(In reply to Alex Deucher from comment #9)
> (In reply to Kai from comment #8)
> > (In reply to Alex Deucher from comment #6)
> > > Does reverting 5e031d9fe8b0741f11d49667dfc3ebf5454121fd (drm/radeon/pm:
> > > update current crtc info after setting the powerstate) help?
> > 
> > No, it does not for me (I fetched the patch from
> > <https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/patch/
> > ?id=5e031d9fe8b0741f11d49667dfc3ebf5454121fd> and applied it with patch -p1
> > -R < /path/to.patch). The Talos Principle is still down to 43 FPS, haven't
> > tested XCOM 2 or anything else.
> > 
> > Btw, not sure if it can help tracking down the cause: the GPU doesn't seem
> > to go into its highest performance mode or at least the fan is not reaching
> > its highest RPM when I'm on 4.7.0 (with or without the revert).
> 
> You can check by running apps and monitoring the content of
> /sys/kernel/debug/dri/64/radeon_pm_info
> Do you see it scaling up under load on the problematic kernels?  Does
> forcing the clocks to high via sysfs work ok?

While the clocks *do* scale up on 4.7.0, it doesn't go as high as 4.6.4. On
4.6.4 I'm reaching the maximum clocks for my GPU (power level avg    sclk:
98000 mclk: 125000). With 4.7.0 the highest I'm seeing is "power level avg   
sclk: 90843 mclk: 125000" and the overall level is way lower (lots of sclk
values starting with a 3) compared to 4.6.4 where most values are > 60000 for
sclk.

Note: I used watch to dump /sys/kernel/debug/dri/64/radeon_pm_info every five
seconds to a file. Between runs the actual numbers logged vary, but the general
trend stays the same.

Writing "high" to /sys/class/drm/card0/device/power_dpm_force_performance_level
locks the clock indeed to the highest values (sclk: 98000 mclk: 125000) on
4.7.0 and recovers almost all of the lost performance. There's still a small
hit to performance.

Note: I've only tested "The Talos Principle" so far, if you need me to test
XCOM 2 or other titles as well, let me know.

Do you still need the bisect?