Re: PowerMac G5 fans run out of control with kernel 4.17.0-3-powerpc64 but not with 4.16.0-1-powerpc64

[Dennis Clarke <dclarke@blastwave.org>]

On 08/25/2018 04:10 AM, Rick Thomas wrote:
> On Aug 24, 2018, at 9:26 PM, Dennis Clarke <dclarke@blastwave.org> wrote:
>
> > On 08/24/2018 09:31 PM, Rick Thomas wrote:
> > > I just loaded the latest Debian-ports powerpc64 installer on a PowerMac dual-core G5 that I had lying around.
> > > It installed kernel 4.16.0-1-powerpc64 from the CD.  After the install finished, I did an update/upgrade and that installed kernel 4.17.0-3-powerpc64.
> > > A few minutes after rebooting with the new kernel the “wind tunnel” fans started up.  I then rebooted with the old (4.16) kernel.  The fans did not start up.
> > > Back in the old days of Linux kernel 3.x, the fix for wind tunnel fans was to load the “i2c_powermac" kernel module.  Nowadays, that module is built-in so it isn’t necessary (or even possible) to manually load it.  I checked the config files, and it is still built-in on both the 4.16 and the 4.17 kernels.
> > > Anybody know what changed and what can be done about it?
> > > Thanks! for any help you can give,
> > > Rick
> >
> > Have a look around for something called "windfarm". It may even be
> > located somewhere down under /proc and should be a kernel module.
> >
> > I have had the same behavior with a G5.  Wind farm sorted it all out.
> >
> > Dennis
>
> So, with this as a clue, I did a little digging and wound up adding to /etc/modules a line for “windfarm_core”.  With that, I can run either kernel (4.16 or 4.17) without getting the “wind tunnel” fans.
>
> Now, the question is:  Why?  What has changed between 4.16 and 4.17 that makes this necessary?  And, is it a bug or a feature?
>
> Other things I have observed about this installation:
>
> 1) I can’t install the “printer-driver-postscript-hp” package, because the “libsane” package is missing.  Is this an oversight that will be fixed in due course?  Or is there something that makes libsane incompatible with powerpc64?
>
> 2) Firefox segfaults when I start it, either from command line or from the system menu.  Is this a known bug?   Are there any other graphical (i.e., non-text-mode) browsers I can use instead?  I can use elinks for most things, but it’s a lot harder to configure cups printers when you don’t have a graphical browser!
>
> Again, Thanks! for any help you can give.

The bucket of things I see back on 4.15.0 are :

4.15.0-2-powerpc64@nix# uname -a
Linux nix 4.15.0-2-powerpc64 #1 SMP Debian 4.15.11-1 (2018-03-20) ppc64 
GNU/Linux
4.15.0-2-powerpc64@nix# lsmod | grep -i "farm"
windfarm_cpufreq_clamp     3085  1
windfarm_smu_sensors     7223  1
windfarm_smu_controls     7622  8
windfarm_pm112         13864  0
windfarm_pid            2995  1 windfarm_pm112
windfarm_max6690_sensor     3823  1
windfarm_lm75_sensor     4317  1
windfarm_smu_sat        7208  9 windfarm_pm112
windfarm_core          10663  7 
windfarm_pm112,windfarm_smu_sensors,windfarm_smu_sat,windfarm_max6690_sensor,windfarm_cpufreq_clamp,windfarm_smu_controls,windfarm_lm75_sensor

I could give a try at a build of 4.18.5 ( current stable ) but from my
experience there was little to gain from such experiments other than to
say "oh gee .. there is a new kernel".

My real interest is in the memory management code wherein Linux systems
seem to swap and use actual pages of swap when there is buckets of real
memory available and no memory pressure to speak of. Far more curious
than fans ripping out of control however those are certainly annoying.

Dennis