Re: [PATCH i-g-t] tests/kms_explicit_fence: Replace fixed sleep with vblank wait

[Karthik B S <karthik.b.s@intel.com>]

Hi Krzysztof,

On 5/14/2026 11:35 AM, Krzysztof Karas wrote:
> Hi Karthik,
>
>> The premature-update detection window between the NONBLOCK atomic
>> commit and the CRC sample used a fixed 100ms sleep. On
>> high-refresh-rate panels this 100ms wait covers many vblank
>> intervals (~24 at 240 Hz vs ~6 at 60 Hz) and is long enough to let
>> the display engine enter PSR/DC5. A subsequent CRC read then comes
>> back as 0xffffffff (read from a powered-down well), causing the
>> test to fail spuriously on these panels.
>>
>> Replace the fixed sleep with 2-vblank wait:
>>
>>   - It is the minimum wait that guarantees one full vblank boundary
>>     has elapsed past the commit, so a same-vblank-latch bug in the
>>     driver still has a deterministic window to manifest before the
>>     CRC is sampled.
>>   - It scales with the panel refresh rate, keeping the wait short
>>     on high-refresh panels (~8 ms at 240 Hz, ~33 ms at 60 Hz).
>>
>> Cc: S Sebinraj <s.sebinraj@intel.com>
>> Cc: Krzysztof Karas <krzysztof.karas@intel.com>
>> Signed-off-by: Karthik B S <karthik.b.s@intel.com>
>> ---
> How did you find this issue? Should there be a "Closes" tag
> somewhere if that was reported by CI or community?

High refresh rate panel not present on CI execution so no bug on gitlab. 
But able to see it consistently on my local runs on multiple HRR panels.

Thanks and Regards,
Karthik.B.S
>