linux-kernel - Re: [PATCH 1/2]cpuidle: makes AMD C1E works in acpi

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Date:	Tue, 19 May 2009 17:24:44 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Shaohua Li <shaohua.li@...el.com>
cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"lenb@...nel.org" <lenb@...nel.org>,
	"thisistempbox@...oo.com" <thisistempbox@...oo.com>,
	"mingo@...hat.com" <mingo@...hat.com>
Subject: Re: [PATCH 1/2]cpuidle: makes AMD C1E works in acpi_idle

On Tue, 19 May 2009, Shaohua Li wrote:

> On Tue, May 19, 2009 at 08:55:10PM +0800, Thomas Gleixner wrote:
> > On Tue, 19 May 2009, Shaohua Li wrote:
> > 
> > > When AMD C1E is enabled, local APIC timer will stop even in C1. This patch uses
> > > broadcast ipi to replace local APIC timer in C1.
> > > 
> > > http://bugzilla.kernel.org/show_bug.cgi?id=13233
> > 
> > Hmm. This was addressed before in 
> > 
> > commit a8d6829044901a67732904be5f1eacdf8539604f (x86: prevent C-states
> > hang on AMD C1E enabled machines)
> > 
> > We limit C-States to 1 via acpi_processor_cstate_check().
> > 
> > And we have the broadcast logic in c1e_idle() already. We also select
> > c1e_idle as the idle routine, so why is the ACPI code not using this. ?
>
> We used to call pm_idle_save() for C1, which will call c1e_idle. But this is
> removed, guess the reason is we want to do C1 enter per the information gotten
> from BIOS. So this bug is a regression actually. The patch follows the logic
> of c1e_idle().

Hmm, ok. As long as the code does not undo something which was already
set up in c1e_idle() I have no objections.

Thanks,

	tglx
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