[RESEND PATCH v2 0/7] Add device tree support for Exynos4412 Trats2 cameras

[RESEND PATCH v2 0/7] Add device tree support for Exynos4412 Trats2 cameras

[Sylwester Nawrocki]

[Sigh, I've forgotten to Cc some mailing lists when submitting this
 previously, resending with device tree and samsung-soc ML added]

This series is intended to add device tree support for both cameras
on the Exynos4412 SoC Trats 2 board. It converts related drivers to use
the v4l2-async API and expose the sensor's master clock supplied by the
camera host interface through the common clock API.

This changeset is an updated version of my patch series [1] separating
the sensor subdev driver from the exynos4-fimc-is module and adding
asynchronous sensor registration support. There is also included next
iteration of the patch adding DT bits to the rear facing S5C73M3 camera
module driver [2].

The S5K6A3 is a raw image sensor of the front facing camera connected
to the SoC local ISP (FIMC-IS).

This series has run-time dependency on the patches adding clk_unregister()
implementation [3].

Any feedback, especially on the "s5k6a3: Add DT binding documentation"
patch, where I've described some issue with the common video-interfaces
binding is welcome.

[1] http://www.spinics.net/lists/linux-media/msg66073.html
[2] https://linuxtv.org/patch/19386/
[3] https://lkml.org/lkml/2013/8/24/63

Thanks,
Sylwester

Andrzej Hajda (1):
  V4L: s5c73m3: Add device tree support

Sylwester Nawrocki (6):
  V4L: s5k6a3: Add DT binding documentation
  V4L: Add driver for s5k6a3 image sensor
  V4L: s5k6a3: Add support for asynchronous subdev registration
  exynos4-is: Add clock provider for the external clocks
  exynos4-is: Use external s5k6a3 sensor driver
  exynos4-is: Add support for asynchronous sensor subddevs registration

 .../devicetree/bindings/media/samsung-fimc.txt     |   21 +-
 .../devicetree/bindings/media/samsung-s5c73m3.txt  |   95 ++++++
 .../devicetree/bindings/media/samsung-s5k6a3.txt   |   31 ++
 drivers/media/i2c/Kconfig                          |    8 +
 drivers/media/i2c/Makefile                         |    1 +
 drivers/media/i2c/s5c73m3/s5c73m3-core.c           |  206 +++++++++---
 drivers/media/i2c/s5c73m3/s5c73m3-spi.c            |    6 +
 drivers/media/i2c/s5c73m3/s5c73m3.h                |    4 +
 drivers/media/i2c/s5k6a3.c                         |  340 ++++++++++++++++++++
 drivers/media/platform/exynos4-is/fimc-is-regs.c   |    2 +-
 drivers/media/platform/exynos4-is/fimc-is-sensor.c |  285 +---------------
 drivers/media/platform/exynos4-is/fimc-is-sensor.h |   49 +--
 drivers/media/platform/exynos4-is/fimc-is.c        |   97 +++---
 drivers/media/platform/exynos4-is/fimc-is.h        |    4 +-
 drivers/media/platform/exynos4-is/media-dev.c      |  335 +++++++++++++------
 drivers/media/platform/exynos4-is/media-dev.h      |   31 +-
 16 files changed, 984 insertions(+), 531 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/media/samsung-s5c73m3.txt
 create mode 100644 Documentation/devicetree/bindings/media/samsung-s5k6a3.txt
 create mode 100644 drivers/media/i2c/s5k6a3.c

--
1.7.9.5

[RESEND PATCH v2 1/7] V4L: s5c73m3: Add device tree support

[Sylwester Nawrocki]

From: Andrzej Hajda <a.hajda@samsung.com>

This patch adds the V4L2 asychronous subdev registration and
device tree support. Common clock API is used to control the
sensor master clock from within the subdev driver.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
Changes since v1:
 - added missing ret assignment on clk_get failure,
 - fixed error paths in probe(),
 - changed clock name to cis_extclk as specified in the datasheet,
 - separate properties used for the XSHUTDOWN, STANDBY GPIOs,
 - multiple correctiond in the binding documentation (improved
   description of data-lanes and clock-frequency properties).
---
 .../devicetree/bindings/media/samsung-s5c73m3.txt  |   95 +++++++++
 drivers/media/i2c/s5c73m3/s5c73m3-core.c           |  206 +++++++++++++++-----
 drivers/media/i2c/s5c73m3/s5c73m3-spi.c            |    6 +
 drivers/media/i2c/s5c73m3/s5c73m3.h                |    4 +
 4 files changed, 261 insertions(+), 50 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/media/samsung-s5c73m3.txt

diff --git a/Documentation/devicetree/bindings/media/samsung-s5c73m3.txt b/Documentation/devicetree/bindings/media/samsung-s5c73m3.txt
new file mode 100644
index 0000000..6d6c0b6
--- /dev/null
+++ b/Documentation/devicetree/bindings/media/samsung-s5c73m3.txt
@@ -0,0 +1,95 @@
+Samsung S5C73M3 8Mp camera ISP
+------------------------------
+
+The S5C73M3 camera ISP supports MIPI CSI-2 and parallel (ITU-R BT.656) video
+data busses. The I2C bus is the main control bus and additionally the SPI bus
+is used, mostly for transferring the firmware to and from the device. Two
+slave device nodes corresponding to these control bus interfaces are required
+and should be placed under respective bus controller nodes.
+
+I2C slave device node
+---------------------
+
+Required properties:
+
+- compatible	    : "samsung,s5c73m3";
+- reg		    : I2C slave address of the sensor;
+- vdd-int-supply    : digital power supply (1.2V);
+- vdda-supply	    : analog power supply (1.2V);
+- vdd-reg-supply    : regulator input power supply (2.8V);
+- vddio-host-supply : host I/O power supply (1.8V to 2.8V);
+- vddio-cis-supply  : CIS I/O power supply (1.2V to 1.8V);
+- vdd-af-supply	    : lens power supply (2.8V);
+- xshutdown-gpios   : specifier of GPIO connected to the XSHUTDOWN pin;
+- standby-gpios     : specifier of GPIO connected to the STANDBY pin;
+- clocks	    : contains the sensor's CIS_EXTCLK clock specifier;
+- clock-names	    : contains "cis_extclk" entry;
+
+Optional properties:
+
+- clock-frequency   : the frequency at which the "cis_extclk" clock should be
+		      configured to operate, in Hz; if this property is not
+		      specified default 24 MHz value will be used.
+
+The common video interfaces bindings (see video-interfaces.txt) should be used
+to specify link from the S5C73M3 to an external image data receiver. The S5C73M3
+device node should contain one 'port' child node with an 'endpoint' subnode for
+this purpose. The data link from a raw image sensor to the S5C73M3 can be
+similarly specified, but it is optional since the S5C73M3 ISP and a raw image
+sensor are usually inseparable and form a hybrid module.
+
+Following properties are valid for the endpoint node(s):
+
+endpoint subnode
+----------------
+
+- data-lanes : (optional) specifies MIPI CSI-2 data lanes as covered in
+  video-interfaces.txt. This sensor doesn't support data lane remapping
+  and physical lane indexes in subsequent elements of the array should
+  be only consecutive ascending values.
+
+SPI device node
+---------------
+
+Required properties:
+
+- compatible	    : "samsung,s5c73m3";
+
+For more details see description of the SPI busses bindings
+(../spi/spi-bus.txt) and bindings of a specific bus controller.
+
+Example:
+
+i2c@138A000000 {
+	...
+	s5c73m3@3c {
+		compatible = "samsung,s5c73m3";
+		reg = <0x3c>;
+		vdd-int-supply = <&buck9_reg>;
+		vdda-supply = <&ldo17_reg>;
+		vdd-reg-supply = <&cam_io_reg>;
+		vddio-host-supply = <&ldo18_reg>;
+		vddio-cis-supply = <&ldo9_reg>;
+		vdd-af-supply = <&cam_af_reg>;
+		clock-frequency = <24000000>;
+		clocks = <&clk 0>;
+		clock-names = "cis_extclk";
+		reset-gpios = <&gpf1 3 1>;
+		standby-gpios = <&gpm0 1 1>;
+		port {
+			s5c73m3_ep: endpoint {
+				remote-endpoint = <&csis0_ep>;
+				data-lanes = <1 2 3 4>;
+			};
+		};
+	};
+};
+
+spi@1392000 {
+	...
+	s5c73m3_spi: s5c73m3 {
+		compatible = "samsung,s5c73m3";
+		reg = <0>;
+		...
+	};
+};
diff --git a/drivers/media/i2c/s5c73m3/s5c73m3-core.c b/drivers/media/i2c/s5c73m3/s5c73m3-core.c
index b76ec0e..270d324 100644
--- a/drivers/media/i2c/s5c73m3/s5c73m3-core.c
+++ b/drivers/media/i2c/s5c73m3/s5c73m3-core.c
@@ -15,7 +15,7 @@
  * GNU General Public License for more details.
  */

-#include <linux/sizes.h>
+#include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/firmware.h>
 #include <linux/gpio.h>
@@ -23,7 +23,9 @@
 #include <linux/init.h>
 #include <linux/media.h>
 #include <linux/module.h>
+#include <linux/of_gpio.h>
 #include <linux/regulator/consumer.h>
+#include <linux/sizes.h>
 #include <linux/slab.h>
 #include <linux/spi/spi.h>
 #include <linux/videodev2.h>
@@ -33,6 +35,7 @@
 #include <media/v4l2-subdev.h>
 #include <media/v4l2-mediabus.h>
 #include <media/s5c73m3.h>
+#include <media/v4l2-of.h>

 #include "s5c73m3.h"

@@ -46,6 +49,8 @@ static int update_fw;
 module_param(update_fw, int, 0644);

 #define S5C73M3_EMBEDDED_DATA_MAXLEN	SZ_4K
+#define S5C73M3_MIPI_DATA_LANES		4
+#define S5C73M3_CLK_NAME		"cis_extclk"

 static const char * const s5c73m3_supply_names[S5C73M3_MAX_SUPPLIES] = {
 	"vdd-int",	/* Digital Core supply (1.2V), CAM_ISP_CORE_1.2V */
@@ -1355,9 +1360,20 @@ static int __s5c73m3_power_on(struct s5c73m3 *state)
 	for (i = 0; i < S5C73M3_MAX_SUPPLIES; i++) {
 		ret = regulator_enable(state->supplies[i].consumer);
 		if (ret)
-			goto err;
+			goto err_reg_dis;
 	}

+	ret = clk_set_rate(state->clock, state->mclk_frequency);
+	if (ret < 0)
+		goto err_reg_dis;
+
+	ret = clk_prepare_enable(state->clock);
+	if (ret < 0)
+		goto err_reg_dis;
+
+	v4l2_dbg(1, s5c73m3_dbg, &state->oif_sd, "clock frequency: %ld\n",
+					clk_get_rate(state->clock));
+
 	s5c73m3_gpio_deassert(state, STBY);
 	usleep_range(100, 200);

@@ -1365,7 +1381,8 @@ static int __s5c73m3_power_on(struct s5c73m3 *state)
 	usleep_range(50, 100);

 	return 0;
-err:
+
+err_reg_dis:
 	for (--i; i >= 0; i--)
 		regulator_disable(state->supplies[i].consumer);
 	return ret;
@@ -1380,6 +1397,9 @@ static int __s5c73m3_power_off(struct s5c73m3 *state)

 	if (s5c73m3_gpio_assert(state, STBY))
 		usleep_range(100, 200);
+
+	clk_disable_unprepare(state->clock);
+
 	state->streaming = 0;
 	state->isp_ready = 0;

@@ -1388,6 +1408,7 @@ static int __s5c73m3_power_off(struct s5c73m3 *state)
 		if (ret)
 			goto err;
 	}
+
 	return 0;
 err:
 	for (++i; i < S5C73M3_MAX_SUPPLIES; i++) {
@@ -1404,6 +1425,7 @@ static int s5c73m3_oif_set_power(struct v4l2_subdev *sd, int on)
 	struct s5c73m3 *state = oif_sd_to_s5c73m3(sd);
 	int ret = 0;

+
 	mutex_lock(&state->lock);

 	if (on && !state->power) {
@@ -1451,17 +1473,6 @@ static int s5c73m3_oif_registered(struct v4l2_subdev *sd)
 			S5C73M3_JPEG_PAD, &state->oif_sd.entity, OIF_JPEG_PAD,
 			MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED);

-	mutex_lock(&state->lock);
-	ret = __s5c73m3_power_on(state);
-	if (ret == 0)
-		s5c73m3_get_fw_version(state);
-
-	__s5c73m3_power_off(state);
-	mutex_unlock(&state->lock);
-
-	v4l2_dbg(1, s5c73m3_dbg, sd, "%s: Booting %s (%d)\n",
-		 __func__, ret ? "failed" : "succeded", ret);
-
 	return ret;
 }

@@ -1519,41 +1530,108 @@ static const struct v4l2_subdev_ops oif_subdev_ops = {
 	.video	= &s5c73m3_oif_video_ops,
 };

-static int s5c73m3_configure_gpios(struct s5c73m3 *state,
-				   const struct s5c73m3_platform_data *pdata)
+static int s5c73m3_configure_gpios(struct s5c73m3 *state)
+{
+	static const char * const gpio_names[] = {
+		"S5C73M3_STBY", "S5C73M3_RST"
+	};
+	struct i2c_client *c = state->i2c_client;
+	struct s5c73m3_gpio *g = state->gpio;
+	int ret, i;
+
+	for (i = 0; i < GPIO_NUM; ++i) {
+		unsigned int flags = GPIOF_DIR_OUT;
+		if (g[i].level)
+			flags |= GPIOF_INIT_HIGH;
+		ret = devm_gpio_request_one(&c->dev, g[i].gpio, flags,
+					    gpio_names[i]);
+		if (ret) {
+			v4l2_err(c, "failed to request gpio %s\n",
+				 gpio_names[i]);
+			return ret;
+		}
+	}
+	return 0;
+}
+
+static int s5c73m3_parse_gpios(struct s5c73m3 *state)
+{
+	static const char * const prop_names[] = {
+		"standby-gpios", "xshutdown-gpios",
+	};
+	struct device *dev = &state->i2c_client->dev;
+	struct device_node *node = dev->of_node;
+	int ret, i;
+
+	for (i = 0; i < GPIO_NUM; ++i) {
+		enum of_gpio_flags of_flags;
+
+		ret = of_get_named_gpio_flags(node, prop_names[i],
+					      0, &of_flags);
+		if (ret < 0) {
+			dev_err(dev, "failed to parse %s DT property\n",
+				prop_names[i]);
+			return -EINVAL;
+		}
+		state->gpio[i].gpio = ret;
+		state->gpio[i].level = !(of_flags & OF_GPIO_ACTIVE_LOW);
+	}
+	return 0;
+}
+
+static int s5c73m3_get_platform_data(struct s5c73m3 *state)
 {
 	struct device *dev = &state->i2c_client->dev;
-	const struct s5c73m3_gpio *gpio;
-	unsigned long flags;
+	const struct s5c73m3_platform_data *pdata = dev->platform_data;
+	struct device_node *node = dev->of_node;
+	struct device_node *node_ep;
+	struct v4l2_of_endpoint ep;
 	int ret;

-	state->gpio[STBY].gpio = -EINVAL;
-	state->gpio[RST].gpio  = -EINVAL;
+	if (!node) {
+		if (!pdata) {
+			dev_err(dev, "Platform data not specified\n");
+			return -EINVAL;
+		}

-	gpio = &pdata->gpio_stby;
-	if (gpio_is_valid(gpio->gpio)) {
-		flags = (gpio->level ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW)
-		      | GPIOF_EXPORT;
-		ret = devm_gpio_request_one(dev, gpio->gpio, flags,
-					    "S5C73M3_STBY");
-		if (ret < 0)
-			return ret;
+		state->mclk_frequency = pdata->mclk_frequency;
+		state->gpio[STBY] = pdata->gpio_stby;
+		state->gpio[RST] = pdata->gpio_reset;
+		return 0;
+	}

-		state->gpio[STBY] = *gpio;
+	if (of_property_read_u32(node, "clock-frequency",
+				 &state->mclk_frequency)) {
+		state->mclk_frequency = S5C73M3_DEFAULT_MCLK_FREQ;
+		dev_info(dev, "using default %u Hz clock frequency\n",
+					state->mclk_frequency);
 	}

-	gpio = &pdata->gpio_reset;
-	if (gpio_is_valid(gpio->gpio)) {
-		flags = (gpio->level ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW)
-		      | GPIOF_EXPORT;
-		ret = devm_gpio_request_one(dev, gpio->gpio, flags,
-					    "S5C73M3_RST");
-		if (ret < 0)
-			return ret;
+	ret = s5c73m3_parse_gpios(state);
+	if (ret < 0)
+		return -EINVAL;

-		state->gpio[RST] = *gpio;
+	node_ep = v4l2_of_get_next_endpoint(node, NULL);
+	if (!node_ep) {
+		dev_warn(dev, "no endpoint defined for node: %s\n",
+						node->full_name);
+		return 0;
 	}

+	v4l2_of_parse_endpoint(node_ep, &ep);
+	of_node_put(node_ep);
+
+	if (ep.bus_type != V4L2_MBUS_CSI2) {
+		dev_err(dev, "unsupported bus type\n");
+		return -EINVAL;
+	}
+	/*
+	 * Number of MIPI CSI-2 data lanes is currently not configurable,
+	 * always a default value of 4 lanes is used.
+	 */
+	if (ep.bus.mipi_csi2.num_data_lanes != S5C73M3_MIPI_DATA_LANES)
+		dev_info(dev, "falling back to 4 MIPI CSI-2 data lanes\n");
+
 	return 0;
 }

@@ -1561,21 +1639,24 @@ static int s5c73m3_probe(struct i2c_client *client,
 				const struct i2c_device_id *id)
 {
 	struct device *dev = &client->dev;
-	const struct s5c73m3_platform_data *pdata = client->dev.platform_data;
 	struct v4l2_subdev *sd;
 	struct v4l2_subdev *oif_sd;
 	struct s5c73m3 *state;
 	int ret, i;

-	if (pdata == NULL) {
-		dev_err(&client->dev, "Platform data not specified\n");
-		return -EINVAL;
-	}
-
 	state = devm_kzalloc(dev, sizeof(*state), GFP_KERNEL);
 	if (!state)
 		return -ENOMEM;

+	state->clock = devm_clk_get(dev, S5C73M3_CLK_NAME);
+	if (IS_ERR(state->clock))
+		return -EPROBE_DEFER;
+
+	state->i2c_client = client;
+	ret = s5c73m3_get_platform_data(state);
+	if (ret < 0)
+		return ret;
+
 	mutex_init(&state->lock);
 	sd = &state->sensor_sd;
 	oif_sd = &state->oif_sd;
@@ -1613,11 +1694,7 @@ static int s5c73m3_probe(struct i2c_client *client,
 	if (ret < 0)
 		return ret;

-	state->mclk_frequency = pdata->mclk_frequency;
-	state->bus_type = pdata->bus_type;
-	state->i2c_client = client;
-
-	ret = s5c73m3_configure_gpios(state, pdata);
+	ret = s5c73m3_configure_gpios(state);
 	if (ret)
 		goto out_err;

@@ -1651,9 +1728,29 @@ static int s5c73m3_probe(struct i2c_client *client,
 	if (ret < 0)
 		goto out_err;

+	oif_sd->dev = dev;
+
+	ret = __s5c73m3_power_on(state);
+	if (ret < 0)
+		goto out_err1;
+
+	ret = s5c73m3_get_fw_version(state);
+	__s5c73m3_power_off(state);
+
+	if (ret < 0) {
+		dev_err(dev, "Device detection failed: %d\n", ret);
+		goto out_err1;
+	}
+
+	ret = v4l2_async_register_subdev(oif_sd);
+	if (ret < 0)
+		goto out_err1;
+
 	v4l2_info(sd, "%s: completed succesfully\n", __func__);
 	return 0;

+out_err1:
+	s5c73m3_unregister_spi_driver(state);
 out_err:
 	media_entity_cleanup(&sd->entity);
 	return ret;
@@ -1665,7 +1762,7 @@ static int s5c73m3_remove(struct i2c_client *client)
 	struct s5c73m3 *state = oif_sd_to_s5c73m3(oif_sd);
 	struct v4l2_subdev *sensor_sd = &state->sensor_sd;

-	v4l2_device_unregister_subdev(oif_sd);
+	v4l2_async_unregister_subdev(oif_sd);

 	v4l2_ctrl_handler_free(oif_sd->ctrl_handler);
 	media_entity_cleanup(&oif_sd->entity);
@@ -1684,8 +1781,17 @@ static const struct i2c_device_id s5c73m3_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, s5c73m3_id);

+#ifdef CONFIG_OF
+static const struct of_device_id s5c73m3_of_match[] = {
+	{ .compatible = "samsung,s5c73m3" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, s5c73m3_of_match);
+#endif
+
 static struct i2c_driver s5c73m3_i2c_driver = {
 	.driver = {
+		.of_match_table = of_match_ptr(s5c73m3_of_match),
 		.name	= DRIVER_NAME,
 	},
 	.probe		= s5c73m3_probe,
diff --git a/drivers/media/i2c/s5c73m3/s5c73m3-spi.c b/drivers/media/i2c/s5c73m3/s5c73m3-spi.c
index 8079e26..f60b265 100644
--- a/drivers/media/i2c/s5c73m3/s5c73m3-spi.c
+++ b/drivers/media/i2c/s5c73m3/s5c73m3-spi.c
@@ -27,6 +27,11 @@

 #define S5C73M3_SPI_DRV_NAME "S5C73M3-SPI"

+static const struct of_device_id s5c73m3_spi_ids[] = {
+	{ .compatible = "samsung,s5c73m3" },
+	{ }
+};
+
 enum spi_direction {
 	SPI_DIR_RX,
 	SPI_DIR_TX
@@ -146,6 +151,7 @@ int s5c73m3_register_spi_driver(struct s5c73m3 *state)
 	spidrv->driver.name = S5C73M3_SPI_DRV_NAME;
 	spidrv->driver.bus = &spi_bus_type;
 	spidrv->driver.owner = THIS_MODULE;
+	spidrv->driver.of_match_table = s5c73m3_spi_ids;

 	return spi_register_driver(spidrv);
 }
diff --git a/drivers/media/i2c/s5c73m3/s5c73m3.h b/drivers/media/i2c/s5c73m3/s5c73m3.h
index 9d2c086..2917857 100644
--- a/drivers/media/i2c/s5c73m3/s5c73m3.h
+++ b/drivers/media/i2c/s5c73m3/s5c73m3.h
@@ -17,6 +17,7 @@
 #ifndef S5C73M3_H_
 #define S5C73M3_H_

+#include <linux/clk.h>
 #include <linux/kernel.h>
 #include <linux/regulator/consumer.h>
 #include <media/v4l2-common.h>
@@ -321,6 +322,7 @@ enum s5c73m3_oif_pads {


 #define S5C73M3_MAX_SUPPLIES			6
+#define S5C73M3_DEFAULT_MCLK_FREQ		24000000U

 struct s5c73m3_ctrls {
 	struct v4l2_ctrl_handler handler;
@@ -391,6 +393,8 @@ struct s5c73m3 {
 	struct regulator_bulk_data supplies[S5C73M3_MAX_SUPPLIES];
 	struct s5c73m3_gpio gpio[GPIO_NUM];

+	struct clk *clock;
+
 	/* External master clock frequency */
 	u32 mclk_frequency;
 	/* Video bus type - MIPI-CSI2/paralell */
--
1.7.9.5

[RESEND PATCH v2 2/7] V4L: s5k6a3: Add DT binding documentation

[Sylwester Nawrocki]

This patch adds binding documentation for the Samsung S5K6A3(YX)
raw image sensor.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---

The binding of this sensors shows some issue in the generic video-interfaces
binding. Namely The video bus type (serial MIPI CSI-2, parallel ITU-R BT.656,
etc.) is being determined by the binding parser (v4l2-of.c) depending on what
properties are found in an enddpoint node.

Please have a look at the data-lanes property description. The sensor supports
MIPI CSI-2 and SMIA CCP2 interfaces which both use one data lane. One data lane
is everything this sensors supports. During our discussions on the generic
bidings in the past I proposed to introduce a property in the endpoint node
that would indicate what bus type (standard/protocol) is used, e.g. MIPI CSI-2,
ITU-R BT.656, SMIA CCP2, etc. It was argued though that we can well determine
bus type based on properties found in the endpoint node.

So now in case of this sensor I'm not sure how it can be differentiated
whether MIPI CSI-2 or CCP2 bus is used. There is no CCP2 specific generic
properties yet. Anyway I'm not really happy there is no property like bus_type
that would clearly indicate what data bus type is used. Then would would for
instance not specify "data-lanes" in endpoint node just to differentiate
between MIPI CSI-2 and the parallel busses.

The main issue for this particular binding is that even with data-lanes = <1>;
it is still impossible to figure out whether MIPI CSI-2 or SMIA CCP2 data bus
is used.

So how about introducing, e.g. a string type "bus_type" common property ?
I'm considering starting a separate thread for discussing this.
---
 .../devicetree/bindings/media/samsung-s5k6a3.txt   |   31 ++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/media/samsung-s5k6a3.txt

diff --git a/Documentation/devicetree/bindings/media/samsung-s5k6a3.txt b/Documentation/devicetree/bindings/media/samsung-s5k6a3.txt
new file mode 100644
index 0000000..a51fbe8
--- /dev/null
+++ b/Documentation/devicetree/bindings/media/samsung-s5k6a3.txt
@@ -0,0 +1,31 @@
+Samsung S5K6A3(YX) raw image sensor
+---------------------------------
+
+S5K6A3YX is a raw image sensor with MIPI CSI-2 and CCP2 image data interfaces
+and CCI (I2C compatible) control bus.
+
+Required properties:
+
+- compatible	: "samsung,s5k6a3yx";
+- reg		: I2C slave address of the sensor;
+- svdda-supply	: core voltage supply;
+- svddio-supply	: I/O voltage supply;
+- gpios		: specifier of a GPIO connected to the RESET pin;
+- clocks	: should contain the sensor's EXTCLK clock specifier, from
+		  the common clock bindings.
+- clock-names	: should contain "extclk" entry;
+
+Optional properties:
+
+- clock-frequency : the frequency at which the "extclk" clock should be
+		    configured to operate, in Hz; if this property is not
+		    specified default 24 MHz value will be used.
+
+The common video interfaces bindings (see video-interfaces.txt) should be
+used to specify link to the image data receiver. The S5K6A3(YX) device
+node should contain one 'port' child node with an 'endpoint' subnode.
+
+Following properties are valid for the endpoint node:
+
+- data-lanes : (optional) specifies MIPI CSI-2 data lanes as covered in
+  video-interfaces.txt.  The sensor supports only one data lane.
--
1.7.9.5