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sata_sil24: fix IRQ clearing race when PCIX_IRQ_WOC is used 

When PCIX_IRQ_WOC is used, sil24 has an inherent race condition
between clearing IRQ pending and reading IRQ status.  If IRQ pending
is cleared after reading IRQ status, there's possibility of lost IRQ.
If IRQ pending is cleared before reading IRQ status, spurious IRQs
will occur.

sata_sil24 till now cleared IRQ pending after reading IRQ status thus
losing IRQs on machines where PCIX_IRQ_WOC was used.  Reverse the
order and ignore spurious IRQs if PCIX_IRQ_WOC.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This commit is contained in:
Tejun Heo 2007-09-23 12:37:05 +09:00 committed by Jeff Garzik
parent 4942de4a0e
commit 228f47b959
1 changed files with 12 additions and 4 deletions
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16
drivers/ata/sata_sil24.c
View File

@ -888,6 +888,16 @@ static inline void sil24_host_intr(struct ata_port *ap)
u32 slot_stat, qc_active;
int rc;
/* If PCIX_IRQ_WOC, there's an inherent race window between
* clearing IRQ pending status and reading PORT_SLOT_STAT
* which may cause spurious interrupts afterwards. This is
* unavoidable and much better than losing interrupts which
* happens if IRQ pending is cleared after reading
* PORT_SLOT_STAT.
*/
if (ap->flags & SIL24_FLAG_PCIX_IRQ_WOC)
writel(PORT_IRQ_COMPLETE, port + PORT_IRQ_STAT);
slot_stat = readl(port + PORT_SLOT_STAT);
if (unlikely(slot_stat & HOST_SSTAT_ATTN)) {
@ -895,9 +905,6 @@ static inline void sil24_host_intr(struct ata_port *ap)
return;
}
if (ap->flags & SIL24_FLAG_PCIX_IRQ_WOC)
writel(PORT_IRQ_COMPLETE, port + PORT_IRQ_STAT);
qc_active = slot_stat & ~HOST_SSTAT_ATTN;
rc = ata_qc_complete_multiple(ap, qc_active, sil24_finish_qc);
if (rc > 0)
@ -910,7 +917,8 @@ static inline void sil24_host_intr(struct ata_port *ap)
return;
}
if (ata_ratelimit())
/* spurious interrupts are expected if PCIX_IRQ_WOC */
if (!(ap->flags & SIL24_FLAG_PCIX_IRQ_WOC) && ata_ratelimit())
ata_port_printk(ap, KERN_INFO, "spurious interrupt "
"(slot_stat 0x%x active_tag %d sactive 0x%x)\n",
slot_stat, ap->active_tag, ap->sactive);