[PATCH] drm/bridge: stm_lvds: Do not fail atomic_check on disabled connector

[Marek Vasut <marex@nabladev.com>]

If the connector is disabled, the new connector state has .crtc field
set to NULL and there is nothing more to validate after that point.
The .crtc field being NULL is not an error. Test for .crtc being NULL,
and if it is NULL, exit early with return 0.

This fixes a failure in suspend/resume path, where the connector is
already disabled, but .atomic_check is called, fails, returns -EINVAL
and blocks the suspend entry.

Fixes: aca1cbc1c986 ("drm/stm: lvds: add new STM32 LVDS Display Interface Transmitter driver")
Signed-off-by: Marek Vasut <marex@nabladev.com>
---
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Philippe Cornu <philippe.cornu@foss.st.com>
Cc: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Yannick Fertre <yannick.fertre@foss.st.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com
---
 drivers/gpu/drm/stm/lvds.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/stm/lvds.c b/drivers/gpu/drm/stm/lvds.c
index fe38c0984b2b5..25e2ba98f36ae 100644
--- a/drivers/gpu/drm/stm/lvds.c
+++ b/drivers/gpu/drm/stm/lvds.c
@@ -897,14 +897,14 @@ static int lvds_connector_atomic_check(struct drm_connector *connector,
 	if (!conn_state)
 		return -EINVAL;
 
+	if (!conn_state->crtc)
+		return 0;
+
 	if (list_empty(&connector->modes)) {
 		drm_dbg(connector->dev, "connector: empty modes list\n");
 		return -EINVAL;
 	}
 
-	if (!conn_state->crtc)
-		return -EINVAL;
-
 	panel_mode = list_first_entry(&connector->modes,
 				      struct drm_display_mode, head);
 
-- 
2.53.0