drm/stm: ltdc: add a 2nd endpoint

ltdc can have up to 2 endpoints:
 - dpi external gpios: for rgb panels or external bridge ICs.
 - dpi internal ios: connected internally to dsi.

Note: Refer to the reference manual to know if the dsi is
present on your device.
Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1509018489-19641-3-git-send-email-philippe.cornu@st.com

drivers/gpu/drm/stm/ltdc.c

@@ -33,6 +33,8 @@
 
 #define MAX_IRQ 4
 
+#define MAX_ENDPOINTS 2
+
 #define HWVER_10200 0x010200
 #define HWVER_10300 0x010300
 #define HWVER_20101 0x020101
@@ -856,18 +858,33 @@ 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;
-	struct drm_panel *panel;
+	struct drm_bridge *bridge[MAX_ENDPOINTS] = {NULL};
+	struct drm_panel *panel[MAX_ENDPOINTS] = {NULL};
 	struct drm_crtc *crtc;
 	struct reset_control *rstc;
 	struct resource *res;
-	int irq, ret, i;
+	int irq, ret, i, endpoint_not_ready = -ENODEV;
 
 	DRM_DEBUG_DRIVER("\n");
 
-	ret = drm_of_find_panel_or_bridge(np, 0, 0, &panel, &bridge);
-	if (ret)
-		return ret;
+	/* 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 ready, continue probing,
+		 * else if at least one endpoint is -EPROBE_DEFER and
+		 * there is no previous ready endpoints, defer probing.
+		 */
+		if (!ret)
+			endpoint_not_ready = 0;
+		else if (ret == -EPROBE_DEFER && endpoint_not_ready)
+			endpoint_not_ready = -EPROBE_DEFER;
+	}
+
+	if (endpoint_not_ready)
+		return endpoint_not_ready;
 
 	rstc = devm_reset_control_get_exclusive(dev, NULL);
 
@@ -928,19 +945,25 @@ int ltdc_load(struct drm_device *ddev)
 
 	DRM_INFO("ltdc hw version 0x%08x - ready\n", ldev->caps.hw_version);
 
-	if (panel) {
-		bridge = drm_panel_bridge_add(panel, DRM_MODE_CONNECTOR_DPI);
-		if (IS_ERR(bridge)) {
-			DRM_ERROR("Failed to create panel-bridge\n");
-			ret = PTR_ERR(bridge);
-			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(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;
+			}
 		}
-	}
 
-	ret = ltdc_encoder_init(ddev, bridge);
-	if (ret) {
-		DRM_ERROR("Failed to init encoder\n");
-		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);
@@ -968,7 +991,8 @@ int ltdc_load(struct drm_device *ddev)
 	return 0;
 
 err:
-	drm_panel_bridge_remove(bridge);
+	for (i = 0; i < MAX_ENDPOINTS; i++)
+		drm_panel_bridge_remove(bridge[i]);
 
 	clk_disable_unprepare(ldev->pixel_clk);
 
@@ -978,10 +1002,12 @@ int ltdc_load(struct drm_device *ddev)
 void ltdc_unload(struct drm_device *ddev)
 {
 	struct ltdc_device *ldev = ddev->dev_private;
+	int i;
 
 	DRM_DEBUG_DRIVER("\n");
 
-	drm_of_panel_bridge_remove(ddev->dev->of_node, 0, 0);
+	for (i = 0; i < MAX_ENDPOINTS; i++)
+		drm_of_panel_bridge_remove(ddev->dev->of_node, 0, i);
 
 	clk_disable_unprepare(ldev->pixel_clk);
 }