linux-kernel - Re: [PATCH] HPET: Drop WARN_ON for mismatch on HPET CMP readback

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Date:	Thu, 04 Feb 2010 11:22:15 -0800
From:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] HPET: Drop WARN_ON for mismatch on HPET CMP readback

On Thu, 2010-02-04 at 11:11 -0800, Andi Kleen wrote:
>  HPET: Drop WARN_ON for mismatch on HPET CMP readback
>     
>     At least one Intel chipset seems to always return a constant value
>     when reading back the HPET CMP register. This triggers the WARN_ON_ONCE
>     on each boot.

I don't know of chipset returning a constant value. Which chipset is
this one?
There is a chipset ICH9/10 errata where it returns a previous value,
instead of most recently written value. I had a patch for that here.

http://marc.info/?l=linux-kernel&m=125849385330302&w=2

I wanted to send out final patch with a pointer to ICH9/10 spec update
which describes the errata. But, look like that spec update hasn't
happened yet. As we found issue with atleast one chipset with this
warn_on, I would prefer retaining it, with a fix like above.

Thanks,
Venki

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