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From: Pavel Emelyanov <xemul@openvz.org>
To: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Kirill Korotaev <dev@openvz.org>
Subject: Re: [PATCH] x86: fix hpet timer reinit for x86_64
Date: Wed, 04 Feb 2009 14:51:43 +0300	[thread overview]
Message-ID: <4989814F.1030000@openvz.org> (raw)
In-Reply-To: <m3myd21ldn.wl%vmayatsk@redhat.com>

Vitaly Mayatskikh wrote:
> At Wed, 04 Feb 2009 13:40:31 +0300, Pavel Emelyanov wrote:
>> There's a small problem with hpet_rtc_reinit function - it checks
>> for the
>> 	hpet_readl(HPET_COUNTER) - hpet_t1_cmp > 0
>> to continue increasing both the HPET_T1_CMP (register) and the 
>> hpet_t1_cmp (variable).
>>
>> But since the HPET_COUNTER is always 32-bit, if the hpet_t1_cmp
>> is 64-bit this condition will always be FALSE once the latter hits
>> the 32-bit boundary, and we can have a situation, when we don't
>> increase the HPET_T1_CMP register high enough.
>>
>> The result - timer stops ticking, since HPET_T1_CMP becomes less, 
>> than the COUNTER and never increased again.
>>
>> The solution is to cut the upper 32-bit from the hpet_t1_cmp
>> variable to make the comparison to HPET_COUNTER correct.
> 
> Why not to use u32 as a type for hpet_t1_cmp then?

That's the matter of taste from my POV, so I can re-send the patch
if x86 maintainers agree with your version.

> --
> wbr, Vitaly
> 


  parent reply	other threads:[~2009-02-04 11:52 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-02-04 10:40 [PATCH] x86: fix hpet timer reinit for x86_64 Pavel Emelyanov
2009-02-04 11:39 ` Vitaly Mayatskikh
2009-02-04 11:43   ` Kirill Korotaev
2009-02-04 11:51   ` Pavel Emelyanov [this message]
2009-02-04 13:49 ` Ingo Molnar
2009-02-05  8:01   ` Kirill Korotaev
2009-02-05 14:53     ` Ingo Molnar

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