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

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Message-Id: <1177368785.12242.9.camel@localhost>
Date:	Mon, 23 Apr 2007 15:53:05 -0700
From:	john stultz <johnstul@...ibm.com>
To:	"Guilherme M. Schroeder" <guilherme@...tralinf.com.br>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: 2.6.21-rc7: HPET enabled freeze my machine at boot

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@...tralinf.com.br> wrote:
> > >> Hi,
> > >>
> > >> 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?

thanks
-john

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,
 
 	case CLOCK_EVT_MODE_UNUSED:
 	case CLOCK_EVT_MODE_SHUTDOWN:
-		cfg = hpet_readl(HPET_T0_CFG);
-		cfg &= ~HPET_TN_ENABLE;
-		hpet_writel(cfg, HPET_T0_CFG);
 		break;
 	}
 }


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