rockchip_drm_sys_suspend/resume() obains a struct drm_device pointer
from drvdata, the pointer is then dereferenced to obtain private data.
drvdata is set when a display is bound, on systems without a
(successfully probed) display drvdata is NULL and the PM functions
try to dereference a NULL pointer.

The suspend/resume code relies on a valid drm_device object, skip it if
the pointer is NULL.

Signed-off-by: Matthias Kaehlcke <m...@chromium.org>
---
 drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c 
b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index c6b1b7f3a2a3..6228145d9496 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -275,11 +275,16 @@ static void rockchip_drm_fb_resume(struct drm_device *drm)
 static int rockchip_drm_sys_suspend(struct device *dev)
 {
        struct drm_device *drm = dev_get_drvdata(dev);
-       struct rockchip_drm_private *priv = drm->dev_private;
+       struct rockchip_drm_private *priv;
+
+       if (!drm)
+               /* no display attached */
+               return 0;
 
        drm_kms_helper_poll_disable(drm);
        rockchip_drm_fb_suspend(drm);
 
+       priv = drm->dev_private;
        priv->state = drm_atomic_helper_suspend(drm);
        if (IS_ERR(priv->state)) {
                rockchip_drm_fb_resume(drm);
@@ -293,8 +298,13 @@ static int rockchip_drm_sys_suspend(struct device *dev)
 static int rockchip_drm_sys_resume(struct device *dev)
 {
        struct drm_device *drm = dev_get_drvdata(dev);
-       struct rockchip_drm_private *priv = drm->dev_private;
+       struct rockchip_drm_private *priv;
+
+       if (!drm)
+               /* no display attached */
+               return 0;
 
+       priv = drm->dev_private;
        drm_atomic_helper_resume(drm, priv->state);
        rockchip_drm_fb_resume(drm);
        drm_kms_helper_poll_enable(drm);
-- 
2.14.0.434.g98096fd7a8-goog

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