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@xxxxxxxxx>
> > ---
> > + /*
> > + * 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
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