Re: Recent linux-image update broke CPU fan
On Sun, 29 Nov 2015 14:35:15 +0100
Sven Arvidsson <sa@whiz.se> wrote:
> On Sun, 2015-11-29 at 02:16 -0500, Neal P. Murphy wrote:
> > I think the last linux-image update broke my CPU fan. OK, it didn't
> > actually break it. But since the last update, my CPU fan (stock with
> > vishera 8350 black) will NOT turn faster than about 3500 RPM.
> >
> > I have been using fancontrol for months. It took weeks to get it set
> > correctly. At maximum speed, I've seen (and heard) the fan turn in
> > excess of 6500 RPM.
> >
> > Until the recent kernel update, the CPU and case fans have ramped up
> > with increasing temp and ramped down with decreasing temp. The CPU
> > never exceeded about 60C when compiling linux using all 8 CPUs for 5
> > minutes. And that was with a mild overclock (4.4GHz, 1866 RAM at
> > 2133).
> >
> > Now, the CPU fan will not exceed about 3700 RPM. That's barely fast
> > enough to keep 4 non-overclocked CPUs cool.
> >
> > Has anyone else experienced this? Is it related to the kernel update?
> > Or do I have a power supply or motherboard failing (again)?
>
> If this was on a stable system it seems odd, if it was unstable or
> testing it might just be one of the "charms" of running something that
> is in development.
Jessie: stable.
>
> You need to figure out what package is responsible for the change, boot
> the previous kernel for example. Then figure out if it's a bug or just
> changed behaviour.
As of 28 November 2015, the latest update to linux-image-3.16.0-4-amd64 versus the previous update. I think the latest update is:
linux-image-3.16.0-4-amd64_3.16.7-ckt11-1+deb8u6_amd64.deb
and the previous is probably ...deb8u5.... So how do I tell it to uninstall 'u6' and install 'u5'?
>
> I'm not sure how fancontrol works. What exactly broke? Do you not get
> readings from the temperature sensors, or is it not possible to control
> the fan speed?
Exactly: the CPU fan no longer exceeds about 3700 RPM. It is capable of exceeding 6000 RPM. Around 4500-5000 RPM is needed to keep the CPU from exceeding about 60C.
Fancontrol uses the interfaces in /sys/class/hwmon (in my case, the IT87 in .../hwmon/hwmon0/pwm1*). Fancontrol writes "0" to "255" to pwm[1-3]. "0" is the slowest allowed RPM; at "0", the CPU fan slows to around 1300 RPM and the case fans stop. "255" is the fastest RPM; this should have the CPU fan screaming painfully loud while the case fans top out at around 1300 RPM. But the CPU fan now refuses to go faster than around 3700 RPM, even with clocking restored to stock timings.
The sensors work and report sane RPM and temp readings; they are generally where I expect them to be with respect to CPU load. But the CPU fan just won't go any faster.
Thus my query: did the latest linux-image update do anything with sensors and/or sensor drivers? That is, mayhap the IT87 driver changed to scale the pwm1 input? (No, it doesn't make sense, but strange things happen with software now and again.)
I can live with "It's a coincidence." A lot of things can change; the obvious one was the recent kernel update, thus my query. If the latest changes/patches to 3.16 are well away from sensors and drivers, then the kernel update probably is not the cause and I should look elsewhere (like checking the capacitors on the M5A99FX mainboard; there are probably still some bad caps floating around.)
Thanks,
Neal
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