Re: SMU support for PowerMac G5 11,2

[Michael <macallan%netbsd.org@localhost>]

Hello,

On Wed, 10 Jul 2013 14:06:47 +0200
Phileas Fogg <phileas-fogg%mail.ru@localhost> wrote:

> at length i implemented the initial support of SMU and sensors for 
> PowerMac G5.

Nice!

> Now it's possible to control fan RPM and see current temperature of the 
> CPUs too.

I need that to verify that my power saving hack actually works...

> At boot all fans are at the maximum RPM which makes it impossible to
> work on G5 due to loud noise made by fans. With SMU we can control it and
> set to values which make fans noiseless.
> I implemented the necessary drivers with syctl and envsys support.
> 
> We also need to send "quisce" command to OFW at boot else
> it's not possible to communicate with SMU.

IIRC some PMUs are like that. If you don't poke them within a certain
time frame after boot they refuse to talk.

> Quastion:
> ----------
> I'm not very familiar with envsys but is it possible to
> make it control fan speed automatically depending on the current 
> temperature ? Or is it better to control fan speed in the kernel space, 
> like Linux or FreeBSD kernels do it. I would appreciate any pointers here.

I don't think there's a generic mechanism in envsys to do that, since
most of the supported sensors / fan controllers do this automatically.
There is some prior art though, I think sparc64's tda driver ( for the
Sun Blade 1000 / 2000, see arch/sparc64/dev/tda.c ) does this by
software as well.

> Currently i'm doing it with a shell script which runs periodically.
> One odd thing i noticed is that if i set e.g. all fan speeds to 1500
> but then do not read fan rpm back for a while, SMU automatically 
> increases all fan speeds. If i read fan rpms periodically then it remains
> at the speed which i configured last. Very odd.

Weird. Maybe it needs a command to tell it to control fans automatically?

have fun
Michael