[BNX2]: Reduce spurious INTA interrupts.
Michael Chan [Sun, 8 Jul 2007 05:51:03 +0000 (22:51 -0700)]
Spurious interrupts are often encountered especially on systems
using the 8259 PIC mode.  This is because the I/O write to deassert
the interrupt is posted and won't get to the chip immediately.  As
a result, the IRQ may remain asserted after the IRQ handler exits,
causing spurious interrupts.

Add read back to flush the I/O write to deassert the IRQ immediately.
We also store the last_status_idx immediately in the IRQ handler to
help detect whether the interrupt is ours or not when the IRQ is
entered again before ->poll gets called.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bnx2.c

index 439f482..a806a8e 100644 (file)
@@ -2547,6 +2547,7 @@ bnx2_interrupt(int irq, void *dev_instance)
 {
        struct net_device *dev = dev_instance;
        struct bnx2 *bp = netdev_priv(dev);
+       struct status_block *sblk = bp->status_blk;
 
        /* When using INTx, it is possible for the interrupt to arrive
         * at the CPU before the status block posted prior to the
@@ -2554,7 +2555,7 @@ bnx2_interrupt(int irq, void *dev_instance)
         * When using MSI, the MSI message will always complete after
         * the status block write.
         */
-       if ((bp->status_blk->status_idx == bp->last_status_idx) &&
+       if ((sblk->status_idx == bp->last_status_idx) &&
            (REG_RD(bp, BNX2_PCICFG_MISC_STATUS) &
             BNX2_PCICFG_MISC_STATUS_INTA_VALUE))
                return IRQ_NONE;
@@ -2563,11 +2564,19 @@ bnx2_interrupt(int irq, void *dev_instance)
                BNX2_PCICFG_INT_ACK_CMD_USE_INT_HC_PARAM |
                BNX2_PCICFG_INT_ACK_CMD_MASK_INT);
 
+       /* Read back to deassert IRQ immediately to avoid too many
+        * spurious interrupts.
+        */
+       REG_RD(bp, BNX2_PCICFG_INT_ACK_CMD);
+
        /* Return here if interrupt is shared and is disabled. */
        if (unlikely(atomic_read(&bp->intr_sem) != 0))
                return IRQ_HANDLED;
 
-       netif_rx_schedule(dev);
+       if (netif_rx_schedule_prep(dev)) {
+               bp->last_status_idx = sblk->status_idx;
+               __netif_rx_schedule(dev);
+       }
 
        return IRQ_HANDLED;
 }