linux-kernel - Re: [PATCH v2] acpi: Fix regression where _PPC is not read at boot even when ignore

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Message-ID: <20090429220037.GA8604@srcf.ucam.org>
Date:	Wed, 29 Apr 2009 23:00:37 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	"Darrick J. Wong" <djwong@...ibm.com>
Cc:	Thomas Renninger <trenn@...e.de>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, cpufreq@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2] acpi: Fix regression where _PPC is not read at boot
	even when ignore_ppc=0

On Wed, Apr 29, 2009 at 02:39:31PM -0700, Darrick J. Wong wrote:

> I don't know about XP's copy of intelppm.sys, but this would seem to confirm
> that WS03 and WS08 check _PPC at boot time.

Ok, so that makes things interesting. From what we know about the T60 
(and based on Ingo's report), _PPC may evaluate to 2 on bootup. However, 
if this is ignored then later notifications are correct. This implies 
that Windows either ignores the initial evaluation or does something 
that triggers a notification.

The only notifications appear to be sent from event methods, so there's 
nothing obvious there that we can trigger. I'm actually quite confused 
by this now. Ingo, if you re-add that block, does your system stop 
working again?

-- 
Matthew Garrett | mjg59@...f.ucam.org
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