[PATCH v2 18/21] drm/bridge: lvds-encoder: Implement basic bus format negotiation

[Boris Brezillon]

Some LVDS encoder might support several input/output bus formats. Add
a way to describe the one used on a specific design by adding optional
'data-mapping' properties to the input/output ports.

Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
---
Changes in v2:
* Make the bus-format negotiation logic more generic
---
 .../display/bridge/lvds-transmitter.txt       |  12 ++
 drivers/gpu/drm/bridge/lvds-encoder.c         | 105 ++++++++++++++++++
 2 files changed, 117 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt b/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt
index 60091db5dfa5..db51eab216f7 100644
--- a/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt
+++ b/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt
@@ -36,6 +36,18 @@ graph bindings specified in Documentation/devicetree/bindings/graph.txt.
 - Video port 0 for parallel input
 - Video port 1 for LVDS output
 
+Optional port 0 node properties:
+
+- data-mapping: can be one of the following values
+	"rgb-24"
+	"rgb-18"
+
+Optional port 0 node properties:
+
+- data-mapping: can be one of the following values
+	"jeida-18"
+	"jeida-24"
+	"vesa-24"
 
 Example
 -------
diff --git a/drivers/gpu/drm/bridge/lvds-encoder.c b/drivers/gpu/drm/bridge/lvds-encoder.c
index 2ab2c234f26c..38cad7a7d828 100644
--- a/drivers/gpu/drm/bridge/lvds-encoder.c
+++ b/drivers/gpu/drm/bridge/lvds-encoder.c
@@ -6,6 +6,7 @@
 #include <linux/gpio/consumer.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/of_graph.h>
 #include <linux/platform_device.h>
 
@@ -16,6 +17,8 @@ struct lvds_encoder {
 	struct drm_bridge bridge;
 	struct drm_bridge *panel_bridge;
 	struct gpio_desc *powerdown_gpio;
+	u32 output_fmt;
+	u32 input_fmt;
 };
 
 static int lvds_encoder_attach(struct drm_bridge *bridge)
@@ -48,12 +51,86 @@ static void lvds_encoder_disable(struct drm_bridge *bridge)
 		gpiod_set_value_cansleep(lvds_encoder->powerdown_gpio, 1);
 }
 
+static void lvds_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
+					   struct drm_bridge_state *bridge_state,
+					   struct drm_crtc_state *crtc_state,
+					   struct drm_connector_state *conn_state,
+					   u32 output_fmt,
+					   unsigned int *num_input_fmts,
+					   u32 *input_fmts)
+{
+	struct lvds_encoder *lvds_encoder = container_of(bridge,
+							 struct lvds_encoder,
+							 bridge);
+
+	if (output_fmt == MEDIA_BUS_FMT_FIXED ||
+	    output_fmt == lvds_encoder->output_fmt)
+		*num_input_fmts = 1;
+	else
+		*num_input_fmts = 0;
+
+	if (*num_input_fmts && input_fmts)
+		input_fmts[0] = lvds_encoder->input_fmt;
+}
+
+static int lvds_encoder_atomic_check(struct drm_bridge *bridge,
+				     struct drm_bridge_state *bridge_state,
+				     struct drm_crtc_state *crtc_state,
+				     struct drm_connector_state *conn_state)
+{
+	/* Propagate the bus_flags. */
+	bridge_state->input_bus_cfg.flags = bridge_state->output_bus_cfg.flags;
+	return 0;
+}
+
 static struct drm_bridge_funcs funcs = {
 	.attach = lvds_encoder_attach,
 	.enable = lvds_encoder_enable,
 	.disable = lvds_encoder_disable,
+	.atomic_get_input_bus_fmts = lvds_atomic_get_input_bus_fmts,
+	.atomic_check = lvds_encoder_atomic_check,
 };
 
+struct of_data_mapping {
+	const char *name;
+	u32 id;
+};
+
+static const struct of_data_mapping output_data_mappings[] = {
+	{ "jeida-18", MEDIA_BUS_FMT_RGB666_1X7X3_SPWG },
+	{ "jeida-24", MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA },
+	{ "vesa-24", MEDIA_BUS_FMT_RGB888_1X7X4_SPWG },
+};
+
+static const struct of_data_mapping input_data_mappings[] = {
+	{ "rgb-24", MEDIA_BUS_FMT_RGB888_1X24 },
+	{ "rgb-18", MEDIA_BUS_FMT_RGB666_1X18 },
+};
+
+static int of_get_data_mapping(struct device_node *port,
+			       const struct of_data_mapping *mappings,
+			       unsigned int num_mappings,
+			       u32 *fmt)
+{
+	const char *name = NULL;
+	unsigned int i;
+
+	of_property_read_string(port, "data-mapping", &name);
+	if (!name) {
+		*fmt = MEDIA_BUS_FMT_FIXED;
+		return 0;
+	}
+
+	for (i = 0; i < num_mappings; i++) {
+		if (!strcmp(mappings[i].name, name)) {
+			*fmt = mappings[i].id;
+			return 0;
+		}
+	}
+
+	return -ENOTSUPP;
+}
+
 static int lvds_encoder_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -62,11 +139,15 @@ static int lvds_encoder_probe(struct platform_device *pdev)
 	struct device_node *panel_node;
 	struct drm_panel *panel;
 	struct lvds_encoder *lvds_encoder;
+	int ret;
 
 	lvds_encoder = devm_kzalloc(dev, sizeof(*lvds_encoder), GFP_KERNEL);
 	if (!lvds_encoder)
 		return -ENOMEM;
 
+	lvds_encoder->input_fmt = MEDIA_BUS_FMT_FIXED;
+	lvds_encoder->output_fmt = MEDIA_BUS_FMT_FIXED;
+
 	lvds_encoder->powerdown_gpio = devm_gpiod_get_optional(dev, "powerdown",
 							       GPIOD_OUT_HIGH);
 	if (IS_ERR(lvds_encoder->powerdown_gpio)) {
@@ -77,6 +158,21 @@ static int lvds_encoder_probe(struct platform_device *pdev)
 		return err;
 	}
 
+	port = of_graph_get_port_by_id(dev->of_node, 0);
+	if (!port) {
+		dev_dbg(dev, "port 0 not found\n");
+		return -ENXIO;
+	}
+
+	ret = of_get_data_mapping(port, input_data_mappings,
+				  ARRAY_SIZE(input_data_mappings),
+				  &lvds_encoder->input_fmt);
+	of_node_put(port);
+	if (ret) {
+		dev_dbg(dev, "unsupported input data-mapping\n");
+		return ret;
+	}
+
 	/* Locate the panel DT node. */
 	port = of_graph_get_port_by_id(dev->of_node, 1);
 	if (!port) {
@@ -84,6 +180,15 @@ static int lvds_encoder_probe(struct platform_device *pdev)
 		return -ENXIO;
 	}
 
+	ret = of_get_data_mapping(port, output_data_mappings,
+				  ARRAY_SIZE(output_data_mappings),
+				  &lvds_encoder->output_fmt);
+	if (ret) {
+		of_node_put(port);
+		dev_dbg(dev, "unsupported output data-mapping\n");
+		return ret;
+	}
+
 	endpoint = of_get_child_by_name(port, "endpoint");
 	of_node_put(port);
 	if (!endpoint) {
-- 
2.21.0