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

[Belgaumkar, Vinay]

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 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.

Does adding a delay help (around 20 ms for the h2g to go through 
typically)? Also, is there a workload running when we change the 
min=max=boost to 300?

We already check these things in our SLPC selftests.

Thanks,

Vinay.

>
> Thanks.
> --
> Ashutosh