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

[Dixit, Ashutosh]

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 at 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 at 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.

Thanks.
--
Ashutosh