Re: [igt-dev] [PATCH i-g-t v2 1/2] kms_hdr: Skip HDR tests on pre-Kaby Lake Intel devices

[Jeremy Cline <jcline@redhat.com>]

On Mon, Mar 08, 2021 at 02:53:39PM +0200, Petri Latvala wrote:
> On Mon, Mar 08, 2021 at 06:11:09PM +0530, Sharma, Swati2 wrote:
> > 
> > 
> > On 08-Mar-21 2:17 PM, Petri Latvala wrote:
> > > On Fri, Mar 05, 2021 at 11:42:52AM -0500, Jeremy Cline wrote:
> > > > According to the Intel documentation[0] I could find, HDR support is
> > > > only in Kaby Lake+. Skip tests in kms_hdr if the hardware doesn't
> > > > support HDR.
> > > > 
> > > > [0] https://www.intel.com/content/dam/support/us/en/documents/graphics/HDR_Intel_Graphics_TechWhitePaper.pdf
> > > > 
> > > > Signed-off-by: Jeremy Cline <jcline@redhat.com>
> > > 
> > > 
> > > While that might be true, strictly speaking IGT tests are not testing
> > > the HW capabilities but the kernel interfaces. The difference is often
> > > only interesting for nitpicking.
> > > 
> > > However, in this case a good argument can be made either way, with
> > > what the correct behaviour with setting the "max bpc" property when
> > > the HW doesn't support HDR _output_ should be. IGT tests should be
> > > written the way one would expect "real" userspace to behave; does the
> > > documented kernel interface require userspace to detect the device id
> > > somehow? The connector property is there so one would assume setting
> > > it should work and do something.
> > > 
> > > A good argument can also be made that even though we're testing "just
> > > the interface", we (Intel) should have a separate test that requires
> > > actual HW support...
> > > 
> > > Swati, Maarten, thoughts on this? Are we even testing the right things
> > > for i915 at all? Are we able to express the HW requirement for HDR
> > > with something other than comparing devid? Should we? (If we should
> > > not, please suggest a better way to get around the issue being fixed
> > > here)
> > 
> > There are 2 types of tests which are being validated in kms_hdr
> > (i) bpc switch
> > (ii) hdr metadata
> > And both these tests will skip on platforms which doesn't support respective
> > connector
> > properties (MAX_BPC, HDR_OUTPUT_METADATA resp). These tests are independent
> > of platforms on which they are being tested.
> > This can be validated from the link below:
> > https://intel-gfx-ci.01.org/tree/drm-tip/shards-all.html?testfilter=kms_hdr
> > where you can see platforms which doesn't support either max_bpc or
> > hdr_metadata
> > connector properties; tests are being skipped.
> > 
> > And I don't think anything is being fixed here
> 
> What I meant is the fix in patch 2, removing the removal of the
> primary plane, which was done because of a HSW limitation. Patch 1
> (this thread) is then making sure HSW is unaffected by a spurious
> failure. Sorry for not being clear when pulling more CCs.
> 

There are definitely finer-grain ways to do this, but this "works" so I
figured it'd be good to start here and have a discussion about it.

One option would be to just wrap the plane-removal call in a device
check. Another would be to try and find a plane size that meets whatever
the scaling requirements are for hsw (assuming there's overlap between
the conflicting requirements of hardware).

I don't have a strong opinion about where the checks happen, it seems
like a trade-off between in-test complexity and the breadth of the test
matrix, and I can't say how useful it is to make sure the MAX_BPC
interface works on a specific generation of hardware. I'm happy to do
either of those options (or another option I've not considered),
whatever you folks think is the best trade-off.

Thanks,
Jeremy

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