linux-kernel - PMTMR running too fast

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Message-Id: <1165153834.5499.40.camel@localhost.localdomain>
Date:	Sun, 03 Dec 2006 13:50:34 +0000
From:	Ian Campbell <ijc@...lion.org.uk>
To:	John Stultz <johnstul@...ibm.com>
Cc:	linux-kernel@...r.kernel.org
Subject: PMTMR running too fast

Hi,

In older kernels arch/i386/kernel/timers/timer_pm.c:verify_pmtmr_rate
contained a check for sensible PMTMR rate and disabled that clocksource
if it was found to be out of spec[0]. This check seems to have been lost
in the transition to drivers/clocksource/acpi_pm.c, the removal is in
61743fe445213b87fb55a389c8d073785323ca3e "Time: i386 Conversion - part
4: Remove Old timer_opts Code"[1] and the check is not present in the
replacement 5d0cf410e94b1f1ff852c3f210d22cc6c5a27ffa "Time: i386
Clocksource Drivers"[2].

Is there a specific reason the check was removed (I couldn't see on in
the archives) or was it simply overlooked? Without it I need to pass
clocksource=tsc to have 2.6.18 work correctly on an older K6 system with
an Aladdin chipset (will dig out the precise details if required). Would
a patch to reintroduce the check be acceptable or would some sort of
blacklist based solution be more acceptable?

Cheers,
Ian.

[0] "PM-Timer running at invalid rate: 200% of normal - aborting." from
http://www.kernel.org/git/?p=linux/kernel/git/tglx/history.git;a=commit;h=6d58b1286c7ac88741374c158867f564e602b288
see also http://bugme.osdl.org/show_bug.cgi?id=2375
[1]
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=61743fe445213b87fb55a389c8d073785323ca3e
[2]
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=5d0cf410e94b1f1ff852c3f210d22cc6c5a27ffa

-- 
Ian Campbell

Any time things appear to be going better, you have overlooked something.

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