On Tue, 4 Jul 2023 at 00:40, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote: > > > > On 6/19/2023 5:08 PM, Dmitry Baryshkov wrote: > > DPU performance module contains code to change performance state > > calculations. In addition to normal (sum plane and CRTC requirements), > > it can work in 'minimal' or 'fixed' modes. Both modes are impractical, > > since they can easily end up with the display underruns. Userspace also > > should not depend on these modes availability, since they are tuned > > through debugfs, which might not be available. > > > > Drop relevant code to simplify performance state calculations. > > > > Suggested-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx> > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > > --- > > Sorry but NAK on this change for two reasons: > > This mode is not for usermode to depend on but for debugging. I have > personally used both the perf max and perf min modes for debug. > > 1) The purpose is that, if you do see an underrun, you can force the > perf mode as it will select max clk and bw rate > > So something like below: > > localhost /sys/kernel/debug/dri/1/debug/core_perf # echo 2 > perf_mode > localhost /sys/kernel/debug/dri/1/debug/core_perf # echo 300000000 > > fix_core_clk_rate > > This will allow us to force the clk to a particular value to see at what > point it starts underruning > > Also you can even do > > localhost /sys/kernel/debug/dri/1/debug/core_perf # echo 1 > perf_mode > > This will automatically max out the clk and BW > > With this, you can figure out if underrun is a performance related > underrun or a misconfiguration. We used it even recently to debug the > performance issue with pclk reduction Hmm, 1 is minimum, not maxumum. > > 2) Sometimes, you even want to force an underrun to debug devcoredump OR > the recovery code. Forcing the min clk mode by doing > > localhost /sys/kernel/debug/dri/1/debug/core_perf # echo 19200000 > > fix_core_clk_rate > localhost /sys/kernel/debug/dri/1/debug/core_perf # echo 2 > perf_mode > > Is the easiest way to trigger the recovery handler. > > Hence I am not at all convinced of dropping this. I see, thanks for sharing the usecases. However I still think that it is overcomplicated for the debugging feature. What about dropping all perf modes and providing just 'override_core_clk_rate' and 'override_avg_bw', 'override_peak_bw'? -- With best wishes Dmitry
