linux-kernel - Re: [lm-sensors] Hardware running hot and without the fan

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Date:	Thu, 3 Nov 2011 09:55:28 -0700
From:	Guenter Roeck <guenter.roeck@...csson.com>
To:	Jean Delvare <khali@...ux-fr.org>
CC:	Lars Noodén <lars.nooden@...il.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>
Subject: Re: [lm-sensors] Hardware running hot and without the fan

On Thu, 2011-11-03 at 12:43 -0400, Jean Delvare wrote:
> On Thu, 3 Nov 2011 08:32:02 -0700, Guenter Roeck wrote:
> > On Thu, 2011-11-03 at 11:19 -0400, Lars Noodén wrote:
> > > I can set the fan speed manually.  e.g.:
> > > 
> > >  echo 3500 > /sys/class/hwmon/hwmon0/device/fan1_output
> > > 
> > > That helps some.
> > > 
> > If you can do that, you should be able to set up fancontrol to
> > automatically control fan speed based on system temperatures.
> 
> This won't work, as fancontrol wants pwmX attributes which the applesmc
> driver doesn't implement.
> 
Yes, you are right - it won't work without patching it to use
fanX_output and to accept larger values for the limits.

Wonder how this works for other Apple systems. Maybe there is an
Apple-specific script out there to control fan speed.

> > There is another sysfs attribute - fanX_manual. I don't find driver
> > documentation, so I have no idea what it is doing. The name indicates
> > that it might set manual vs. automatic fan control. What is it set to in
> > your system ? From the code, looks like it should be 0 or 1. Try to
> > toggle it and see what happens - after all, it can not get worse ;).
> 
> Might be worth looking at files fanX_min, _max and _safe too. Too bad
> there doesn't seem to be any documentation available for all these
> non-standard attributes :(
> 
Here is some info from the web about the problem. See
http://ubuntuforums.org/archive/index.php/t-981280.html.

So, for those that have reported high temperatures due to low fan
speeds: check the value of

cat /sys/devices/platform/applesmc.768/fan1_manual

With no software control of the fans, which is the case with the
macbooks (fancontrol and pwmconfig does not work), the fan speed seems
to be controlled automatically by the SMC without issues - but only if
fan1_manual is zero.

Guenter


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