Re: 2.6.21-rc7: HPET enabled freeze my machine at boot

From: Guilherme M. Schroeder
Date: Wed Apr 25 2007 - 04:39:03 EST


Just a doubt, you want me to test the patch with dynticks disabled?

Guilherme M. Schroeder
Network Administrator
Central de Vendas Informatica LTDA
Tel.: (11) 3665-2000 Ramal: 2008

john stultz wrote:
On Mon, 2007-04-23 at 15:30 -0700, john stultz wrote:
On Sat, 2007-04-21 at 20:07 -0300, Guilherme M. Schroeder wrote:
john stultz wrote:
On 4/19/07, guilherme <guilherme@xxxxxxxxxxxxxxxxx> wrote:

If i enable "High Resolution Timer Support", my machine stops here at boot:

Clocksource tsc unstable (delta = -297340790165 ns)
Time: hpet clocksource has been installed.

If i disable HPET, it boots fine.
Hmmm.. What happens if you boot w/ clocksource=acpi_pm ?

Boot ok with clocksource=acpi_pm and HPET enabled.
Any clue?

I'm suspecting that your HPET counter is being stopped for some reason,
although why I have no idea.

Just to get a clear picture, does this happen w/ "Tickless System
(Dynamic ticks)" disabled in the menuconfig?

Thomas, might we be actually stopping the HPET counter instead of
disabling the HPET interrupt w/ dynticks?

Just a shot in the dark, but does this patch affect the behavior?


diff --git a/arch/i386/kernel/hpet.c b/arch/i386/kernel/hpet.c
index 17d7345..14e76a5 100644
--- a/arch/i386/kernel/hpet.c
+++ b/arch/i386/kernel/hpet.c
@@ -183,9 +183,6 @@ static void hpet_set_mode(enum clock_event_mode mode,
- cfg = hpet_readl(HPET_T0_CFG);
- cfg &= ~HPET_TN_ENABLE;
- hpet_writel(cfg, HPET_T0_CFG);

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