drm/bridge: analogix_dp: Ensure the panel is properly prepared/unprepared

Instead of just preparing the panel on bind, actually prepare/unprepare
during modeset/disable. The panel must be prepared in order to read hpd
status and edid, so we need to keep state around the prepares in order
to ensure we don't accidentally turn the panel off at the wrong time.

Reviewed-by: Yakir Yang <ykk@rock-chips.com>
Tested-by: Yakir Yang <ykk@rock-chips.com>
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>

drivers/gpu/drm/bridge/analogix/analogix_dp_core.c

@@ -923,11 +923,63 @@ static void analogix_dp_commit(struct analogix_dp_device *dp)
 	analogix_dp_start_video(dp);
 }
 
+/*
+ * This function is a bit of a catch-all for panel preparation, hopefully
+ * simplifying the logic of functions that need to prepare/unprepare the panel
+ * below.
+ *
+ * If @prepare is true, this function will prepare the panel. Conversely, if it
+ * is false, the panel will be unprepared.
+ *
+ * If @is_modeset_prepare is true, the function will disregard the current state
+ * of the panel and either prepare/unprepare the panel based on @prepare. Once
+ * it finishes, it will update dp->panel_is_modeset to reflect the current state
+ * of the panel.
+ */
+static int analogix_dp_prepare_panel(struct analogix_dp_device *dp,
+				     bool prepare, bool is_modeset_prepare)
+{
+	int ret = 0;
+
+	if (!dp->plat_data->panel)
+		return 0;
+
+	mutex_lock(&dp->panel_lock);
+
+	/*
+	 * Exit early if this is a temporary prepare/unprepare and we're already
+	 * modeset (since we neither want to prepare twice or unprepare early).
+	 */
+	if (dp->panel_is_modeset && !is_modeset_prepare)
+		goto out;
+
+	if (prepare)
+		ret = drm_panel_prepare(dp->plat_data->panel);
+	else
+		ret = drm_panel_unprepare(dp->plat_data->panel);
+
+	if (ret)
+		goto out;
+
+	if (is_modeset_prepare)
+		dp->panel_is_modeset = prepare;
+
+out:
+	mutex_unlock(&dp->panel_lock);
+	return ret;
+}
+
 int analogix_dp_get_modes(struct drm_connector *connector)
 {
 	struct analogix_dp_device *dp = to_dp(connector);
 	struct edid *edid = (struct edid *)dp->edid;
-	int num_modes = 0;
+	int ret, num_modes = 0;
+
+	ret = analogix_dp_prepare_panel(dp, true, false);
+	if (ret) {
+		DRM_ERROR("Failed to prepare panel (%d)\n", ret);
+		return 0;
+	}
 
 	if (analogix_dp_handle_edid(dp) == 0) {
 		drm_mode_connector_update_edid_property(&dp->connector, edid);
@@ -940,6 +992,10 @@ int analogix_dp_get_modes(struct drm_connector *connector)
 	if (dp->plat_data->get_modes)
 		num_modes += dp->plat_data->get_modes(dp->plat_data, connector);
 
+	ret = analogix_dp_prepare_panel(dp, false, false);
+	if (ret)
+		DRM_ERROR("Failed to unprepare panel (%d)\n", ret);
+
 	return num_modes;
 }
 
@@ -960,11 +1016,23 @@ enum drm_connector_status
 analogix_dp_detect(struct drm_connector *connector, bool force)
 {
 	struct analogix_dp_device *dp = to_dp(connector);
+	enum drm_connector_status status = connector_status_disconnected;
+	int ret;
 
-	if (analogix_dp_detect_hpd(dp))
+	ret = analogix_dp_prepare_panel(dp, true, false);
+	if (ret) {
+		DRM_ERROR("Failed to prepare panel (%d)\n", ret);
 		return connector_status_disconnected;
+	}
 
-	return connector_status_connected;
+	if (!analogix_dp_detect_hpd(dp))
+		status = connector_status_connected;
+
+	ret = analogix_dp_prepare_panel(dp, false, false);
+	if (ret)
+		DRM_ERROR("Failed to unprepare panel (%d)\n", ret);
+
+	return status;
 }
 
 static void analogix_dp_connector_destroy(struct drm_connector *connector)
@@ -1035,6 +1103,16 @@ static int analogix_dp_bridge_attach(struct drm_bridge *bridge)
 	return 0;
 }
 
+static void analogix_dp_bridge_pre_enable(struct drm_bridge *bridge)
+{
+	struct analogix_dp_device *dp = bridge->driver_private;
+	int ret;
+
+	ret = analogix_dp_prepare_panel(dp, true, true);
+	if (ret)
+		DRM_ERROR("failed to setup the panel ret = %d\n", ret);
+}
+
 static void analogix_dp_bridge_enable(struct drm_bridge *bridge)
 {
 	struct analogix_dp_device *dp = bridge->driver_private;
@@ -1058,6 +1136,7 @@ static void analogix_dp_bridge_enable(struct drm_bridge *bridge)
 static void analogix_dp_bridge_disable(struct drm_bridge *bridge)
 {
 	struct analogix_dp_device *dp = bridge->driver_private;
+	int ret;
 
 	if (dp->dpms_mode != DRM_MODE_DPMS_ON)
 		return;
@@ -1077,6 +1156,10 @@ static void analogix_dp_bridge_disable(struct drm_bridge *bridge)
 
 	pm_runtime_put_sync(dp->dev);
 
+	ret = analogix_dp_prepare_panel(dp, false, true);
+	if (ret)
+		DRM_ERROR("failed to setup the panel ret = %d\n", ret);
+
 	dp->dpms_mode = DRM_MODE_DPMS_OFF;
 }
 
@@ -1165,9 +1248,9 @@ static void analogix_dp_bridge_nop(struct drm_bridge *bridge)
 }
 
 static const struct drm_bridge_funcs analogix_dp_bridge_funcs = {
+	.pre_enable = analogix_dp_bridge_pre_enable,
 	.enable = analogix_dp_bridge_enable,
 	.disable = analogix_dp_bridge_disable,
-	.pre_enable = analogix_dp_bridge_nop,
 	.post_disable = analogix_dp_bridge_nop,
 	.mode_set = analogix_dp_bridge_mode_set,
 	.attach = analogix_dp_bridge_attach,
@@ -1254,6 +1337,9 @@ int analogix_dp_bind(struct device *dev, struct drm_device *drm_dev,
 	dp->dev = &pdev->dev;
 	dp->dpms_mode = DRM_MODE_DPMS_OFF;
 
+	mutex_init(&dp->panel_lock);
+	dp->panel_is_modeset = false;
+
 	/*
 	 * platform dp driver need containor_of the plat_data to get
 	 * the driver private data, so we need to store the point of
@@ -1333,13 +1419,6 @@ int analogix_dp_bind(struct device *dev, struct drm_device *drm_dev,
 
 	phy_power_on(dp->phy);
 
-	if (dp->plat_data->panel) {
-		if (drm_panel_prepare(dp->plat_data->panel)) {
-			DRM_ERROR("failed to setup the panel\n");
-			return -EBUSY;
-		}
-	}
-
 	analogix_dp_init_dp(dp);
 
 	ret = devm_request_threaded_irq(&pdev->dev, dp->irq,

drivers/gpu/drm/bridge/analogix/analogix_dp_core.h

@@ -178,6 +178,9 @@ struct analogix_dp_device {
 	bool                    force_hpd;
 	unsigned char           edid[EDID_BLOCK_LENGTH * 2];
 
+	struct mutex		panel_lock;
+	bool			panel_is_modeset;
+
 	struct analogix_dp_plat_data *plat_data;
 };