linux-kernel - Re: [RFC PATCH 0/5] Add support for S3 non-stop TSC support.

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Message-ID: <20130330181451.GF28947@amd.pavel.ucw.cz>
Date:	Sat, 30 Mar 2013 19:14:51 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc:	Feng Tang <feng.tang@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...ux.intel.com>, x86@...nel.org,
	Len Brown <lenb@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/5] Add support for S3 non-stop TSC support.

Hi!

> >On some new Intel Atom processors (Penwell and Cloverview), there is
> >a feature that the TSC won't stop S3, say the TSC value won't be
> >reset to 0 after resume. This feature makes TSC a more reliable
> >clocksource and could benefit the timekeeping code during system
> >suspend/resume cycles.
> >
> >The enabling efforts include adding new flags for this feature,
> >modifying clocksource.c and timekeeping.c to support and utilizing
> >it.
> >
> >One remaining question is inside the timekeeping_resume(), we don't
> >know if it is called by resuming from suspend(s2ram) or from
> >hibernate(s2disk), as there is no easy way to check it currently.
> >But it doesn't hurt as these Penwell/Cloverview platforms only have
> >S3 state, and no S4.
> >
> >Please help to review them, thanks!
> 
> The patches look reasonable to me.

Not sure... what are advantages? TSC is high resolution, but not
exactly precise time source... and this only makes resume more
complex.

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