[PATCH] x86, hpet: fix "IO-APIC + timer doesn't work!"

[Jan Kiszka]

Jeff Mahoney wrote:

> I saw this while booting 2.6.30-rc1, -rc2, and today's git, on one of
> my development nodes. This output is with apic=debug. With noapic,
> it still hung. Both outputs follow.
>
> git bisect leads to commit 8d6f0c8214928f7c5083dd54ecb69c5d615b516e,
> but I'm not seeing anything obvious there. Backing just that change
> out doesn't fix it.
>
>  enabled ExtINT on CPU#0
>  ESR value before enabling vector: 0x00000004  after: 0x00000000
>  ENABLING IO-APIC IRQs
>  ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=0 pin2=0
>  ..MP-BIOS bug: 8254 timer not connected to IO-APIC
>  ...trying to set up timer (IRQ0) through the 8259A ...
>  ..... (found apic 0 pin 0) ...
>  ....... failed.
>  ...trying to set up timer as Virtual Wire IRQ...
>  ..... failed.
>  ...trying to set up timer as ExtINT IRQ...
>  ..... failed :(.
>  Kernel panic - not syncing: IO-APIC + timer doesn't work!  Boot with apic=debug and send a report.  Then try booting with the 'noapic' option.

Hmmmmm. That somehow reminds me of what I thought I had to fix in the
HPET emulation of QEMU just recently [1] - because of 2.6.30-rc's behavior.

Lets try a quirk: write 'delta' a second time.

 [1] http://permalink.gmane.org/gmane.comp.emulators.qemu/41570

[ Impact: fix rare boot panic ]

Tested-by: Jeff Mahoney <jeffm@xxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 arch/x86/kernel/hpet.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 648b3a2..523d72b 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -324,6 +324,7 @@ static void hpet_set_mode(enum clock_event_mode mode,
 		       HPET_TN_SETVAL | HPET_TN_32BIT;
 		hpet_writel(cfg, HPET_Tn_CFG(timer));
 		hpet_writel((unsigned long) delta, HPET_Tn_CMP(timer));
+		hpet_writel((unsigned long) delta, HPET_Tn_CMP(timer));
 		hpet_start_counter();
 		hpet_print_config();
 		break;
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