linux-kernel - Re: [PATCH] i386: add command line option "local_apic_timer_c2

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Message-ID: <20070326123141.GA11288@ucw.cz>
Date:	Mon, 26 Mar 2007 12:31:42 +0000
From:	Pavel Machek <pavel@....cz>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Mingming Cao <cmm@...ibm.com>, Adrian Bunk <bunk@...sta.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
	Mariusz Kozlowski <m.kozlowski@...land.pl>,
	Oliver Pinter <oliver.pntr@...il.com>,
	Sid Boyce <g3vbv@...eyonder.co.uk>,
	Nick Piggin <npiggin@...e.de>,
	Jens Axboe <jens.axboe@...cle.com>,
	Thomas Renninger <trenn@...e.de>,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH] i386: add command line option "local_apic_timer_c2_ok"

Hi!

> It turned out that it is almost impossible to trust ACPI, BIOS & Co.
> regarding the C states. This was the reason to switch the local apic
> timer off in C2 state already. OTOH there are sane and well behaving
> systems, which get punished by that decision.
> 
> Allow the user to confirm that the local apic timer is trustworthy in C2
> state. This keeps the default behaviour on the safe side.
...
> @@ -780,6 +780,9 @@ and is between 256 and 4096 characters. It is defined in the file
>  	lapic		[IA-32,APIC] Enable the local APIC even if BIOS
>  			disabled it.
>  
> +	lapic_timer_c2_ok	[IA-32,APIC] trust the local apic timer in
> +			C2 power state.
> +

Could you add comment saying that this is always ok on non-broken
systems? That way perhaps it can be added to linux-firmware-test-cd,
etc.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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