[igt-dev] [PATCH i-g-t v4] tests/kms_async_flips: Add test to validate asynchronous flips

[Michel Dänzer]

On 2020-08-07 11:31 a.m., Karthik B S wrote:
> On 8/6/2020 8:19 PM, Michel Dänzer wrote:
>> On 2020-08-06 3:29 p.m., Karthik B S wrote:
>>> Asynchronous flips are issued using the page flip IOCTL.
>>> The test consists of two subtests. The first subtest waits for
>>> the page flip event to be received before giving the next flip,
>>> and the second subtest doesn't wait for page flip events.
>>
>> The latter sounds sketchy. It might get lucky most of the time, but if
>> the previous flip is still pending, the ioctl will fail with EBUSY.
>>
> 
> Thanks for the review.
> I will update the test to retry on getting EBUSY until 1 vblank time and
> then fail if we're still getting EBUSY.

That could still fail with AMD GPUs, where the vblank interrupt can fire
earlier than the flip completion interrupt.

I don't get the point of such a sub-test TBH. Userspace should always
use the flip completion event to know when a flip has completed and
another one can be submitted.


-- 
Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer