pasemi_mac: Fix TX ring wrap checking

The old logic didn't detect full (tx) ring cases properly, causing
overruns and general badness. Clean it up a bit and abstract out the
ring size checks, always making sure to leave 1 slot open.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

diff --git a/drivers/net/pasemi_mac.c b/drivers/net/pasemi_mac.c
index 4836d40..dc710a0 100644 (file)
--- a/drivers/net/pasemi_mac.c
+++ b/drivers/net/pasemi_mac.c
@@ -69,6 +69,10 @@
 #define RX_DESC_INFO(mac, num) ((mac)->rx->desc_info[(num) & (RX_RING_SIZE-1)])
 #define RX_BUFF(mac, num)      ((mac)->rx->buffers[(num) & (RX_RING_SIZE-1)])
 
+#define RING_USED(ring)                (((ring)->next_to_fill - (ring)->next_to_clean) \
+                                & ((ring)->size - 1))
+#define RING_AVAIL(ring)       ((ring->size) - RING_USED(ring))
+
 #define BUF_SIZE 1646 /* 1500 MTU + ETH_HLEN + VLAN_HLEN + 2 64B cachelines */
 
 MODULE_LICENSE("GPL");
@@ -174,6 +178,7 @@ static int pasemi_mac_setup_rx_resources(struct net_device *dev)
 
        spin_lock_init(&ring->lock);
 
+       ring->size = RX_RING_SIZE;
        ring->desc_info = kzalloc(sizeof(struct pasemi_mac_buffer) *
                                  RX_RING_SIZE, GFP_KERNEL);
 
@@ -253,6 +258,7 @@ static int pasemi_mac_setup_tx_resources(struct net_device *dev)
 
        spin_lock_init(&ring->lock);
 
+       ring->size = TX_RING_SIZE;
        ring->desc_info = kzalloc(sizeof(struct pasemi_mac_buffer) *
                                  TX_RING_SIZE, GFP_KERNEL);
        if (!ring->desc_info)
@@ -281,7 +287,7 @@ static int pasemi_mac_setup_tx_resources(struct net_device *dev)
                           PAS_DMA_TXCHAN_CFG_UP |
                           PAS_DMA_TXCHAN_CFG_WT(2));
 
-       ring->next_to_use = 0;
+       ring->next_to_fill = 0;
        ring->next_to_clean = 0;
 
        snprintf(ring->irq_name, sizeof(ring->irq_name),
@@ -376,9 +382,7 @@ static void pasemi_mac_replenish_rx_ring(struct net_device *dev)
        int start = mac->rx->next_to_fill;
        unsigned int limit, count;
 
-       limit = (mac->rx->next_to_clean + RX_RING_SIZE -
-                mac->rx->next_to_fill) & (RX_RING_SIZE - 1);
-
+       limit = RING_AVAIL(mac->rx);
        /* Check to see if we're doing first-time setup */
        if (unlikely(mac->rx->next_to_clean == 0 && mac->rx->next_to_fill == 0))
                limit = RX_RING_SIZE;
@@ -562,7 +566,7 @@ restart:
        spin_lock_irqsave(&mac->tx->lock, flags);
 
        start = mac->tx->next_to_clean;
-       limit = min(mac->tx->next_to_use, start+32);
+       limit = min(mac->tx->next_to_fill, start+32);
 
        count = 0;
 
@@ -1004,14 +1008,13 @@ static int pasemi_mac_start_tx(struct sk_buff *skb, struct net_device *dev)
 
        spin_lock_irqsave(&txring->lock, flags);
 
-       if (txring->next_to_clean - txring->next_to_use == TX_RING_SIZE) {
+       if (RING_AVAIL(txring) <= 1) {
                spin_unlock_irqrestore(&txring->lock, flags);
                pasemi_mac_clean_tx(mac);
                pasemi_mac_restart_tx_intr(mac);
                spin_lock_irqsave(&txring->lock, flags);
 
-               if (txring->next_to_clean - txring->next_to_use ==
-                   TX_RING_SIZE) {
+               if (RING_AVAIL(txring) <= 1) {
                        /* Still no room -- stop the queue and wait for tx
                         * intr when there's room.
                         */
@@ -1020,15 +1023,15 @@ static int pasemi_mac_start_tx(struct sk_buff *skb, struct net_device *dev)
                }
        }
 
-       dp = &TX_DESC(mac, txring->next_to_use);
-       info = &TX_DESC_INFO(mac, txring->next_to_use);
+       dp = &TX_DESC(mac, txring->next_to_fill);
+       info = &TX_DESC_INFO(mac, txring->next_to_fill);
 
        dp->mactx = mactx;
        dp->ptr   = ptr;
        info->dma = map;
        info->skb = skb;
 
-       txring->next_to_use++;
+       txring->next_to_fill++;
        mac->stats.tx_packets++;
        mac->stats.tx_bytes += skb->len;
 

diff --git a/drivers/net/pasemi_mac.h b/drivers/net/pasemi_mac.h
index fbbc17a..c5b0adb 100644 (file)
--- a/drivers/net/pasemi_mac.h
+++ b/drivers/net/pasemi_mac.h
@@ -31,7 +31,7 @@ struct pasemi_mac_txring {
        struct pas_dma_xct_descr        *desc;
        dma_addr_t       dma;
        unsigned int     size;
-       unsigned int     next_to_use;
+       unsigned int     next_to_fill;
        unsigned int     next_to_clean;
        struct pasemi_mac_buffer *desc_info;
        char             irq_name[10];  /* "eth%d tx" */