linux-kernel - Re: [PATCH] x86: fix hpet timer reinit for x86

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Message-ID: <m3myd21ldn.wl%vmayatsk@redhat.com>
Date:	Wed, 04 Feb 2009 12:39:48 +0100
From:	Vitaly Mayatskikh <v.mayatskih@...il.com>
To:	Pavel Emelyanov <xemul@...nvz.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kirill Korotaev <dev@...nvz.org>
Subject: Re: [PATCH] x86: fix hpet timer reinit for x86_64

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?
--
wbr, Vitaly
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