Re: [igt-dev] [PATCH i-g-t] tests/perf_pmu: Compare against requested freq in frequency subtest

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Mon, 07 Nov 2022 16:57:24 -0800, Belgaumkar, Vinay wrote:
>
>
> On 11/7/2022 4:22 PM, Dixit, Ashutosh wrote:
> > On Mon, 07 Nov 2022 16:18:31 -0800, Dixit, Ashutosh wrote:
> > Hi Vinay,
> >
> > A question for you below.
> >
> >> So I submitted this patch to repro the issue and to print out the requested
> >> freq from sysfs:
> >>
> >> https://patchwork.freedesktop.org/series/110630/
> >>
> >> And we can see the output here:
> >>
> >> https://intel-gfx-ci.01.org/tree/drm-tip/IGTPW_8061/bat-dg2-11/igt@perf_pmu@frequency.html
> >>
> >> ```
> >> IGT-Version: 1.26-g1bef4d081 (x86_64) (Linux: 6.1.0-rc4-CI_DRM_12352-gc55ac6a74bd1+ x86_64)
> >> Starting subtest: frequency
> >> Frequency: min=300, max=2050, boost=2050 MHz
> >> Min frequency: requested 349.7, actual 349.7
> >> Max frequency: requested 2048.0, actual 2048.0
> >> Sysfs requested: min 350, max 2050
> >> Stack trace:
> >>    #0 ../../../usr/src/igt-gpu-tools/lib/igt_core.c:1908 __igt_fail_assert()
> >>    #1 ../../../usr/src/igt-gpu-tools/tests/i915/perf_pmu.c:1656 __igt_unique____real_main2147()
> >>    #2 ../../../usr/src/igt-gpu-tools/tests/i915/perf_pmu.c:2147 main()
> >>    #3 [__libc_start_main+0xf3]
> >>    #4 [_start+0x2e]
> >> Subtest frequency: FAIL (2.212s)
> >> ```
> >>
> >> So we clearly see the requested freq from sysfs is indeed 350 MHz so
> >> SLPC/PCODE is not honoring the set min == max == boost freq (and PMU is
> >> measuring what sysfs is showing). In general PCODE is the final arbiter in
> >> such cases and we do occasionally see instances where set freq limits are
> >> not honored.
> >>
> >> I would say if igt@perf_pmu@frequency is testing freq measured by PMU then
> >> the patch below is correct. Whether SLPC/PCODE is honoring the set freq
> >> limits should be tested in a SLPC test (which we also have).
> >
> > igt@perf_pmu@frequency sets 'min == max == boost == 300 MHz' but we still
> > see the requested freq to be 350 MHz. Do we have a SLPC test covering this
> > scenario or should we add one? This is failing on one of the DG2's.
>
> Does adding a delay help (around 20 ms for the h2g to go through
> typically)?

There is no delay but the test calls gem_quiescent_gpu() after setting 'min
== max == boost == 300 MHz' and then launches a spinner. We are checking
the requested freq 500 ms after the spinner is started (so plenty of time
for the h2g) and still the requested freq is 350 MHz.

> Also, is there a workload running when we change the min=max=boost to
> 300?

No, the workload is started after setting the freq and calling
gem_quiescent_gpu().

>
> We already check these things in our SLPC selftests.
>
> Thanks,
>
> Vinay.
>
> >
> > Thanks.
> > --
> > Ashutosh