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

[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.

-- 
Ville Syrjälä
Intel OTC