drm/rockchip: analogix_dp: Do not call Analogix code before bind

Driver callbacks, such as system suspend or resume can be called any
time, specifically they can be called before the component bind
callback. Let's use dp->adp pointer as a safeguard and skip calling
Analogix entry points if it is an ERR_PTR().

Signed-off-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180423105003.9004-24-enric.balletbo@collabora.com

drivers/gpu/drm/rockchip/analogix_dp-rockchip.c

@@ -368,6 +368,8 @@ static void rockchip_dp_unbind(struct device *dev, struct device *master,
 	analogix_dp_unbind(dp->adp);
 	rockchip_drm_psr_unregister(&dp->encoder);
 	dp->encoder.funcs->destroy(&dp->encoder);
+
+	dp->adp = ERR_PTR(-ENODEV);
 }
 
 static const struct component_ops rockchip_dp_component_ops = {
@@ -391,6 +393,7 @@ static int rockchip_dp_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	dp->dev = dev;
+	dp->adp = ERR_PTR(-ENODEV);
 	dp->plat_data.panel = panel;
 
 	ret = rockchip_dp_of_probe(dp);
@@ -414,6 +417,9 @@ static int rockchip_dp_suspend(struct device *dev)
 {
 	struct rockchip_dp_device *dp = dev_get_drvdata(dev);
 
+	if (IS_ERR(dp->adp))
+		return 0;
+
 	return analogix_dp_suspend(dp->adp);
 }
 
@@ -421,6 +427,9 @@ static int rockchip_dp_resume(struct device *dev)
 {
 	struct rockchip_dp_device *dp = dev_get_drvdata(dev);
 
+	if (IS_ERR(dp->adp))
+		return 0;
+
 	return analogix_dp_resume(dp->adp);
 }
 #endif