[Intel-gfx] Tracing PM-triggered GPU frequency changes from user space

[Heinrich Fink]

Hi,

is there a simple way for user space to trace PM-triggered changes of
GPU frequency on GEN9/Skylake? 

i915:intel_gpu_freq_change seems to only report SW-triggered frequency
change requests. The best option I currently see is to poll
gt_act_freq_mhz, but I was hoping for a more elegant solution.

Use-case: I am using GPUVis to understand problematic workloads of some
applications, and it would be useful to have the actual GPU freq
showing up in that trace along with the rest.

I found an old email thread [0] on this topic from 2012, but it's not
clear to me what eventually turned out to be the outcome of that
discussion.

Thanks,

Heinrich

[0] https://lists.freedesktop.org/archives/intel-gfx/2012-September/thr
ead.html#19951