Re: [PATCH i-g-t] kms_rotation_crc: 90 degree flip test is not a stress test

From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>,
	Tvrtko Ursulin <tursulin@ursulin.net>,
	Intel-gfx@lists.freedesktop.org
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Subject: Re: [PATCH i-g-t] kms_rotation_crc: 90 degree flip test is not a stress test
Date: Thu, 3 Aug 2017 14:41:34 +0100	[thread overview]
Message-ID: <4edb3d48-e506-f226-9001-7208a28e919a@linux.intel.com> (raw)
In-Reply-To: <150176683623.20927.4510984957794506499@mail.alporthouse.com>

On 03/08/2017 14:27, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2017-08-03 14:09:59)
>>
>> On 03/08/2017 13:53, Chris Wilson wrote:
>>> Quoting Tvrtko Ursulin (2017-08-03 13:42:50)
>>>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>>
>>>> To the best of my recollection the page flipping test was added
>>>> simply to start exercising page flips with 90/270 rotation.
>>>>
>>>> There is no need to do 60 flips which can take quite some time
>>>> because we test each pipe and then each fb geometry. And
>>>> calling this a stress test is also not matching the original
>>>> idea of the test.
>>>>
>>>> So remove the stress from the name and reduce the number of
>>>> flips to three only.
>>>
>>> Considering this found a bug, do we have an explicit test that says a
>>> rotated page flip takes no longer than a vblank (given the right
>>> conditions, i.e subsequent flips)?
>>
>> That was just me misremembering how the test work, wasn't a bug. Once I
>> looked at the code in more detail I realized the test does much more
>> flipping than it initially seemed. Num_pipes * 4 fb geometries * 2
>> framebuffers * 60 flips. In total around 8 seconds of flipping per pipe.
>> So the 25 second runtime is in line with 3 pipes at 60Hz plus some test
>> setup time.
> 
> Ah. But do we have a test that says we can hit vrefresh with rotated
> pipes? I know we check the timings for the ordinary case, but from a
> quick check of the likely suspects, I can't see such a test.

Not in kms_rotation_crc, so one to pencil in on the TODO list.

> PS please add the explanation for why it took longer than expected into
> the commit log.

I mentioned in the commit why it takes long ("...60 flips which can take 
quite some time because we test each pipe and then each fb 
geometry..."), but I am not sure that is longer than expected. Or to 
better say I am not sure what is expected. One could even say, since the 
test had stress in its name, that 25 seconds was not unexpected. :) Now 
it is not a stress test any more and it finishes in five seconds so all 
is good. I am not sure what exactly you think I should add? The formula 
for exact number of flips test was doing?

Tvrtko
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