FAILED: patch "[PATCH] drm/atomic: Check old_plane_state->crtc in" failed to apply to 4.14-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>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()

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

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 130da5195f3b..ff858b890045 100644
--- 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 drm_device *dev,
 	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;