Spidernet DMA coalescing

The current driver code performs 512 DMA mappings of a bunch of
32-byte ring descriptor structures. This is silly, as they are
all in contiguous memory. This patch changes the code to
dma_map_coherent() each rx/tx ring as a whole.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

diff --git a/drivers/net/spider_net.c b/drivers/net/spider_net.c
index 8ea2fc1..8c8381c 100644 (file)
--- a/drivers/net/spider_net.c
+++ b/drivers/net/spider_net.c
@@ -280,72 +280,67 @@ spider_net_free_chain(struct spider_net_card *card,
 {
        struct spider_net_descr *descr;
 
-       for (descr = chain->tail; !descr->bus_addr; descr = descr->next) {
-               pci_unmap_single(card->pdev, descr->bus_addr,
-                                SPIDER_NET_DESCR_SIZE, PCI_DMA_BIDIRECTIONAL);
+       descr = chain->ring;
+       do {
                descr->bus_addr = 0;
-       }
+               descr->next_descr_addr = 0;
+               descr = descr->next;
+       } while (descr != chain->ring);
+
+       dma_free_coherent(&card->pdev->dev, chain->num_desc,
+           chain->ring, chain->dma_addr);
 }
 
 /**
- * spider_net_init_chain - links descriptor chain
+ * spider_net_init_chain - alloc and link descriptor chain
  * @card: card structure
  * @chain: address of chain
- * @start_descr: address of descriptor array
- * @no: number of descriptors
  *
- * we manage a circular list that mirrors the hardware structure,
+ * We manage a circular list that mirrors the hardware structure,
  * except that the hardware uses bus addresses.
  *
- * returns 0 on success, <0 on failure
+ * Returns 0 on success, <0 on failure
  */
 static int
 spider_net_init_chain(struct spider_net_card *card,
-                      struct spider_net_descr_chain *chain,
-                      struct spider_net_descr *start_descr,
-                      int no)
+                      struct spider_net_descr_chain *chain)
 {
        int i;
        struct spider_net_descr *descr;
        dma_addr_t buf;
+       size_t alloc_size;
 
-       descr = start_descr;
-       memset(descr, 0, sizeof(*descr) * no);
+       alloc_size = chain->num_desc * sizeof (struct spider_net_descr);
 
-       /* set up the hardware pointers in each descriptor */
-       for (i=0; i<no; i++, descr++) {
-               descr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
+       chain->ring = dma_alloc_coherent(&card->pdev->dev, alloc_size,
+               &chain->dma_addr, GFP_KERNEL);
 
-               buf = pci_map_single(card->pdev, descr,
-                                    SPIDER_NET_DESCR_SIZE,
-                                    PCI_DMA_BIDIRECTIONAL);
+       if (!chain->ring)
+               return -ENOMEM;
 
-               if (pci_dma_mapping_error(buf))
-                       goto iommu_error;
+       descr = chain->ring;
+       memset(descr, 0, alloc_size);
+
+       /* Set up the hardware pointers in each descriptor */
+       buf = chain->dma_addr;
+       for (i=0; i < chain->num_desc; i++, descr++) {
+               descr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
 
                descr->bus_addr = buf;
+               descr->next_descr_addr = 0;
                descr->next = descr + 1;
                descr->prev = descr - 1;
 
+               buf += sizeof(struct spider_net_descr);
        }
        /* do actual circular list */
-       (descr-1)->next = start_descr;
-       start_descr->prev = descr-1;
+       (descr-1)->next = chain->ring;
+       chain->ring->prev = descr-1;
 
        spin_lock_init(&chain->lock);
-       chain->head = start_descr;
-       chain->tail = start_descr;
-
+       chain->head = chain->ring;
+       chain->tail = chain->ring;
        return 0;
-
-iommu_error:
-       descr = start_descr;
-       for (i=0; i < no; i++, descr++)
-               if (descr->bus_addr)
-                       pci_unmap_single(card->pdev, descr->bus_addr,
-                                        SPIDER_NET_DESCR_SIZE,
-                                        PCI_DMA_BIDIRECTIONAL);
-       return -ENOMEM;
 }
 
 /**
@@ -707,7 +702,7 @@ spider_net_set_low_watermark(struct spider_net_card *card)
        }
 
        /* If TX queue is short, don't even bother with interrupts */
-       if (cnt < card->num_tx_desc/4)
+       if (cnt < card->tx_chain.num_desc/4)
                return cnt;
 
        /* Set low-watermark 3/4th's of the way into the queue. */
@@ -1652,26 +1647,25 @@ spider_net_open(struct net_device *netdev)
 {
        struct spider_net_card *card = netdev_priv(netdev);
        struct spider_net_descr *descr;
-       int i, result;
+       int result;
 
-       result = -ENOMEM;
-       if (spider_net_init_chain(card, &card->tx_chain, card->descr,
-                                 card->num_tx_desc))
+       result = spider_net_init_chain(card, &card->tx_chain);
+       if (result)
                goto alloc_tx_failed;
-
        card->low_watermark = NULL;
 
-       /* rx_chain is after tx_chain, so offset is descr + tx_count */
-       if (spider_net_init_chain(card, &card->rx_chain,
-                                 card->descr + card->num_tx_desc,
-                                 card->num_rx_desc))
+       result = spider_net_init_chain(card, &card->rx_chain);
+       if (result)
                goto alloc_rx_failed;
 
-       descr = card->rx_chain.head;
-       for (i=0; i < card->num_rx_desc; i++, descr++)
+       /* Make a ring of of bus addresses */
+       descr = card->rx_chain.ring;
+       do {
                descr->next_descr_addr = descr->next->bus_addr;
+               descr = descr->next;
+       } while (descr != card->rx_chain.ring);
 
-       /* allocate rx skbs */
+       /* Allocate rx skbs */
        if (spider_net_alloc_rx_skbs(card))
                goto alloc_skbs_failed;
 
@@ -1924,6 +1918,7 @@ spider_net_stop(struct net_device *netdev)
 
        /* release chains */
        spider_net_release_tx_chain(card, 1);
+       spider_net_free_rx_chain_contents(card);
 
        spider_net_free_rx_chain_contents(card);
 
@@ -2057,8 +2052,8 @@ spider_net_setup_netdev(struct spider_net_card *card)
 
        card->options.rx_csum = SPIDER_NET_RX_CSUM_DEFAULT;
 
-       card->num_tx_desc = tx_descriptors;
-       card->num_rx_desc = rx_descriptors;
+       card->tx_chain.num_desc = tx_descriptors;
+       card->rx_chain.num_desc = rx_descriptors;
 
        spider_net_setup_netdev_ops(netdev);
 
@@ -2107,12 +2102,8 @@ spider_net_alloc_card(void)
 {
        struct net_device *netdev;
        struct spider_net_card *card;
-       size_t alloc_size;
 
-       alloc_size = sizeof (*card) +
-               sizeof (struct spider_net_descr) * rx_descriptors +
-               sizeof (struct spider_net_descr) * tx_descriptors;
-       netdev = alloc_etherdev(alloc_size);
+       netdev = alloc_etherdev(sizeof(struct spider_net_card));
        if (!netdev)
                return NULL;
 

diff --git a/drivers/net/spider_net.h b/drivers/net/spider_net.h
index 3e196df..4b76ef9 100644 (file)
--- a/drivers/net/spider_net.h
+++ b/drivers/net/spider_net.h
@@ -378,6 +378,9 @@ struct spider_net_descr_chain {
        spinlock_t lock;
        struct spider_net_descr *head;
        struct spider_net_descr *tail;
+       struct spider_net_descr *ring;
+       int num_desc;
+       dma_addr_t dma_addr;
 };
 
 /* descriptor data_status bits */
@@ -397,8 +400,6 @@ struct spider_net_descr_chain {
  * 701b8000 would be correct, but every packets gets that flag */
 #define SPIDER_NET_DESTROY_RX_FLAGS    0x700b8000
 
-#define SPIDER_NET_DESCR_SIZE          32
-
 /* this will be bigger some time */
 struct spider_net_options {
        int rx_csum; /* for rx: if 0 ip_summed=NONE,
@@ -441,25 +442,17 @@ struct spider_net_card {
        struct spider_net_descr_chain rx_chain;
        struct spider_net_descr *low_watermark;
 
-       struct net_device_stats netdev_stats;
-
-       struct spider_net_options options;
-
-       spinlock_t intmask_lock;
        struct tasklet_struct rxram_full_tl;
        struct timer_list tx_timer;
-
        struct work_struct tx_timeout_task;
        atomic_t tx_timeout_task_counter;
        wait_queue_head_t waitq;
 
        /* for ethtool */
        int msg_enable;
-       int num_rx_desc;
-       int num_tx_desc;
+       struct net_device_stats netdev_stats;
        struct spider_net_extra_stats spider_stats;
-
-       struct spider_net_descr descr[0];
+       struct spider_net_options options;
 };
 
 #define pr_err(fmt,arg...) \

diff --git a/drivers/net/spider_net_ethtool.c b/drivers/net/spider_net_ethtool.c
index 91b9951..6bcf03f 100644 (file)
--- a/drivers/net/spider_net_ethtool.c
+++ b/drivers/net/spider_net_ethtool.c
@@ -158,9 +158,9 @@ spider_net_ethtool_get_ringparam(struct net_device *netdev,
        struct spider_net_card *card = netdev->priv;
 
        ering->tx_max_pending = SPIDER_NET_TX_DESCRIPTORS_MAX;
-       ering->tx_pending = card->num_tx_desc;
+       ering->tx_pending = card->tx_chain.num_desc;
        ering->rx_max_pending = SPIDER_NET_RX_DESCRIPTORS_MAX;
-       ering->rx_pending = card->num_rx_desc;
+       ering->rx_pending = card->rx_chain.num_desc;
 }
 
 static int spider_net_get_stats_count(struct net_device *netdev)