[PATCH 2/4] DRM: BRIDGE: TFP410: Support basic I2C interface

[Jonathan Cormier <jcormier@criticallink.com>]

From: Michael Williamson <michael.williamson@criticallink.com>

The TFP410 driver does not support I2C.  As such, the device remains in
Power Down if the I2C is enabled by the bootstrap pins.

Add basic support for the I2C interface, and provide support to take
the device out of power down when enabled.  Also read the bootstrap mode
pins via the CTL_1_MODE register when using the I2C bus.

Signed-off-by: Michael Williamson <michael.williamson@criticallink.com>
Signed-off-by: Jonathan Cormier <jcormier@criticallink.com>
---
 drivers/gpu/drm/bridge/ti-tfp410.c | 95 +++++++++++++++++++++++++++-----------
 1 file changed, 68 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-tfp410.c b/drivers/gpu/drm/bridge/ti-tfp410.c
index b9635abbad16..323a6d9ed188 100644
--- a/drivers/gpu/drm/bridge/ti-tfp410.c
+++ b/drivers/gpu/drm/bridge/ti-tfp410.c
@@ -6,6 +6,7 @@
 
 #include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
+#include <linux/regmap.h>
 #include <linux/media-bus-format.h>
 #include <linux/module.h>
 #include <linux/of_graph.h>
@@ -21,6 +22,20 @@
 
 #define HOTPLUG_DEBOUNCE_MS		1100
 
+#define TFP410_REG_CTL_1_MODE	0x08
+#define TFP410_BIT_PD   BIT(0)
+#define TFP410_BIT_EDGE BIT(1)
+#define TFP410_BIT_BSEL BIT(2)
+#define TFP410_BIT_DSEL BIT(3)
+
+static const struct regmap_config tfp410_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.max_register = 0xff,
+	.cache_type = REGCACHE_NONE,
+};
+
 struct tfp410 {
 	struct drm_bridge	bridge;
 	struct drm_connector	connector;
@@ -33,6 +48,8 @@ struct tfp410 {
 	struct drm_bridge	*next_bridge;
 
 	struct device *dev;
+	struct i2c_client *i2c;
+	struct regmap *regmap;
 };
 
 static inline struct tfp410 *
@@ -183,6 +200,9 @@ static void tfp410_enable(struct drm_bridge *bridge)
 {
 	struct tfp410 *dvi = drm_bridge_to_tfp410(bridge);
 
+	if (dvi->i2c)
+		regmap_set_bits(dvi->regmap, TFP410_REG_CTL_1_MODE, TFP410_BIT_PD);
+
 	gpiod_set_value_cansleep(dvi->powerdown, 0);
 }
 
@@ -190,6 +210,9 @@ static void tfp410_disable(struct drm_bridge *bridge)
 {
 	struct tfp410 *dvi = drm_bridge_to_tfp410(bridge);
 
+	if (dvi->i2c)
+		regmap_clear_bits(dvi->regmap, TFP410_REG_CTL_1_MODE, TFP410_BIT_PD);
+
 	gpiod_set_value_cansleep(dvi->powerdown, 1);
 }
 
@@ -221,38 +244,48 @@ static const struct drm_bridge_timings tfp410_default_timings = {
 	.hold_time_ps = 1300,
 };
 
-static int tfp410_parse_timings(struct tfp410 *dvi, bool i2c)
+static int tfp410_parse_timings(struct tfp410 *dvi)
 {
 	struct drm_bridge_timings *timings = &dvi->timings;
 	struct device_node *ep;
 	u32 pclk_sample = 0;
 	u32 bus_width = 24;
 	u32 deskew = 0;
+	unsigned int val = 0;
+	int ret = 0;
 
 	/* Start with defaults. */
 	*timings = tfp410_default_timings;
 
-	if (i2c)
+	if (dvi->i2c) {
 		/*
-		 * In I2C mode timings are configured through the I2C interface.
-		 * As the driver doesn't support I2C configuration yet, we just
-		 * go with the defaults (BSEL=1, DSEL=1, DKEN=0, EDGE=1).
+		 * For now, assume settings are latched from pins on reset / power up.
+		 * Should add options to optionally set them out of DT properties.
 		 */
-		return 0;
-
-	/*
-	 * In non-I2C mode, timings are configured through the BSEL, DSEL, DKEN
-	 * and EDGE pins. They are specified in DT through endpoint properties
-	 * and vendor-specific properties.
-	 */
-	ep = of_graph_get_endpoint_by_regs(dvi->dev->of_node, 0, 0);
-	if (!ep)
-		return -EINVAL;
-
-	/* Get the sampling edge from the endpoint. */
-	of_property_read_u32(ep, "pclk-sample", &pclk_sample);
-	of_property_read_u32(ep, "bus-width", &bus_width);
-	of_node_put(ep);
+		ret = regmap_read(dvi->regmap, TFP410_REG_CTL_1_MODE, &val);
+		if (ret) {
+			dev_err(dvi->dev, "Read failed on CTL_1_MODE\n");
+			return ret;
+		}
+		pclk_sample = (val & TFP410_BIT_EDGE) ? 1 : 0;
+		bus_width = (val & TFP410_BIT_BSEL) ? 24 : 12;
+		dev_dbg(dvi->dev, "(0x%02X) : detected %d bus width, %s edge sampling\n",
+			val, bus_width, pclk_sample ? "positive" : "negative");
+	} else {
+		/*
+		 * In non-I2C mode, timings are configured through the BSEL, DSEL, DKEN
+		 * and EDGE pins. They are specified in DT through endpoint properties
+		 * and vendor-specific properties.
+		 */
+		ep = of_graph_get_endpoint_by_regs(dvi->dev->of_node, 0, 0);
+		if (!ep)
+			return -EINVAL;
+
+		/* Get the sampling edge from the endpoint. */
+		of_property_read_u32(ep, "pclk-sample", &pclk_sample);
+		of_property_read_u32(ep, "bus-width", &bus_width);
+		of_node_put(ep);
+	}
 
 	timings->input_bus_flags = DRM_BUS_FLAG_DE_HIGH;
 
@@ -291,7 +324,7 @@ static int tfp410_parse_timings(struct tfp410 *dvi, bool i2c)
 	return 0;
 }
 
-static int tfp410_init(struct device *dev, bool i2c)
+static int tfp410_init(struct device *dev, struct i2c_client *i2c)
 {
 	struct device_node *node;
 	struct tfp410 *dvi;
@@ -313,15 +346,24 @@ static int tfp410_init(struct device *dev, bool i2c)
 	dvi->bridge.of_node = dev->of_node;
 	dvi->bridge.timings = &dvi->timings;
 	dvi->bridge.type = DRM_MODE_CONNECTOR_DVID;
+	dvi->i2c = i2c;
+
+	if (i2c) {
+		dvi->regmap = devm_regmap_init_i2c(i2c, &tfp410_regmap_config);
+		if (IS_ERR(dvi->regmap))
+			return PTR_ERR(dvi->regmap);
+	}
 
-	ret = tfp410_parse_timings(dvi, i2c);
+	ret = tfp410_parse_timings(dvi);
 	if (ret)
 		return ret;
 
 	/* Get the next bridge, connected to port@1. */
 	node = of_graph_get_remote_node(dev->of_node, 1, -1);
-	if (!node)
+	if (!node) {
+		dev_err(dev, "Could not find remote node\n");
 		return -ENODEV;
+	}
 
 	dvi->next_bridge = of_drm_find_bridge(node);
 	of_node_put(node);
@@ -352,7 +394,7 @@ static void tfp410_fini(struct device *dev)
 
 static int tfp410_probe(struct platform_device *pdev)
 {
-	return tfp410_init(&pdev->dev, false);
+	return tfp410_init(&pdev->dev, NULL);
 }
 
 static int tfp410_remove(struct platform_device *pdev)
@@ -378,7 +420,6 @@ static struct platform_driver tfp410_platform_driver = {
 };
 
 #if IS_ENABLED(CONFIG_I2C)
-/* There is currently no i2c functionality. */
 static int tfp410_i2c_probe(struct i2c_client *client,
 			    const struct i2c_device_id *id)
 {
@@ -391,7 +432,7 @@ static int tfp410_i2c_probe(struct i2c_client *client,
 		return -ENXIO;
 	}
 
-	return tfp410_init(&client->dev, true);
+	return tfp410_init(&client->dev, client);
 }
 
 static void tfp410_i2c_remove(struct i2c_client *client)
@@ -408,7 +449,7 @@ MODULE_DEVICE_TABLE(i2c, tfp410_i2c_ids);
 static struct i2c_driver tfp410_i2c_driver = {
 	.driver = {
 		.name	= "tfp410",
-		.of_match_table = of_match_ptr(tfp410_match),
+		.of_match_table = tfp410_match,
 	},
 	.id_table	= tfp410_i2c_ids,
 	.probe		= tfp410_i2c_probe,

-- 
2.25.1