From 603ba2dfb338b307aebe95fe344c479a59b3a175 Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon@bootlin.com>
Date: Tue, 24 Jul 2018 15:32:15 +0200
Subject: [PATCH] drm/atomic: Check old_plane_state->crtc in drm_atomic_helper_async_check()
Git-commit: 603ba2dfb338b307aebe95fe344c479a59b3a175
Patch-mainline: v4.18-rc8
References: bsc#1051510

Async plane update is supposed to work only when updating the FB or FB
position of an already enabled plane. That does not apply to requests
where the plane was previously disabled or assigned to a different
CTRC.

Check old_plane_state->crtc value to make sure async plane update is
allowed.

Fixes: fef9df8b5945 ("drm/atomic: initial support for asynchronous plane update")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20180724133215.31917-1-boris.brezillon@bootlin.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/drm_atomic_helper.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1527,7 +1527,8 @@ int drm_atomic_helper_async_check(struct
 	if (n_planes != 1)
 		return -EINVAL;
 
-	if (!new_plane_state->crtc)
+	if (!new_plane_state->crtc ||
+	    old_plane_state->crtc != new_plane_state->crtc)
 		return -EINVAL;
 
 	funcs = plane->helper_private;