[PATCH 2.6.8-rc3-mm1 1/2] 8139too: Rx fifo/overflow recovery

[Francois Romieu <romieu@xxxxxxxxxxxxx>]

This patch allows to update the interrupt status register after an 
Rx overflow or a Rx fifo error even when the Rx buffer contains no packet.
As a side effect it saves a few heavy (i.e. flushed) pci ops per received
packet when several packets are received at the same time.

Signed-off-by: Francois Romieu <romieu@xxxxxxxxxxxxx>

diff -puN drivers/net/8139too.c~r8139-10 drivers/net/8139too.c
--- linux-2.6.8-rc3/drivers/net/8139too.c~r8139-10      2004-08-05 
23:09:26.000000000 +0200
+++ linux-2.6.8-rc3-romieu/drivers/net/8139too.c        2004-08-05 
23:14:31.000000000 +0200
@@ -1934,12 +1934,15 @@ static int rtl8139_rx(struct net_device 
        int received = 0;
        unsigned char *rx_ring = tp->rx_ring;
        unsigned int cur_rx = tp->cur_rx;
+       u16 status;
 
        DPRINTK ("%s: In rtl8139_rx(), current %4.4x BufAddr %4.4x,"
                 " free to %4.4x, Cmd %2.2x.\n", dev->name, cur_rx,
                 RTL_R16 (RxBufAddr),
                 RTL_R16 (RxBufPtr), RTL_R8 (ChipCmd));
 
+       status = RTL_R16 (IntrStatus) & RxAckBits;
+
        while (netif_running(dev) && received < budget 
               && (RTL_R8 (ChipCmd) & RxBufEmpty) == 0) {
                u32 ring_offset = cur_rx % RX_BUF_LEN;
@@ -1947,7 +1950,6 @@ static int rtl8139_rx(struct net_device 
                unsigned int rx_size;
                unsigned int pkt_size;
                struct sk_buff *skb;
-               u16 status;
 
                rmb();
 
@@ -1977,7 +1979,7 @@ static int rtl8139_rx(struct net_device 
                 */
                if (unlikely(rx_size == 0xfff0)) {
                        tp->xstats.early_rx++;
-                       goto done;
+                       break;
                }
 
                /* If Rx err or invalid rx_size/rx_status received
@@ -1989,7 +1991,8 @@ static int rtl8139_rx(struct net_device 
                             (rx_size < 8) ||
                             (!(rx_status & RxStatusOK)))) {
                        rtl8139_rx_err (rx_status, dev, tp, ioaddr);
-                       return -1;
+                       received = -1;
+                       goto out;
                }
 
                /* Malloc up new buffer, compatible with net-2e. */
@@ -2024,21 +2027,18 @@ static int rtl8139_rx(struct net_device 
 
                cur_rx = (cur_rx + rx_size + 4 + 3) & ~3;
                RTL_W16 (RxBufPtr, (u16) (cur_rx - 16));
+       }
 
-               /* Clear out errors and receive interrupts */
-               status = RTL_R16 (IntrStatus) & RxAckBits;
-               if (likely(status != 0)) {
-                       if (unlikely(status & (RxFIFOOver | RxOverflow))) {
-                               tp->stats.rx_errors++;
-                               if (status & RxFIFOOver)
-                                       tp->stats.rx_fifo_errors++;
-                       }
-                       RTL_W16_F (IntrStatus, RxAckBits);
+       /* Clear out errors and receive interrupts */
+       if (likely(status != 0)) {
+               if (unlikely(status & (RxFIFOOver | RxOverflow))) {
+                       tp->stats.rx_errors++;
+                       if (status & RxFIFOOver)
+                               tp->stats.rx_fifo_errors++;
                }
+               RTL_W16_F (IntrStatus, RxAckBits);
        }
 
- done:
-
 #if RTL8139_DEBUG > 1
        DPRINTK ("%s: Done rtl8139_rx(), current %4.4x BufAddr %4.4x,"
                 " free to %4.4x, Cmd %2.2x.\n", dev->name, cur_rx,
@@ -2047,6 +2047,7 @@ static int rtl8139_rx(struct net_device 
 #endif
 
        tp->cur_rx = cur_rx;
+out:
        return received;
 }
 

_