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 <imre.deak@intel.com>
Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231204202443.31247-1-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>

diff --git a/drivers/gpu/drm/i915/display/intel_fb.c b/drivers/gpu/drm/i915/display/intel_fb.c
index 96663f9ac431d9bd86259850b0fb2401f05abd82..32a7ee1c5b343cc9d4110f7a2dd03b3844f0e0d7 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_fb.c
+++ b/drivers/gpu/drm/i915/display/intel_fb.c
@@ -1381,7 +1381,8 @@ 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;