drm/stm: ltdc: check number of endpoints

Number of endpoints could exceed the fix value MAX_ENDPOINTS(2).
Instead of increase simply this value, the number of endpoint
could be read from device tree. Load sequence has been a little
rework to take care of several panel or bridge which can be
connected/disconnected or enable/disable.
Signed-off-by: Yannick Fertre <yannick.fertre@st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1582877258-1112-1-git-send-email-yannick.fertre@st.com

drivers/gpu/drm/stm/ltdc.c

@@ -42,8 +42,6 @@
 
 #define MAX_IRQ 4
 
-#define MAX_ENDPOINTS 2
-
 #define HWVER_10200 0x010200
 #define HWVER_10300 0x010300
 #define HWVER_20101 0x020101
@@ -1201,36 +1199,20 @@ int ltdc_load(struct drm_device *ddev)
 	struct ltdc_device *ldev = ddev->dev_private;
 	struct device *dev = ddev->dev;
 	struct device_node *np = dev->of_node;
-	struct drm_bridge *bridge[MAX_ENDPOINTS] = {NULL};
-	struct drm_panel *panel[MAX_ENDPOINTS] = {NULL};
+	struct drm_bridge *bridge;
+	struct drm_panel *panel;
 	struct drm_crtc *crtc;
 	struct reset_control *rstc;
 	struct resource *res;
-	int irq, ret, i, endpoint_not_ready = -ENODEV;
+	int irq, i, nb_endpoints;
+	int ret = -ENODEV;
 
 	DRM_DEBUG_DRIVER("\n");
 
-	/* Get endpoints if any */
-	for (i = 0; i < MAX_ENDPOINTS; i++) {
-		ret = drm_of_find_panel_or_bridge(np, 0, i, &panel[i],
-						  &bridge[i]);
-
-		/*
-		 * If at least one endpoint is -EPROBE_DEFER, defer probing,
-		 * else if at least one endpoint is ready, continue probing.
-		 */
-		if (ret == -EPROBE_DEFER)
-			return ret;
-		else if (!ret)
-			endpoint_not_ready = 0;
-	}
-
-	if (endpoint_not_ready)
-		return endpoint_not_ready;
-
-	rstc = devm_reset_control_get_exclusive(dev, NULL);
-
-	mutex_init(&ldev->err_lock);
+	/* Get number of endpoints */
+	nb_endpoints = of_graph_get_endpoint_count(np);
+	if (!nb_endpoints)
+		return -ENODEV;
 
 	ldev->pixel_clk = devm_clk_get(dev, "lcd");
 	if (IS_ERR(ldev->pixel_clk)) {
@@ -1244,6 +1226,43 @@ int ltdc_load(struct drm_device *ddev)
 		return -ENODEV;
 	}
 
+	/* Get endpoints if any */
+	for (i = 0; i < nb_endpoints; i++) {
+		ret = drm_of_find_panel_or_bridge(np, 0, i, &panel, &bridge);
+
+		/*
+		 * If at least one endpoint is -ENODEV, continue probing,
+		 * else if at least one endpoint returned an error
+		 * (ie -EPROBE_DEFER) then stop probing.
+		 */
+		if (ret == -ENODEV)
+			continue;
+		else if (ret)
+			goto err;
+
+		if (panel) {
+			bridge = drm_panel_bridge_add_typed(panel,
+							    DRM_MODE_CONNECTOR_DPI);
+			if (IS_ERR(bridge)) {
+				DRM_ERROR("panel-bridge endpoint %d\n", i);
+				ret = PTR_ERR(bridge);
+				goto err;
+			}
+		}
+
+		if (bridge) {
+			ret = ltdc_encoder_init(ddev, bridge);
+			if (ret) {
+				DRM_ERROR("init encoder endpoint %d\n", i);
+				goto err;
+			}
+		}
+	}
+
+	rstc = devm_reset_control_get_exclusive(dev, NULL);
+
+	mutex_init(&ldev->err_lock);
+
 	if (!IS_ERR(rstc)) {
 		reset_control_assert(rstc);
 		usleep_range(10, 20);
@@ -1285,27 +1304,7 @@ int ltdc_load(struct drm_device *ddev)
 			DRM_ERROR("Failed to register LTDC interrupt\n");
 			goto err;
 		}
-	}
-
-	/* Add endpoints panels or bridges if any */
-	for (i = 0; i < MAX_ENDPOINTS; i++) {
-		if (panel[i]) {
-			bridge[i] = drm_panel_bridge_add_typed(panel[i],
-							       DRM_MODE_CONNECTOR_DPI);
-			if (IS_ERR(bridge[i])) {
-				DRM_ERROR("panel-bridge endpoint %d\n", i);
-				ret = PTR_ERR(bridge[i]);
-				goto err;
-			}
-		}
 
-		if (bridge[i]) {
-			ret = ltdc_encoder_init(ddev, bridge[i]);
-			if (ret) {
-				DRM_ERROR("init encoder endpoint %d\n", i);
-				goto err;
-			}
-		}
 	}
 
 	crtc = devm_kzalloc(dev, sizeof(*crtc), GFP_KERNEL);
@@ -1340,8 +1339,8 @@ int ltdc_load(struct drm_device *ddev)
 
 	return 0;
 err:
-	for (i = 0; i < MAX_ENDPOINTS; i++)
-		drm_panel_bridge_remove(bridge[i]);
+	for (i = 0; i < nb_endpoints; i++)
+		drm_of_panel_bridge_remove(ddev->dev->of_node, 0, i);
 
 	clk_disable_unprepare(ldev->pixel_clk);
 
@@ -1350,11 +1349,14 @@ int ltdc_load(struct drm_device *ddev)
 
 void ltdc_unload(struct drm_device *ddev)
 {
-	int i;
+	struct device *dev = ddev->dev;
+	int nb_endpoints, i;
 
 	DRM_DEBUG_DRIVER("\n");
 
-	for (i = 0; i < MAX_ENDPOINTS; i++)
+	nb_endpoints = of_graph_get_endpoint_count(dev->of_node);
+
+	for (i = 0; i < nb_endpoints; i++)
 		drm_of_panel_bridge_remove(ddev->dev->of_node, 0, i);
 
 	pm_runtime_disable(ddev->dev);