[Intel-gfx] [PATCH 1/2] drm/i915: Add display WA #1175 for planes ending close to right screen edge

[Imre Deak]

On Fri, Jan 12, 2018 at 03:13:19PM +0000, Chris Wilson wrote:
> Quoting Imre Deak (2018-01-12 14:54:36)
> > As described in the WA on GLK and CNL planes on the right edge of the
> > screen that have less than 4 pixels visible from the beginning of the
> > plane to the edge of the screen can cause FIFO underflow and display
> > corruption.
> > 
> > On GLK/CNL I could trigger the problem only if the plane was at the same
> > time also aligned to the top edge of the screen (after clipping) and
> > there were exactly 2 pixels visible from the start of the plane to the
> > right edge of the screen (so couldn't trigger it with 1 or 3 pixels
> > visible). Nevertheless, to be sure, I also applied the WA for these cases.
> > 
> > I also couldn't see any problem with the cursor plane and later Art
> > confirmed that it's not affected, so the WA is applied only for the
> > other plane types.
> > 
> > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > ---
> > +       /*
> > +        * Display WA #1175: cnl,glk
> > +        * Planes other than the cursor may cause FIFO underflow and display
> > +        * corruption if starting less than 4 pixels from the right edge of
> > +        * the screen.
> > +        */
> > +       if ((IS_GEMINILAKE(dev_priv) || IS_CANNONLAKE(dev_priv)) &&
> > +           dst_x > pipe_src_w - 4) {
> > +               DRM_DEBUG_KMS("requested plane X start position %d invalid (valid range %d-%d)\n",
> > +                             dst_x,
> > +                             0, pipe_src_w - 4);
> > +               return -EINVAL;
> 
> Should this be -ERANGE or -ENOSPC?

I don't mind changing it to -ERANGE. (I suppose it'd be used by user
space as detection of platforms with the problem, falling back to
something else.)

--Imre