Looking for a start point for fixing a bug

[Niels Ole Salscheider]

On Monday 11 August 2014, 01:19:32, Адонай Элохим wrote:
> Hello again, hope you are still reading my texts...
> 
> I digged through the code and narrowed down the issue I wanted to fix.
> It appears to be related to the `bool thermal_active` dpm struct
> member and this piece of code:
> 
> if (rdev->asic->dpm.force_performance_level) {
>         if (rdev->pm.dpm.thermal_active) {
>             enum radeon_dpm_forced_level level = rdev->pm.dpm.forced_level;
>             /* force low perf level for thermal */
>             radeon_dpm_force_performance_level(rdev,
> RADEON_DPM_FORCED_LEVEL_LOW);
>             /* save the user's level */
>             rdev->pm.dpm.forced_level = level;
>         } else {
>             /* otherwise, user selected level */
>             radeon_dpm_force_performance_level(rdev,
> rdev->pm.dpm.forced_level); }
>     }
> 
> I did a double check here - at boot `thermal_active` is `false` and
> thus, performance level is properly initiated. But at resume from
> suspend `thermal_active` is true and performance level is strictly
> bound to low profile.
> Besides you cannot change it via echo 1 > /sys/.../force_dpm_level,
> again thanks to `thermal_active` checked there.
> 
> Could you explain meaning of this small boolean to me? I'd like to
> make a small neat patch fixing this, but I'm scared of doing it in
> wrong way.
> Sorry if I'm being too persistent.

I think thermal_active means that the temperature got too high so that low 
clocks have to be used.

Just some idea, but thermal.work only gets scheduled when the high to low 
temperature interrupt occurs. When the temperature is too high before suspend 
(so that thermal_active is true) and it gets low during standby this interrupt 
will not occur. thermal.work is therefore not scheduled...

Ole

> Thanks,
> Oleg
> 
> 2014-07-22 20:05 GMT+04:00 Alex Deucher <alexdeucher at gmail.com>:
> > On Tue, Jul 22, 2014 at 8:39 AM, Адонай Элохим <algonkvel at gmail.com> 
wrote:
> >> Hello all!
> >> 
> >> I have some spare time and knowledge in C to try to fix some bugs I am
> >> seeing on my machine.
> >> So I've checked out and compiled all git trees that I may need and now
> >> I'm
> >> beginning to read articles.
> >> 
> >> And this is the point from where I don't know where to go. I want to fix
> >> particular bug #79806 [1].
> >> For me there are many places where this bug can hide - mesa? dri? radeon
> >> kernel module? and I just don't know whether should I start reading
> >> articles about mesa hacking or about dri architecture or about kernel
> >> module development.
> >> 
> >> Now I think the best thing for me is to start looking through radeon
> >> kernel
> >> module code (I've got ingenious idea that power management resides there)
> >> and read more about its architecture. Is this right? I mean, I just want
> >> to
> >> find out, is this a right place to start looking at for this bug?
> > 
> > The power management is handled in the kernel driver.  See radeon_pm.c
> > and the relevant *_dpm.c files depending on what asic you have.
> > 
> > Alex
> > 
> >> P.S. Sorry for my English in case it's not good, I'm learning it now
> >> 
> >> P.P.S. And thanks for your hard work!
> >> 
> >> -------------------------------------------
> >> [1] https://bugs.freedesktop.org/show_bug.cgi?id=79806
> >> 
> >> _______________________________________________
> >> dri-devel mailing list
> >> dri-devel at lists.freedesktop.org
> >> http://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
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