupt handler.  This needs to handle data events from
 * SGE response queues as well as error and other async events as they all use
 * the same interrupt pin.  We use one SGE response queue per port in this mode
 * and protect all response queues with queue 0's lock.
 */
static irqreturn_t t3_intr(int irq, void *cookie)
{
        int work_done, w0, w1;
        struct adapter *adap = cookie;
        struct sge_rspq *q0 = &adap->sge.qs[0].rspq;
        struct sge_rspq *q1 = &adap->sge.qs[1].rspq;

        spin_lock(&q0->lock);

        w0 = is_new_response(&q0->desc[q0->cidx], q0);
        w1 = adap->params.nports == 2 &&
            is_new_response(&q1->desc[q1->cidx], q1);

        if (likely(w0 | w1)) {
                t3_write_reg(adap, A_PL_CLI, 0);
                t3_read_reg(adap, A_PL_CLI);    /* flush */

                if (likely(w0))
                        process_responses_gts(adap, q0);

                if (w1)
                        process_responses_gts(adap, q1);

                work_done = w0 | w1;
        } else
                work_done = t3_slow_intr_handler(adap);

        spin_unlock(&q0->lock);
        return IRQ_RETVAL(work_done != 0);
}

/*
 * Interrupt handler for legacy INTx interrupts for T3B-based cards.
 * Handles data events from SGE response queues as well as error and other
 * async events as they all use the same interrupt pin.  We use one SGE
 * response queue per port in this mode and protect all response queues with
 * queue 0's lock.
 */
static irqreturn_t t3b_intr(int irq, void *cookie)
{
        u32 map;
        struct adapter *adap = cookie;
        struct sge_rspq *q0 = &adap->sge.qs[0].rspq;

        t3_write_reg(adap, A_PL_CLI, 0);
        map = t3_read_reg(adap, A_SG_DATA_INTR);

        if (unlikely(!map))     /* shared interrupt, most likely */
                return IRQ_NONE;

        spin_lock(&q0->lock);

        if (unlikely(map & F_ERRINTR))
                t3_slow_intr_handler(adap);

        if (likely(map & 1))
                process_responses_gts(adap, q0);

        if (map & 2)
                process_responses_gts(adap, &adap->sge.qs[1].rspq);

        spin_unlock(&q0->lock);
        return IRQ_HANDLED;
}

/*
 * NAPI interrupt handler for legacy INTx interrupts for T3B-based cards.
 * Handles data events from SGE response queues as well as error and other
 * async events as they all use the same interrupt pin.  We use one SGE
 * response queue per port in this mode and protect all response queues with
 * queue 0's lock.
 */
static irqreturn_t t3b_intr_napi(int irq, void *cookie)
{
        u32 map;
        struct net_device *dev;
        struct adapter *adap = cookie;
        struct sge_rspq *q0 = &adap->sge.qs[0].rspq;

        t3_write_reg(adap, A_PL_CLI, 0);
        map = t3_read_reg(adap, A_SG_DATA_INTR);

        if (unlikely(!map))     /* shared interrupt, most likely */
                return IRQ_NONE;

        spin_lock(&q0->lock);

        if (unlikely(map & F_ERRINTR))
                t3_slow_intr_handler(adap);

        if (likely(map & 1)) {
                dev = adap->sge.qs[0].netdev;

                BUG_ON(napi_is_scheduled(dev));
                if (likely(__netif_rx_schedule_prep(dev)))
                        __netif_rx_schedule(dev);
        }
        if (map & 2) {
                dev = adap->sge.qs[1].netdev;

                BUG_ON(napi_is_scheduled(dev));
                if (likely(__netif_rx_schedule_prep(dev)))
                        __netif_rx_schedule(dev);
        }

        spin_unlock(&q0->lock);
        return IRQ_HANDLED;
}

/**
 *      t3_intr_handler - select the top-level interrupt handler
 *      @adap: the adapter
 *      @polling: whether using NAPI to service response queues
 *
 *      Selects the top-level interrupt handler based on the type of interrupts
 *      (MSI-X, MSI, or legacy) and whether NAPI will be used to service the
 *      response queues.
 */
intr_handler_t t3_intr_handler(struct adapter *adap, int polling)
{
        if (adap->flags & USING_MSIX)
                return polling ? t3_sge_intr_msix_napi : t3_sge_intr_msix;
        if (adap->flags & USING_MSI)
                return polling ? t3_intr_msi_napi : t3_intr_msi;
        if (adap->params.rev > 0)
                return polling ? t3b_intr_napi : t3b_intr;
        return t3_intr;
}

/**
 *      t3_sge_err_intr_handler - SGE async event interrupt handler
 *      @adapter: the adapter
 *
 *      Interrupt handler for SGE asynchronous (non-data) events.
 */
void t3_sge_err_intr_handler(struct adapter *adapter)
{
        unsigned int v, status = t3_read_reg(adapter, A_SG_INT_CAUSE);

        if (status & F_RSPQCREDITOVERFOW)
                CH_ALERT(adapter, "SGE response queue credit overflow\n");

        if (status & F_RSPQDISABLED) {
                v = t3_read_reg(adapter, A_SG_RSPQ_FL_STATUS);

                CH_ALERT(adapter,
                         "packet delivered to disabled response queue "
                         "(0x%x)\n", (v >> S_RSPQ0DISABLED) & 0xff);
        }

        t3_write_reg(adapter, A_SG_INT_CAUSE, status);
        if (status & (F_RSPQCREDITOVERFOW | F_RSPQDISABLED))
                t3_fatal_err(adapter);
}

/**
 *      sge_timer_cb - perform periodic maintenance of an SGE qset
 *      @data: the SGE queue set to maintain
 *
 *      Runs periodically from a timer to perform maintenance of an SGE queue
 *      set.  It performs two tasks:
 *
 *      a) Cleans up any completed Tx descriptors that may still be pending.
 *      Normal descriptor cleanup happens when new packets are added to a Tx
 *      queue so this timer is relatively infrequent and does any cleanup only
 *      if the Tx queue has not seen any new packets in a while.  We make a
 *      best effort attempt to reclaim descriptors, in that we don't wait
 *      around if we cannot get a queue's lock (which most likely is because
 *      someone else is queueing new packets and so will also handle the clean
 *      up).  Since control queues use immediate data exclusively we don't
 *      bother cleaning them up here.
 *
 *      b) Replenishes Rx queues that have run out due to memory shortage.
 *      Normally new Rx buffers are added when existing ones are consumed but
 *      when out of memory a queue can become empty.  We try to add only a few
 *      buffers here, the queue will be replenished fully as these new buffers
 *      are used up if memory shortage has subsided.
 */
static void sge_timer_cb(unsigned long data)
{
        spinlock_t *lock;
        struct sge_qset *qs = (struct sge_qset *)data;
        struct adapter *adap = qs->netdev->priv;

        if (spin_trylock(&qs->txq[TXQ_ETH].lock)) {
                reclaim_completed_tx(adap, &qs->txq[TXQ_ETH]);
                spin_unlock(&qs->txq[TXQ_ETH].lock);
        }
        if (spin_trylock(&qs->txq[TXQ_OFLD].lock)) {
                reclaim_completed_tx(adap, &qs->txq[TXQ_OFLD]);
                spin_unlock(&qs->txq[TXQ_OFLD].lock);
        }
        lock = (adap->flags & USING_MSIX) ? &qs->rspq.lock :
            &adap->sge.qs[0].rspq.lock;
        if (spin_trylock_irq(lock)) {
                if (!napi_is_scheduled(qs->netdev)) {
                        if (qs->fl[0].credits < qs->fl[0].size)
                                __refill_fl(adap, &qs->fl[0]);
                        if (qs->fl[1].credits < qs->fl[1].size)
                                __refill_fl(adap, &qs->fl[1]);
                }
                spin_unlock_irq(lock);
        }
        mod_timer(&qs->tx_reclaim_timer, jiffies + TX_RECLAIM_PERIOD);
}

/**
 *      t3_update_qset_coalesce - update coalescing settings for a queue set
 *      @qs: the SGE queue set
 *      @p: new queue set parameters
 *
 *      Update the coalescing settings for an SGE queue set.  Nothing is done
 *      if the queue set is not initialized yet.
 */
void t3_update_qset_coalesce(struct sge_qset *qs, const struct qset_params *p)
{
        if (!qs->netdev)
                return;

        qs->rspq.holdoff_tmr = max(p->coalesce_usecs * 10, 1U);/* can't be 0 */
        qs->rspq.polling = p->polling;
        qs->netdev->poll = p->polling ? napi_rx_handler : ofld_poll;
}

/**
 *      t3_sge_alloc_qset - initialize an SGE queue set
 *      @adapter: the adapter
 *      @id: the queue set id
 *      @nports: how many Ethernet ports will be using this queue set
 *      @irq_vec_idx: the IRQ vector index for response queue interrupts
 *      @p: configuration parameters for this queue set
 *      @ntxq: number of Tx queues for the queue set
 *      @netdev: net device associated with this queue set
 *
 *      Allocate resources and initialize an SGE queue set.  A queue set
 *      comprises a response queue, two Rx free-buffer queues, and up to 3
 *      Tx queues.  The Tx queues are assigned roles in the order Ethernet
 *      queue, offload queue, and control queue.
 */
int t3_sge_alloc_qset(struct adapter *adapter, unsigned int id, int nports,
                      int irq_vec_idx, const struct qset_params *p,
                      int ntxq, struct net_device *netdev)
{
        int i, ret = -ENOMEM;
        struct sge_qset *q = &adapter->sge.qs[id];

        init_qset_cntxt(q, id);
        init_timer(&q->tx_reclaim_timer);
        q->tx_reclaim_timer.data = (unsigned long)q;
        q->tx_reclaim_timer.function = sge_timer_cb;

        q->fl[0].desc = alloc_ring(adapter->pdev, p->fl_size,
                                   sizeof(struct rx_desc),
                                   sizeof(struct rx_sw_desc),
                                   &q->fl[0].phys_addr, &q->fl[0].sdesc);
        if (!q->fl[0].desc)
                goto err;

        q->fl[1].desc = alloc_ring(adapter->pdev, p->jumbo_size,
                                   sizeof(struct rx_desc),
                                   sizeof(struct rx_sw_desc),
                                   &q->fl[1].phys_addr, &q->fl[1].sdesc);
        if (!q->fl[1].desc)
                goto err;

        q->rspq.desc = alloc_ring(adapter->pdev, p->rspq_size,
                                  sizeof(struct rsp_desc), 0,
                                  &q->rspq.phys_addr, NULL);
        if (!q->rspq.desc)
                goto err;

        for (i = 0; i < ntxq; ++i) {
                /*
                 * The control queue always uses immediate data so does not
                 * need to keep track of any sk_buffs.
                 */
                size_t sz = i == TXQ_CTRL ? 0 : sizeof(struct tx_sw_desc);

                q->txq[i].desc = alloc_ring(adapter->pdev, p->txq_size[i],
                                            sizeof(struct tx_desc), sz,
                                            &q->txq[i].phys_addr,
                                            &q->txq[i].sdesc);
                if (!q->txq[i].desc)
                        goto err;

                q->txq[i].gen = 1;
                q->txq[i].size = p->txq_size[i];
                spin_lock_init(&q->txq[i].lock);
                skb_queue_head_init(&q->txq[i].sendq);
        }

        tasklet_init(&q->txq[TXQ_OFLD].qresume_tsk, restart_offloadq,
                     (unsigned long)q);
        tasklet_init(&q->txq[TXQ_CTRL].qresume_tsk, restart_ctrlq,
                     (unsigned long)q);

        q->fl[0].gen = q->fl[1].gen = 1;
        q->fl[0].size = p->fl_size;
        q->fl[1].size = p->jumbo_size;

        q->rspq.gen = 1;
        q->rspq.size = p->rspq_size;
        spin_lock_init(&q->rspq.lock);

        q->txq[TXQ_ETH].stop_thres = nports *
            flits_to_desc(sgl_len(MAX_SKB_FRAGS + 1) + 3);

        if (ntxq == 1) {
                q->fl[0].buf_size = SGE_RX_SM_BUF_SIZE + 2 +
                    sizeof(struct cpl_rx_pkt);
                q->fl[1].buf_size = MAX_FRAME_SIZE + 2 +
                    sizeof(struct cpl_rx_pkt);
        } else {
                q->fl[0].buf_size = SGE_RX_SM_BUF_SIZE +
                    sizeof(struct cpl_rx_data);
                q->fl[1].buf_size = (16 * 1024) -
                    SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
        }

        spin_lock(&adapter->sge.reg_lock);

        /* FL threshold comparison uses < */
        ret = t3_sge_init_rspcntxt(adapter, q->rspq.cntxt_id, irq_vec_idx,
                                   q->rspq.phys_addr, q->rspq.size,
                                   q->fl[0].buf_size, 1, 0);
        if (ret)
                goto err_unlock;

        for (i = 0; i < SGE_RXQ_PER_SET; ++i) {
                ret = t3_sge_init_flcntxt(adapter, q->fl[i].cntxt_id, 0,
                                          q->fl[i].phys_addr, q->fl[i].size,
                                          q->fl[i].buf_size, p->cong_thres, 1,
                                          0);
                if (ret)
                        goto err_unlock;
        }

        ret = t3_sge_init_ecntxt(adapter, q->txq[TXQ_ETH].cntxt_id, USE_GTS,
                                 SGE_CNTXT_ETH, id, q->txq[TXQ_ETH].phys_addr,
                                 q->txq[TXQ_ETH].size, q->txq[TXQ_ETH].token,
                                 1, 0);
        if (ret)
                goto err_unlock;

        if (ntxq > 1) {
                ret = t3_sge_init_ecntxt(adapter, q->txq[TXQ_OFLD].cntxt_id,
                                         USE_GTS, SGE_CNTXT_OFLD, id,
                                         q->txq[TXQ_OFLD].phys_addr,
                                         q->txq[TXQ_OFLD].size, 0, 1, 0);
                if (ret)
                        goto err_unlock;
        }

        if (ntxq > 2) {
                ret = t3_sge_init_ecntxt(adapter, q->txq[TXQ_CTRL].cntxt_id, 0,
                                         SGE_CNTXT_CTRL, id,
                                         q->txq[TXQ_CTRL].phys_addr,
                                         q->txq[TXQ_CTRL].size,
                                         q->txq[TXQ_CTRL].token, 1, 0);
                if (ret)
                        goto err_unlock;
        }

        spin_unlock(&adapter->sge.reg_lock);
        q->netdev = netdev;
        t3_update_qset_coalesce(q, p);

        /*
         * We use atalk_ptr as a backpointer to a qset.  In case a device is
         * associated with multiple queue sets only the first one sets
         * atalk_ptr.
         */
        if (netdev->atalk_ptr == NULL)
                netdev->atalk_ptr = q;

        refill_fl(adapter, &q->fl[0], q->fl[0].size, GFP_KERNEL);
        refill_fl(adapter, &q->fl[1], q->fl[1].size, GFP_KERNEL);
        refill_rspq(adapter, &q->rspq, q->rspq.size - 1);

        t3_write_reg(adapter, A_SG_GTS, V_RSPQ(q->rspq.cntxt_id) |
                     V_NEWTIMER(q->rspq.holdoff_tmr));

        mod_timer(&q->tx_reclaim_timer, jiffies + TX_RECLAIM_PERIOD);
        return 0;

      err_unlock:
        spin_unlock(&adapter->sge.reg_lock);
      err:
        t3_free_qset(adapter, q);
        return ret;
}

/**
 *      t3_free_sge_resources - free SGE resources
 *      @adap: the adapter
 *
 *      Frees resources used by the SGE queue sets.
 */
void t3_free_sge_resources(struct adapter *adap)
{
        int i;

        for (i = 0; i < SGE_QSETS; ++i)
                t3_free_qset(adap, &adap->sge.qs[i]);
}

/**
 *      t3_sge_start - enable SGE
 *      @adap: the adapter
 *
 *      Enables the SGE for DMAs.  This is the last step in starting packet
 *      transfers.
 */
void t3_sge_start(struct adapter *adap)
{
        t3_set_reg_field(adap, A_SG_CONTROL, F_GLOBALENABLE, F_GLOBALENABLE);
}

/**
 *      t3_sge_stop - disable SGE operation
 *      @adap: the adapter
 *
 *      Disables the DMA engine.  This can be called in emeregencies (e.g.,
 *      from error interrupts) or from normal process context.  In the latter
 *      case it also disables any pending queue restart tasklets.  Note that
 *      if it is called in interrupt context it cannot disable the restart
 *      tasklets as it cannot wait, however the tasklets will have no effect
 *      since the doorbells are disabled and the driver will call this again
 *      later from process context, at which time the tasklets will be stopped
 *      if they are still running.
 */
void t3_sge_stop(struct adapter *adap)
{
        t3_set_reg_field(adap, A_SG_CONTROL, F_GLOBALENABLE, 0);
        if (!in_interrupt()) {
                int i;

                for (i = 0; i < SGE_QSETS; ++i) {
                        struct sge_qset *qs = &adap->sge.qs[i];

                        tasklet_kill(&qs->txq[TXQ_OFLD].qresume_tsk);
                        tasklet_kill(&qs->txq[TXQ_CTRL].qresume_tsk);
                }
        }
}

/**
 *      t3_sge_init - initialize SGE
 *      @adap: the adapter
 *      @p: the SGE parameters
 *
 *      Performs SGE initialization needed every time after a chip reset.
 *      We do not initialize any of the queue sets here, instead the driver
 *      top-level must request those individually.  We also do not enable DMA
 *      here, that should be done after the queues have been set up.
 */
void t3_sge_init(struct adapter *adap, struct sge_params *p)
{
        unsigned int ctrl, ups = ffs(pci_resource_len(adap->pdev, 2) >> 12);

        ctrl = F_DROPPKT | V_PKTSHIFT(2) | F_FLMODE | F_AVOIDCQOVFL |
            F_CQCRDTCTRL |
            V_HOSTPAGESIZE(PAGE_SHIFT - 11) | F_BIGENDIANINGRESS |
            V_USERSPACESIZE(ups ? ups - 1 : 0) | F_ISCSICOALESCING;
#if SGE_NUM_GENBITS == 1
        ctrl |= F_EGRGENCTRL;
#endif
        if (adap->params.rev > 0) {
                if (!(adap->flags & (USING_MSIX | USING_MSI)))
                        ctrl |= F_ONEINTMULTQ | F_OPTONEINTMULTQ;
                ctrl |= F_CQCRDTCTRL | F_AVOIDCQOVFL;
        }
        t3_write_reg(adap, A_SG_CONTROL, ctrl);
        t3_write_reg(adap, A_SG_EGR_RCQ_DRB_THRSH, V_HIRCQDRBTHRSH(512) |
                     V_LORCQDRBTHRSH(512));
        t3_write_reg(adap, A_SG_TIMER_TICK, core_ticks_per_usec(adap) / 10);
        t3_write_reg(adap, A_SG_CMDQ_CREDIT_TH, V_THRESHOLD(32) |
                     V_TIMEOUT(100 * core_ticks_per_usec(adap)));
        t3_write_reg(adap, A_SG_HI_DRB_HI_THRSH, 1000);
        t3_write_reg(adap, A_SG_HI_DRB_LO_THRSH, 256);
        t3_write_reg(adap, A_SG_LO_DRB_HI_THRSH, 1000);
        t3_write_reg(adap, A_SG_LO_DRB_LO_THRSH, 256);
        t3_write_reg(adap, A_SG_OCO_BASE, V_BASE1(0xfff));
        t3_write_reg(adap, A_SG_DRB_PRI_THRESH, 63 * 1024);
}

/**
 *      t3_sge_prep - one-time SGE initialization
 *      @adap: the associated adapter
 *      @p: SGE parameters
 *
 *      Performs one-time initialization of SGE SW state.  Includes determining
 *      defaults for the assorted SGE parameters, which admins can change until
 *      they are used to initialize the SGE.
 */
void __devinit t3_sge_prep(struct adapter *adap, struct sge_params *p)
{
        int i;

        p->max_pkt_size = (16 * 1024) - sizeof(struct cpl_rx_data) -
            SKB_DATA_ALIGN(sizeof(struct skb_shared_info));

        for (i = 0; i < SGE_QSETS; ++i) {
                struct qset_params *q = p->qset + i;

                q->polling = adap->params.rev > 0;
                q->coalesce_usecs = 5;
                q->rspq_size = 1024;
                q->fl_size = 4096;
                q->jumbo_size = 512;
                q->txq_size[TXQ_ETH] = 1024;
                q->txq_size[TXQ_OFLD] = 1024;
                q->txq_size[TXQ_CTRL] = 256;
                q->cong_thres = 0;
        }

        spin_lock_init(&adap->sge.reg_lock);
}

/**
 *      t3_get_desc - dump an SGE descriptor for debugging purposes
 *      @qs: the queue set
 *      @qnum: identifies the specific queue (0..2: Tx, 3:response, 4..5: Rx)
 *      @idx: the descriptor index in the queue
 *      @data: where to dump the descriptor contents
 *
 *      Dumps the contents of a HW descriptor of an SGE queue.  Returns the
 *      size of the descriptor.
 */
int t3_get_desc(const struct sge_qset *qs, unsigned int qnum, unsigned int idx,
                unsigned char *data)
{
        if (qnum >= 6)
                return -EINVAL;

        if (qnum < 3) {
                if (!qs->txq[qnum].desc || idx >= qs->txq[qnum].size)
                        return -EINVAL;
                memcpy(data, &qs->txq[qnum].desc[idx], sizeof(struct tx_desc));
                return sizeof(struct tx_desc);
        }

        if (qnum == 3) {
                if (!qs->rspq.desc || idx >= qs->rspq.size)
                        return -EINVAL;
                memcpy(data, &qs->rspq.desc[idx], sizeof(struct rsp_desc));
                return sizeof(struct rsp_desc);
        }

        qnum -= 4;
        if (!qs->fl[qnum].desc || idx >= qs->fl[qnum].size)
                return -EINVAL;
        memcpy(data, &qs->fl[qnum].desc[idx], sizeof(struct rx_desc));
        return sizeof(struct rx_desc);
}