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Date: Fri, 04 May 2007 17:55:21 -0700
From: "Michael Chan" <mchan@...adcom.com>
To: davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 10/11][TG3]: Reduce spurious interrupts.
[TG3]: Reduce spurious interrupts.
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.
An unconditional read to flush the I/O write to force the IRQ to de-
assert immediately is not desirable because it impacts performance in
the fast path. So we only do this after we have some indications of
spurious interrupts.
Signed-off-by: Michael Chan <mchan@...adcom.com>
diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index b3681e4..c264eb0 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -3608,12 +3608,31 @@ out:
return IRQ_RETVAL(handled);
}
+static void tg3_check_spurious_int(struct tg3 *tp)
+{
+ if (tp->spurious_int_mode)
+ return;
+
+ /* Interrupt mailbox and status block have been flushed at this
+ * point. If the tag is unchanged, we are either getting a spurious
+ * interrupt or sharing interrupt with another device.
+ */
+ if (tp->hw_status->status_tag == tp->last_tag) {
+ tp->spurious_int++;
+ if (tp->spurious_int > 500)
+ /* Assume we're getting too many spurious interrupts.
+ * Setting the flag will cause the IRQ handler to
+ * do a read back to immediately deassert the IRQ.
+ */
+ tp->spurious_int_mode = 1;
+ }
+}
+
static irqreturn_t tg3_interrupt_tagged(int irq, void *dev_id)
{
struct net_device *dev = dev_id;
struct tg3 *tp = netdev_priv(dev);
struct tg3_hw_status *sblk = tp->hw_status;
- unsigned int handled = 1;
/* In INTx mode, it is possible for the interrupt to arrive at
* the CPU before the status block posted prior to the interrupt.
@@ -3621,11 +3640,15 @@ static irqreturn_t tg3_interrupt_tagged(int irq, void *dev_id)
* interrupt is ours and will flush the status block.
*/
if (unlikely(sblk->status_tag == tp->last_tag)) {
- if ((tp->tg3_flags & TG3_FLAG_CHIP_RESETTING) ||
- (tr32(TG3PCI_PCISTATE) & PCISTATE_INT_NOT_ACTIVE)) {
- handled = 0;
- goto out;
- }
+ u32 inta;
+
+ if (tp->tg3_flags & TG3_FLAG_CHIP_RESETTING)
+ return IRQ_NONE;
+
+ inta = tr32(TG3PCI_PCISTATE);
+ tg3_check_spurious_int(tp);
+ if (inta & PCISTATE_INT_NOT_ACTIVE)
+ return IRQ_NONE;
}
/*
@@ -3636,6 +3659,8 @@ static irqreturn_t tg3_interrupt_tagged(int irq, void *dev_id)
* event coalescing.
*/
tw32_mailbox(MAILBOX_INTERRUPT_0 + TG3_64BIT_REG_LOW, 0x00000001);
+ if (unlikely(tp->spurious_int_mode))
+ tr32_mailbox(MAILBOX_INTERRUPT_0 + TG3_64BIT_REG_LOW);
if (tg3_irq_sync(tp))
goto out;
if (netif_rx_schedule_prep(dev)) {
@@ -3649,7 +3674,7 @@ static irqreturn_t tg3_interrupt_tagged(int irq, void *dev_id)
__netif_rx_schedule(dev);
}
out:
- return IRQ_RETVAL(handled);
+ return IRQ_HANDLED;
}
/* ISR for interrupt test */
@@ -6886,6 +6911,8 @@ static int tg3_request_irq(struct tg3 *tp)
unsigned long flags;
struct net_device *dev = tp->dev;
+ tp->spurious_int = 0;
+ tp->spurious_int_mode = 0;
if (tp->tg3_flags2 & TG3_FLG2_USING_MSI) {
fn = tg3_msi;
if (tp->tg3_flags2 & TG3_FLG2_1SHOT_MSI)
diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h
index d88a859..7413643 100644
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -2151,6 +2151,9 @@ struct tg3 {
dma_addr_t status_mapping;
u32 last_tag;
+ u16 spurious_int;
+ u16 spurious_int_mode;
+
u32 msg_enable;
/* begin "tx thread" cacheline section */
-
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