drm/mediatek: dpi/dsi: Fix possible_crtcs calculation

mtk_find_possible_crtcs() assumes that the main path will always have
the CRTC with id 0, the ext id 1 and the third id 2. This is only true
if the paths are all available. But paths are optional (see also
comment in mtk_drm_kms_init()), e.g. the main path might not be enabled
or available at all. Then the CRTC IDs will shift one up, e.g. ext will
be 0 and the third path will be 1.

To fix that, dynamically calculate the IDs by the presence of the paths.

While at it, make the return code a signed one and return -ENODEV if no
path is found and handle the error in the callers.

Fixes: 5aa8e76476 ("drm/mediatek: dpi/dsi: Change the getting possible_crtc way")
Suggested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Signed-off-by: Michael Walle <mwalle@kernel.org>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240606092122.2026313-1-mwalle@kernel.org/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

drivers/gpu/drm/mediatek/mtk_ddp_comp.c

@@ -514,29 +514,42 @@ static bool mtk_ddp_comp_find(struct device *dev,
 	return false;
 }
 
-static unsigned int mtk_ddp_comp_find_in_route(struct device *dev,
-					       const struct mtk_drm_route *routes,
-					       unsigned int num_routes,
-					       struct mtk_ddp_comp *ddp_comp)
+static int mtk_ddp_comp_find_in_route(struct device *dev,
+				      const struct mtk_drm_route *routes,
+				      unsigned int num_routes,
+				      struct mtk_ddp_comp *ddp_comp)
 {
-	int ret;
 	unsigned int i;
 
-	if (!routes) {
-		ret = -EINVAL;
-		goto err;
-	}
+	if (!routes)
+		return -EINVAL;
 
 	for (i = 0; i < num_routes; i++)
 		if (dev == ddp_comp[routes[i].route_ddp].dev)
 			return BIT(routes[i].crtc_id);
 
-	ret = -ENODEV;
-err:
+	return -ENODEV;
+}
 
-	DRM_INFO("Failed to find comp in ddp table, ret = %d\n", ret);
+static bool mtk_ddp_path_available(const unsigned int *path,
+				   unsigned int path_len,
+				   struct device_node **comp_node)
+{
+	unsigned int i;
 
-	return 0;
+	if (!path || !path_len)
+		return false;
+
+	for (i = 0U; i < path_len; i++) {
+		/* OVL_ADAPTOR doesn't have a device node */
+		if (path[i] == DDP_COMPONENT_DRM_OVL_ADAPTOR)
+			continue;
+
+		if (!comp_node[path[i]])
+			return false;
+	}
+
+	return true;
 }
 
 int mtk_ddp_comp_get_id(struct device_node *node,
@@ -554,31 +567,53 @@ int mtk_ddp_comp_get_id(struct device_node *node,
 	return -EINVAL;
 }
 
-unsigned int mtk_find_possible_crtcs(struct drm_device *drm, struct device *dev)
+int mtk_find_possible_crtcs(struct drm_device *drm, struct device *dev)
 {
 	struct mtk_drm_private *private = drm->dev_private;
-	unsigned int ret = 0;
+	const struct mtk_mmsys_driver_data *data;
+	struct mtk_drm_private *priv_n;
+	int i = 0, j;
+	int ret;
 
-	if (mtk_ddp_comp_find(dev,
-			      private->data->main_path,
-			      private->data->main_len,
-			      private->ddp_comp))
-		ret = BIT(0);
-	else if (mtk_ddp_comp_find(dev,
-				   private->data->ext_path,
-				   private->data->ext_len,
-				   private->ddp_comp))
-		ret = BIT(1);
-	else if (mtk_ddp_comp_find(dev,
-				   private->data->third_path,
-				   private->data->third_len,
-				   private->ddp_comp))
-		ret = BIT(2);
-	else
-		ret = mtk_ddp_comp_find_in_route(dev,
-						 private->data->conn_routes,
-						 private->data->num_conn_routes,
-						 private->ddp_comp);
+	for (j = 0; j < private->data->mmsys_dev_num; j++) {
+		priv_n = private->all_drm_private[j];
+		data = priv_n->data;
+
+		if (mtk_ddp_path_available(data->main_path, data->main_len,
+					   priv_n->comp_node)) {
+			if (mtk_ddp_comp_find(dev, data->main_path,
+					      data->main_len,
+					      priv_n->ddp_comp))
+				return BIT(i);
+			i++;
+		}
+
+		if (mtk_ddp_path_available(data->ext_path, data->ext_len,
+					   priv_n->comp_node)) {
+			if (mtk_ddp_comp_find(dev, data->ext_path,
+					      data->ext_len,
+					      priv_n->ddp_comp))
+				return BIT(i);
+			i++;
+		}
+
+		if (mtk_ddp_path_available(data->third_path, data->third_len,
+					   priv_n->comp_node)) {
+			if (mtk_ddp_comp_find(dev, data->third_path,
+					      data->third_len,
+					      priv_n->ddp_comp))
+				return BIT(i);
+			i++;
+		}
+	}
+
+	ret = mtk_ddp_comp_find_in_route(dev,
+					 private->data->conn_routes,
+					 private->data->num_conn_routes,
+					 private->ddp_comp);
+
+	if (ret < 0)
+		DRM_INFO("Failed to find comp in ddp table, ret = %d\n", ret);
 
 	return ret;
 }

drivers/gpu/drm/mediatek/mtk_ddp_comp.h

@@ -330,7 +330,7 @@ static inline void mtk_ddp_comp_encoder_index_set(struct mtk_ddp_comp *comp)
 
 int mtk_ddp_comp_get_id(struct device_node *node,
 			enum mtk_ddp_comp_type comp_type);
-unsigned int mtk_find_possible_crtcs(struct drm_device *drm, struct device *dev);
+int mtk_find_possible_crtcs(struct drm_device *drm, struct device *dev);
 int mtk_ddp_comp_init(struct device_node *comp_node, struct mtk_ddp_comp *comp,
 		      unsigned int comp_id);
 enum mtk_ddp_comp_type mtk_ddp_comp_get_type(unsigned int comp_id);

drivers/gpu/drm/mediatek/mtk_dpi.c

@@ -805,7 +805,10 @@ static int mtk_dpi_bind(struct device *dev, struct device *master, void *data)
 		return ret;
 	}
 
-	dpi->encoder.possible_crtcs = mtk_find_possible_crtcs(drm_dev, dpi->dev);
+	ret = mtk_find_possible_crtcs(drm_dev, dpi->dev);
+	if (ret < 0)
+		goto err_cleanup;
+	dpi->encoder.possible_crtcs = ret;
 
 	ret = drm_bridge_attach(&dpi->encoder, &dpi->bridge, NULL,
 				DRM_BRIDGE_ATTACH_NO_CONNECTOR);

drivers/gpu/drm/mediatek/mtk_dsi.c

@@ -837,7 +837,10 @@ static int mtk_dsi_encoder_init(struct drm_device *drm, struct mtk_dsi *dsi)
 		return ret;
 	}
 
-	dsi->encoder.possible_crtcs = mtk_find_possible_crtcs(drm, dsi->host.dev);
+	ret = mtk_find_possible_crtcs(drm, dsi->host.dev);
+	if (ret < 0)
+		goto err_cleanup_encoder;
+	dsi->encoder.possible_crtcs = ret;
 
 	ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL,
 				DRM_BRIDGE_ATTACH_NO_CONNECTOR);