Re: [PATCH v5 1/8] media: i2c: Add driver for RDACM21 camera module

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

On 17/11/2020 13:36, Jacopo Mondi wrote:
> Hi Kieran,
> 
> On Mon, Nov 16, 2020 at 02:47:49PM +0000, Kieran Bingham wrote:
>> On 16/11/2020 13:52, Jacopo Mondi wrote:
>>> 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 | 595 ++++++++++++++++++++++++++++++++++++
>>>  4 files changed, 622 insertions(+)
>>>  create mode 100644 drivers/media/i2c/rdacm21.c
>>>
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index cef6b6090d76..9a5026fd6788 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -14750,6 +14750,18 @@ 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 c64326ca331c..64f4316d11ad 100644
>>> --- a/drivers/media/i2c/Kconfig
>>> +++ b/drivers/media/i2c/Kconfig
>>> @@ -1185,6 +1185,19 @@ 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..5f9267e26258
>>> --- /dev/null
>>> +++ b/drivers/media/i2c/rdacm21.c
>>> @@ -0,0 +1,595 @@
>>> +// 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_ID_LOW			0xa6

Should we keep the two OV10640 defines together?

>>> +
>>> +#define OV490_I2C_ADDRESS		0x24
>>> +
>>> +#define OV490_PAGE_HIGH_REG		0xfffd
>>> +#define OV490_PAGE_LOW_REG		0xfffe
>>> +
>>> +#define OV490_DVP_CTRL3			0x80286009
>>> +
>>> +#define OV490_ODS_CTRL_FRAME_OUTPUT_EN	0x0c
>>> +#define OV490_ODS_CTRL			0x8029d000
>>> +
>>> +#define OV490_ID_VAL			0x0490
>>> +#define OV490_ID(_p, _v)		((((_p) & 0xff) << 8) | ((_v) & 0xff))
>>> +#define OV490_PID			0x8080300a
>>> +#define OV490_VER			0x8080300b
>>> +
>>> +#define OV490_ISP_HSIZE_LOW		0x80820060
>>> +#define OV490_ISP_HSIZE_HIGH		0x80820061
>>> +#define OV490_ISP_VSIZE_LOW		0x80820062
>>> +#define OV490_ISP_VSIZE_HIGH		0x80820063
>>> +
>>> +#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];
>>> +	u16				last_page;
>>> +};
>>> +
>>> +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 };
>>> +	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, val };
>>> +	int ret;
>>> +
>>> +	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 ov490_set_page(struct rdacm21_device *dev, u16 reg)
>>> +{
>>> +	bool page_new = false;
>>> +	u8 page_high = reg >> 8;
>>> +	u8 page_low = reg;
>>> +	int ret;
>>> +
>>> +	if (page_high != (dev->last_page >> 8)) {
>>> +		ret = ov490_write(dev, OV490_PAGE_HIGH_REG, page_high);
>>> +		if (ret)
>>> +			return ret;
>>> +		page_new = true;
>>> +	}
>>> +
>>> +	if (page_low != (u8)dev->last_page) {
>>> +		ret = ov490_write(dev, OV490_PAGE_LOW_REG, page_low);
>>> +		if (ret)
>>> +			return ret;
>>> +		page_new = true;
>>> +	}
>>> +
>>> +	if (page_new) {
>>> +		dev->last_page = reg;
>>> +		usleep_range(100, 150);
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int ov490_read_reg(struct rdacm21_device *dev, u32 reg, u8 *val)
>>> +{
>>> +	int ret;
>>> +
>>> +	ret = ov490_set_page(dev, reg >> 16);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	ret = ov490_read(dev, (u16)reg, val);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	dev_dbg(dev->dev, "%s: 0x%08x = 0x%02x\n", __func__, reg, *val);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int ov490_write_reg(struct rdacm21_device *dev, u32 reg, u8 val)
>>> +{
>>> +	int ret;
>>> +
>>> +	ret = ov490_set_page(dev, reg >> 16);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	ret = ov490_write(dev, (u16)reg, val);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	dev_dbg(dev->dev, "%s: 0x%08x = 0x%02x\n", __func__, reg, val);
>>> +
>>> +	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_read_reg(dev, OV490_PID, &pid);
>>> +	if (ret < 0) {
>>> +		/* Give OV490 a few more cycles to exit from reset. */
>>> +		if (ov490_pid_retry--) {
>>> +			usleep_range(1000, 2000);
>>> +			goto pid_retry;
>>> +		}
>>> +
>>> +		dev_err(dev->dev, "OV490 PID read failed (%d)\n", ret);
>>> +		return ret;
>>> +	}
>>> +
>>> +	ret = ov490_read_reg(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. */
>>> +	for (timeout = 300; timeout > 0; timeout--) {
>>> +		ov490_read_reg(dev, OV490_ODS_CTRL, &val);
>>> +		if (val == OV490_ODS_CTRL_FRAME_OUTPUT_EN)
>>> +			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);
>>
>> Is that setting a page? Or doing something else?
>>
>>> +
>>> +	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);
>> And here?
>>
>> Can this not go through the new helpers?
>>
>> If the 'read_reg', 'write_reg', helpers are not appropriate, at least
>> setting the pages could be done with set_page() ... but I'd be surprised
>> if those couldn't be handled with ov490_write_reg() ?
> 
> As I've said in previous reply, I prefer the comunication with ov10640
> to be kept explicit as long as we don't have more users and I don't
> better understand what register 0x5000 is for.
> 

Ok, I understand, but we 'know' it's the register page for communicating
with the Sensor though?

Do we have any documentation on this at all?


> I can go through set_page() but the I have to pass 0x8019 which kind
> of defeat the purpose of defining registers by name
> 
> I prefer to keep this as it is.


The issue I would have is you now have an invalid lastPage setting in
dev. So you're potentially letting yourself access registers on an
incorrect page, next time you use ov490_write_reg().


You could quite easily define:

/*
 * The OV10640 is interacted with through
 * registers in page 0x8019 using registers from 0x5000 to 0x5003,
 * However the definition of these is currently unknown.
 */
#define SENSOR_REGISTER_0 0x80195000
#define SENSOR_REGISTER_1 0x80195001
#define SENSOR_REGISTER_2 0x80195002

To me that would be better than leaving some raw code inline
or maybe a short wrapper to make it even clearer that this talks to
/another component/:

#define SENSOR_PAGE 0x8019

sensor_write(dev, reg, val) {
	reg |= (SENSOR_PAGE << 16);
	return ov490_write_reg(dev, reg, val);
}

..
	sensor_write(dev, 0x5000, 0x01);
	sensor_write(dev, 0x5001, 0x30);
	sensor_write(dev, 0x5002, 0x0a);
...



>>> +	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);
>>> +

Even if you want to keep the register writes raw, we know this code
block is handling the OV10640, so I'd be at least tempted to move it all
to a

int ov10640_initialise(dev);

but it's your code, and you seem quite against this, so I won't push
anymore.



>>> +	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);
>>> +	}

You should almost certainly mark dev->lastPage as something invalid here
anyway (0xFFFF?).

Otherwise the hardware page will be set to whatever was last used in the
ov490_regs_wizard table, and the ov490_read_reg() won't necessarily
update if it was on the same page last usage.


The incorrect lastPage is potentially a more critical issue though so
with that (if confirmed):

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



>>> +
>>> +	/*
>>> +	 * The ISP is programmed with the content of a serial flash memory.
>>> +	 * Read the firmware configuration to reflect it through the V4L2 APIs.
>>> +	 */
>>> +	ov490_read_reg(dev, OV490_ISP_HSIZE_HIGH, &val);
>>> +	dev->fmt.width = (val & 0xf) << 8;
>>> +	ov490_read_reg(dev, OV490_ISP_HSIZE_LOW, &val);
>>> +	dev->fmt.width |= (val & 0xff);
>>> +
>>> +	ov490_read_reg(dev, OV490_ISP_VSIZE_HIGH, &val);
>>> +	dev->fmt.height = (val & 0xf) << 8;
>>> +	ov490_read_reg(dev, OV490_ISP_VSIZE_LOW, &val);
>>> +	dev->fmt.height |= val & 0xff;
>>> +
>>
>>
>> Hrm, these look like "ov490_read_reg_long()", but given they're the only
>> occurrences of a "long read" I think we could leave it as is.
>>
>>
>>> +	/* Set bus width to 12 bits with [0:11] ordering. */
>>> +	ov490_write_reg(dev, OV490_DVP_CTRL3, 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);
>>> +	v4l2_ctrl_handler_free(&dev->ctrls);
>>> +	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");
>>>
>>