drm/i915: Fix ADL+ tiled plane stride when the POT stride is smaller …

…than the original

plane_view_scanout_stride() currently assumes that we had to pad the
mapping stride with dummy pages in order to align it. But that is not
the case if the original fb stride exceeds the aligned stride used
to populate the remapped view, which is calculated from the user
specified framebuffer width rather than the user specified framebuffer
stride.

Ignore the original fb stride in this case and just stick to the POT
aligned stride. Getting this wrong will cause the plane to fetch the
wrong data, and can lead to fault errors if the page tables at the
bogus location aren't even populated.

TODO: figure out if this is OK for CCS, or if we should instead increase
the width of the view to cover the entire user specified fb stride
instead...

Cc: Imre Deak <[email protected]>
Cc: Juha-Pekka Heikkila <[email protected]>
Signed-off-by: Ville Syrjälä <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Reviewed-by: Imre Deak <[email protected]>
Reviewed-by: Juha-Pekka Heikkila <[email protected]>
(cherry picked from commit 01a39f1)
Cc: [email protected]
Signed-off-by: Jani Nikula <[email protected]>

drivers/gpu/drm/i915/display/intel_fb.c

@@ -1374,7 +1374,8 @@ plane_view_scanout_stride(const struct intel_framebuffer *fb, int color_plane,
 	struct drm_i915_private *i915 = to_i915(fb->base.dev);
 	unsigned int stride_tiles;
 
-	if (IS_ALDERLAKE_P(i915) || DISPLAY_VER(i915) >= 14)
+	if ((IS_ALDERLAKE_P(i915) || DISPLAY_VER(i915) >= 14) &&
+	    src_stride_tiles < dst_stride_tiles)
 		stride_tiles = src_stride_tiles;
 	else
 		stride_tiles = dst_stride_tiles;