drm/i915: Disallow plane x+w>stride on ilk+ with X-tiling

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: 6ede6b0616b2 ("drm/i915: Implement async flips for vlv/chv")
Fixes: 4bb18054adc4 ("drm/i915: Implement async flip for ilk/snb")
Fixes: 2a636e240c77 ("drm/i915: Implement async flip for ivb/hsw")
Fixes: cda195f13abd ("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>

diff --git a/drivers/gpu/drm/i915/display/i9xx_plane.c b/drivers/gpu/drm/i915/display/i9xx_plane.c
index 0523e2c79d1613d8bc4b3c8d2996e6c4ddc7b418..8a52beaed2daaa1f0444f95f77219ca8a30a9bb0 100644 (file)
--- a/drivers/gpu/drm/i915/display/i9xx_plane.c
+++ b/drivers/gpu/drm/i915/display/i9xx_plane.c
@@ -255,6 +255,33 @@ int i9xx_check_plane_surface(struct intel_plane_state *plane_state)
        else
                offset = 0;
 
+       /*
+        * When using an X-tiled surface the plane starts to
+        * misbehave if the x offset + width exceeds the stride.
+        * hsw/bdw: underrun galore
+        * ilk/snb/ivb: wrap to the next tile row mid scanout
+        * i965/g4x: so far appear immune to this
+        * vlv/chv: TODO check
+        *
+        * Linear surfaces seem to work just fine, even on hsw/bdw
+        * despite them not using the linear offset anymore.
+        */
+       if (INTEL_GEN(dev_priv) >= 4 && fb->modifier == I915_FORMAT_MOD_X_TILED) {
+               u32 alignment = intel_surf_alignment(fb, 0);
+               int cpp = fb->format->cpp[0];
+
+               while ((src_x + src_w) * cpp > plane_state->color_plane[0].stride) {
+                       if (offset == 0) {
+                               drm_dbg_kms(&dev_priv->drm,
+                                           "Unable to find suitable display surface offset due to X-tiling\n");
+                               return -EINVAL;
+                       }
+
+                       offset = intel_plane_adjust_aligned_offset(&src_x, &src_y, plane_state, 0,
+                                                                  offset, offset - alignment);
+               }
+       }
+
        /*
         * Put the final coordinates back so that the src
         * coordinate checks will see the right values.