[PATCH 2/2] net/tg3.c: use mmiowb in tg3_poll

[akepner@xxxxxxx]

Returning from tg3_poll() without flushing the PIO write which 
reenables interrupts can result in lower cpu utilization and higher 
throughput. So use a memory barrier, mmiowb(), instead of flushing the 
write with a PIO read.

Signed-off-by: Arthur Kepner <akepner@xxxxxxx>
---

--- linux.2/drivers/net/tg3.c   2004-10-12 14:00:40.000000000 -0700
+++ linux/drivers/net/tg3.c     2004-10-12 14:13:02.000000000 -0700
@@ -417,6 +417,20 @@
        tg3_cond_int(tp);
 }
 
+/* tg3_restart_ints
+ *  similar to tg3_enable_ints, but it can return without flushing the 
+ *  PIO write which reenables interrupts
+ */
+static void tg3_restart_ints(struct tg3 *tp)
+{
+       tw32(TG3PCI_MISC_HOST_CTRL,
+               (tp->misc_host_ctrl & ~MISC_HOST_CTRL_MASK_PCI_INT));
+       tw32_mailbox(MAILBOX_INTERRUPT_0 + TG3_64BIT_REG_LOW, 0x00000000);
+       mmiowb();
+
+       tg3_cond_int(tp);
+}
+
 static inline void tg3_netif_stop(struct tg3 *tp)
 {
        netif_poll_disable(tp->dev);
@@ -2788,7 +2802,7 @@
        if (done) {
                spin_lock_irqsave(&tp->lock, flags);
                __netif_rx_complete(netdev);
-               tg3_enable_ints(tp);
+               tg3_restart_ints(tp);
                spin_unlock_irqrestore(&tp->lock, flags);
        }