drm/mediatek: Implement OF graphs support for display paths

It is impossible to add each and every possible DDP path combination
for each and every possible combination of SoC and board: right now,
this driver hardcodes configuration for 10 SoCs and this is going to
grow larger and larger, and with new hacks like the introduction of
mtk_drm_route which is anyway not enough for all final routes as the
DSI cannot be connected to MERGE if it's not a dual-DSI, or enabling
DSC preventively doesn't work if the display doesn't support it, or
others.

Since practically all display IPs in MediaTek SoCs support being
interconnected with different instances of other, or the same, IPs
or with different IPs and in different combinations, the final DDP
pipeline is effectively a board specific configuration.

Implement OF graphs support to the mediatek-drm drivers, allowing to
stop hardcoding the paths, and preventing this driver to get a huge
amount of arrays for each board and SoC combination, also paving the
way to share the same mtk_mmsys_driver_data between multiple SoCs,
making it more straightforward to add support for new chips.

Note that the OVL_ADAPTOR software component driver needs relatively
big changes in order to fully support OF Graphs (and more SoCs anyway)
and such changes will come at a later time.
As of now, the mtk_disp_ovl_adaptor driver takes the MERGE components
(for example, on mt8195, merge 1 to 4) dynamically so, even though
later updates to the ovl-adaptor driver will *not* require bindings
changes, the merge1-4 will be temporarily omitted in the graph for the
MT8195 SoC.

This means that an example graph for this SoC looks like:

mdp_rdma (0 ~ 7) -> padding (0 ~ 7) -> ethdr -> merge5

and the resulting path in this driver will be `ovl_adaptor -> merge5`

Later updates to the ovl adaptor will expand it to support more SoCs
and, in turn, to also fully support graphs.

Reviewed-by: Alexandre Mergnat <[email protected]>
Tested-by: Alexandre Mergnat <[email protected]>
Acked-by: Sui Jingfeng <[email protected]>
Tested-by: Michael Walle <[email protected]> # on kontron-sbc-i1200
Reviewed-by: CK Hu <[email protected]>
Signed-off-by: AngeloGioacchino Del Regno <[email protected]>
Link: https://patchwork.kernel.org/project/dri-devel/patch/[email protected]/
Signed-off-by: Chun-Kuang Hu <[email protected]>

Author: AngeloGioacchino Del Regno

drivers/gpu/drm/mediatek/mtk_disp_drv.h

@@ -108,6 +108,7 @@ size_t mtk_ovl_get_num_formats(struct device *dev);
 
 void mtk_ovl_adaptor_add_comp(struct device *dev, struct mtk_mutex *mutex);
 void mtk_ovl_adaptor_remove_comp(struct device *dev, struct mtk_mutex *mutex);
+bool mtk_ovl_adaptor_is_comp_present(struct device_node *node);
 void mtk_ovl_adaptor_connect(struct device *dev, struct device *mmsys_dev,
 			     unsigned int next);
 void mtk_ovl_adaptor_disconnect(struct device *dev, struct device *mmsys_dev,

drivers/gpu/drm/mediatek/mtk_disp_ovl_adaptor.c

@@ -490,6 +490,41 @@ static int compare_of(struct device *dev, void *data)
 	return dev->of_node == data;
 }
 
+static int ovl_adaptor_of_get_ddp_comp_type(struct device_node *node,
+					    enum mtk_ovl_adaptor_comp_type *ctype)
+{
+	const struct of_device_id *of_id = of_match_node(mtk_ovl_adaptor_comp_dt_ids, node);
+
+	if (!of_id)
+		return -EINVAL;
+
+	*ctype = (enum mtk_ovl_adaptor_comp_type)((uintptr_t)of_id->data);
+
+	return 0;
+}
+
+bool mtk_ovl_adaptor_is_comp_present(struct device_node *node)
+{
+	enum mtk_ovl_adaptor_comp_type type;
+	int ret;
+
+	ret = ovl_adaptor_of_get_ddp_comp_type(node, &type);
+	if (ret)
+		return false;
+
+	if (type >= OVL_ADAPTOR_TYPE_NUM)
+		return false;
+
+	/*
+	 * In the context of mediatek-drm, ETHDR, MDP_RDMA and Padding are
+	 * used exclusively by OVL Adaptor: if this component is not one of
+	 * those, it's likely not an OVL Adaptor path.
+	 */
+	return type == OVL_ADAPTOR_TYPE_ETHDR ||
+	       type == OVL_ADAPTOR_TYPE_MDP_RDMA ||
+	       type == OVL_ADAPTOR_TYPE_PADDING;
+}
+
 static int ovl_adaptor_comp_init(struct device *dev, struct component_match **match)
 {
 	struct mtk_disp_ovl_adaptor *priv = dev_get_drvdata(dev);
@@ -499,12 +534,11 @@ static int ovl_adaptor_comp_init(struct device *dev, struct component_match **ma
 	parent = dev->parent->parent->of_node->parent;
 
 	for_each_child_of_node_scoped(parent, node) {
-		const struct of_device_id *of_id;
 		enum mtk_ovl_adaptor_comp_type type;
-		int id;
+		int id, ret;
 
-		of_id = of_match_node(mtk_ovl_adaptor_comp_dt_ids, node);
-		if (!of_id)
+		ret = ovl_adaptor_of_get_ddp_comp_type(node, &type);
+		if (ret)
 			continue;
 
 		if (!of_device_is_available(node)) {
@@ -513,7 +547,6 @@ static int ovl_adaptor_comp_init(struct device *dev, struct component_match **ma
 			continue;
 		}
 
-		type = (enum mtk_ovl_adaptor_comp_type)(uintptr_t)of_id->data;
 		id = ovl_adaptor_comp_get_id(dev, node, type);
 		if (id < 0) {
 			dev_warn(dev, "Skipping unknown component %pOF\n",

drivers/gpu/drm/mediatek/mtk_dpi.c

@@ -704,6 +704,20 @@ static int mtk_dpi_bridge_attach(struct drm_bridge *bridge,
 				 enum drm_bridge_attach_flags flags)
 {
 	struct mtk_dpi *dpi = bridge_to_dpi(bridge);
+	int ret;
+
+	dpi->next_bridge = devm_drm_of_get_bridge(dpi->dev, dpi->dev->of_node, 1, -1);
+	if (IS_ERR(dpi->next_bridge)) {
+		ret = PTR_ERR(dpi->next_bridge);
+		if (ret == -EPROBE_DEFER)
+			return ret;
+
+		/* Old devicetree has only one endpoint */
+		dpi->next_bridge = devm_drm_of_get_bridge(dpi->dev, dpi->dev->of_node, 0, 0);
+		if (IS_ERR(dpi->next_bridge))
+			return dev_err_probe(dpi->dev, PTR_ERR(dpi->next_bridge),
+					     "Failed to get bridge\n");
+	}
 
 	return drm_bridge_attach(bridge->encoder, dpi->next_bridge,
 				 &dpi->bridge, flags);
@@ -1058,13 +1072,6 @@ static int mtk_dpi_probe(struct platform_device *pdev)
 	if (dpi->irq < 0)
 		return dpi->irq;
 
-	dpi->next_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 0, 0);
-	if (IS_ERR(dpi->next_bridge))
-		return dev_err_probe(dev, PTR_ERR(dpi->next_bridge),
-				     "Failed to get bridge\n");
-
-	dev_info(dev, "Found bridge node: %pOF\n", dpi->next_bridge->of_node);
-
 	platform_set_drvdata(pdev, dpi);
 
 	dpi->bridge.funcs = &mtk_dpi_bridge_funcs;