tg3: Allow screaming interrupt detection
The tg3 driver's ISR is coded to accept interrupts as its own if the
status block tag does not equal the last tag the driver has seen. The
last_tag field is updated from tg3_poll. In a screaming interrupt
situation from another device sharing tg3's IRQ, tg3_poll does not get
a chance to be called, so the last_tag will always be out of sync with
the status block tag. Consequently, the driver will continually
declare the screaming interrupts as its own, thus thwarting the
screaming interrupt detection logic.
This patch solves the problem by creating a new last_irq_tag member and
recording the status block tag in the ISR. The ISR then checks the
last_irq_tag for interrupt ownership.
Many thanks to John Marvin for the detailed bug report and analysis and
Michael Chan for the bugfix.
Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Tested-by: John Marvin <jsm@fc.hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 201be42..e4fa02c 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -4656,6 +4656,7 @@
* so we must read it before checking for more work.
*/
tp->last_tag = sblk->status_tag;
+ tp->last_irq_tag = tp->last_tag;
rmb();
} else
sblk->status &= ~SD_STATUS_UPDATED;
@@ -4811,7 +4812,7 @@
* Reading the PCI State register will confirm whether the
* interrupt is ours and will flush the status block.
*/
- if (unlikely(sblk->status_tag == tp->last_tag)) {
+ if (unlikely(sblk->status_tag == tp->last_irq_tag)) {
if ((tp->tg3_flags & TG3_FLAG_CHIP_RESETTING) ||
(tr32(TG3PCI_PCISTATE) & PCISTATE_INT_NOT_ACTIVE)) {
handled = 0;
@@ -4831,18 +4832,22 @@
* excessive spurious interrupts can be worse in some cases.
*/
tw32_mailbox_f(MAILBOX_INTERRUPT_0 + TG3_64BIT_REG_LOW, 0x00000001);
+
+ /*
+ * In a shared interrupt configuration, sometimes other devices'
+ * interrupts will scream. We record the current status tag here
+ * so that the above check can report that the screaming interrupts
+ * are unhandled. Eventually they will be silenced.
+ */
+ tp->last_irq_tag = sblk->status_tag;
+
if (tg3_irq_sync(tp))
goto out;
- if (napi_schedule_prep(&tp->napi)) {
- prefetch(&tp->rx_rcb[tp->rx_rcb_ptr]);
- /* Update last_tag to mark that this status has been
- * seen. Because interrupt may be shared, we may be
- * racing with tg3_poll(), so only update last_tag
- * if tg3_poll() is not scheduled.
- */
- tp->last_tag = sblk->status_tag;
- __napi_schedule(&tp->napi);
- }
+
+ prefetch(&tp->rx_rcb[tp->rx_rcb_ptr]);
+
+ napi_schedule(&tp->napi);
+
out:
return IRQ_RETVAL(handled);
}
@@ -6156,6 +6161,7 @@
tp->hw_status->status_tag = 0;
}
tp->last_tag = 0;
+ tp->last_irq_tag = 0;
smp_mb();
synchronize_irq(tp->pdev->irq);
@@ -7138,7 +7144,6 @@
udelay(100);
tw32_mailbox_f(MAILBOX_INTERRUPT_0 + TG3_64BIT_REG_LOW, 0);
- tp->last_tag = 0;
if (!(tp->tg3_flags2 & TG3_FLG2_5705_PLUS)) {
tw32_f(DMAC_MODE, DMAC_MODE_ENABLE);