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>

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index 2db5092..887f3ca 100644 (file)
--- 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;