ilk+ planes get notably unhappy when the plane x+w exceeds
the stride. This wasn't a problem previously because we
always aligned SURF to the closest tile boundary so the
x offset never got particularly large. But now with async
flips we have to align to 256KiB instead and thus this
becomes a real issue.

On ilk/snb/ivb it looks like the accesses just wrap
early to the next tile row when scanout goes past the
SURF+n*stride boundary, hsw/bdw suffer more heavily and
start to underrun constantly. i965/g4x appear to be immune.
vlv/chv I've not yet checked.

Let's borrow another trick from the skl+ code and search
backwards for a better SURF offset in the hopes of getting the
x offset below the limit. IIRC when I ran into a similar issue
on skl years ago it was causing the hardware to fall over
pretty hard as well.

And let's be consistent and include i965/g4x in the check
as well, just in case I just got super lucky somehow when
I wasn't able to reproduce the issue. Not that it really
matters since we still use 4k SURF alignment for i965/g4x
anyway.

Fixes: 6ede6b06 ("drm/i915: Implement async flips for vlv/chv")
Fixes: 4bb18054 ("drm/i915: Implement async flip for ilk/snb")
Fixes: 2a636e24 ("drm/i915: Implement async flip for ivb/hsw")
Fixes: cda195f1 ("drm/i915: Implement async flips for bdw")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210209021918.16234-1-ville.syrjala@linux.intel.comReviewed-by: Chris Wilson <chris@chris-wilson.co.uk>