drm: bpp and depth changes require full mode sets

To properly drive a framebuffer with a new depth or bpp, dither settings
and link bandwidth calculations may change, so make sure we go through a
full mode set in that case.

Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Keith Packard <keithp@keithp.com>

drivers/gpu/drm/drm_crtc_helper.c

@@ -560,6 +560,11 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
 			mode_changed = true;
 		} else if (set->fb == NULL) {
 			mode_changed = true;
+		} else if (set->fb->depth != set->crtc->fb->depth) {
+			mode_changed = true;
+		} else if (set->fb->bits_per_pixel !=
+			   set->crtc->fb->bits_per_pixel) {
+			mode_changed = true;
 		} else
 			fb_changed = true;
 	}