linux-kernel - Re: [lm-sensors] [PATCH] therm_adt746x: Record pwm invert bit at module load time

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Date:	Fri, 4 Dec 2009 09:44:05 +0100
From:	Jean Delvare <khali@...ux-fr.org>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	djwong@...ibm.com,
	Michel Dänzer <michel@...nzer.net>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	lm-sensors <lm-sensors@...sensors.org>
Subject: Re: [lm-sensors] [PATCH] therm_adt746x: Record pwm invert bit at 
 module load time

On Fri, 04 Dec 2009 13:20:11 +1100, Benjamin Herrenschmidt wrote:
> On Mon, 2009-11-30 at 15:47 -0800, Darrick J. Wong wrote:
> > In commit 0512a9a8e277a9de2820211eef964473b714ae65, we unilaterally zero the
> > "pwm invert" bit in the fan behavior configuration register.  On my PowerBook
> > G4, this results in the fans going to full speed at low temperature and
> > shutting off at high temperature because the pwm invert bit is supposed to be
> > set.
> > 
> > Therefore, record the pwm invert bit at driver load time, and write the bit
> > into the fan behavior control register.  This restores correct behavior on my
> > PBG4 and should work around the bit being set to the wrong value after
> > suspend/resume (which is what the original patch was trying to fix).  It also
> > fixes a minor omission where the pwm invert bit correction is NOT performed
> > when switching into automatic mode.
> 
> Thanks, I'll apply.

This is a pretty serious bug, please make sure to send the fix to the
stable team for kernels 2.6.31 and 2.6.32.

-- 
Jean Delvare
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