[Bug 112169] [regression] (recoverable) GPU resets & fails in slower 3D benchmarks

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=112169

--- Comment #8 from Eero Tamminen <eero.t.tamminen at intel.com> ---
(In reply to Chris Wilson from comment #7)
> GPU reclocking is dysfunctional on Tigerlake (at least as far as observation
> goes and the randomly reported frequencies), so not too surprising as other
> observations back up that Tigerlake is clocking lower than intended.

Looking at:
- /sys/class/drm/card0/gt_act_freq_mhz
- i915:intel_gpu_freq_change tracepoint values

For first minutes of running 3D benchmarks without a pause, tracepoint reports
i915 to have requested 300MHz speed from GPU, but sampling gt_act_freq_mhz
tells GPU to run at 400MHz.

After that tracepoint tells 900Mhz to be requested, but gt_act_freq_mhz tells
GPU to run at 700MHz.

That indeed seems bogus power management behavior, but some of the tests where
the TGL pre-emption reset issues are seen, are still running at > 100FPS, so
they're definitely not too slow from the user point of view.

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