drm/amd/display: add cursor FB size check

This patch expands the cursor checks added in "drm/amd/display: add basic
atomic check for cursor plane" to also include a FB size check. Without
this patch, setting a FB smaller than max_cursor_size with an invalid
width would result in amdgpu error messages and a fallback to a 64-byte
width:

    [drm:hubp1_cursor_set_attributes [amdgpu]] *ERROR* Invalid cursor pitch of 100. Only 64/128/256 is supported on DCN.

Note that DC uses the word "pitch" when actually checking the FB width.
Indeed, the function handle_cursor_update does this:

    attributes.pitch = attributes.width;

In my tests, the cursor FB actually had a pitch of 512 bytes.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Simon Ser <contact@emersion.fr>
Reported-by: Pierre-Loup A. Griffais <pgriffais@valvesoftware.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Harry Wentland <hwentlan@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -8982,6 +8982,28 @@ static int dm_update_plane_state(struct dc *dc,
 			return -EINVAL;
 		}
 
+		if (new_plane_state->fb) {
+			if (new_plane_state->fb->width > new_acrtc->max_cursor_width ||
+			    new_plane_state->fb->height > new_acrtc->max_cursor_height) {
+				DRM_DEBUG_ATOMIC("Bad cursor FB size %dx%d\n",
+						 new_plane_state->fb->width,
+						 new_plane_state->fb->height);
+				return -EINVAL;
+			}
+
+			switch (new_plane_state->fb->width) {
+			case 64:
+			case 128:
+			case 256:
+				/* FB width is supported by cursor plane */
+				break;
+			default:
+				DRM_DEBUG_ATOMIC("Bad cursor FB width %d\n",
+						 new_plane_state->fb->width);
+				return -EINVAL;
+			}
+		}
+
 		return 0;
 	}