[PATCH v4 3/4] media: i2c: Add MAX9286 driver

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

From: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

The MAX9286 is a 4-channel GMSL deserializer with coax or STP input and
CSI-2 output. The device supports multicamera streaming applications,
and features the ability to synchronise the attached cameras.

CSI-2 output can be configured with 1 to 4 lanes, and a control channel
is supported over I2C, which implements an I2C mux to facilitate
communications with connected cameras across the reverse control
channel.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>

--
v2:
 - Fix MAINTAINERS entry

This posting is released with the following modifications to work
without Sakari's VC developments:
 - max9286_g_mbus_config() re-instated
 - max9286_get_frame_desc() is not bus/csi aware
 - max9286_{get,set}_routing() removed

v3:
 - Initialise notifier with v4l2_async_notifier_init
 - Update for new mbus csi2 format V4L2_MBUS_CSI2_DPHY

v4: - Re-introduce required code to function with the VC series.

 - Implement max9286_get_routing, max9286_set_routing
 - Remove max9286_g_mbus_config
---
 MAINTAINERS                 |   10 +
 drivers/media/i2c/Kconfig   |   11 +
 drivers/media/i2c/Makefile  |    1 +
 drivers/media/i2c/max9286.c | 1189 +++++++++++++++++++++++++++++++++++
 4 files changed, 1211 insertions(+)
 create mode 100644 drivers/media/i2c/max9286.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 23021e0df5d7..745f0fd1fff1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8864,6 +8864,16 @@ F:	Documentation/devicetree/bindings/hwmon/max6697.txt
 F:	drivers/hwmon/max6697.c
 F:	include/linux/platform_data/max6697.h
 
+MAX9286 QUAD GMSL DESERIALIZER DRIVER
+M:	Jacopo Mondi <jacopo+renesas@jmondi.org>
+M:	Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
+M:	Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
+M:	Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
+L:	linux-media@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/media/i2c/max9286.txt
+F:	drivers/media/i2c/max9286.c
+
 MAX9860 MONO AUDIO VOICE CODEC DRIVER
 M:	Peter Rosin <peda@axentia.se>
 L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
index 704af210e270..eadc00bdd3bf 100644
--- a/drivers/media/i2c/Kconfig
+++ b/drivers/media/i2c/Kconfig
@@ -472,6 +472,17 @@ config VIDEO_VPX3220
 	  To compile this driver as a module, choose M here: the
 	  module will be called vpx3220.
 
+config VIDEO_MAX9286
+	tristate "Maxim MAX9286 GMSL deserializer support"
+	depends on I2C && I2C_MUX
+	depends on VIDEO_V4L2_SUBDEV_API && MEDIA_CONTROLLER
+	select V4L2_FWNODE
+	help
+	  This driver supports the Maxim MAX9286 GMSL deserializer.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called max9286.
+
 comment "Video and audio decoders"
 
 config VIDEO_SAA717X
diff --git a/drivers/media/i2c/Makefile b/drivers/media/i2c/Makefile
index 260d4d9ec2a1..4de7fe62b179 100644
--- a/drivers/media/i2c/Makefile
+++ b/drivers/media/i2c/Makefile
@@ -110,5 +110,6 @@ obj-$(CONFIG_VIDEO_IMX258)	+= imx258.o
 obj-$(CONFIG_VIDEO_IMX274)	+= imx274.o
 obj-$(CONFIG_VIDEO_IMX319)	+= imx319.o
 obj-$(CONFIG_VIDEO_IMX355)	+= imx355.o
+obj-$(CONFIG_VIDEO_MAX9286)	+= max9286.o
 
 obj-$(CONFIG_SDR_MAX2175) += max2175.o
diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
new file mode 100644
index 000000000000..c39c2f86e07d
--- /dev/null
+++ b/drivers/media/i2c/max9286.c
@@ -0,0 +1,1189 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Maxim MAX9286 GMSL Deserializer Driver
+ *
+ * Copyright (C) 2017-2018 Jacopo Mondi
+ * Copyright (C) 2017-2018 Kieran Bingham
+ * Copyright (C) 2017-2018 Laurent Pinchart
+ * Copyright (C) 2017-2018 Niklas Söderlund
+ * Copyright (C) 2016 Renesas Electronics Corporation
+ * Copyright (C) 2015 Cogent Embedded, Inc.
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/fwnode.h>
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+#include <linux/module.h>
+#include <linux/of_graph.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#include <media/v4l2-async.h>
+#include <media/v4l2-ctrls.h>
+#include <media/v4l2-device.h>
+#include <media/v4l2-fwnode.h>
+#include <media/v4l2-subdev.h>
+
+/* Register 0x00 */
+#define MAX9286_MSTLINKSEL_AUTO		(7 << 5)
+#define MAX9286_MSTLINKSEL(n)		((n) << 5)
+#define MAX9286_EN_VS_GEN		BIT(4)
+#define MAX9286_LINKEN(n)		(1 << (n))
+/* Register 0x01 */
+#define MAX9286_FSYNCMODE_ECU		(3 << 6)
+#define MAX9286_FSYNCMODE_EXT		(2 << 6)
+#define MAX9286_FSYNCMODE_INT_OUT	(1 << 6)
+#define MAX9286_FSYNCMODE_INT_HIZ	(0 << 6)
+#define MAX9286_GPIEN			BIT(5)
+#define MAX9286_ENLMO_RSTFSYNC		BIT(2)
+#define MAX9286_FSYNCMETH_AUTO		(2 << 0)
+#define MAX9286_FSYNCMETH_SEMI_AUTO	(1 << 0)
+#define MAX9286_FSYNCMETH_MANUAL	(0 << 0)
+#define MAX9286_REG_FSYNC_PERIOD_L	0x06
+#define MAX9286_REG_FSYNC_PERIOD_M	0x07
+#define MAX9286_REG_FSYNC_PERIOD_H	0x08
+/* Register 0x0a */
+#define MAX9286_FWDCCEN(n)		(1 << ((n) + 4))
+#define MAX9286_REVCCEN(n)		(1 << (n))
+/* Register 0x0c */
+#define MAX9286_HVEN			BIT(7)
+#define MAX9286_EDC_6BIT_HAMMING	(2 << 5)
+#define MAX9286_EDC_6BIT_CRC		(1 << 5)
+#define MAX9286_EDC_1BIT_PARITY		(0 << 5)
+#define MAX9286_DESEL			BIT(4)
+#define MAX9286_INVVS			BIT(3)
+#define MAX9286_INVHS			BIT(2)
+#define MAX9286_HVSRC_D0		(2 << 0)
+#define MAX9286_HVSRC_D14		(1 << 0)
+#define MAX9286_HVSRC_D18		(0 << 0)
+/* Register 0x12 */
+#define MAX9286_CSILANECNT(n)		(((n) - 1) << 6)
+#define MAX9286_CSIDBL			BIT(5)
+#define MAX9286_DBL			BIT(4)
+#define MAX9286_DATATYPE_USER_8BIT	(11 << 0)
+#define MAX9286_DATATYPE_USER_YUV_12BIT	(10 << 0)
+#define MAX9286_DATATYPE_USER_24BIT	(9 << 0)
+#define MAX9286_DATATYPE_RAW14		(8 << 0)
+#define MAX9286_DATATYPE_RAW11		(7 << 0)
+#define MAX9286_DATATYPE_RAW10		(6 << 0)
+#define MAX9286_DATATYPE_RAW8		(5 << 0)
+#define MAX9286_DATATYPE_YUV422_10BIT	(4 << 0)
+#define MAX9286_DATATYPE_YUV422_8BIT	(3 << 0)
+#define MAX9286_DATATYPE_RGB555		(2 << 0)
+#define MAX9286_DATATYPE_RGB565		(1 << 0)
+#define MAX9286_DATATYPE_RGB888		(0 << 0)
+/* Register 0x15 */
+#define MAX9286_VC(n)			((n) << 5)
+#define MAX9286_VCTYPE			BIT(4)
+#define MAX9286_CSIOUTEN		BIT(3)
+#define MAX9286_0X15_RESV		(3 << 0)
+/* Register 0x1b */
+#define MAX9286_SWITCHIN(n)		(1 << ((n) + 4))
+#define MAX9286_ENEQ(n)			(1 << (n))
+/* Register 0x27 */
+#define MAX9286_LOCKED			BIT(7)
+/* Register 0x31 */
+#define MAX9286_FSYNC_LOCKED		BIT(6)
+/* Register 0x34 */
+#define MAX9286_I2CLOCACK		BIT(7)
+#define MAX9286_I2CSLVSH_1046NS_469NS	(3 << 5)
+#define MAX9286_I2CSLVSH_938NS_352NS	(2 << 5)
+#define MAX9286_I2CSLVSH_469NS_234NS	(1 << 5)
+#define MAX9286_I2CSLVSH_352NS_117NS	(0 << 5)
+#define MAX9286_I2CMSTBT_837KBPS	(7 << 2)
+#define MAX9286_I2CMSTBT_533KBPS	(6 << 2)
+#define MAX9286_I2CMSTBT_339KBPS	(5 << 2)
+#define MAX9286_I2CMSTBT_173KBPS	(4 << 2)
+#define MAX9286_I2CMSTBT_105KBPS	(3 << 2)
+#define MAX9286_I2CMSTBT_84KBPS		(2 << 2)
+#define MAX9286_I2CMSTBT_28KBPS		(1 << 2)
+#define MAX9286_I2CMSTBT_8KBPS		(0 << 2)
+#define MAX9286_I2CSLVTO_NONE		(3 << 0)
+#define MAX9286_I2CSLVTO_1024US		(2 << 0)
+#define MAX9286_I2CSLVTO_256US		(1 << 0)
+#define MAX9286_I2CSLVTO_64US		(0 << 0)
+/* Register 0x3b */
+#define MAX9286_REV_TRF(n)		((n) << 4)
+#define MAX9286_REV_AMP(n)		((((n) - 30) / 10) << 1) /* in mV */
+#define MAX9286_REV_AMP_X		BIT(0)
+/* Register 0x3f */
+#define MAX9286_EN_REV_CFG		BIT(6)
+#define MAX9286_REV_FLEN(n)		((n) - 20)
+/* Register 0x49 */
+#define MAX9286_VIDEO_DETECT_MASK	0x0f
+/* Register 0x69 */
+#define MAX9286_LFLTBMONMASKED		BIT(7)
+#define MAX9286_LOCKMONMASKED		BIT(6)
+#define MAX9286_AUTOCOMBACKEN		BIT(5)
+#define MAX9286_AUTOMASKEN		BIT(4)
+#define MAX9286_MASKLINK(n)		((n) << 0)
+
+#define MAX9286_NUM_GMSL		4
+#define MAX9286_N_SINKS			4
+#define MAX9286_N_PADS			5
+#define MAX9286_SRC_PAD			4
+
+#define MAXIM_I2C_I2C_SPEED_400KHZ	MAX9286_I2CMSTBT_339KBPS
+#define MAXIM_I2C_I2C_SPEED_100KHZ	MAX9286_I2CMSTBT_105KBPS
+#define MAXIM_I2C_SPEED			MAXIM_I2C_I2C_SPEED_100KHZ
+
+struct max9286_source {
+	struct v4l2_async_subdev asd;
+	struct v4l2_subdev *sd;
+	struct fwnode_handle *fwnode;
+};
+
+#define asd_to_max9286_source(_asd) \
+	container_of(_asd, struct max9286_source, asd)
+
+struct max9286_device {
+	struct i2c_client *client;
+	struct v4l2_subdev sd;
+	struct media_pad pads[MAX9286_N_PADS];
+	struct regulator *regulator;
+	bool poc_enabled;
+	int streaming;
+
+	struct i2c_mux_core *mux;
+	unsigned int mux_channel;
+
+	struct v4l2_ctrl_handler ctrls;
+
+	struct v4l2_mbus_framefmt fmt[MAX9286_N_SINKS];
+
+	unsigned int nsources;
+	unsigned int source_mask;
+	unsigned int route_mask;
+	unsigned int csi2_data_lanes;
+	struct max9286_source sources[MAX9286_NUM_GMSL];
+	struct v4l2_async_notifier notifier;
+};
+
+static struct max9286_source *next_source(struct max9286_device *max9286,
+					  struct max9286_source *source)
+{
+	if (!source)
+		source = &max9286->sources[0];
+	else
+		source++;
+
+	for (; source < &max9286->sources[MAX9286_NUM_GMSL]; source++) {
+		if (source->fwnode)
+			return source;
+	}
+
+	return NULL;
+}
+
+#define for_each_source(max9286, source) \
+	for (source = NULL; (source = next_source(max9286, source)); )
+
+#define to_index(max9286, source) (source - &max9286->sources[0])
+
+#define sd_to_max9286(_sd) container_of(_sd, struct max9286_device, sd)
+
+/* -----------------------------------------------------------------------------
+ * I2C IO
+ */
+
+static int max9286_read(struct max9286_device *dev, u8 reg)
+{
+	int ret;
+
+	ret = i2c_smbus_read_byte_data(dev->client, reg);
+	if (ret < 0)
+		dev_err(&dev->client->dev,
+			"%s: register 0x%02x read failed (%d)\n",
+			__func__, reg, ret);
+
+	return ret;
+}
+
+static int max9286_write(struct max9286_device *dev, u8 reg, u8 val)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(dev->client, reg, val);
+	if (ret < 0)
+		dev_err(&dev->client->dev,
+			"%s: register 0x%02x write failed (%d)\n",
+			__func__, reg, ret);
+
+	return ret;
+}
+
+/* -----------------------------------------------------------------------------
+ * I2C Multiplexer
+ */
+
+static int max9286_i2c_mux_close(struct max9286_device *dev)
+{
+
+	/* FIXME: See note in max9286_i2c_mux_select() */
+	if (dev->streaming)
+		return 0;
+	/*
+	 * Ensure that both the forward and reverse channel are disabled on the
+	 * mux, and that the channel ID is invalidated to ensure we reconfigure
+	 * on the next select call.
+	 */
+	dev->mux_channel = -1;
+	max9286_write(dev, 0x0a, 0x00);
+	usleep_range(3000, 5000);
+
+	return 0;
+}
+
+static int max9286_i2c_mux_select(struct i2c_mux_core *muxc, u32 chan)
+{
+	struct max9286_device *dev = i2c_mux_priv(muxc);
+
+	/*
+	 * FIXME: This state keeping is a hack and do the job. It should
+	 * be should be reworked. One option to consider is that once all
+	 * cameras are programmed the mux selection logic should be disabled
+	 * and all all reverse and forward channels enable all the time.
+	 *
+	 * In any case this logic with a int that have two states should be
+	 * reworked!
+	 */
+	if (dev->streaming == 1) {
+		max9286_write(dev, 0x0a, 0xff);
+		dev->streaming = 2;
+		return 0;
+	} else if (dev->streaming == 2) {
+		return 0;
+	}
+
+	if (dev->mux_channel == chan)
+		return 0;
+
+	dev->mux_channel = chan;
+
+	max9286_write(dev, 0x0a, MAX9286_FWDCCEN(chan) | MAX9286_REVCCEN(chan));
+
+	/*
+	 * We must sleep after any change to the forward or reverse channel
+	 * configuration.
+	 */
+	usleep_range(3000, 5000);
+
+	return 0;
+}
+
+static int max9286_i2c_mux_init(struct max9286_device *dev)
+{
+	struct max9286_source *source;
+	int ret;
+
+	if (!i2c_check_functionality(dev->client->adapter,
+				     I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
+		return -ENODEV;
+
+	dev->mux = i2c_mux_alloc(dev->client->adapter, &dev->client->dev,
+				 dev->nsources, 0, I2C_MUX_LOCKED,
+				 max9286_i2c_mux_select, NULL);
+	if (!dev->mux)
+		return -ENOMEM;
+
+	dev->mux->priv = dev;
+
+	for_each_source(dev, source) {
+		unsigned int index = to_index(dev, source);
+
+		ret = i2c_mux_add_adapter(dev->mux, 0, index, 0);
+		if (ret < 0)
+			goto error;
+	}
+
+	return 0;
+
+error:
+	i2c_mux_del_adapters(dev->mux);
+	return ret;
+}
+
+static void max9286_configure_i2c(struct max9286_device *dev, bool localack)
+{
+	u8 config = MAX9286_I2CSLVSH_469NS_234NS | MAX9286_I2CSLVTO_1024US |
+		    MAXIM_I2C_SPEED;
+
+	if (localack)
+		config |= MAX9286_I2CLOCACK;
+
+	max9286_write(dev, 0x34, config);
+	usleep_range(3000, 5000);
+}
+
+/* -----------------------------------------------------------------------------
+ * V4L2 Subdev
+ */
+
+static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
+				struct v4l2_subdev *subdev,
+				struct v4l2_async_subdev *asd)
+{
+	struct max9286_device *dev = sd_to_max9286(notifier->sd);
+	struct max9286_source *source = asd_to_max9286_source(asd);
+	unsigned int index = to_index(dev, source);
+	unsigned int src_pad;
+	int ret;
+
+	ret = media_entity_get_fwnode_pad(&subdev->entity,
+					  source->fwnode,
+					  MEDIA_PAD_FL_SOURCE);
+	if (ret < 0) {
+		dev_err(&dev->client->dev,
+			"Failed to find pad for %s\n", subdev->name);
+		return ret;
+	}
+
+	source->sd = subdev;
+	src_pad = ret;
+
+	ret = media_create_pad_link(&source->sd->entity, src_pad,
+				    &dev->sd.entity, index,
+				    MEDIA_LNK_FL_ENABLED |
+				    MEDIA_LNK_FL_IMMUTABLE);
+	if (ret) {
+		dev_err(&dev->client->dev,
+			"Unable to link %s:%u -> %s:%u\n",
+			source->sd->name, src_pad, dev->sd.name, index);
+		return ret;
+	}
+
+	dev_dbg(&dev->client->dev, "Bound %s pad: %u on index %u\n",
+		subdev->name, src_pad, index);
+
+	return 0;
+}
+
+static void max9286_notify_unbind(struct v4l2_async_notifier *notifier,
+				  struct v4l2_subdev *subdev,
+				  struct v4l2_async_subdev *asd)
+{
+	struct max9286_source *source = asd_to_max9286_source(asd);
+
+	source->sd = NULL;
+}
+
+static const struct v4l2_async_notifier_operations max9286_notify_ops = {
+	.bound = max9286_notify_bound,
+	.unbind = max9286_notify_unbind,
+};
+
+/*
+ * max9286_check_video_links() - Make sure video links are detected and locked
+ *
+ * Performs safety checks on video link status. Make sure they are detected
+ * and all enabled links are locked.
+ *
+ * Returns 0 for success, -EIO for errors.
+ */
+static int max9286_check_video_links(struct max9286_device *dev)
+{
+	unsigned int i;
+	int ret;
+
+	/*
+	 * Make sure valid video links are detected.
+	 * The delay is not characterized in de-serializer manual, wait up
+	 * to 5 ms.
+	 */
+	for (i = 0; i < 10; i++) {
+		ret = max9286_read(dev, 0x49);
+		if (ret < 0)
+			return -EIO;
+
+		if ((ret & MAX9286_VIDEO_DETECT_MASK) == dev->source_mask)
+			break;
+
+		usleep_range(350, 500);
+	}
+
+	if (i == 10) {
+		dev_err(&dev->client->dev,
+			"Unable to detect video links: 0x%2x\n", ret);
+		return -EIO;
+	}
+
+	/* Make sure all enabled links are locked (4ms max). */
+	for (i = 0; i < 10; i++) {
+		ret = max9286_read(dev, 0x27);
+		if (ret < 0)
+			return -EIO;
+
+		if (ret & MAX9286_LOCKED)
+			break;
+
+		usleep_range(350, 450);
+	}
+
+	if (i == 10) {
+		dev_err(&dev->client->dev, "Not all enabled links locked\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int max9286_s_stream(struct v4l2_subdev *sd, int enable)
+{
+	struct max9286_device *dev = sd_to_max9286(sd);
+	struct max9286_source *source;
+	unsigned int i;
+	bool sync = false;
+	int ret;
+
+	if (enable) {
+		/* FIXME: See note in max9286_i2c_mux_select() */
+		dev->streaming = 1;
+
+		/* Start all cameras. */
+		for_each_source(dev, source) {
+			ret = v4l2_subdev_call(source->sd, video, s_stream, 1);
+			if (ret)
+				return ret;
+		}
+
+		ret = max9286_check_video_links(dev);
+		if (ret)
+			return ret;
+
+		/*
+		 * Wait until frame synchronization is locked.
+		 *
+		 * Manual says frame sync locking should take ~6 VTS.
+		 * From pratical experience at least 8 are required. Give
+		 * 12 complete frames time (~33ms at 30 fps) to achieve frame
+		 * locking before returning error.
+		 */
+		for (i = 0; i < 36; i++) {
+			if (max9286_read(dev, 0x31) & MAX9286_FSYNC_LOCKED) {
+				sync = true;
+				break;
+			}
+			usleep_range(9000, 11000);
+		}
+
+		if (!sync) {
+			dev_err(&dev->client->dev,
+				"Failed to get frame synchronization\n");
+			return -EINVAL;
+		}
+
+		/*
+		 * Enable CSI output, VC set according to link number.
+		 * Bit 7 must be set (chip manual says it's 0 and reserved).
+		 */
+		max9286_write(dev, 0x15, 0x80 | MAX9286_VCTYPE |
+			      MAX9286_CSIOUTEN | MAX9286_0X15_RESV);
+	} else {
+		max9286_write(dev, 0x15, MAX9286_VCTYPE | MAX9286_0X15_RESV);
+
+		/* Stop all cameras. */
+		for_each_source(dev, source)
+			v4l2_subdev_call(source->sd, video, s_stream, 0);
+
+		/* FIXME: See note in max9286_i2c_mux_select() */
+		dev->streaming = 0;
+	}
+
+	return 0;
+}
+
+static int max9286_enum_mbus_code(struct v4l2_subdev *sd,
+				  struct v4l2_subdev_pad_config *cfg,
+				  struct v4l2_subdev_mbus_code_enum *code)
+{
+	if (code->pad || code->index > 0)
+		return -EINVAL;
+
+	code->code = MEDIA_BUS_FMT_UYVY8_2X8;
+
+	return 0;
+}
+
+static struct v4l2_mbus_framefmt *
+max9286_get_pad_format(struct max9286_device *dev,
+		       struct v4l2_subdev_pad_config *cfg,
+		       unsigned int pad, u32 which)
+{
+	switch (which) {
+	case V4L2_SUBDEV_FORMAT_TRY:
+		return v4l2_subdev_get_try_format(&dev->sd, cfg, pad);
+	case V4L2_SUBDEV_FORMAT_ACTIVE:
+		return &dev->fmt[pad];
+	default:
+		return NULL;
+	}
+}
+
+static int max9286_set_fmt(struct v4l2_subdev *sd,
+			   struct v4l2_subdev_pad_config *cfg,
+			   struct v4l2_subdev_format *format)
+{
+	struct max9286_device *dev = sd_to_max9286(sd);
+	struct v4l2_mbus_framefmt *cfg_fmt;
+
+	if (format->pad >= MAX9286_SRC_PAD)
+		return -EINVAL;
+
+	/* Refuse non YUV422 formats as we hardcode DT to 8 bit YUV422 */
+	switch (format->format.code) {
+	case MEDIA_BUS_FMT_UYVY8_2X8:
+	case MEDIA_BUS_FMT_VYUY8_2X8:
+	case MEDIA_BUS_FMT_YUYV8_2X8:
+	case MEDIA_BUS_FMT_YVYU8_2X8:
+		break;
+	default:
+		format->format.code = MEDIA_BUS_FMT_YUYV8_2X8;
+		break;
+	}
+
+	cfg_fmt = max9286_get_pad_format(dev, cfg, format->pad, format->which);
+	if (!cfg_fmt)
+		return -EINVAL;
+
+	*cfg_fmt = format->format;
+
+	return 0;
+}
+
+static int max9286_get_fmt(struct v4l2_subdev *sd,
+			   struct v4l2_subdev_pad_config *cfg,
+			   struct v4l2_subdev_format *format)
+{
+	struct max9286_device *dev = sd_to_max9286(sd);
+	struct v4l2_mbus_framefmt *cfg_fmt;
+
+	if (format->pad >= MAX9286_SRC_PAD)
+		return -EINVAL;
+
+	cfg_fmt = max9286_get_pad_format(dev, cfg, format->pad, format->which);
+	if (!cfg_fmt)
+		return -EINVAL;
+
+	format->format = *cfg_fmt;
+
+	return 0;
+}
+
+static int max9286_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
+			   struct v4l2_mbus_frame_desc *fd)
+{
+	struct max9286_device *dev = sd_to_max9286(sd);
+	struct max9286_source *source;
+	unsigned int i = 0;
+
+	memset(fd, 0, sizeof(*fd));
+
+	for_each_source(dev, source) {
+		unsigned int index = to_index(dev, source);
+
+		fd->entry[i].stream = i;
+		fd->entry[i].bus.csi2.channel = index;
+		fd->entry[i].bus.csi2.data_type = 0x1e;
+		i++;
+	}
+
+	fd->type = V4L2_MBUS_FRAME_DESC_TYPE_CSI2;
+	fd->num_entries = dev->nsources;
+
+	return 0;
+}
+
+static int max9286_get_routing(struct v4l2_subdev *sd,
+				 struct v4l2_subdev_routing *routing)
+{
+	struct max9286_device *dev = sd_to_max9286(sd);
+	struct v4l2_subdev_route *r = routing->routes;
+	struct max9286_source *source;
+
+	/* There is one route per sink pad. */
+	if (routing->num_routes < dev->nsources) {
+		routing->num_routes = dev->nsources;
+		return -ENOSPC;
+	}
+
+	routing->num_routes = dev->nsources;
+
+	for_each_source(dev, source) {
+		unsigned int index = to_index(dev, source);
+
+		r->sink_pad = index;
+		r->sink_stream = 0;
+		r->source_pad = MAX9286_SRC_PAD;
+		r->source_stream = index;
+		r->flags = dev->route_mask & BIT(index) ?
+			V4L2_SUBDEV_ROUTE_FL_ACTIVE : 0;
+		r++;
+	}
+
+	return 0;
+}
+
+static int max9286_set_routing(struct v4l2_subdev *sd,
+			       struct v4l2_subdev_routing *routing)
+{
+
+	struct max9286_device *dev = sd_to_max9286(sd);
+	struct v4l2_subdev_route *r = routing->routes;
+	unsigned int i;
+
+	if (routing->num_routes > dev->nsources)
+		return -ENOSPC;
+
+	for (i = 0; i < routing->num_routes; i++) {
+		if (r->sink_pad >= MAX9286_SRC_PAD ||
+		    r->sink_stream != 0 ||
+		    r->source_pad != MAX9286_SRC_PAD ||
+		    r->source_stream != r->sink_pad)
+			return -EINVAL;
+
+		if (r->flags & V4L2_SUBDEV_ROUTE_FL_ACTIVE)
+			dev->route_mask |= BIT(r->sink_pad);
+		else
+			dev->route_mask &= ~BIT(r->sink_pad);
+
+		r++;
+	}
+
+	return 0;
+}
+
+static const struct v4l2_subdev_video_ops max9286_video_ops = {
+	.s_stream	= max9286_s_stream,
+};
+
+static const struct v4l2_subdev_pad_ops max9286_pad_ops = {
+	.enum_mbus_code = max9286_enum_mbus_code,
+	.get_fmt	= max9286_get_fmt,
+	.set_fmt	= max9286_set_fmt,
+	.get_frame_desc = max9286_get_frame_desc,
+	.get_routing	= max9286_get_routing,
+	.set_routing	= max9286_set_routing,
+};
+
+static const struct v4l2_subdev_ops max9286_subdev_ops = {
+	.video		= &max9286_video_ops,
+	.pad		= &max9286_pad_ops,
+};
+
+static void max9286_init_format(struct v4l2_mbus_framefmt *fmt)
+{
+	fmt->width		= 1280;
+	fmt->height		= 800;
+	fmt->code		= MEDIA_BUS_FMT_UYVY8_2X8;
+	fmt->colorspace		= V4L2_COLORSPACE_SRGB;
+	fmt->field		= V4L2_FIELD_NONE;
+	fmt->ycbcr_enc		= V4L2_YCBCR_ENC_DEFAULT;
+	fmt->quantization	= V4L2_QUANTIZATION_DEFAULT;
+	fmt->xfer_func		= V4L2_XFER_FUNC_DEFAULT;
+}
+
+static int max9286_open(struct v4l2_subdev *subdev, struct v4l2_subdev_fh *fh)
+{
+	struct v4l2_mbus_framefmt *format;
+	unsigned int i;
+
+	for (i = 0; i < MAX9286_N_SINKS; i++) {
+		format = v4l2_subdev_get_try_format(subdev, fh->pad, i);
+		max9286_init_format(format);
+	}
+
+	return 0;
+}
+
+static const struct v4l2_subdev_internal_ops max9286_subdev_internal_ops = {
+	.open = max9286_open,
+};
+
+/* -----------------------------------------------------------------------------
+ * Probe/Remove
+ */
+
+static int max9286_setup(struct max9286_device *dev)
+{
+	/*
+	 * Link ordering values for all enabled links combinations. Orders must
+	 * be assigned sequentially from 0 to the number of enabled links
+	 * without leaving any hole for disabled links. We thus assign orders to
+	 * enabled links first, and use the remaining order values for disabled
+	 * links are all links must have a different order value;
+	 */
+	static const u8 link_order[] = {
+		(3 << 6) | (2 << 4) | (1 << 2) | (0 << 0), /* xxxx */
+		(3 << 6) | (2 << 4) | (1 << 2) | (0 << 0), /* xxx0 */
+		(3 << 6) | (2 << 4) | (0 << 2) | (1 << 0), /* xx0x */
+		(3 << 6) | (2 << 4) | (1 << 2) | (0 << 0), /* xx10 */
+		(3 << 6) | (0 << 4) | (2 << 2) | (1 << 0), /* x0xx */
+		(3 << 6) | (1 << 4) | (2 << 2) | (0 << 0), /* x1x0 */
+		(3 << 6) | (1 << 4) | (0 << 2) | (2 << 0), /* x10x */
+		(3 << 6) | (1 << 4) | (1 << 2) | (0 << 0), /* x210 */
+		(0 << 6) | (3 << 4) | (2 << 2) | (1 << 0), /* 0xxx */
+		(1 << 6) | (3 << 4) | (2 << 2) | (0 << 0), /* 1xx0 */
+		(1 << 6) | (3 << 4) | (0 << 2) | (2 << 0), /* 1x0x */
+		(2 << 6) | (3 << 4) | (1 << 2) | (0 << 0), /* 2x10 */
+		(1 << 6) | (0 << 4) | (3 << 2) | (2 << 0), /* 10xx */
+		(2 << 6) | (1 << 4) | (3 << 2) | (0 << 0), /* 21x0 */
+		(2 << 6) | (1 << 4) | (0 << 2) | (3 << 0), /* 210x */
+		(3 << 6) | (2 << 4) | (1 << 2) | (0 << 0), /* 3210 */
+	};
+
+	/*
+	 * Set the I2C bus speed.
+	 *
+	 * Enable I2C Local Acknowledge during the probe sequences of the camera
+	 * only. This should be disabled after the mux is initialised.
+	 */
+	max9286_configure_i2c(dev, true);
+
+	/*
+	 * Reverse channel setup.
+	 *
+	 * - Enable custom reverse channel configuration (through register 0x3f)
+	 *   and set the first pulse length to 35 clock cycles.
+	 * - Increase the reverse channel amplitude to 170mV to accommodate the
+	 *   high threshold enabled by the serializer driver.
+	 */
+	max9286_write(dev, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
+	max9286_write(dev, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) |
+		      MAX9286_REV_AMP_X);
+
+	/*
+	 * Enable GMSL links, mask unused ones and autodetect link
+	 * used as CSI clock source.
+	 */
+	max9286_write(dev, 0x00, MAX9286_MSTLINKSEL_AUTO | dev->route_mask);
+	max9286_write(dev, 0x0b, link_order[dev->route_mask]);
+	max9286_write(dev, 0x69, (0xf & ~dev->route_mask));
+
+	/*
+	 * Video format setup:
+	 * Disable CSI output, VC is set accordingly to Link number.
+	 */
+	max9286_write(dev, 0x15, MAX9286_VCTYPE | MAX9286_0X15_RESV);
+
+	/* Enable CSI-2 Lane D0-D3 only, DBL mode, YUV422 8-bit. */
+	max9286_write(dev, 0x12, MAX9286_CSIDBL	| MAX9286_DBL |
+		      MAX9286_CSILANECNT(dev->csi2_data_lanes) |
+		      MAX9286_DATATYPE_YUV422_8BIT);
+
+	/* Automatic: FRAMESYNC taken from the slowest Link. */
+	max9286_write(dev, 0x01, MAX9286_FSYNCMODE_INT_HIZ |
+		      MAX9286_FSYNCMETH_AUTO);
+
+	/* Enable HS/VS encoding, use D14/15 for HS/VS, invert VS. */
+	max9286_write(dev, 0x0c, MAX9286_HVEN | MAX9286_INVVS |
+		      MAX9286_HVSRC_D14);
+
+	/*
+	 * Wait for 2ms to allow the link to resynchronize after the
+	 * configuration change.
+	 */
+	usleep_range(2000, 5000);
+
+	return 0;
+}
+
+static const struct of_device_id max9286_dt_ids[] = {
+	{ .compatible = "maxim,max9286" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, max9286_dt_ids);
+
+static int max9286_init(struct device *dev, void *data)
+{
+	struct max9286_device *max9286;
+	struct i2c_client *client;
+	struct device_node *ep;
+	unsigned int i;
+	int ret;
+
+	/* Skip non-max9286 devices. */
+	if (!dev->of_node || !of_match_node(max9286_dt_ids, dev->of_node))
+		return 0;
+
+	client = to_i2c_client(dev);
+	max9286 = i2c_get_clientdata(client);
+
+	/* Enable the bus power. */
+	ret = regulator_enable(max9286->regulator);
+	if (ret < 0) {
+		dev_err(&client->dev, "Unable to turn PoC on\n");
+		return ret;
+	}
+
+	max9286->poc_enabled = true;
+
+	ret = max9286_setup(max9286);
+	if (ret) {
+		dev_err(dev, "Unable to setup max9286\n");
+		goto err_regulator;
+	}
+
+	v4l2_i2c_subdev_init(&max9286->sd, client, &max9286_subdev_ops);
+	max9286->sd.internal_ops = &max9286_subdev_internal_ops;
+	max9286->sd.flags = V4L2_SUBDEV_FL_HAS_DEVNODE;
+
+	v4l2_ctrl_handler_init(&max9286->ctrls, 1);
+	/*
+	 * FIXME: Compute the real pixel rate. The 50 MP/s value comes from the
+	 * hardcoded frequency in the BSP CSI-2 receiver driver.
+	 */
+	v4l2_ctrl_new_std(&max9286->ctrls, NULL, V4L2_CID_PIXEL_RATE,
+			  50000000, 50000000, 1, 50000000);
+	max9286->sd.ctrl_handler = &max9286->ctrls;
+	ret = max9286->ctrls.error;
+	if (ret)
+		goto err_regulator;
+
+	max9286->sd.entity.function = MEDIA_ENT_F_PROC_VIDEO_PIXEL_FORMATTER;
+
+	max9286->pads[MAX9286_SRC_PAD].flags = MEDIA_PAD_FL_SOURCE;
+	for (i = 0; i < MAX9286_SRC_PAD; i++)
+		max9286->pads[i].flags = MEDIA_PAD_FL_SINK;
+	ret = media_entity_pads_init(&max9286->sd.entity, MAX9286_N_PADS,
+				     max9286->pads);
+	if (ret)
+		goto err_regulator;
+
+	ep = of_graph_get_endpoint_by_regs(dev->of_node, MAX9286_SRC_PAD, -1);
+	if (!ep) {
+		dev_err(dev, "Unable to retrieve endpoint on \"port@4\"\n");
+		ret = -ENOENT;
+		goto err_regulator;
+	}
+	max9286->sd.fwnode = of_fwnode_handle(ep);
+
+	ret = v4l2_async_register_subdev(&max9286->sd);
+	if (ret < 0) {
+		dev_err(dev, "Unable to register subdevice\n");
+		goto err_put_node;
+	}
+
+	ret = max9286_i2c_mux_init(max9286);
+	if (ret) {
+		dev_err(dev, "Unable to initialize I2C multiplexer\n");
+		goto err_subdev_unregister;
+	}
+
+	/*
+	 * Re-configure I2C with local acknowledge disabled after cameras
+	 * have probed.
+	 */
+	max9286_configure_i2c(max9286, false);
+
+	/* Leave the mux channels disabled until they are selected. */
+	max9286_i2c_mux_close(max9286);
+
+	return 0;
+
+err_subdev_unregister:
+	v4l2_async_unregister_subdev(&max9286->sd);
+	max9286_i2c_mux_close(max9286);
+err_put_node:
+	of_node_put(ep);
+err_regulator:
+	regulator_disable(max9286->regulator);
+	max9286->poc_enabled = false;
+
+	return ret;
+}
+
+static int max9286_is_bound(struct device *dev, void *data)
+{
+	struct device *this = data;
+	int ret;
+
+	if (dev == this)
+		return 0;
+
+	/* Skip non-max9286 devices. */
+	if (!dev->of_node || !of_match_node(max9286_dt_ids, dev->of_node))
+		return 0;
+
+	ret = device_is_bound(dev);
+	if (!ret)
+		return -EPROBE_DEFER;
+
+	return 0;
+}
+
+static struct device_node *max9286_get_i2c_by_id(struct device_node *parent,
+						 u32 id)
+{
+	struct device_node *child;
+
+	for_each_child_of_node(parent, child) {
+		u32 i2c_id = 0;
+
+		if (of_node_cmp(child->name, "i2c") != 0)
+			continue;
+		of_property_read_u32(child, "reg", &i2c_id);
+		if (id == i2c_id)
+			return child;
+	}
+
+	return NULL;
+}
+
+static int max9286_check_i2c_bus_by_id(struct device *dev, int id)
+{
+	struct device_node *i2c_np;
+
+	i2c_np = max9286_get_i2c_by_id(dev->of_node, id);
+	if (!i2c_np) {
+		dev_err(dev, "Failed to find corresponding i2c@%u\n", id);
+		return -ENODEV;
+	}
+
+	if (!of_device_is_available(i2c_np)) {
+		dev_dbg(dev, "Skipping port %u with disabled I2C bus\n", id);
+		of_node_put(i2c_np);
+		return -ENODEV;
+	}
+
+	of_node_put(i2c_np);
+
+	return 0;
+}
+
+static void max9286_cleanup_dt(struct max9286_device *max9286)
+{
+	struct max9286_source *source;
+
+	/*
+	 * Not strictly part of the DT, but the notifier is registered during
+	 * max9286_parse_dt(), and the notifier holds references to the fwnodes
+	 * thus the cleanup is here to mirror the registration.
+	 */
+	v4l2_async_notifier_unregister(&max9286->notifier);
+
+	for_each_source(max9286, source) {
+		fwnode_handle_put(source->fwnode);
+		source->fwnode = NULL;
+	}
+}
+
+static int max9286_parse_dt(struct max9286_device *max9286)
+{
+	struct device *dev = &max9286->client->dev;
+	struct device_node *ep_np = NULL;
+	int ret;
+
+	v4l2_async_notifier_init(&max9286->notifier);
+
+	for_each_endpoint_of_node(dev->of_node, ep_np) {
+		struct max9286_source *source;
+		struct of_endpoint ep;
+
+		of_graph_parse_endpoint(ep_np, &ep);
+		dev_dbg(dev, "Endpoint %pOF on port %d",
+			ep.local_node, ep.port);
+
+		if (ep.port > MAX9286_NUM_GMSL) {
+			dev_err(dev, "Invalid endpoint %s on port %d",
+				of_node_full_name(ep.local_node),
+				ep.port);
+
+			continue;
+		}
+
+		/* For the source endpoint just parse the bus configuration. */
+		if (ep.port == MAX9286_SRC_PAD) {
+			struct v4l2_fwnode_endpoint vep;
+			int ret;
+
+			ret = v4l2_fwnode_endpoint_alloc_parse(
+					of_fwnode_handle(ep_np), &vep);
+			if (ret)
+				return ret;
+
+			if (vep.bus_type != V4L2_MBUS_CSI2_DPHY) {
+				dev_err(dev,
+					"Media bus %u type not supported\n",
+					vep.bus_type);
+				v4l2_fwnode_endpoint_free(&vep);
+				return -EINVAL;
+			}
+
+			max9286->csi2_data_lanes =
+				vep.bus.mipi_csi2.num_data_lanes;
+			v4l2_fwnode_endpoint_free(&vep);
+
+			continue;
+		}
+
+		/* Skip if the corresponding GMSL link is unavailable. */
+		if (max9286_check_i2c_bus_by_id(dev, ep.port))
+			continue;
+
+		if (max9286->sources[ep.port].fwnode) {
+			dev_err(dev,
+				"Multiple port endpoints are not supported: %d",
+				ep.port);
+
+			continue;
+		}
+
+		source = &max9286->sources[ep.port];
+		source->fwnode = fwnode_graph_get_remote_endpoint(
+						of_fwnode_handle(ep_np));
+		if (!source->fwnode) {
+			dev_err(dev,
+				"Endpoint %pOF has no remote endpoint connection\n",
+				ep.local_node);
+
+			continue;
+		}
+
+		source->asd.match_type = V4L2_ASYNC_MATCH_FWNODE;
+		source->asd.match.fwnode = source->fwnode;
+
+		ret = v4l2_async_notifier_add_subdev(&max9286->notifier,
+						     &source->asd);
+		if (ret) /* TODO: Cleanup notifier! */
+			return ret;
+
+		max9286->source_mask |= BIT(ep.port);
+		max9286->nsources++;
+	}
+
+	/* Do not register the subdev notifier if there are no devices. */
+	if (!max9286->nsources)
+		return 0;
+
+	max9286->route_mask = max9286->source_mask;
+	max9286->notifier.ops = &max9286_notify_ops;
+
+	return v4l2_async_subdev_notifier_register(&max9286->sd,
+						   &max9286->notifier);
+}
+
+static int max9286_probe(struct i2c_client *client,
+			 const struct i2c_device_id *did)
+{
+	struct max9286_device *dev;
+	unsigned int i;
+	int ret;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	dev->client = client;
+	i2c_set_clientdata(client, dev);
+
+	for (i = 0; i < MAX9286_N_SINKS; i++)
+		max9286_init_format(&dev->fmt[i]);
+
+	ret = max9286_parse_dt(dev);
+	if (ret)
+		return ret;
+
+	dev->regulator = regulator_get(&client->dev, "poc");
+	if (IS_ERR(dev->regulator)) {
+		if (PTR_ERR(dev->regulator) != -EPROBE_DEFER)
+			dev_err(&client->dev,
+				"Unable to get PoC regulator (%ld)\n",
+				PTR_ERR(dev->regulator));
+		ret = PTR_ERR(dev->regulator);
+		goto err_free;
+	}
+
+	/*
+	 * We can have multiple MAX9286 instances on the same physical I2C
+	 * bus, and I2C children behind ports of separate MAX9286 instances
+	 * having the same I2C address. As the MAX9286 starts by default with
+	 * all ports enabled, we need to disable all ports on all MAX9286
+	 * instances before proceeding to further initialize the devices and
+	 * instantiate children.
+	 *
+	 * Start by just disabling all channels on the current device. Then,
+	 * if all other MAX9286 on the parent bus have been probed, proceed
+	 * to initialize them all, including the current one.
+	 */
+	max9286_i2c_mux_close(dev);
+
+	/*
+	 * The MAX9286 initialises with auto-acknowledge enabled by default.
+	 * This means that if multiple MAX9286 devices are connected to an I2C
+	 * bus, another MAX9286 could ack I2C transfers meant for a device on
+	 * the other side of the GMSL links for this MAX9286 (such as a
+	 * MAX9271). To prevent that disable auto-acknowledge early on; it
+	 * will be enabled later as needed.
+	 */
+	max9286_configure_i2c(dev, false);
+
+	ret = device_for_each_child(client->dev.parent, &client->dev,
+				    max9286_is_bound);
+	if (ret)
+		return 0;
+
+	dev_dbg(&client->dev,
+		"All max9286 probed: start initialization sequence\n");
+	ret = device_for_each_child(client->dev.parent, NULL,
+				    max9286_init);
+	if (ret < 0)
+		goto err_regulator;
+
+	/* Leave the mux channels disabled until they are selected. */
+	max9286_i2c_mux_close(dev);
+
+	return 0;
+
+err_regulator:
+	regulator_put(dev->regulator);
+	max9286_i2c_mux_close(dev);
+	max9286_configure_i2c(dev, false);
+err_free:
+	max9286_cleanup_dt(dev);
+	kfree(dev);
+
+	return ret;
+}
+
+static int max9286_remove(struct i2c_client *client)
+{
+	struct max9286_device *dev = i2c_get_clientdata(client);
+
+	i2c_mux_del_adapters(dev->mux);
+
+	fwnode_handle_put(dev->sd.fwnode);
+	v4l2_async_unregister_subdev(&dev->sd);
+
+	if (dev->poc_enabled)
+		regulator_disable(dev->regulator);
+	regulator_put(dev->regulator);
+
+	max9286_cleanup_dt(dev);
+	kfree(dev);
+
+	return 0;
+}
+
+static const struct i2c_device_id max9286_id[] = {
+	{ "max9286", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max9286_id);
+
+static struct i2c_driver max9286_i2c_driver = {
+	.driver	= {
+		.name		= "max9286",
+		.of_match_table	= of_match_ptr(max9286_dt_ids),
+	},
+	.probe		= max9286_probe,
+	.remove		= max9286_remove,
+	.id_table	= max9286_id,
+};
+
+module_i2c_driver(max9286_i2c_driver);
+
+MODULE_DESCRIPTION("Maxim MAX9286 GMSL Deserializer Driver");
+MODULE_AUTHOR("Vladimir Barinov");
+MODULE_LICENSE("GPL");
-- 
2.17.1