drm/i915: check for supported depth at fb init time

This will catch bad fb configs earlier.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NKeith Packard <keithp@keithp.com>

drivers/gpu/drm/i915/intel_display.c

@@ -7061,6 +7061,11 @@ int intel_framebuffer_init(struct drm_device *dev,
 	switch (mode_cmd->bpp) {
 	case 8:
 	case 16:
+		/* Only pre-ILK can handle 5:5:5 */
+		if (mode_cmd->depth == 15 && !HAS_PCH_SPLIT(dev))
+			return -EINVAL;
+		break;
+
 	case 24:
 	case 32:
 		break;