drm/vc4: Make sure that planes aren't scaled.

We would scan out the memory around them if an upscale was attempted,
and would just scan out incorrectly for downscaling.

Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index 2db509210d62..887f3caad0be 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -157,6 +157,16 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
         int crtc_w = state->crtc_w;
         int crtc_h = state->crtc_h;
 
+        if (state->crtc_w << 16 != state->src_w ||
+            state->crtc_h << 16 != state->src_h) {
+                /* We don't support scaling yet, which involves
+                 * allocating the LBM memory for scaling temporary
+                 * storage, and putting filter kernels in the HVS
+                 * context.
+                 */
+                return -EINVAL;
+        }
+
         if (crtc_x < 0) {
                 offset += drm_format_plane_cpp(fb->pixel_format, 0) * -crtc_x;
                 crtc_w += crtc_x;