[Intel-gfx] [PATCH 0/3] drm/i915: Fix SKL+ 90/270 degree rotated scanout

[Maarten Lankhorst]

Op 05-04-17 om 15:49 schreef Ville Syrjälä:
> On Fri, Mar 31, 2017 at 10:23:18PM +0100, Chris Wilson wrote:
>> On Fri, Mar 31, 2017 at 09:00:53PM +0300, ville.syrjala at linux.intel.com wrote:
>>> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>>>
>>> I figured it's about time I fix what I broke with my fb offset stuff.
>>> I've posted the scaler thing before, but the watermark and fbc stuff
>>> is new.
>>>
>>> Based on some quick tests the WM fixes seem effective. Or at least
>>> underruns seemed to disappear when I was running xonotic with 90/270
>>> degree rotation.
>> The key question for me is would we be able to detect any of the errors
>> in igt? How can we improve our testing?
> The rotation test definitely would need some love. It fails to detect
> these problems because it scans out a square image. Making it non-square
> would at least catch the use of the scaler when it shouldn't be used.
>
> Detecting the watermark breakage is less clear. I suppose making the
> plane have a very wide or very tall aspect ratio might help induce
> underruns with the broken wm code.
>
> Another thing that may or may not be missing from the test is panning.
> I'd also like to test scaling, but sadly our hardware makes that
> rather hard by not allowing us to force nearest and/or linear filtering,
> and bspec doesn't actually document what kind of algorithm the hardware
> uses for the different filter modes.
>
Agreed, the whole series is useful but until we have some tests we may as well not commit it. Nothing prevents it from being broken again in the next commit. :(

I'll take a look and see if I can make kms_rotation_crc break without this test.

~Maarten