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

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Date:	Tue, 24 Apr 2007 09:33:49 -0300
From:	"Guilherme M. Schroeder" <guilherme@...tralinf.com.br>
To:	john stultz <johnstul@...ibm.com>
CC:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: 2.6.21-rc7: HPET enabled freeze my machine at boot

John,

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
http://www.centralinf.com.br


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@...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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