[PATCH v2 0/7] media: i2c: Add support for RDACM21 camera module

[PATCH v2 0/7] media: i2c: Add support for RDACM21 camera module

[Jacopo Mondi]

Hello,
  v2 of support for RDACM21 camera module in this series.

Patch [1/7] introduces the camera module driver.
Only change compared to v1:
- Increase pixel clock to 55MHz

From [2/7] to [5/7] there's a proposal of a possible way to support
both RDACM20 and RDACM21 with the same deserializer driver.
See v1 cover letter for details:
https://www.spinics.net/lists/linux-renesas-soc/msg52886.html

I have tested on Eagle V3M with 4 RDACM21, but the whole point of
this series is to retain compatibility with RDACM20.

For this reason I have included 2 patches on top, not intended for merge
that re-propose DTS support for the MAXIM max9286 expansion board connected
to Salvator-X and add the newly introduced property to the DTS file.

Kieran, I know you have a working setup with RDACM20, the final two patches are
meant for ease your testing. Can you give this series a spin ?
For your convenience I pushed a branch
git://jmondi.org/linux #gmsl/jmondi/renesas-drivers-2020-10-13-v5.9/rdacm21_high-threshold

Series based on latest renesas-drivers tag: renesas-drivers-2020-10-13-v5.9

If I get a confirmation this setup works on Salvator-X, I'll submit the new
property for inclusion to devicetree people, which I have left out at the
moment.

Thanks
  j

Jacopo Mondi (6):
  media: i2c: Add driver for RDACM21 camera module
  dt-bindings: media: max9286: Document 'maxim,high-threshold'
  media: i2c: max9286: Break-out reverse channel setup
  media: i2c: max9286: Make channel amplitude programmable
  media: i2c: max9286: Configure reverse channel amplitude
  [DNI] arm64: dts: renesas: salvator-x-max9286: Use high-threshold

Laurent Pinchart (1):
  arm64: dts: renesas: salvator-x: Add MAX9286 expansion board

 .../bindings/media/i2c/maxim,max9286.yaml     |  15 +
 MAINTAINERS                                   |  12 +
 .../boot/dts/renesas/salvator-x-max9286.dtsi  | 396 +++++++++++++
 drivers/media/i2c/Kconfig                     |  13 +
 drivers/media/i2c/Makefile                    |   2 +
 drivers/media/i2c/max9286.c                   |  54 +-
 drivers/media/i2c/rdacm21.c                   | 538 ++++++++++++++++++
 7 files changed, 1020 insertions(+), 10 deletions(-)
 create mode 100644 arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi
 create mode 100644 drivers/media/i2c/rdacm21.c

--
2.28.0

[PATCH v2 1/7] media: i2c: Add driver for RDACM21 camera module

[Jacopo Mondi]

The RDACM21 is a GMSL camera supporting 1280x1080 resolution images
developed by IMI based on an Omnivision OV10640 sensor, an Omnivision
OV490 ISP and a Maxim MAX9271 GMSL serializer.

The driver uses the max9271 library module, to maximize code reuse with
other camera module drivers using the same serializer, such as rdacm20.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 MAINTAINERS                 |  12 +
 drivers/media/i2c/Kconfig   |  13 +
 drivers/media/i2c/Makefile  |   2 +
 drivers/media/i2c/rdacm21.c | 538 ++++++++++++++++++++++++++++++++++++
 4 files changed, 565 insertions(+)
 create mode 100644 drivers/media/i2c/rdacm21.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 05ebf59d7685..574fe011c661 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14668,6 +14668,18 @@ F:	drivers/media/i2c/max9271.c
 F:	drivers/media/i2c/max9271.h
 F:	drivers/media/i2c/rdacm20.c
 
+RDACM21 Camera Sensor
+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/rdacm2x-gmsl.yaml
+F:	drivers/media/i2c/max9271.c
+F:	drivers/media/i2c/max9271.h
+F:	drivers/media/i2c/rdacm21.c
+
 RDC R-321X SoC
 M:	Florian Fainelli <florian@openwrt.org>
 S:	Maintained
diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
index 878f66ef2719..cfb3f0bcc4fc 100644
--- a/drivers/media/i2c/Kconfig
+++ b/drivers/media/i2c/Kconfig
@@ -1184,6 +1184,19 @@ config VIDEO_RDACM20
 	  This camera should be used in conjunction with a GMSL
 	  deserialiser such as the MAX9286.
 
+config VIDEO_RDACM21
+	tristate "IMI RDACM21 camera support"
+	depends on I2C
+	select V4L2_FWNODE
+	select VIDEO_V4L2_SUBDEV_API
+	select MEDIA_CONTROLLER
+	help
+	  This driver supports the IMI RDACM21 GMSL camera, used in
+	  ADAS systems.
+
+	  This camera should be used in conjunction with a GMSL
+	  deserialiser such as the MAX9286.
+
 config VIDEO_RJ54N1
 	tristate "Sharp RJ54N1CB0C sensor support"
 	depends on I2C && VIDEO_V4L2
diff --git a/drivers/media/i2c/Makefile b/drivers/media/i2c/Makefile
index f0a77473979d..f3641b58929d 100644
--- a/drivers/media/i2c/Makefile
+++ b/drivers/media/i2c/Makefile
@@ -122,6 +122,8 @@ obj-$(CONFIG_VIDEO_IMX355)	+= imx355.o
 obj-$(CONFIG_VIDEO_MAX9286)	+= max9286.o
 rdacm20-camera_module-objs	:= rdacm20.o max9271.o
 obj-$(CONFIG_VIDEO_RDACM20)	+= rdacm20-camera_module.o
+rdacm21-camera_module-objs	:= rdacm21.o max9271.o
+obj-$(CONFIG_VIDEO_RDACM21)	+= rdacm21-camera_module.o
 obj-$(CONFIG_VIDEO_ST_MIPID02) += st-mipid02.o
 
 obj-$(CONFIG_SDR_MAX2175) += max2175.o
diff --git a/drivers/media/i2c/rdacm21.c b/drivers/media/i2c/rdacm21.c
new file mode 100644
index 000000000000..279cbe213f32
--- /dev/null
+++ b/drivers/media/i2c/rdacm21.c
@@ -0,0 +1,538 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * IMI RDACM21 GMSL Camera Driver
+ *
+ * Copyright (C) 2017-2020 Jacopo Mondi
+ * Copyright (C) 2017-2019 Kieran Bingham
+ * Copyright (C) 2017-2019 Laurent Pinchart
+ * Copyright (C) 2017-2019 Niklas Söderlund
+ * Copyright (C) 2016 Renesas Electronics Corporation
+ * Copyright (C) 2015 Cogent Embedded, Inc.
+ */
+
+#include <linux/delay.h>
+#include <linux/fwnode.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/videodev2.h>
+
+#include <media/v4l2-async.h>
+#include <media/v4l2-ctrls.h>
+#include <media/v4l2-subdev.h>
+#include "max9271.h"
+
+#define OV10640_I2C_ADDRESS		0x30
+#define OV10640_ID_LOW			0xa6
+
+#define OV490_I2C_ADDRESS		0x24
+
+#define OV490_ISP_HSIZE_LOW		0x60
+#define OV490_ISP_HSIZE_HIGH		0x61
+#define OV490_ISP_VSIZE_LOW		0x62
+#define OV490_ISP_VSIZE_HIGH		0x63
+
+#define OV490_PID			0x300a
+#define OV490_VER			0x300b
+#define OV490_ID_VAL			0x0490
+#define OV490_ID(_p, _v)		((((_p) & 0xff) << 8) | ((_v) & 0xff))
+
+#define OV10640_PIXEL_RATE		(55000000)
+
+struct rdacm21_device {
+	struct device			*dev;
+	struct max9271_device		*serializer;
+	struct i2c_client		*isp;
+	struct v4l2_subdev		sd;
+	struct media_pad		pad;
+	struct v4l2_mbus_framefmt	fmt;
+	struct v4l2_ctrl_handler	ctrls;
+	u32				addrs[32];
+};
+
+static inline struct rdacm21_device *sd_to_rdacm21(struct v4l2_subdev *sd)
+{
+	return container_of(sd, struct rdacm21_device, sd);
+}
+
+static inline struct rdacm21_device *i2c_to_rdacm21(struct i2c_client *client)
+{
+	return sd_to_rdacm21(i2c_get_clientdata(client));
+}
+
+static const struct ov490_reg {
+	u16 reg;
+	u8 val;
+} ov490_regs_wizard[] = {
+	{0xfffd, 0x80},
+	{0xfffe, 0x82},
+	{0x0071, 0x11},
+	{0x0075, 0x11},
+	{0xfffe, 0x29},
+	{0x6010, 0x01},
+	/*
+	 * OV490 EMB line disable in YUV and RAW data,
+	 * NOTE: EMB line is still used in ISP and sensor
+	 */
+	{0xe000, 0x14},
+	{0xfffe, 0x28},
+	{0x6000, 0x04},
+	{0x6004, 0x00},
+	/*
+	 * PCLK polarity - useless due to silicon bug.
+	 * Use 0x808000bb register instead.
+	 */
+	{0x6008, 0x00},
+	{0xfffe, 0x80},
+	{0x0091, 0x00},
+	/* bit[3]=0 - PCLK polarity workaround. */
+	{0x00bb, 0x1d},
+	/* Ov490 FSIN: app_fsin_from_fsync */
+	{0xfffe, 0x85},
+	{0x0008, 0x00},
+	{0x0009, 0x01},
+	/* FSIN0 source. */
+	{0x000A, 0x05},
+	{0x000B, 0x00},
+	/* FSIN0 delay. */
+	{0x0030, 0x02},
+	{0x0031, 0x00},
+	{0x0032, 0x00},
+	{0x0033, 0x00},
+	/* FSIN1 delay. */
+	{0x0038, 0x02},
+	{0x0039, 0x00},
+	{0x003A, 0x00},
+	{0x003B, 0x00},
+	/* FSIN0 length. */
+	{0x0070, 0x2C},
+	{0x0071, 0x01},
+	{0x0072, 0x00},
+	{0x0073, 0x00},
+	/* FSIN1 length. */
+	{0x0074, 0x64},
+	{0x0075, 0x00},
+	{0x0076, 0x00},
+	{0x0077, 0x00},
+	{0x0000, 0x14},
+	{0x0001, 0x00},
+	{0x0002, 0x00},
+	{0x0003, 0x00},
+	/*
+	 * Load fsin0,load fsin1,load other,
+	 * It will be cleared automatically.
+	 */
+	{0x0004, 0x32},
+	{0x0005, 0x00},
+	{0x0006, 0x00},
+	{0x0007, 0x00},
+	{0xfffe, 0x80},
+	/* Sensor FSIN. */
+	{0x0081, 0x00},
+	/* ov10640 FSIN enable */
+	{0xfffe, 0x19},
+	{0x5000, 0x00},
+	{0x5001, 0x30},
+	{0x5002, 0x8c},
+	{0x5003, 0xb2},
+	{0xfffe, 0x80},
+	{0x00c0, 0xc1},
+	/* ov10640 HFLIP=1 by default */
+	{0xfffe, 0x19},
+	{0x5000, 0x01},
+	{0x5001, 0x00},
+	{0xfffe, 0x80},
+	{0x00c0, 0xdc},
+};
+
+static int ov490_read(struct rdacm21_device *dev, u16 reg, u8 *val)
+{
+	u8 buf[2] = { reg >> 8, reg & 0xff };
+	int ret;
+
+	ret = i2c_master_send(dev->isp, buf, 2);
+	if (ret == 2)
+		ret = i2c_master_recv(dev->isp, val, 1);
+
+	if (ret < 0) {
+		dev_dbg(dev->dev, "%s: register 0x%04x read failed (%d)\n",
+			__func__, reg, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int ov490_write(struct rdacm21_device *dev, u16 reg, u8 val)
+{
+	u8 buf[3] = { reg >> 8, reg & 0xff, val };
+	int ret;
+
+	dev_dbg(dev->dev, "%s: 0x%04x = 0x%02x\n", __func__, reg, val);
+
+	ret = i2c_master_send(dev->isp, buf, 3);
+	if (ret < 0) {
+		dev_err(dev->dev, "%s: register 0x%04x write failed (%d)\n",
+			__func__, reg, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int rdacm21_s_stream(struct v4l2_subdev *sd, int enable)
+{
+	struct rdacm21_device *dev = sd_to_rdacm21(sd);
+
+	/*
+	 * Enable serial link now that the ISP provides a valid pixel clock
+	 * to start serializing video data on the GMSL link.
+	 */
+	return max9271_set_serial_link(dev->serializer, enable);
+}
+
+static int rdacm21_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_YUYV8_1X16;
+
+	return 0;
+}
+
+static int rdacm21_get_fmt(struct v4l2_subdev *sd,
+			   struct v4l2_subdev_pad_config *cfg,
+			   struct v4l2_subdev_format *format)
+{
+	struct v4l2_mbus_framefmt *mf = &format->format;
+	struct rdacm21_device *dev = sd_to_rdacm21(sd);
+
+	if (format->pad)
+		return -EINVAL;
+
+	mf->width		= dev->fmt.width;
+	mf->height		= dev->fmt.height;
+	mf->code		= MEDIA_BUS_FMT_YUYV8_1X16;
+	mf->colorspace		= V4L2_COLORSPACE_SRGB;
+	mf->field		= V4L2_FIELD_NONE;
+	mf->ycbcr_enc		= V4L2_YCBCR_ENC_601;
+	mf->quantization	= V4L2_QUANTIZATION_FULL_RANGE;
+	mf->xfer_func		= V4L2_XFER_FUNC_NONE;
+
+	return 0;
+}
+
+static struct v4l2_subdev_video_ops rdacm21_video_ops = {
+	.s_stream	= rdacm21_s_stream,
+};
+
+static const struct v4l2_subdev_pad_ops rdacm21_subdev_pad_ops = {
+	.enum_mbus_code = rdacm21_enum_mbus_code,
+	.get_fmt	= rdacm21_get_fmt,
+	.set_fmt	= rdacm21_get_fmt,
+};
+
+static struct v4l2_subdev_ops rdacm21_subdev_ops = {
+	.video		= &rdacm21_video_ops,
+	.pad		= &rdacm21_subdev_pad_ops,
+};
+
+static int ov490_initialize(struct rdacm21_device *dev)
+{
+	unsigned int ov490_pid_retry = 20;
+	unsigned int timeout;
+	u8 pid, ver, val;
+	unsigned int i;
+	int ret;
+
+	/* Read OV490 Id to test communications. */
+pid_retry:
+	ret = ov490_write(dev, 0xfffd, 0x80);
+	ret = ov490_write(dev, 0xfffe, 0x80);
+	usleep_range(100, 150);
+
+	ret = ov490_read(dev, OV490_PID, &pid);
+	if (ret < 0) {
+		/* Give OV490 a few more cycles to exit from reset. */
+		if (ov490_pid_retry--) {
+			usleep_range(500, 1000);
+			goto pid_retry;
+		}
+
+		dev_err(dev->dev, "OV490 PID read failed (%d)\n", ret);
+		return ret;
+	}
+
+	ret = ov490_read(dev, OV490_VER, &ver);
+	if (ret < 0) {
+		dev_err(dev->dev, "OV490 VERSION read failed (%d)\n", ret);
+		return ret;
+	}
+
+	if (OV490_ID(pid, ver) != OV490_ID_VAL) {
+		dev_err(dev->dev, "OV490 ID mismatch: (0x%04x)\n",
+			OV490_ID(pid, ver));
+		return -ENODEV;
+	}
+
+	/* Wait for firmware boot by reading streamon status. */
+	ov490_write(dev, 0xfffd, 0x80);
+	ov490_write(dev, 0xfffe, 0x29);
+	usleep_range(100, 150);
+	for (timeout = 300; timeout > 0; timeout--) {
+		ov490_read(dev, 0xd000, &val);
+		if (val == 0x0c)
+			break;
+		mdelay(1);
+	}
+	if (!timeout) {
+		dev_err(dev->dev, "Timeout firmware boot wait\n");
+		return -ENODEV;
+	}
+	dev_dbg(dev->dev, "Firmware booted in %u msec\n", 300 - timeout);
+
+	/* Read OV10640 Id to test communications. */
+	ov490_write(dev, 0xfffd, 0x80);
+	ov490_write(dev, 0xfffe, 0x19);
+	usleep_range(100, 150);
+
+	ov490_write(dev, 0x5000, 0x01);
+	ov490_write(dev, 0x5001, 0x30);
+	ov490_write(dev, 0x5002, 0x0a);
+
+	ov490_write(dev, 0xfffe, 0x80);
+	usleep_range(100, 150);
+	ov490_write(dev, 0xc0, 0xc1);
+	ov490_write(dev, 0xfffe, 0x19);
+	usleep_range(1000, 1500);
+	ov490_read(dev, 0x5000, &val);
+	if (val != OV10640_ID_LOW) {
+		dev_err(dev->dev, "OV10640 ID mismatch: (0x%02x)\n", val);
+		return -ENODEV;
+	}
+
+	dev_dbg(dev->dev, "OV10640 ID = 0x%2x\n", val);
+
+	for (i = 0; i < ARRAY_SIZE(ov490_regs_wizard); ++i) {
+		ret = ov490_write(dev, ov490_regs_wizard[i].reg,
+				  ov490_regs_wizard[i].val);
+		if (ret < 0) {
+			dev_err(dev->dev,
+				"%s: register %u (0x%04x) write failed (%d)\n",
+				__func__, i, ov490_regs_wizard[i].reg, ret);
+
+			return -EIO;
+		}
+
+		usleep_range(100, 150);
+	}
+
+	/*
+	 * The ISP is programmed with the content of a serial flash memory.
+	 * Read the firmware configuration to reflect it through the V4L2 APIs.
+	 */
+	ov490_write(dev, 0xfffd, 0x80);
+	ov490_write(dev, 0xfffe, 0x82);
+	usleep_range(100, 150);
+	ov490_read(dev, OV490_ISP_HSIZE_HIGH, &val);
+	dev->fmt.width = (val & 0xf) << 8;
+	ov490_read(dev, OV490_ISP_HSIZE_LOW, &val);
+	dev->fmt.width |= (val & 0xff);
+
+	ov490_read(dev, OV490_ISP_VSIZE_HIGH, &val);
+	dev->fmt.height = (val & 0xf) << 8;
+	ov490_read(dev, OV490_ISP_VSIZE_LOW, &val);
+	dev->fmt.height |= val & 0xff;
+
+	/* Set bus width to 12 bits [0:11] */
+	ov490_write(dev, 0xfffd, 0x80);
+	ov490_write(dev, 0xfffe, 0x28);
+	usleep_range(100, 150);
+	ov490_write(dev, 0x6009, 0x10);
+
+	dev_info(dev->dev, "Identified RDACM21 camera module\n");
+
+	return 0;
+}
+
+static int rdacm21_initialize(struct rdacm21_device *dev)
+{
+	int ret;
+
+	/* Verify communication with the MAX9271: ping to wakeup. */
+	dev->serializer->client->addr = MAX9271_DEFAULT_ADDR;
+	i2c_smbus_read_byte(dev->serializer->client);
+
+	/* Serial link disabled during config as it needs a valid pixel clock. */
+	ret = max9271_set_serial_link(dev->serializer, false);
+	if (ret)
+		return ret;
+
+	/* Set GPO high to hold OV490 in reset during max9271 configuration. */
+	ret = max9271_set_gpios(dev->serializer, MAX9271_GPO);
+	if (ret)
+		return ret;
+
+	/* Configure I2C bus at 105Kbps speed and configure GMSL link. */
+	ret = max9271_configure_i2c(dev->serializer,
+				    MAX9271_I2CSLVSH_469NS_234NS |
+				    MAX9271_I2CSLVTO_1024US |
+				    MAX9271_I2CMSTBT_105KBPS);
+	if (ret)
+		return ret;
+
+	ret = max9271_configure_gmsl_link(dev->serializer);
+	if (ret)
+		return ret;
+
+	ret = max9271_set_address(dev->serializer, dev->addrs[0]);
+	if (ret)
+		return ret;
+	dev->serializer->client->addr = dev->addrs[0];
+
+	/*
+	 * Release OV490 from reset and program address translation
+	 * before performing OV490 configuration.
+	 */
+	ret = max9271_clear_gpios(dev->serializer, MAX9271_GPO);
+	if (ret)
+		return ret;
+
+	ret = max9271_set_translation(dev->serializer, dev->addrs[1],
+				      OV490_I2C_ADDRESS);
+	if (ret)
+		return ret;
+	dev->isp->addr = dev->addrs[1];
+
+	ret = ov490_initialize(dev);
+	if (ret)
+		return ret;
+
+	/*
+	 * Set reverse channel high threshold to increase noise immunity.
+	 *
+	 * This should be compensated by increasing the reverse channel
+	 * amplitude on the remote deserializer side.
+	 */
+	ret = max9271_set_high_threshold(dev->serializer, true);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int rdacm21_probe(struct i2c_client *client)
+{
+	struct rdacm21_device *dev;
+	struct fwnode_handle *ep;
+	int ret;
+
+	dev = devm_kzalloc(&client->dev, sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+	dev->dev = &client->dev;
+
+	dev->serializer = devm_kzalloc(&client->dev, sizeof(*dev->serializer),
+				       GFP_KERNEL);
+	if (!dev->serializer)
+		return -ENOMEM;
+
+	dev->serializer->client = client;
+
+	ret = of_property_read_u32_array(client->dev.of_node, "reg",
+					 dev->addrs, 2);
+	if (ret < 0) {
+		dev_err(dev->dev, "Invalid DT reg property: %d\n", ret);
+		return -EINVAL;
+	}
+
+	/* Create the dummy I2C client for the sensor. */
+	dev->isp = i2c_new_dummy_device(client->adapter, OV490_I2C_ADDRESS);
+	if (IS_ERR(dev->isp))
+		return PTR_ERR(dev->isp);
+
+	ret = rdacm21_initialize(dev);
+	if (ret < 0)
+		goto error;
+
+	/* Initialize and register the subdevice. */
+	v4l2_i2c_subdev_init(&dev->sd, client, &rdacm21_subdev_ops);
+	dev->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
+
+	v4l2_ctrl_handler_init(&dev->ctrls, 1);
+	v4l2_ctrl_new_std(&dev->ctrls, NULL, V4L2_CID_PIXEL_RATE,
+			  OV10640_PIXEL_RATE, OV10640_PIXEL_RATE, 1,
+			  OV10640_PIXEL_RATE);
+	dev->sd.ctrl_handler = &dev->ctrls;
+
+	ret = dev->ctrls.error;
+	if (ret)
+		goto error_free_ctrls;
+
+	dev->pad.flags = MEDIA_PAD_FL_SOURCE;
+	dev->sd.entity.flags |= MEDIA_ENT_F_CAM_SENSOR;
+	ret = media_entity_pads_init(&dev->sd.entity, 1, &dev->pad);
+	if (ret < 0)
+		goto error_free_ctrls;
+
+	ep = fwnode_graph_get_next_endpoint(dev_fwnode(&client->dev), NULL);
+	if (!ep) {
+		dev_err(&client->dev,
+			"Unable to get endpoint in node %pOF\n",
+			client->dev.of_node);
+		ret = -ENOENT;
+		goto error_free_ctrls;
+	}
+	dev->sd.fwnode = ep;
+
+	ret = v4l2_async_register_subdev(&dev->sd);
+	if (ret)
+		goto error_put_node;
+
+	return 0;
+
+error_put_node:
+	fwnode_handle_put(dev->sd.fwnode);
+error_free_ctrls:
+	v4l2_ctrl_handler_free(&dev->ctrls);
+error:
+	i2c_unregister_device(dev->isp);
+
+	return ret;
+}
+
+static int rdacm21_remove(struct i2c_client *client)
+{
+	struct rdacm21_device *dev = i2c_to_rdacm21(client);
+
+	fwnode_handle_put(dev->sd.fwnode);
+	v4l2_async_unregister_subdev(&dev->sd);
+	i2c_unregister_device(dev->isp);
+
+	return 0;
+}
+
+static const struct of_device_id rdacm21_of_ids[] = {
+	{ .compatible = "imi,rdacm21" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, rdacm21_of_ids);
+
+static struct i2c_driver rdacm21_i2c_driver = {
+	.driver	= {
+		.name	= "rdacm21",
+		.of_match_table = rdacm21_of_ids,
+	},
+	.probe_new	= rdacm21_probe,
+	.remove		= rdacm21_remove,
+};
+
+module_i2c_driver(rdacm21_i2c_driver);
+
+MODULE_DESCRIPTION("GMSL Camera driver for RDACM21");
+MODULE_AUTHOR("Jacopo Mondi, Kieran Bingham, Laurent Pinchart, Niklas Söderlund, Vladimir Barinov");
+MODULE_LICENSE("GPL v2");
-- 
2.28.0

[PATCH v2 2/7] dt-bindings: media: max9286: Document 'maxim,high-threshold'

[Jacopo Mondi]

Document the 'maxim,high-threshold' vendor property in the bindings
document of the max9286 driver.

The newly introduced boolean property allows controlling the initial
configuration of the GMSL reverse control channel to accommodate
remote serializers pre-programmed with the high threshold power
supply noise immunity enabled.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 .../bindings/media/i2c/maxim,max9286.yaml         | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
index 9ea827092fdd..50e08a7d3204 100644
--- a/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
+++ b/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
@@ -51,6 +51,19 @@ properties:
   '#gpio-cells':
     const: 2
 
+  maxim,high-threshold:
+    description: |
+      A boolean property to increase the initial amplitude of the reverse
+      control channel to compensate for remote serializers pre-programmed with
+      high threshold noise-immunity.
+
+      Some camera modules (in example the RDACM20 one) include an on-board MCU
+      that pre-programs the embedded serializer with reverse channel power
+      supply noise immunity enabled. The deserializer shall increase its
+      reverse channel amplitude to compensate that and be able to communicate
+      with the remote end.
+    type: boolean
+
   ports:
     type: object
     description: |
@@ -243,6 +256,8 @@ examples:
         gpio-controller;
         #gpio-cells = <2>;
 
+        maxim,high-threshold;
+
         ports {
           #address-cells = <1>;
           #size-cells = <0>;
-- 
2.28.0

[PATCH v2 3/7] media: i2c: max9286: Break-out reverse channel setup

[Jacopo Mondi]

Break out the reverse channel setup configuration procedure to its own
function.

This change prepares for configuring the reverse channel conditionally
to the remote side high threshold configuration.

No functional changes intended.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 drivers/media/i2c/max9286.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
index d969ac21a058..89a7248f5c25 100644
--- a/drivers/media/i2c/max9286.c
+++ b/drivers/media/i2c/max9286.c
@@ -906,6 +906,22 @@ static void max9286_v4l2_unregister(struct max9286_priv *priv)
  * Probe/Remove
  */
 
+static void max9286_reverse_channel_setup(struct max9286_priv *priv)
+{
+	/*
+	 * 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(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
+	max9286_write(priv, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) |
+		      MAX9286_REV_AMP_X);
+	usleep_range(2000, 2500);
+}
+
 static int max9286_setup(struct max9286_priv *priv)
 {
 	/*
@@ -941,19 +957,7 @@ static int max9286_setup(struct max9286_priv *priv)
 	 * only. This should be disabled after the mux is initialised.
 	 */
 	max9286_configure_i2c(priv, 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(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
-	max9286_write(priv, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) |
-		      MAX9286_REV_AMP_X);
-	usleep_range(2000, 2500);
+	max9286_reverse_channel_setup(priv);
 
 	/*
 	 * Enable GMSL links, mask unused ones and autodetect link
-- 
2.28.0

[PATCH v2 4/7] media: i2c: max9286: Make channel amplitude programmable

[Jacopo Mondi]

Instrument the function that configures the reverse channel with a
programmable amplitude value.

This change serves to prepare to adjust the reverse channel amplitude
depending on the remote end high-threshold configuration.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 drivers/media/i2c/max9286.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
index 89a7248f5c25..163e102199e3 100644
--- a/drivers/media/i2c/max9286.c
+++ b/drivers/media/i2c/max9286.c
@@ -906,19 +906,29 @@ static void max9286_v4l2_unregister(struct max9286_priv *priv)
  * Probe/Remove
  */
 
-static void max9286_reverse_channel_setup(struct max9286_priv *priv)
+static void max9286_reverse_channel_setup(struct max9286_priv *priv,
+					  unsigned int chan_amplitude)
 {
+	/* Reverse channel transmission time: default to 1. */
+	u8 chan_config = MAX9286_REV_TRF(1);
+
 	/*
 	 * 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.
+	 * - Adjust reverse channel amplitude: values > 130 are programmed
+	 *   using the additional +100mV REV_AMP_X boost flag
 	 */
 	max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
-	max9286_write(priv, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) |
-		      MAX9286_REV_AMP_X);
+
+	if (chan_amplitude > 100) {
+		/* It is not possible express values (100 < x < 130) */
+		chan_amplitude = chan_amplitude < 130
+			       ? 30 : chan_amplitude - 100;
+		chan_config |= MAX9286_REV_AMP_X;
+	}
+	max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
 	usleep_range(2000, 2500);
 }
 
@@ -957,7 +967,7 @@ static int max9286_setup(struct max9286_priv *priv)
 	 * only. This should be disabled after the mux is initialised.
 	 */
 	max9286_configure_i2c(priv, true);
-	max9286_reverse_channel_setup(priv);
+	max9286_reverse_channel_setup(priv, 170);
 
 	/*
 	 * Enable GMSL links, mask unused ones and autodetect link
-- 
2.28.0

[PATCH v2 5/7] media: i2c: max9286: Configure reverse channel amplitude

[Jacopo Mondi]

Adjust reverse channel amplitude according to the presence of
the 'high-threshold" DTS property.

If no high threshold compensation is required, start with a low
amplitude (100mV) and increase it after the remote serializers
have probed and have enabled noise immunity on their reverse
channels.

If high threshold compensation is required, configure the reverse
channel with a 170mV amplitude before the remote serializers have
probed.

This change is required for both rdacm20 and rdacm21 camera modules
to be correctly probed when used in combination with the max9286
deserializer.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 drivers/media/i2c/max9286.c | 74 +++++++++++++++++++++++--------------
 1 file changed, 47 insertions(+), 27 deletions(-)

diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
index 163e102199e3..4b59a9e0228a 100644
--- a/drivers/media/i2c/max9286.c
+++ b/drivers/media/i2c/max9286.c
@@ -163,6 +163,8 @@ struct max9286_priv {
 	unsigned int mux_channel;
 	bool mux_open;
 
+	bool high_threshold;
+
 	struct v4l2_ctrl_handler ctrls;
 	struct v4l2_ctrl *pixelrate;
 
@@ -436,6 +438,32 @@ static int max9286_check_config_link(struct max9286_priv *priv,
 	return 0;
 }
 
+static void max9286_reverse_channel_setup(struct max9286_priv *priv,
+					  unsigned int chan_amplitude)
+{
+	/* Reverse channel transmission time: default to 1. */
+	u8 chan_config = MAX9286_REV_TRF(1);
+
+	/*
+	 * Reverse channel setup.
+	 *
+	 * - Enable custom reverse channel configuration (through register 0x3f)
+	 *   and set the first pulse length to 35 clock cycles.
+	 * - Adjust reverse channel amplitude: values > 130 are programmed
+	 *   using the additional +100mV REV_AMP_X boost flag
+	 */
+	max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
+
+	if (chan_amplitude > 100) {
+		/* It is not possible express values (100 < x < 130) */
+		chan_amplitude = chan_amplitude < 130
+			       ? 30 : chan_amplitude - 100;
+		chan_config |= MAX9286_REV_AMP_X;
+	}
+	max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
+	usleep_range(2000, 2500);
+}
+
 /* -----------------------------------------------------------------------------
  * V4L2 Subdev
  */
@@ -531,10 +559,14 @@ static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
 	 * All enabled sources have probed and enabled their reverse control
 	 * channels:
 	 *
+	 * - Increase the reverse channel amplitude to compensate for the
+	 *   remote ends high threshold, if not done already
 	 * - Verify all configuration links are properly detected
 	 * - Disable auto-ack as communication on the control channel are now
 	 *   stable.
 	 */
+	if (!priv->high_threshold)
+		max9286_reverse_channel_setup(priv, 170);
 	max9286_check_config_link(priv, priv->source_mask);
 
 	/*
@@ -906,32 +938,6 @@ static void max9286_v4l2_unregister(struct max9286_priv *priv)
  * Probe/Remove
  */
 
-static void max9286_reverse_channel_setup(struct max9286_priv *priv,
-					  unsigned int chan_amplitude)
-{
-	/* Reverse channel transmission time: default to 1. */
-	u8 chan_config = MAX9286_REV_TRF(1);
-
-	/*
-	 * Reverse channel setup.
-	 *
-	 * - Enable custom reverse channel configuration (through register 0x3f)
-	 *   and set the first pulse length to 35 clock cycles.
-	 * - Adjust reverse channel amplitude: values > 130 are programmed
-	 *   using the additional +100mV REV_AMP_X boost flag
-	 */
-	max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
-
-	if (chan_amplitude > 100) {
-		/* It is not possible express values (100 < x < 130) */
-		chan_amplitude = chan_amplitude < 130
-			       ? 30 : chan_amplitude - 100;
-		chan_config |= MAX9286_REV_AMP_X;
-	}
-	max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
-	usleep_range(2000, 2500);
-}
-
 static int max9286_setup(struct max9286_priv *priv)
 {
 	/*
@@ -967,7 +973,15 @@ static int max9286_setup(struct max9286_priv *priv)
 	 * only. This should be disabled after the mux is initialised.
 	 */
 	max9286_configure_i2c(priv, true);
-	max9286_reverse_channel_setup(priv, 170);
+
+	/*
+	 * Compensate the remote end high threshold with a larger channel
+	 * amplitude if necessary.
+	 */
+	if (priv->high_threshold)
+		max9286_reverse_channel_setup(priv, 170);
+	else
+		max9286_reverse_channel_setup(priv, 100);
 
 	/*
 	 * Enable GMSL links, mask unused ones and autodetect link
@@ -1235,6 +1249,12 @@ static int max9286_parse_dt(struct max9286_priv *priv)
 	}
 	of_node_put(node);
 
+	/*
+	 * Parse 'high_threshold' property to configure the reverse channel
+	 * amplitude.
+	 */
+	priv->high_threshold = device_property_present(dev, "high_threshold");
+
 	priv->route_mask = priv->source_mask;
 
 	return 0;
-- 
2.28.0

[PATCH v2 6/7] [DNI] arm64: dts: renesas: salvator-x: Add MAX9286 expansion board

[Jacopo Mondi]

From: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

Add a .dtsi fragment to describe the MAX9286-based expansion board for
the Renesas Salvator-X board.

The MAX9286 expansion board has eight RDACM20 cameras connected to it.
They can be individually controlled by enabling or disabling the macro
defines.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

---
v2:
 - Use SPDX headers
 - Remove link from ADV748x TXA (HDMI)
 - Use 0x31-0x38, and 0x41-0x48 for the 8 cameras. 0x30 and 0x40 are the
   base addresses for the OV10635 and MAX9271 (0x50 for the MCU)
 - Provide RDACM20 MCU I2C address reservations. (0x51-0x58)

v3:
 - Fix gmsl-serializer@ i2c node addressing

v6:
 - Make i2c-mux child node and update to be conformant to new bindings.

v7:
 - Separate register arguments
---
 .../boot/dts/renesas/salvator-x-max9286.dtsi  | 394 ++++++++++++++++++
 1 file changed, 394 insertions(+)
 create mode 100644 arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi

diff --git a/arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi b/arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi
new file mode 100644
index 000000000000..6f4798859542
--- /dev/null
+++ b/arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi
@@ -0,0 +1,394 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Device Tree Source for the Salvator-X MAX9286 expansion board
+ *
+ * Copyright (C) 2017 Ideas on Board <laurent.pinchart@ideasonboard.com>
+ */
+
+#include <dt-bindings/gpio/gpio.h>
+
+/*
+ * MAX9286 A
+ */
+#define MAXIM_CAMERA0 "imi,rdacm20"
+#define MAXIM_CAMERA1 "imi,rdacm20"
+#define MAXIM_CAMERA2 "imi,rdacm20"
+#define MAXIM_CAMERA3 "imi,rdacm20"
+
+/*
+ * MAX9286 B
+ */
+#define MAXIM_CAMERA4 "imi,rdacm20"
+#define MAXIM_CAMERA5 "imi,rdacm20"
+#define MAXIM_CAMERA6 "imi,rdacm20"
+#define MAXIM_CAMERA7 "imi,rdacm20"
+
+/ {
+/*
+ * Powered MCU IMI cameras need delay between power-on and R-Car access
+ * to avoid I2C bus conflicts since the R-Car I2C does not support I2C
+ * multi-master. The I2C bus conflict would result in R-Car I2C IP stall.
+ */
+#define IMI_MCU_V0_DELAY	8000000	/* delay for powered MCU firmware v0 */
+#define IMI_MCU_V1_DELAY	3000000	/* delay for powered MCU firmware v1 */
+#define IMI_MCU_NO_DELAY	0	/* delay for unpowered MCU  */
+#define IMI_MCU_DELAY		IMI_MCU_V0_DELAY
+
+	poc_12v: regulator-vcc-poc-12v {
+		compatible = "regulator-fixed";
+
+		regulator-name = "Camera PoC 12V";
+		regulator-min-microvolt = <12000000>;
+		regulator-max-microvolt = <12000000>;
+		startup-delay-us = <(250000 + IMI_MCU_DELAY)>;
+
+		gpio = <&gpio6 30 GPIO_ACTIVE_HIGH>;
+		enable-active-high;
+	};
+};
+
+&vin0 {
+	status = "okay";
+};
+
+&vin1 {
+	status = "okay";
+};
+
+&vin2 {
+	status = "okay";
+};
+
+&vin3 {
+	status = "okay";
+};
+
+&vin4 {
+	status = "okay";
+};
+
+&vin5 {
+	status = "okay";
+};
+
+&vin6 {
+	status = "okay";
+};
+
+&vin7 {
+	status = "okay";
+};
+
+/* Disconnect the csi40 endpoint from the ADV748x TXA (HDMI) */
+&adv7482_txa {
+	/delete-property/ remote-endpoint;
+	status = "disabled";
+};
+
+&csi40 {
+	status = "okay";
+
+	ports {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		port@0 {
+			reg = <0>;
+
+			csi40_in: endpoint {
+				clock-lanes = <0>;
+				data-lanes = <1 2 3 4>;
+				remote-endpoint = <&max9286_out0>;
+			};
+		};
+	};
+};
+
+&csi41 {
+	status = "okay";
+
+	ports {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		port@0 {
+			reg = <0>;
+
+			csi41_in: endpoint {
+				clock-lanes = <0>;
+				data-lanes = <1 2 3 4>;
+				remote-endpoint = <&max9286_out1>;
+			};
+		};
+	};
+};
+
+&i2c4 {
+	gmsl-deserializer@4c {
+		compatible = "maxim,max9286";
+		reg = <0x4c>;
+		poc-supply = <&poc_12v>;
+
+		ports {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			port@0 {
+				reg = <0>;
+				max9286_in0: endpoint {
+#ifdef MAXIM_CAMERA0
+					remote-endpoint = <&rdacm20_out0>;
+#endif
+				};
+			};
+
+			port@1 {
+				reg = <1>;
+				max9286_in1: endpoint {
+#ifdef MAXIM_CAMERA1
+					remote-endpoint = <&rdacm20_out1>;
+#endif
+				};
+			};
+
+			port@2 {
+				reg = <2>;
+				max9286_in2: endpoint {
+#ifdef MAXIM_CAMERA2
+					remote-endpoint = <&rdacm20_out2>;
+#endif
+				};
+			};
+
+			port@3 {
+				reg = <3>;
+				max9286_in3: endpoint {
+#ifdef MAXIM_CAMERA3
+					remote-endpoint = <&rdacm20_out3>;
+#endif
+				};
+			};
+
+			port@4 {
+				reg = <4>;
+				max9286_out0: endpoint {
+					clock-lanes = <0>;
+					data-lanes = <1 2 3 4>;
+					remote-endpoint = <&csi40_in>;
+				};
+			};
+		};
+
+		i2c-mux {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			i2c@0 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+				reg = <0>;
+
+#ifdef MAXIM_CAMERA0
+				camera@31 {
+					compatible = MAXIM_CAMERA0;
+					reg = <0x31>, <0x41>, <0x51>;
+
+					port {
+						rdacm20_out0: endpoint {
+							remote-endpoint = <&max9286_in0>;
+						};
+					};
+
+				};
+#endif
+			};
+
+			i2c@1 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+				reg = <1>;
+
+#ifdef MAXIM_CAMERA1
+				camera@32 {
+					compatible = MAXIM_CAMERA1;
+					reg = <0x32>, <0x42>, <0x52>;
+					port {
+						rdacm20_out1: endpoint {
+							remote-endpoint = <&max9286_in1>;
+						};
+					};
+				};
+#endif
+			};
+
+			i2c@2 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+				reg = <2>;
+
+#ifdef MAXIM_CAMERA2
+				camera@33 {
+					compatible = MAXIM_CAMERA2;
+					reg = <0x33>, <0x43>, <0x53>;
+					port {
+						rdacm20_out2: endpoint {
+							remote-endpoint = <&max9286_in2>;
+						};
+					};
+				};
+#endif
+			};
+
+			i2c@3 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+				reg = <3>;
+
+#ifdef MAXIM_CAMERA3
+				camera@34 {
+					compatible = MAXIM_CAMERA3;
+					reg = <0x34>, <0x44>, <0x54>;
+					port {
+						rdacm20_out3: endpoint {
+							remote-endpoint = <&max9286_in3>;
+						};
+					};
+				};
+#endif
+			};
+		};
+	};
+
+	gmsl-deserializer@6c {
+		compatible = "maxim,max9286";
+		reg = <0x6c>;
+		poc-supply = <&poc_12v>;
+
+		ports {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			port@0 {
+				reg = <0>;
+				max9286_in4: endpoint {
+#ifdef MAXIM_CAMERA4
+					remote-endpoint = <&rdacm20_out4>;
+#endif
+				};
+			};
+
+			port@1 {
+				reg = <1>;
+				max9286_in5: endpoint {
+#ifdef MAXIM_CAMERA5
+					remote-endpoint = <&rdacm20_out5>;
+#endif
+				};
+			};
+
+			port@2 {
+				reg = <2>;
+				max9286_in6: endpoint {
+#ifdef MAXIM_CAMERA6
+					remote-endpoint = <&rdacm20_out6>;
+#endif
+				};
+			};
+
+			port@3 {
+				reg = <3>;
+				max9286_in7: endpoint {
+#ifdef MAXIM_CAMERA7
+					remote-endpoint = <&rdacm20_out7>;
+#endif
+				};
+			};
+
+			port@4 {
+				reg = <4>;
+				max9286_out1: endpoint {
+					clock-lanes = <0>;
+					data-lanes = <1 2 3 4>;
+					remote-endpoint = <&csi41_in>;
+				};
+			};
+		};
+
+		i2c-mux {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			i2c@0 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+				reg = <0>;
+
+#ifdef MAXIM_CAMERA4
+				camera@35 {
+					compatible = MAXIM_CAMERA4;
+					reg = <0x35>, <0x45>, <0x55>;
+					port {
+						rdacm20_out4: endpoint {
+							remote-endpoint = <&max9286_in4>;
+						};
+					};
+				};
+#endif
+			};
+
+			i2c@1 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+				reg = <1>;
+
+#ifdef MAXIM_CAMERA5
+				camera@36 {
+					compatible = MAXIM_CAMERA5;
+					reg = <0x36>, <0x46>, <0x56>;
+					port {
+						rdacm20_out5: endpoint {
+							remote-endpoint = <&max9286_in5>;
+						};
+					};
+				};
+#endif
+			};
+
+			i2c@2 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+				reg = <2>;
+
+#ifdef MAXIM_CAMERA6
+				camera@37 {
+					compatible = MAXIM_CAMERA6;
+					reg = <0x37>, <0x47>, <0x57>;
+					port {
+						rdacm20_out6: endpoint {
+							remote-endpoint = <&max9286_in6>;
+						};
+					};
+				};
+#endif
+			};
+
+			i2c@3 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+				reg = <3>;
+
+#ifdef MAXIM_CAMERA7
+				camera@38 {
+					compatible = MAXIM_CAMERA7;
+					reg = <0x38>, <0x48>, <0x58>;
+					port {
+						rdacm20_out7: endpoint {
+							remote-endpoint = <&max9286_in7>;
+						};
+					};
+				};
+#endif
+			};
+		};
+	};
+};
--
2.28.0

[PATCH v2 7/7] [DNI] arm64: dts: renesas: salvator-x-max9286: Use high-threshold

[Jacopo Mondi]

Use the newly introduced 'maxim,high-threshold' property to maintain
compatibility with RDACM20 camera module.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi b/arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi
index 6f4798859542..e207436f8690 100644
--- a/arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi
+++ b/arch/arm64/boot/dts/renesas/salvator-x-max9286.dtsi
@@ -128,6 +128,7 @@ gmsl-deserializer@4c {
 		compatible = "maxim,max9286";
 		reg = <0x4c>;
 		poc-supply = <&poc_12v>;
+		maxim,high-threshold;
 
 		ports {
 			#address-cells = <1>;
@@ -263,6 +264,7 @@ gmsl-deserializer@6c {
 		compatible = "maxim,max9286";
 		reg = <0x6c>;
 		poc-supply = <&poc_12v>;
+		maxim,high-threshold;
 
 		ports {
 			#address-cells = <1>;
-- 
2.28.0

Re: [PATCH v2 5/7] media: i2c: max9286: Configure reverse channel amplitude

[Kieran Bingham]

Hi Jacopo,

On 15/10/2020 19:27, Jacopo Mondi wrote:
> Adjust reverse channel amplitude according to the presence of
> the 'high-threshold" DTS property.
> 
> If no high threshold compensation is required, start with a low
> amplitude (100mV) and increase it after the remote serializers
> have probed and have enabled noise immunity on their reverse
> channels.
> 
> If high threshold compensation is required, configure the reverse
> channel with a 170mV amplitude before the remote serializers have
> probed.
> 
> This change is required for both rdacm20 and rdacm21 camera modules
> to be correctly probed when used in combination with the max9286
> deserializer.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
>  drivers/media/i2c/max9286.c | 74 +++++++++++++++++++++++--------------
>  1 file changed, 47 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> index 163e102199e3..4b59a9e0228a 100644
> --- a/drivers/media/i2c/max9286.c
> +++ b/drivers/media/i2c/max9286.c
> @@ -163,6 +163,8 @@ struct max9286_priv {
>  	unsigned int mux_channel;
>  	bool mux_open;
>  
> +	bool high_threshold;
> +
>  	struct v4l2_ctrl_handler ctrls;
>  	struct v4l2_ctrl *pixelrate;
>  
> @@ -436,6 +438,32 @@ static int max9286_check_config_link(struct max9286_priv *priv,
>  	return 0;
>  }
>  
> +static void max9286_reverse_channel_setup(struct max9286_priv *priv,
> +					  unsigned int chan_amplitude)

This looks like you're adding a new function - how about we add this
function here, in the first place when you add it in 3/7

> +{
> +	/* Reverse channel transmission time: default to 1. */
> +	u8 chan_config = MAX9286_REV_TRF(1);
> +
> +	/*
> +	 * Reverse channel setup.
> +	 *
> +	 * - Enable custom reverse channel configuration (through register 0x3f)
> +	 *   and set the first pulse length to 35 clock cycles.
> +	 * - Adjust reverse channel amplitude: values > 130 are programmed
> +	 *   using the additional +100mV REV_AMP_X boost flag
> +	 */
> +	max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
> +
> +	if (chan_amplitude > 100) {
> +		/* It is not possible express values (100 < x < 130) */
> +		chan_amplitude = chan_amplitude < 130
> +			       ? 30 : chan_amplitude - 100;
> +		chan_config |= MAX9286_REV_AMP_X;
> +	}
> +	max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
> +	usleep_range(2000, 2500);
> +}
> +
>  /* -----------------------------------------------------------------------------
>   * V4L2 Subdev
>   */
> @@ -531,10 +559,14 @@ static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
>  	 * All enabled sources have probed and enabled their reverse control
>  	 * channels:
>  	 *
> +	 * - Increase the reverse channel amplitude to compensate for the
> +	 *   remote ends high threshold, if not done already
>  	 * - Verify all configuration links are properly detected
>  	 * - Disable auto-ack as communication on the control channel are now
>  	 *   stable.
>  	 */
> +	if (!priv->high_threshold)
> +		max9286_reverse_channel_setup(priv, 170);

is it troublesome to re-set it if it's already set? I guess it's just
unnecessary. so that's fine.

>  	max9286_check_config_link(priv, priv->source_mask);
>  
>  	/*
> @@ -906,32 +938,6 @@ static void max9286_v4l2_unregister(struct max9286_priv *priv)
>   * Probe/Remove
>   */
>  
> -static void max9286_reverse_channel_setup(struct max9286_priv *priv,
> -					  unsigned int chan_amplitude)
> -{
> -	/* Reverse channel transmission time: default to 1. */
> -	u8 chan_config = MAX9286_REV_TRF(1);
> -
> -	/*
> -	 * Reverse channel setup.
> -	 *
> -	 * - Enable custom reverse channel configuration (through register 0x3f)
> -	 *   and set the first pulse length to 35 clock cycles.
> -	 * - Adjust reverse channel amplitude: values > 130 are programmed
> -	 *   using the additional +100mV REV_AMP_X boost flag
> -	 */
> -	max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
> -
> -	if (chan_amplitude > 100) {
> -		/* It is not possible express values (100 < x < 130) */
> -		chan_amplitude = chan_amplitude < 130
> -			       ? 30 : chan_amplitude - 100;
> -		chan_config |= MAX9286_REV_AMP_X;
> -	}
> -	max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
> -	usleep_range(2000, 2500);
> -}
> -
>  static int max9286_setup(struct max9286_priv *priv)
>  {
>  	/*
> @@ -967,7 +973,15 @@ static int max9286_setup(struct max9286_priv *priv)
>  	 * only. This should be disabled after the mux is initialised.
>  	 */
>  	max9286_configure_i2c(priv, true);
> -	max9286_reverse_channel_setup(priv, 170);
> +
> +	/*
> +	 * Compensate the remote end high threshold with a larger channel
> +	 * amplitude if necessary.
> +	 */
> +	if (priv->high_threshold)
> +		max9286_reverse_channel_setup(priv, 170);
> +	else
> +		max9286_reverse_channel_setup(priv, 100);

Hrm... ternery is more concise here, but is it helpful?

  max9286_reverse_channel_setup(priv, priv->high_threshold ? 170 : 100);

The high-threshold could also be parsed in
max9286_reverse_channel_setup(), but I like it being passed in.

>  
>  	/*
>  	 * Enable GMSL links, mask unused ones and autodetect link
> @@ -1235,6 +1249,12 @@ static int max9286_parse_dt(struct max9286_priv *priv)
>  	}
>  	of_node_put(node);
>  
> +	/*
> +	 * Parse 'high_threshold' property to configure the reverse channel
> +	 * amplitude.
> +	 */
> +	priv->high_threshold = device_property_present(dev, "high_threshold");
> +

Oh, I think I like this, it's a neat way to express what it needs to do
from the DT depending on the attached cameras.

It's sort of dependant upon the cameras though, I guess making this
something that we query from the remote endpoint isn't so easy ...?



>  	priv->route_mask = priv->source_mask;
>  
>  	return 0;
> 

Re: [PATCH v2 3/7] media: i2c: max9286: Break-out reverse channel setup

[Kieran Bingham]

Hi Jacopo,

On 15/10/2020 19:27, Jacopo Mondi wrote:
> Break out the reverse channel setup configuration procedure to its own
> function.
> 
> This change prepares for configuring the reverse channel conditionally
> to the remote side high threshold configuration.
> 
> No functional changes intended.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
>  drivers/media/i2c/max9286.c | 30 +++++++++++++++++-------------
>  1 file changed, 17 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> index d969ac21a058..89a7248f5c25 100644
> --- a/drivers/media/i2c/max9286.c
> +++ b/drivers/media/i2c/max9286.c
> @@ -906,6 +906,22 @@ static void max9286_v4l2_unregister(struct max9286_priv *priv)
>   * Probe/Remove
>   */
>  
> +static void max9286_reverse_channel_setup(struct max9286_priv *priv)
> +{
> +	/*
> +	 * 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(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
> +	max9286_write(priv, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) |
> +		      MAX9286_REV_AMP_X);
> +	usleep_range(2000, 2500);
> +}

This gets moved later on in the same series. It's probably better to put
it in the right place now.

With that,

Reviewed-by: Kieran Bingham <kieran.bingham+renesasa@ideasonboard.com>

> +
>  static int max9286_setup(struct max9286_priv *priv)
>  {
>  	/*
> @@ -941,19 +957,7 @@ static int max9286_setup(struct max9286_priv *priv)
>  	 * only. This should be disabled after the mux is initialised.
>  	 */
>  	max9286_configure_i2c(priv, 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(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
> -	max9286_write(priv, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) |
> -		      MAX9286_REV_AMP_X);
> -	usleep_range(2000, 2500);
> +	max9286_reverse_channel_setup(priv);
>  
>  	/*
>  	 * Enable GMSL links, mask unused ones and autodetect link
> 

Re: [PATCH v2 4/7] media: i2c: max9286: Make channel amplitude programmable

[Kieran Bingham]

Hi Jacopo,

On 15/10/2020 19:27, Jacopo Mondi wrote:
> Instrument the function that configures the reverse channel with a
> programmable amplitude value.
> 
> This change serves to prepare to adjust the reverse channel amplitude
> depending on the remote end high-threshold configuration.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
>  drivers/media/i2c/max9286.c | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> index 89a7248f5c25..163e102199e3 100644
> --- a/drivers/media/i2c/max9286.c
> +++ b/drivers/media/i2c/max9286.c
> @@ -906,19 +906,29 @@ static void max9286_v4l2_unregister(struct max9286_priv *priv)
>   * Probe/Remove
>   */
>  
> -static void max9286_reverse_channel_setup(struct max9286_priv *priv)
> +static void max9286_reverse_channel_setup(struct max9286_priv *priv,
> +					  unsigned int chan_amplitude)
>  {
> +	/* Reverse channel transmission time: default to 1. */
> +	u8 chan_config = MAX9286_REV_TRF(1);
> +
>  	/*
>  	 * 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.
> +	 * - Adjust reverse channel amplitude: values > 130 are programmed
> +	 *   using the additional +100mV REV_AMP_X boost flag
>  	 */
>  	max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
> -	max9286_write(priv, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) |
> -		      MAX9286_REV_AMP_X);
> +

Should we also clamp to min/max values at all?
Probably not needed, as it's only an internal helper.


> +	if (chan_amplitude > 100) {
> +		/* It is not possible express values (100 < x < 130) */

'possible to express'

> +		chan_amplitude = chan_amplitude < 130
> +			       ? 30 : chan_amplitude - 100;

We could round < 115 to 100, and >= 115 to 130, but that's probably more
effort that it's worth, so I think this is fine.

I think it's really helpful to codify this parameter though:

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

> +		chan_config |= MAX9286_REV_AMP_X;
> +	}
> +	max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
>  	usleep_range(2000, 2500);
>  }
>  
> @@ -957,7 +967,7 @@ static int max9286_setup(struct max9286_priv *priv)
>  	 * only. This should be disabled after the mux is initialised.
>  	 */
>  	max9286_configure_i2c(priv, true);
> -	max9286_reverse_channel_setup(priv);
> +	max9286_reverse_channel_setup(priv, 170);
>  
>  	/*
>  	 * Enable GMSL links, mask unused ones and autodetect link
> 

Re: [PATCH v2 4/7] media: i2c: max9286: Make channel amplitude programmable

[Sergei Shtylyov]

Hello!

On 15.10.2020 21:27, Jacopo Mondi wrote:

> Instrument the function that configures the reverse channel with a
> programmable amplitude value.
> 
> This change serves to prepare to adjust the reverse channel amplitude
> depending on the remote end high-threshold configuration.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
>   drivers/media/i2c/max9286.c | 22 ++++++++++++++++------
>   1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> index 89a7248f5c25..163e102199e3 100644
> --- a/drivers/media/i2c/max9286.c
> +++ b/drivers/media/i2c/max9286.c
> @@ -906,19 +906,29 @@ static void max9286_v4l2_unregister(struct max9286_priv *priv)
>    * Probe/Remove
>    */
>   
> -static void max9286_reverse_channel_setup(struct max9286_priv *priv)
> +static void max9286_reverse_channel_setup(struct max9286_priv *priv,
> +					  unsigned int chan_amplitude)
>   {
> +	/* Reverse channel transmission time: default to 1. */
> +	u8 chan_config = MAX9286_REV_TRF(1);
> +
>   	/*
>   	 * 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.
> +	 * - Adjust reverse channel amplitude: values > 130 are programmed
> +	 *   using the additional +100mV REV_AMP_X boost flag
>   	 */
>   	max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
> -	max9286_write(priv, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) |
> -		      MAX9286_REV_AMP_X);
> +
> +	if (chan_amplitude > 100) {
> +		/* It is not possible express values (100 < x < 130) */

    "To express", perhaps?

> +		chan_amplitude = chan_amplitude < 130
> +			       ? 30 : chan_amplitude - 100;
> +		chan_config |= MAX9286_REV_AMP_X;
> +	}
> +	max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
>   	usleep_range(2000, 2500);
>   }
>   
[...]

MBR, Sergei

Re: [PATCH v2 5/7] media: i2c: max9286: Configure reverse channel amplitude

[Jacopo Mondi]

Hi Kieran,

On Thu, Oct 15, 2020 at 08:52:01PM +0100, Kieran Bingham wrote:
> Hi Jacopo,
>
> On 15/10/2020 19:27, Jacopo Mondi wrote:
> > Adjust reverse channel amplitude according to the presence of
> > the 'high-threshold" DTS property.
> >
> > If no high threshold compensation is required, start with a low
> > amplitude (100mV) and increase it after the remote serializers
> > have probed and have enabled noise immunity on their reverse
> > channels.
> >
> > If high threshold compensation is required, configure the reverse
> > channel with a 170mV amplitude before the remote serializers have
> > probed.
> >
> > This change is required for both rdacm20 and rdacm21 camera modules
> > to be correctly probed when used in combination with the max9286
> > deserializer.
> >
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> > ---
> >  drivers/media/i2c/max9286.c | 74 +++++++++++++++++++++++--------------
> >  1 file changed, 47 insertions(+), 27 deletions(-)
> >
> > diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> > index 163e102199e3..4b59a9e0228a 100644
> > --- a/drivers/media/i2c/max9286.c
> > +++ b/drivers/media/i2c/max9286.c
> > @@ -163,6 +163,8 @@ struct max9286_priv {
> >  	unsigned int mux_channel;
> >  	bool mux_open;
> >
> > +	bool high_threshold;
> > +
> >  	struct v4l2_ctrl_handler ctrls;
> >  	struct v4l2_ctrl *pixelrate;
> >
> > @@ -436,6 +438,32 @@ static int max9286_check_config_link(struct max9286_priv *priv,
> >  	return 0;
> >  }
> >
> > +static void max9286_reverse_channel_setup(struct max9286_priv *priv,
> > +					  unsigned int chan_amplitude)
>
> This looks like you're adding a new function - how about we add this
> function here, in the first place when you add it in 3/7
>

I'll move it up in 3/7

> > +{
> > +	/* Reverse channel transmission time: default to 1. */
> > +	u8 chan_config = MAX9286_REV_TRF(1);
> > +
> > +	/*
> > +	 * Reverse channel setup.
> > +	 *
> > +	 * - Enable custom reverse channel configuration (through register 0x3f)
> > +	 *   and set the first pulse length to 35 clock cycles.
> > +	 * - Adjust reverse channel amplitude: values > 130 are programmed
> > +	 *   using the additional +100mV REV_AMP_X boost flag
> > +	 */
> > +	max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
> > +
> > +	if (chan_amplitude > 100) {
> > +		/* It is not possible express values (100 < x < 130) */
> > +		chan_amplitude = chan_amplitude < 130
> > +			       ? 30 : chan_amplitude - 100;
> > +		chan_config |= MAX9286_REV_AMP_X;
> > +	}
> > +	max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
> > +	usleep_range(2000, 2500);
> > +}
> > +
> >  /* -----------------------------------------------------------------------------
> >   * V4L2 Subdev
> >   */
> > @@ -531,10 +559,14 @@ static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
> >  	 * All enabled sources have probed and enabled their reverse control
> >  	 * channels:
> >  	 *
> > +	 * - Increase the reverse channel amplitude to compensate for the
> > +	 *   remote ends high threshold, if not done already
> >  	 * - Verify all configuration links are properly detected
> >  	 * - Disable auto-ack as communication on the control channel are now
> >  	 *   stable.
> >  	 */
> > +	if (!priv->high_threshold)
> > +		max9286_reverse_channel_setup(priv, 170);
>
> is it troublesome to re-set it if it's already set? I guess it's just
> unnecessary. so that's fine.
>
> >  	max9286_check_config_link(priv, priv->source_mask);
> >
> >  	/*
> > @@ -906,32 +938,6 @@ static void max9286_v4l2_unregister(struct max9286_priv *priv)
> >   * Probe/Remove
> >   */
> >
> > -static void max9286_reverse_channel_setup(struct max9286_priv *priv,
> > -					  unsigned int chan_amplitude)
> > -{
> > -	/* Reverse channel transmission time: default to 1. */
> > -	u8 chan_config = MAX9286_REV_TRF(1);
> > -
> > -	/*
> > -	 * Reverse channel setup.
> > -	 *
> > -	 * - Enable custom reverse channel configuration (through register 0x3f)
> > -	 *   and set the first pulse length to 35 clock cycles.
> > -	 * - Adjust reverse channel amplitude: values > 130 are programmed
> > -	 *   using the additional +100mV REV_AMP_X boost flag
> > -	 */
> > -	max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
> > -
> > -	if (chan_amplitude > 100) {
> > -		/* It is not possible express values (100 < x < 130) */
> > -		chan_amplitude = chan_amplitude < 130
> > -			       ? 30 : chan_amplitude - 100;
> > -		chan_config |= MAX9286_REV_AMP_X;
> > -	}
> > -	max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
> > -	usleep_range(2000, 2500);
> > -}
> > -
> >  static int max9286_setup(struct max9286_priv *priv)
> >  {
> >  	/*
> > @@ -967,7 +973,15 @@ static int max9286_setup(struct max9286_priv *priv)
> >  	 * only. This should be disabled after the mux is initialised.
> >  	 */
> >  	max9286_configure_i2c(priv, true);
> > -	max9286_reverse_channel_setup(priv, 170);
> > +
> > +	/*
> > +	 * Compensate the remote end high threshold with a larger channel
> > +	 * amplitude if necessary.
> > +	 */
> > +	if (priv->high_threshold)
> > +		max9286_reverse_channel_setup(priv, 170);
> > +	else
> > +		max9286_reverse_channel_setup(priv, 100);
>
> Hrm... ternery is more concise here, but is it helpful?
>

Ternary is nicer, you're right!

>   max9286_reverse_channel_setup(priv, priv->high_threshold ? 170 : 100);
>
> The high-threshold could also be parsed in
> max9286_reverse_channel_setup(), but I like it being passed in.
>
> >
> >  	/*
> >  	 * Enable GMSL links, mask unused ones and autodetect link
> > @@ -1235,6 +1249,12 @@ static int max9286_parse_dt(struct max9286_priv *priv)
> >  	}
> >  	of_node_put(node);
> >
> > +	/*
> > +	 * Parse 'high_threshold' property to configure the reverse channel
> > +	 * amplitude.
> > +	 */
> > +	priv->high_threshold = device_property_present(dev, "high_threshold");
> > +
>
> Oh, I think I like this, it's a neat way to express what it needs to do
> from the DT depending on the attached cameras.
>
> It's sort of dependant upon the cameras though, I guess making this
> something that we query from the remote endpoint isn't so easy ...?

That's the real question. Is it fair to express as a deserializer
property a setting of the remote serializer(s) ? What if the remotes
have different configurations (we had to play with pre-programmed and
non-pre-programmed RDACM20s in the past iirc).

I've detailed a few possible way forward and their pros and cons in
the v1 cover letter [1] and I'm happy to discuss them as I'm not sure
this is the best possible way forward.

Thanks
  j

[1] For reference: https://www.spinics.net/lists/linux-renesas-soc/msg52886.html

>
>
>
> >  	priv->route_mask = priv->source_mask;
> >
> >  	return 0;
> >
>