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

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Message-ID: <20100204193224.GA8957@basil.fritz.box>
Date:	Thu, 4 Feb 2010 20:32:24 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	"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, Feb 04, 2010 at 11:22:15AM -0800, Pallipadi, Venkatesh wrote:
> 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?

Ibex Peak. That is I'm not sure it's fully constant, but at least
it's always the same value on the HPET read triggering on boot.

> 
> 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.

Ok fine for me. I only really care that the ugly backtrace
goes away.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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