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: 6ede6b0616 ("drm/i915: Implement async flips for vlv/chv")
Fixes: 4bb18054ad ("drm/i915: Implement async flip for ilk/snb")
Fixes: 2a636e240c ("drm/i915: Implement async flip for ivb/hsw")
Fixes: cda195f13a ("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.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Limit pre-skl plane stride to below 4k or 8k pixels (depending on
the platform). We do this in order guarantee that TILEOFF/OFFSET.x
does not get too big.
Currently this is not a problem as we align SURF to 4k, and so
TILEOFF/OFFSET only have to deal with a single tile's worth of
pixels. But for async flips we're going to have to bump SURF
alignment to 256k, and thus we can no longer guarantee
TILEOFF/OFFSET.x will stay within acceptable bounds. We can avoid
this by borrowing a trick from the skl+ code and limit the max
plane stride to whatever value we can fit into TILEOFF/OFFSET.x.
The slight downside is that we may end up doing GTT remapping in
a few more cases where previously we did not have to. But since
that will only happen with huge buffers I'm not really concerned
about it.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210111163711.12913-3-ville.syrjala@linux.intel.com
Reviewed-by: Karthik B S <karthik.b.s@intel.com>
