Re: [PATCH v7 2/2] Driver for ON Semi AR0521 camera sensor

Jacopo Mondi
2022-01-09T15:33:45Z

Hi Krzysztof

On Mon, Jan 03, 2022 at 02:36:18PM +0100, Krzysztof Hałasa wrote:
> The driver has been extensively tested in an i.MX6-based system.
> AR0521 is a 5.7 mm x 4.3 mm, 5 MPix RGGB MIPI/HiSPi BSI CMOS sensor
> from On Semiconductor.
>
> Signed-off-by: Krzysztof Hałasa <khalasa@piap.pl>
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 79fd8a012893..5d33f0277ad2 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1383,6 +1383,13 @@ S: Supported
> W: http://www.aquantia.com
> F: drivers/net/ethernet/aquantia/atlantic/aq_ptp*
>
> +AR0521 ON SEMICONDUCTOR CAMERA SENSOR DRIVER
> +M: Krzysztof Hałasa <khalasa@piap.pl>
> +L: linux-media@vger.kernel.org
> +S: Maintained
> +F: Documentation/devicetree/bindings/media/i2c/onnn,ar0521.yaml
> +F: drivers/media/i2c/ar0521.c
> +
> ARASAN NAND CONTROLLER DRIVER
> M: Miquel Raynal <miquel.raynal@bootlin.com>
> M: Naga Sureshkumar Relli <nagasure@xilinx.com>
> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
> index 69c56e24a612..741ae073623e 100644
> --- a/drivers/media/i2c/Kconfig
> +++ b/drivers/media/i2c/Kconfig
> @@ -733,6 +733,19 @@ config VIDEO_APTINA_PLL
> config VIDEO_CCS_PLL
> tristate
>
> +config VIDEO_AR0521
> + tristate "ON Semiconductor AR0521 sensor support"
> + depends on I2C && VIDEO_V4L2
> + select MEDIA_CONTROLLER
> + select VIDEO_V4L2_SUBDEV_API
> + select V4L2_FWNODE
> + help
> + This is a Video4Linux2 sensor driver for the ON Semiconductor
> + AR0521 camera.
> +
> + To compile this driver as a module, choose M here: the
> + module will be called ar0521.
> +
> config VIDEO_HI556
> tristate "Hynix Hi-556 sensor support"
> depends on I2C && VIDEO_V4L2
> diff --git a/drivers/media/i2c/Makefile b/drivers/media/i2c/Makefile
> index b01f6cd05ee8..4e4986e16071 100644
> --- a/drivers/media/i2c/Makefile
> +++ b/drivers/media/i2c/Makefile
> @@ -118,6 +118,7 @@ obj-$(CONFIG_VIDEO_I2C) += video-i2c.o
> obj-$(CONFIG_VIDEO_ML86V7667) += ml86v7667.o
> obj-$(CONFIG_VIDEO_OV2659) += ov2659.o
> obj-$(CONFIG_VIDEO_TC358743) += tc358743.o
> +obj-$(CONFIG_VIDEO_AR0521) += ar0521.o
> obj-$(CONFIG_VIDEO_HI556) += hi556.o
> obj-$(CONFIG_VIDEO_HI846) += hi846.o
> obj-$(CONFIG_VIDEO_IMX208) += imx208.o
> diff --git a/drivers/media/i2c/ar0521.c b/drivers/media/i2c/ar0521.c
> new file mode 100644
> index 000000000000..0adbbd8ea3b5
> --- /dev/null
> +++ b/drivers/media/i2c/ar0521.c
> @@ -0,0 +1,1093 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2021 Sieć Badawcza Łukasiewicz
> + * - Przemysłowy Instytut Automatyki i Pomiarów PIAP
> + * Written by Krzysztof Hałasa
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/pm_runtime.h>
> +
> +#include <media/v4l2-ctrls.h>
> +#include <media/v4l2-fwnode.h>
> +#include <media/v4l2-subdev.h>
> +
> +/* External clock (extclk) frequencies */
> +#define AR0521_EXTCLK_MIN (10 * 1000 * 1000)
> +#define AR0521_EXTCLK_MAX (48 * 1000 * 1000)
> +
> +/* PLL and PLL2 */
> +#define AR0521_PLL_MIN (320 * 1000 * 1000)
> +#define AR0521_PLL_MAX (1280 * 1000 * 1000)
> +
> +/* Effective pixel clocks, the registers may be DDR */
> +#define AR0521_PIXEL_CLOCK_RATE (184 * 1000 * 1000)
> +#define AR0521_PIXEL_CLOCK_MIN (168 * 1000 * 1000)
> +#define AR0521_PIXEL_CLOCK_MAX (414 * 1000 * 1000)
> +
> +#define AR0521_WIDTH_MIN 8u
> +#define AR0521_WIDTH_MAX 2608u
> +#define AR0521_HEIGHT_MIN 8u
> +#define AR0521_HEIGHT_MAX 1958u
> +
> +#define AR0521_WIDTH_BLANKING_MIN 572u
> +#define AR0521_HEIGHT_BLANKING_MIN 38u /* must be even */
> +#define AR0521_TOTAL_WIDTH_MIN 2968u
> +
> +/* AR0521 registers */
> +#define AR0521_REG_VT_PIX_CLK_DIV 0x0300
> +#define AR0521_REG_FRAME_LENGTH_LINES 0x0340
> +
> +#define AR0521_REG_CHIP_ID 0x3000
> +#define AR0521_REG_COARSE_INTEGRATION_TIME 0x3012
> +#define AR0521_REG_ROW_SPEED 0x3016
> +#define AR0521_REG_EXTRA_DELAY 0x3018
> +#define AR0521_REG_RESET 0x301A
> +#define AR0521_REG_RESET_DEFAULTS 0x0238
> +#define AR0521_REG_RESET_GROUP_PARAM_HOLD 0x8000
> +#define AR0521_REG_RESET_STREAM BIT(2)
> +#define AR0521_REG_RESET_RESTART BIT(1)
> +#define AR0521_REG_RESET_INIT BIT(0)
> +
> +#define AR0521_REG_GREEN1_GAIN 0x3056
> +#define AR0521_REG_BLUE_GAIN 0x3058
> +#define AR0521_REG_RED_GAIN 0x305A
> +#define AR0521_REG_GREEN2_GAIN 0x305C
> +#define AR0521_REG_GLOBAL_GAIN 0x305E
> +
> +#define AR0521_REG_HISPI_TEST_MODE 0x3066
> +#define AR0521_REG_HISPI_TEST_MODE_LP11 0x0004
> +
> +#define AR0521_REG_TEST_PATTERN_MODE 0x3070
> +
> +#define AR0521_REG_SERIAL_FORMAT 0x31AE
> +#define AR0521_REG_SERIAL_FORMAT_MIPI 0x0200
> +
> +#define AR0521_REG_HISPI_CONTROL_STATUS 0x31C6
> +#define AR0521_REG_HISPI_CONTROL_STATUS_FRAMER_TEST_MODE_ENABLE 0x80
> +
> +#define be cpu_to_be16
> +
> +static const char * const ar0521_supply_names[] = {
> + "vdd_io", /* I/O (1.8V) supply */
> + "vdd", /* Core, PLL and MIPI (1.2V) supply */
> + "vaa", /* Analog (2.7V) supply */
> +};
> +
> +struct ar0521_ctrls {
> + struct v4l2_ctrl_handler handler;
> + struct {
> + struct v4l2_ctrl *gain;
> + struct v4l2_ctrl *red_balance;
> + struct v4l2_ctrl *blue_balance;
> + };
> + struct {
> + struct v4l2_ctrl *hblank;
> + struct v4l2_ctrl *vblank;
> + };
> + struct v4l2_ctrl *pixrate;
> + struct v4l2_ctrl *exposure;
> + struct v4l2_ctrl *test_pattern;
> +};
> +
> +struct ar0521_dev {
> + struct i2c_client *i2c_client;
> + struct v4l2_subdev sd;
> + struct media_pad pad;
> + struct clk *extclk;
> + u32 extclk_freq;
> +
> + struct regulator *supplies[ARRAY_SIZE(ar0521_supply_names)];
> + struct gpio_desc *reset_gpio;
> +
> + /* lock to protect all members below */
> + struct mutex lock;
> +
> + struct v4l2_mbus_framefmt fmt;
> + struct ar0521_ctrls ctrls;
> + unsigned int lane_count;
> + u16 total_width;
> + u16 total_height;
> + u16 pll_pre;
> + u16 pll_mult;
> + u16 pll_pre2;
> + u16 pll_mult2;
> + bool streaming;
> +};
> +
> +static inline struct ar0521_dev *to_ar0521_dev(struct v4l2_subdev *sd)
> +{
> + return container_of(sd, struct ar0521_dev, sd);
> +}
> +
> +static inline struct v4l2_subdev *ctrl_to_sd(struct v4l2_ctrl *ctrl)
> +{
> + return &container_of(ctrl->handler, struct ar0521_dev,
> + ctrls.handler)->sd;
> +}
> +
> +static u32 div64_round(u64 v, u32 d)
> +{
> + return div_u64(v + (d >> 1), d);
> +}
> +
> +static u32 div64_round_up(u64 v, u32 d)
> +{
> + return div_u64(v + d - 1, d);
> +}
> +
> +/* Data must be BE16, the first value is the register address */
> +static int ar0521_write_regs(struct ar0521_dev *sensor, const __be16 *data,
> + unsigned int count)
> +{
> + struct i2c_client *client = sensor->i2c_client;
> + struct i2c_msg msg;
> + int ret;
> +
> + msg.addr = client->addr;
> + msg.flags = client->flags;
> + msg.buf = (u8 *)data;
> + msg.len = count * sizeof(*data);
> +
> + ret = i2c_transfer(client->adapter, &msg, 1);
> +
> + if (ret < 0) {
> + v4l2_err(&sensor->sd, "%s: I2C write error\n", __func__);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static int ar0521_write_reg(struct ar0521_dev *sensor, u16 reg, u16 val)
> +{
> + __be16 buf[2] = {be(reg), be(val)};
> +
> + return ar0521_write_regs(sensor, buf, 2);
> +}
> +
> +static int ar0521_set_geometry(struct ar0521_dev *sensor)
> +{
> + /* All dimensions are unsigned 12-bit integers */
> + u16 x = (AR0521_WIDTH_MAX - sensor->fmt.width) / 2;
> + u16 y = ((AR0521_HEIGHT_MAX - sensor->fmt.height) / 2) & ~1;
> + __be16 regs[] = {
> + be(AR0521_REG_FRAME_LENGTH_LINES),
> + be(sensor->total_height),
> + be(sensor->total_width),
> + be(x),
> + be(y),
> + be(x + sensor->fmt.width - 1),
> + be(y + sensor->fmt.height - 1),
> + be(sensor->fmt.width),
> + be(sensor->fmt.height)
> + };
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s()\n", __func__);
> +
> + return ar0521_write_regs(sensor, regs, ARRAY_SIZE(regs));
> +}
> +
> +static int ar0521_set_gains(struct ar0521_dev *sensor)
> +{
> + int green = sensor->ctrls.gain->val;
> + int red = max(green + sensor->ctrls.red_balance->val, 0);
> + int blue = max(green + sensor->ctrls.blue_balance->val, 0);
> + unsigned int gain = min(red, min(green, blue));
> + unsigned int analog = min(gain, 64u); /* range is 0 - 127 */
> + __be16 regs[5];
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s()\n", __func__);
> +
> + red = min(red - analog + 64, 511u);
> + green = min(green - analog + 64, 511u);
> + blue = min(blue - analog + 64, 511u);
> + regs[0] = be(AR0521_REG_GREEN1_GAIN);
> + regs[1] = be(green << 7 | analog);
> + regs[2] = be(blue << 7 | analog);
> + regs[3] = be(red << 7 | analog);
> + regs[4] = be(green << 7 | analog);
> +
> + return ar0521_write_regs(sensor, regs, ARRAY_SIZE(regs));
> +}
> +
> +static u32 calc_pll(struct ar0521_dev *sensor, int num, u32 freq, u16 *pre_ptr,
> + u16 *mult_ptr)
> +{
> + u16 pre = 1, mult = 1, new_pre;
> + u32 pll = AR0521_PLL_MAX + 1;
> +
> + for (new_pre = 1; new_pre < 64; new_pre++) {
> + u32 new_pll;
> + u32 new_mult = div64_round_up((u64)freq * new_pre,
> + sensor->extclk_freq);
> +
> + if (new_mult < 32)
> + continue; /* Minimum value */
> + if (new_mult > 254)
> + break; /* Maximum, larger pre won't work either */
> + if (sensor->extclk_freq * (u64)new_mult < AR0521_PLL_MIN *
> + new_pre)
> + continue;
> + if (sensor->extclk_freq * (u64)new_mult > AR0521_PLL_MAX *
> + new_pre)
> + break; /* Larger pre won't work either */
> + new_pll = div64_round_up(sensor->extclk_freq * (u64)new_mult,
> + new_pre);
> + if (new_pll < pll) {
> + pll = new_pll;
> + pre = new_pre;
> + mult = new_mult;
> + }
> + }
> +
> + pll = div64_round(sensor->extclk_freq * (u64)mult, pre);
> + *pre_ptr = pre;
> + *mult_ptr = mult;
> + return pll;
> +}
> +
> +#define DIV 4
> +static void ar0521_calc_mode(struct ar0521_dev *sensor)
> +{
> + unsigned int speed_mod = 4 / sensor->lane_count; /* 1 with 4 DDR lanes */
> + u16 total_width = max(sensor->fmt.width + AR0521_WIDTH_BLANKING_MIN,
> + AR0521_TOTAL_WIDTH_MIN);
> + u16 total_height = sensor->fmt.height + AR0521_HEIGHT_BLANKING_MIN;
> +
> + /* Calculate approximate pixel clock first */
> + u64 pix_clk = AR0521_PIXEL_CLOCK_RATE;
> +
> + /* PLL1 drives pixel clock - dual rate */
> + pix_clk = calc_pll(sensor, 1, pix_clk * (DIV / 2), &sensor->pll_pre,
> + &sensor->pll_mult);
> + pix_clk = div64_round(pix_clk, (DIV / 2));
> + calc_pll(sensor, 2, pix_clk * (DIV / 2) * speed_mod, &sensor->pll_pre2,
> + &sensor->pll_mult2);
> +
> + sensor->total_width = total_width;
> + sensor->total_height = total_height;
> +}
> +
> +static int ar0521_write_mode(struct ar0521_dev *sensor)
> +{
> + __be16 pll_regs[] = {
> + be(AR0521_REG_VT_PIX_CLK_DIV),
> + /* 0x300 */ be(4), /* vt_pix_clk_div = number of bits / 2 */
> + /* 0x302 */ be(1), /* vt_sys_clk_div */
> + /* 0x304 */ be((sensor->pll_pre2 << 8) | sensor->pll_pre),
> + /* 0x306 */ be((sensor->pll_mult2 << 8) | sensor->pll_mult),
> + /* 0x308 */ be(8), /* op_pix_clk_div = 2 * vt_pix_clk_div */
> + /* 0x30A */ be(1) /* op_sys_clk_div */
> + };
> + int ret;
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s()\n", __func__);
> +
> + /* Stop streaming for just a moment */
> + ret = ar0521_write_reg(sensor, AR0521_REG_RESET,
> + AR0521_REG_RESET_DEFAULTS);
> + if (ret)
> + return ret;
> +
> + ret = ar0521_set_geometry(sensor);
> + if (ret)
> + return ret;
> +
> + ret = ar0521_write_regs(sensor, pll_regs, ARRAY_SIZE(pll_regs));
> + if (ret)
> + return ret;
> +
> + ret = ar0521_write_reg(sensor, AR0521_REG_COARSE_INTEGRATION_TIME,
> + sensor->ctrls.exposure->val);
> + if (ret)
> + return ret;
> +
> + ret = ar0521_write_reg(sensor, AR0521_REG_RESET,
> + AR0521_REG_RESET_DEFAULTS |
> + AR0521_REG_RESET_STREAM);
> + if (ret)
> + return ret;
> +
> + ret = ar0521_write_reg(sensor, AR0521_REG_TEST_PATTERN_MODE,
> + sensor->ctrls.test_pattern->val);
> + if (ret)
> + return ret;
> +
> + dev_dbg(&sensor->i2c_client->dev,
> + "AR0521: %ux%u, total %ux%u\n",
> + sensor->fmt.width, sensor->fmt.height, sensor->total_width,
> + sensor->total_height);
> + return 0;
> +}
> +
> +static int ar0521_set_stream(struct ar0521_dev *sensor, bool on)
> +{
> + int ret;
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s(%u)\n", __func__, on);
> +
> + if (on) {
> + ret = pm_runtime_resume_and_get(&sensor->i2c_client->dev);
> + if (ret < 0)
> + return ret;
> +
> + ar0521_calc_mode(sensor);
> + ret = ar0521_write_mode(sensor);
> + if (ret)
> + goto err;
> +
> + ret = ar0521_set_gains(sensor);
> + if (ret)
> + goto err;
> +
> + /* Exit LP-11 mode on clock and data lanes */
> + ret = ar0521_write_reg(sensor, AR0521_REG_HISPI_CONTROL_STATUS,
> + 0);
> + if (ret)
> + goto err;
> +
> + /* Start streaming */
> + ret = ar0521_write_reg(sensor, AR0521_REG_RESET,
> + AR0521_REG_RESET_DEFAULTS |
> + AR0521_REG_RESET_STREAM);
> + if (ret)
> + goto err;
> +
> + return 0;
> +
> +err:
> + pm_runtime_put(&sensor->i2c_client->dev);
> + return ret;
> +
> + } else {
> + /* Reset gain, the sensor may produce all white pixels without
> + this */
> + ret = ar0521_write_reg(sensor, AR0521_REG_GLOBAL_GAIN, 0x2000);
> + if (ret)
> + return ret;
> +
> + /* Stop streaming */
> + ret = ar0521_write_reg(sensor, AR0521_REG_RESET,
> + AR0521_REG_RESET_DEFAULTS);
> + if (ret)
> + return ret;
> +
> + pm_runtime_put(&sensor->i2c_client->dev);
> + return 0;
> + }
> +}
> +
> +static void ar0521_adj_fmt(struct v4l2_mbus_framefmt *fmt)
> +{
> + fmt->width = clamp(ALIGN(fmt->width, 4), AR0521_WIDTH_MIN,
> + AR0521_WIDTH_MAX);
> + fmt->height = clamp(ALIGN(fmt->height, 4), AR0521_HEIGHT_MIN,
> + AR0521_HEIGHT_MAX);
> + fmt->code = MEDIA_BUS_FMT_SGRBG8_1X8;
> + fmt->field = V4L2_FIELD_NONE;
> + fmt->colorspace = V4L2_COLORSPACE_SRGB;
> + fmt->ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
> + fmt->quantization = V4L2_QUANTIZATION_FULL_RANGE;
> + fmt->xfer_func = V4L2_XFER_FUNC_DEFAULT;
> +}
> +
> +static int ar0521_get_fmt(struct v4l2_subdev *sd,
> + struct v4l2_subdev_state *sd_state,
> + struct v4l2_subdev_format *format)
> +{
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> + struct v4l2_mbus_framefmt *fmt;
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s(%u)\n", __func__, format->which);
> +
> + mutex_lock(&sensor->lock);
> +
> + if (format->which == V4L2_SUBDEV_FORMAT_TRY)
> + fmt = v4l2_subdev_get_try_format(&sensor->sd, sd_state, 0
> + /* pad */);
> + else
> + fmt = &sensor->fmt;
> +
> + format->format = *fmt;
> +
> + mutex_unlock(&sensor->lock);
> + return 0;
> +}
> +
> +static int ar0521_set_fmt(struct v4l2_subdev *sd,
> + struct v4l2_subdev_state *sd_state,
> + struct v4l2_subdev_format *format)
> +{
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> + int ret = 0;
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s(%u)\n", __func__, format->which);
> +
> + ar0521_adj_fmt(&format->format);
> +
> + mutex_lock(&sensor->lock);
> +
> + if (format->which == V4L2_SUBDEV_FORMAT_TRY) {
> + struct v4l2_mbus_framefmt *fmt;
> +
> + fmt = v4l2_subdev_get_try_format(sd, sd_state, 0 /* pad */);
> + *fmt = format->format;
> + } else {
> + sensor->fmt = format->format;
> + ar0521_calc_mode(sensor);
> + }
> +
> + mutex_unlock(&sensor->lock);
> + return ret;
> +}
> +
> +static int ar0521_s_ctrl(struct v4l2_ctrl *ctrl)
> +{
> + struct v4l2_subdev *sd = ctrl_to_sd(ctrl);
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> + int ret;
> +
> + /* v4l2_ctrl_lock() locks our own mutex */
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s(0x%X)\n", __func__, ctrl->id);
> +
> + switch (ctrl->id) {
> + case V4L2_CID_HBLANK:
> + case V4L2_CID_VBLANK:
> + sensor->total_width = sensor->fmt.width +
> + sensor->ctrls.hblank->val;
> + sensor->total_height = sensor->fmt.width +
> + sensor->ctrls.vblank->val;
> + break;
> + default:
> + ret = -EINVAL;
> + break;
> + }
> +
> + // access the sensor only if it's powered up
> + if (!pm_runtime_get_if_in_use(&sensor->i2c_client->dev))

As you correctly do not access the chip's registers if it's powered
off, you have to call __v4l2_ctrl_handler_setup() at power on time to
make sure controls are actually set.

> + return 0;
> +
> + switch (ctrl->id) {
> + case V4L2_CID_HBLANK:
> + case V4L2_CID_VBLANK:
> + ret = ar0521_set_geometry(sensor);
> + break;
> + case V4L2_CID_GAIN:
> + case V4L2_CID_RED_BALANCE:
> + case V4L2_CID_BLUE_BALANCE:
> + ret = ar0521_set_gains(sensor);
> + break;
> + case V4L2_CID_EXPOSURE:
> + ret = ar0521_write_reg(sensor,
> + AR0521_REG_COARSE_INTEGRATION_TIME,
> + ctrl->val);
> + break;
> + case V4L2_CID_TEST_PATTERN:
> + ret = ar0521_write_reg(sensor, AR0521_REG_TEST_PATTERN_MODE,
> + ctrl->val);
> + break;
> + }
> +
> + pm_runtime_put(&sensor->i2c_client->dev);
> + return ret;
> +}
> +
> +static const struct v4l2_ctrl_ops ar0521_ctrl_ops = {
> + .s_ctrl = ar0521_s_ctrl,
> +};
> +
> +static const char * const test_pattern_menu[] = {
> + "Disabled",
> + "Solid color",
> + "Color bars",
> + "Faded color bars"
> +};
> +
> +static int ar0521_init_controls(struct ar0521_dev *sensor)
> +{
> + const struct v4l2_ctrl_ops *ops = &ar0521_ctrl_ops;
> + struct ar0521_ctrls *ctrls = &sensor->ctrls;
> + struct v4l2_ctrl_handler *hdl = &ctrls->handler;
> + int ret;
> +
> + v4l2_ctrl_handler_init(hdl, 32);
> +
> + /* We can use our own mutex for the ctrl lock */
> + hdl->lock = &sensor->lock;
> +
> + /* Manual gain */
> + ctrls->gain = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_GAIN, 0, 511, 1, 0);
> + ctrls->red_balance = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_RED_BALANCE,
> + -512, 511, 1, 0);
> + ctrls->blue_balance = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_BLUE_BALANCE,
> + -512, 511, 1, 0);
> + v4l2_ctrl_cluster(3, &ctrls->gain);
> +
> + ctrls->hblank = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_HBLANK,
> + AR0521_WIDTH_BLANKING_MIN, 4094, 1,
> + AR0521_WIDTH_BLANKING_MIN);
> + ctrls->vblank = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_VBLANK,
> + AR0521_HEIGHT_BLANKING_MIN, 4094, 2,
> + AR0521_HEIGHT_BLANKING_MIN);
> + v4l2_ctrl_cluster(2, &ctrls->hblank);

Is it intended to have vblank and hblank as cluster, can't they change
independently ?

> +
> + /* Read-only */
> + ctrls->pixrate = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_PIXEL_RATE,
> + AR0521_PIXEL_CLOCK_MIN,
> + AR0521_PIXEL_CLOCK_MAX, 1,
> + AR0521_PIXEL_CLOCK_RATE);

so you have to mark it as read-only

ctrl->pixelrate->flags = V4L2_CTRL_FLAG_READ_ONLY;

> +
> + /* Manual exposure time */
> + ctrls->exposure = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_EXPOSURE, 0,
> + 65535, 1, 360);
> +
> + ctrls->test_pattern = v4l2_ctrl_new_std_menu_items(hdl, ops,
> + V4L2_CID_TEST_PATTERN,
> + ARRAY_SIZE(test_pattern_menu) - 1,
> + 0, 0, test_pattern_menu);
> +
> + if (hdl->error) {
> + ret = hdl->error;
> + goto free_ctrls;
> + }
> +
> + sensor->sd.ctrl_handler = hdl;
> + return 0;
> +
> +free_ctrls:
> + v4l2_ctrl_handler_free(hdl);
> + return ret;
> +}
> +
> +#define REGS_ENTRY(a) {(a), ARRAY_SIZE(a)}
> +#define REGS(...) REGS_ENTRY(((const __be16[]){__VA_ARGS__}))
> +
> +static const struct initial_reg {
> + const __be16 *data; /* data[0] is register address */
> + unsigned int count;
> +} initial_regs[] = {
> + REGS(be(0x0112), be(0x0808)), /* 8-bit/8-bit mode */
> +
> + /* PEDESTAL+2 :+2 is a workaround for 10bit mode +0.5 rounding */
> + REGS(be(0x301E), be(0x00AA)),
> +
> + /* corrections_recommended_bayer */
> + REGS(be(0x3042),
> + be(0x0004), /* 3042: RNC: enable b/w rnc mode */
> + be(0x4580)), /* 3044: RNC: enable row noise correction */
> +
> + REGS(be(0x30D2),
> + be(0x0000), /* 30D2: CRM/CC: enable crm on Visible and CC rows */
> + be(0x0000), /* 30D4: CC: CC enabled with 16 samples per column */
> + /* 30D6: CC: bw mode enabled/12 bit data resolution/bw mode */
> + be(0x2FFF)),
> +
> + REGS(be(0x30DA),
> + be(0x0FFF), /* 30DA: CC: column correction clip level 2 is 0 */
> + be(0x0FFF), /* 30DC: CC: column correction clip level 3 is 0 */
> + be(0x0000)), /* 30DE: CC: Group FPN correction */
> +
> + /* RNC: rnc scaling factor = * 54 / 64 (32 / 38 * 64 = 53.9) */
> + REGS(be(0x30EE), be(0x1136)),
> + REGS(be(0x30FA), be(0xFD00)), /* GPIO0 = flash, GPIO1 = shutter */
> + REGS(be(0x3120), be(0x0005)), /* p1 dither enabled for 10bit mode */
> + REGS(be(0x3172), be(0x0206)), /* txlo clk divider options */
> + /* FDOC:fdoc settings with fdoc every frame turned of */
> + REGS(be(0x3180), be(0x9434)),
> +
> + REGS(be(0x31B0),
> + be(0x008B), /* 31B0: frame_preamble - FIXME check WRT lanes# */
> + be(0x0050)), /* 31B2: line_preamble - FIXME check WRT lanes# */
> +
> + /* don't use continuous clock mode while shut down */
> + REGS(be(0x31BC), be(0x068C)),
> + REGS(be(0x31E0), be(0x0781)), /* Fuse/2DDC: enable 2ddc */
> +
> + /* analog_setup_recommended_10bit */
> + REGS(be(0x341A), be(0x4735)), /* Samp&Hold pulse in ADC */
> + REGS(be(0x3420), be(0x4735)), /* Samp&Hold pulse in ADC */
> + REGS(be(0x3426), be(0x8A1A)), /* ADC offset distribution pulse */
> + REGS(be(0x342A), be(0x0018)), /* pulse_config */
> +
> + /* pixel_timing_recommended */
> + REGS(be(0x3D00),
> + /* 3D00 */ be(0x043E), be(0x4760), be(0xFFFF), be(0xFFFF),
> + /* 3D08 */ be(0x8000), be(0x0510), be(0xAF08), be(0x0252),
> + /* 3D10 */ be(0x486F), be(0x5D5D), be(0x8056), be(0x8313),
> + /* 3D18 */ be(0x0087), be(0x6A48), be(0x6982), be(0x0280),
> + /* 3D20 */ be(0x8359), be(0x8D02), be(0x8020), be(0x4882),
> + /* 3D28 */ be(0x4269), be(0x6A95), be(0x5988), be(0x5A83),
> + /* 3D30 */ be(0x5885), be(0x6280), be(0x6289), be(0x6097),
> + /* 3D38 */ be(0x5782), be(0x605C), be(0xBF18), be(0x0961),
> + /* 3D40 */ be(0x5080), be(0x2090), be(0x4390), be(0x4382),
> + /* 3D48 */ be(0x5F8A), be(0x5D5D), be(0x9C63), be(0x8063),
> + /* 3D50 */ be(0xA960), be(0x9757), be(0x8260), be(0x5CFF),
> + /* 3D58 */ be(0xBF10), be(0x1681), be(0x0802), be(0x8000),
> + /* 3D60 */ be(0x141C), be(0x6000), be(0x6022), be(0x4D80),
> + /* 3D68 */ be(0x5C97), be(0x6A69), be(0xAC6F), be(0x4645),
> + /* 3D70 */ be(0x4400), be(0x0513), be(0x8069), be(0x6AC6),
> + /* 3D78 */ be(0x5F95), be(0x5F70), be(0x8040), be(0x4A81),
> + /* 3D80 */ be(0x0300), be(0xE703), be(0x0088), be(0x4A83),
> + /* 3D88 */ be(0x40FF), be(0xFFFF), be(0xFD70), be(0x8040),
> + /* 3D90 */ be(0x4A85), be(0x4FA8), be(0x4F8C), be(0x0070),
> + /* 3D98 */ be(0xBE47), be(0x8847), be(0xBC78), be(0x6B89),
> + /* 3DA0 */ be(0x6A80), be(0x6986), be(0x6B8E), be(0x6B80),
> + /* 3DA8 */ be(0x6980), be(0x6A88), be(0x7C9F), be(0x866B),
> + /* 3DB0 */ be(0x8765), be(0x46FF), be(0xE365), be(0xA679),
> + /* 3DB8 */ be(0x4A40), be(0x4580), be(0x44BC), be(0x7000),
> + /* 3DC0 */ be(0x8040), be(0x0802), be(0x10EF), be(0x0104),
> + /* 3DC8 */ be(0x3860), be(0x5D5D), be(0x5682), be(0x1300),
> + /* 3DD0 */ be(0x8648), be(0x8202), be(0x8082), be(0x598A),
> + /* 3DD8 */ be(0x0280), be(0x2048), be(0x3060), be(0x8042),
> + /* 3DE0 */ be(0x9259), be(0x865A), be(0x8258), be(0x8562),
> + /* 3DE8 */ be(0x8062), be(0x8560), be(0x9257), be(0x8221),
> + /* 3DF0 */ be(0x10FF), be(0xB757), be(0x9361), be(0x1019),
> + /* 3DF8 */ be(0x8020), be(0x9043), be(0x8E43), be(0x845F),
> + /* 3E00 */ be(0x835D), be(0x805D), be(0x8163), be(0x8063),
> + /* 3E08 */ be(0xA060), be(0x9157), be(0x8260), be(0x5CFF),
> + /* 3E10 */ be(0xFFFF), be(0xFFE5), be(0x1016), be(0x2048),
> + /* 3E18 */ be(0x0802), be(0x1C60), be(0x0014), be(0x0060),
> + /* 3E20 */ be(0x2205), be(0x8120), be(0x908F), be(0x6A80),
> + /* 3E28 */ be(0x6982), be(0x5F9F), be(0x6F46), be(0x4544),
> + /* 3E30 */ be(0x0005), be(0x8013), be(0x8069), be(0x6A80),
> + /* 3E38 */ be(0x7000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E40 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E48 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E50 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E58 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E60 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E68 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E70 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E78 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E80 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E88 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E90 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3E98 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3EA0 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3EA8 */ be(0x0000), be(0x0000), be(0x0000), be(0x0000),
> + /* 3EB0 */ be(0x0000), be(0x0000), be(0x0000)),
> +
> + REGS(be(0x3EB6), be(0x004C)), /* ECL */
> +
> + REGS(be(0x3EBA),
> + be(0xAAAD), /* 3EBA */
> + be(0x0086)), /* 3EBC: Bias currents for FSC/ECL */
> +
> + REGS(be(0x3EC0),
> + be(0x1E00), /* 3EC0: SFbin/SH mode settings */
> + be(0x100A), /* 3EC2: CLK divider for ramp for 10 bit 400MH */
> + /* 3EC4: FSC clamps for HDR mode and adc comp power down co */
> + be(0x3300),
> + be(0xEA44), /* 3EC6: VLN and clk gating controls */
> + be(0x6F6F), /* 3EC8: Txl0 and Txlo1 settings for normal mode */
> + be(0x2F4A), /* 3ECA: CDAC/Txlo2/RSTGHI/RSTGLO settings */
> + be(0x0506), /* 3ECC: RSTDHI/RSTDLO/CDAC/TXHI settings */
> + /* 3ECE: Ramp buffer settings and Booster enable (bits 0-5) */
> + be(0x203B),
> + be(0x13F0), /* 3ED0: TXLO from atest/sf bin settings */
> + be(0xA53D), /* 3ED2: Ramp offset */
> + be(0x862F), /* 3ED4: TXLO open loop/row driver settings */
> + be(0x4081), /* 3ED6: Txlatch fr cfpn rows/vln bias */
> + be(0x8003), /* 3ED8: Ramp step setting for 10 bit 400 Mhz */
> + be(0xA580), /* 3EDA: Ramp Offset */
> + be(0xC000), /* 3EDC: over range for rst and under range for sig */
> + be(0xC103)), /* 3EDE: over range for sig and col dec clk settings */
> +
> + /* corrections_recommended_bayer */
> + REGS(be(0x3F00),
> + be(0x0017), /* 3F00: BM_T0 */
> + be(0x02DD), /* 3F02: BM_T1 */
> + /* 3F04: if Ana_gain less than 2, use noise_floor0, multipl */
> + be(0x0020),
> + /* 3F06: if Ana_gain between 4 and 7, use noise_floor2 and */
> + be(0x0040),
> + /* 3F08: if Ana_gain between 4 and 7, use noise_floor2 and */
> + be(0x0070),
> + /* 3F0A: Define noise_floor0(low address) and noise_floor1 */
> + be(0x0101),
> + be(0x0302)), /* 3F0C: Define noise_floor2 and noise_floor3 */
> +
> + REGS(be(0x3F10),
> + be(0x0505), /* 3F10: single k factor 0 */
> + be(0x0505), /* 3F12: single k factor 1 */
> + be(0x0505), /* 3F14: single k factor 2 */
> + be(0x01FF), /* 3F16: cross factor 0 */
> + be(0x01FF), /* 3F18: cross factor 1 */
> + be(0x01FF), /* 3F1A: cross factor 2 */
> + be(0x0022)), /* 3F1E */
> +
> + /* GTH_THRES_RTN: 4max,4min filtered out of every 46 samples and */
> + REGS(be(0x3F2C), be(0x442E)),
> +
> + REGS(be(0x3F3E),
> + be(0x0000), /* 3F3E: Switch ADC from 12 bit to 10 bit mode */
> + be(0x1511), /* 3F40: couple k factor 0 */
> + be(0x1511), /* 3F42: couple k factor 1 */
> + be(0x0707)), /* 3F44: couple k factor 2 */
> +};
> +
> +static int ar0521_power_off(struct device *dev)
> +{
> + struct v4l2_subdev *sd = dev_get_drvdata(dev);
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> + int i;
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s()\n", __func__);
> + clk_disable_unprepare(sensor->extclk);
> +
> + if (sensor->reset_gpio)
> + gpiod_set_value(sensor->reset_gpio, 1); /* assert RESET signal */
> +
> + for (i = ARRAY_SIZE(ar0521_supply_names) - 1; i >= 0; i--) {
> + if (sensor->supplies[i])
> + regulator_disable(sensor->supplies[i]);
> + }
> + return 0;
> +}
> +
> +static int ar0521_power_on(struct device *dev)
> +{
> + struct v4l2_subdev *sd = dev_get_drvdata(dev);
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> + unsigned int cnt;
> + int ret;
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s()\n", __func__);
> + for (cnt = 0; cnt < ARRAY_SIZE(ar0521_supply_names); cnt++)
> + if (sensor->supplies[cnt]) {
> + ret = regulator_enable(sensor->supplies[cnt]);
> + if (ret < 0)
> + goto off;
> +
> + usleep_range(1000, 1500); /* min 1 ms */
> + }
> +
> + ret = clk_prepare_enable(sensor->extclk);
> + if (ret < 0) {
> + v4l2_err(&sensor->sd, "error enabling sensor clock\n");
> + goto off;
> + }
> + usleep_range(1000, 1500); /* min 1 ms */
> +
> + if (sensor->reset_gpio)
> + /* deassert RESET signal */
> + gpiod_set_value(sensor->reset_gpio, 0);
> + usleep_range(4500, 5000); /* min 45000 clocks */
> +
> + for (cnt = 0; cnt < ARRAY_SIZE(initial_regs); cnt++)
> + if (ar0521_write_regs(sensor, initial_regs[cnt].data,
> + initial_regs[cnt].count))
> + goto off;
> +
> + ret = ar0521_write_reg(sensor, AR0521_REG_SERIAL_FORMAT,
> + AR0521_REG_SERIAL_FORMAT_MIPI |
> + sensor->lane_count);
> + if (ret)
> + goto off;
> +
> + /* set MIPI test mode - disabled for now */
> + ret = ar0521_write_reg(sensor, AR0521_REG_HISPI_TEST_MODE,
> + ((0x40 << sensor->lane_count) - 0x40) |
> + AR0521_REG_HISPI_TEST_MODE_LP11);
> + if (ret)
> + goto off;
> +
> + ret = ar0521_write_reg(sensor, AR0521_REG_ROW_SPEED, 0x110 |
> + 4 / sensor->lane_count);
> + if (ret)
> + goto off;
> +
> + return 0;
> +off:
> + ar0521_power_off(dev);
> + return ret;
> +}
> +
> +static int ar0521_enum_mbus_code(struct v4l2_subdev *sd,
> + struct v4l2_subdev_state *sd_state,
> + struct v4l2_subdev_mbus_code_enum *code)
> +{
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> +
> + if (code->index)
> + return -EINVAL;
> +
> + code->code = sensor->fmt.code;
> + dev_dbg(&sensor->i2c_client->dev, "%s() = %X\n", __func__, code->code);
> + return 0;
> +}
> +
> +static int ar0521_pre_streamon(struct v4l2_subdev *sd, u32 flags)
> +{
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> + int ret;
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s(0x%X)\n", __func__, flags);
> + if (!(flags & V4L2_SUBDEV_PRE_STREAMON_FL_MANUAL_LP))
> + return -EACCES;
> +
> + ret = pm_runtime_resume_and_get(&sensor->i2c_client->dev);
> + if (ret < 0)
> + return ret;
> +
> + /* Set LP-11 on clock and data lanes */
> + ret = ar0521_write_reg(sensor, AR0521_REG_HISPI_CONTROL_STATUS,
> + AR0521_REG_HISPI_CONTROL_STATUS_FRAMER_TEST_MODE_ENABLE);
> + if (ret)
> + goto err;
> +
> + /* Start streaming LP-11 */
> + ret = ar0521_write_reg(sensor, AR0521_REG_RESET,
> + AR0521_REG_RESET_DEFAULTS |
> + AR0521_REG_RESET_STREAM);
> + if (ret)
> + goto err;
> + return 0;
> +
> +err:
> + pm_runtime_put(&sensor->i2c_client->dev);
> + return ret;
> +}
> +
> +static int ar0521_post_streamoff(struct v4l2_subdev *sd)
> +{
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s()\n", __func__);
> +
> + pm_runtime_put(&sensor->i2c_client->dev);
> + return 0;
> +}
> +
> +static int ar0521_s_stream(struct v4l2_subdev *sd, int enable)
> +{
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> + int ret;
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s(%i)\n", __func__, enable);
> + mutex_lock(&sensor->lock);
> +
> + ret = ar0521_set_stream(sensor, enable);
> + if (!ret)
> + sensor->streaming = enable;
> +
> + mutex_unlock(&sensor->lock);
> + return ret;
> +}
> +
> +static const struct v4l2_subdev_core_ops ar0521_core_ops = {
> + .log_status = v4l2_ctrl_subdev_log_status,
> +};
> +
> +static const struct v4l2_subdev_video_ops ar0521_video_ops = {
> + .s_stream = ar0521_s_stream,
> + .pre_streamon = ar0521_pre_streamon,
> + .post_streamoff = ar0521_post_streamoff,
> +};
> +
> +static const struct v4l2_subdev_pad_ops ar0521_pad_ops = {
> + .enum_mbus_code = ar0521_enum_mbus_code,
> + .get_fmt = ar0521_get_fmt,
> + .set_fmt = ar0521_set_fmt,
> +};
> +
> +static const struct v4l2_subdev_ops ar0521_subdev_ops = {
> + .core = &ar0521_core_ops,
> + .video = &ar0521_video_ops,
> + .pad = &ar0521_pad_ops,
> +};
> +
> +static int __maybe_unused ar0521_suspend(struct device *dev)
> +{
> + struct v4l2_subdev *sd = dev_get_drvdata(dev);
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s()\n", __func__);
> + if (sensor->streaming)
> + ar0521_set_stream(sensor, 0);
> +
> + return 0;
> +}
> +
> +static int __maybe_unused ar0521_resume(struct device *dev)
> +{
> + struct v4l2_subdev *sd = dev_get_drvdata(dev);
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> +
> + dev_dbg(&sensor->i2c_client->dev, "%s()\n", __func__);
> + if (sensor->streaming)
> + return ar0521_set_stream(sensor, 1);
> +
> + return 0;
> +}
> +
> +static int ar0521_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + struct v4l2_fwnode_endpoint ep = {
> + .bus_type = V4L2_MBUS_CSI2_DPHY
> + };
> + struct device *dev = &client->dev;
> + struct fwnode_handle *endpoint;
> + struct ar0521_dev *sensor;
> + unsigned int cnt;
> + int ret;
> +
> + dev_dbg(dev, "%s()\n", __func__);

Rather useless, please drop. Same for all other debug functions that
just print the current function name in other parts of the driver.
While maybe useful when developing, they're mostly noise for users
imo.

> + sensor = devm_kzalloc(dev, sizeof(*sensor), GFP_KERNEL);
> + if (!sensor)
> + return -ENOMEM;
> +
> + sensor->i2c_client = client;
> + sensor->fmt.width = AR0521_WIDTH_MAX;
> + sensor->fmt.height = AR0521_HEIGHT_MAX;
> + ar0521_adj_fmt(&sensor->fmt);
> +
> + endpoint = fwnode_graph_get_endpoint_by_id(dev_fwnode(dev), 0, 0,
> + FWNODE_GRAPH_ENDPOINT_NEXT);

The drivers supports a single endpoint right ? Then
fwnode_graph_get_next_enpoint() can be used

> + if (!endpoint) {
> + dev_err(dev, "endpoint node not found\n");
> + return -EINVAL;
> + }
> +
> + ret = v4l2_fwnode_endpoint_parse(endpoint, &ep);
> + fwnode_handle_put(endpoint);
> + if (ret) {
> + dev_err(dev, "could not parse endpoint\n");
> + return ret;
> + }
> +
> + if (ep.bus_type != V4L2_MBUS_CSI2_DPHY) {
> + dev_err(dev, "invalid bus type, must be MIPI CSI2\n");
> + return -EINVAL;
> + }
> +
> + sensor->lane_count = ep.bus.mipi_csi2.num_data_lanes;
> + switch (sensor->lane_count) {
> + case 1:
> + case 2:
> + case 4:
> + break;
> + default:
> + dev_err(dev, "invalid number of MIPI data lanes\n");
> + return -EINVAL;
> + }
> +
> + /* Get master clock (extclk) */
> + sensor->extclk = devm_clk_get(dev, "extclk");
> + if (IS_ERR(sensor->extclk)) {
> + dev_err(dev, "failed to get extclk\n");
> + return PTR_ERR(sensor->extclk);
> + }
> +
> + sensor->extclk_freq = clk_get_rate(sensor->extclk);
> +
> + if (sensor->extclk_freq < AR0521_EXTCLK_MIN ||
> + sensor->extclk_freq > AR0521_EXTCLK_MAX) {
> + dev_err(dev, "extclk frequency out of range: %u Hz\n",
> + sensor->extclk_freq);
> + return -EINVAL;
> + }
> +
> + /* Request optional reset pin (usually active low) and assert it */
> + sensor->reset_gpio = devm_gpiod_get_optional(dev, "reset",
> + GPIOD_OUT_HIGH);
> +
> + v4l2_i2c_subdev_init(&sensor->sd, client, &ar0521_subdev_ops);
> +
> + sensor->sd.flags = V4L2_SUBDEV_FL_HAS_DEVNODE;
> + sensor->pad.flags = MEDIA_PAD_FL_SOURCE;
> + sensor->sd.entity.function = MEDIA_ENT_F_CAM_SENSOR;
> + ret = media_entity_pads_init(&sensor->sd.entity, 1, &sensor->pad);
> + if (ret)
> + return ret;
> +
> + for (cnt = 0; cnt < ARRAY_SIZE(ar0521_supply_names); cnt++) {
> + struct regulator *supply = devm_regulator_get(dev,
> + ar0521_supply_names[cnt]);
> +
> + if (IS_ERR(supply)) {
> + dev_info(dev, "no %s regulator found: %li\n",
> + ar0521_supply_names[cnt], PTR_ERR(supply));
> + return PTR_ERR(supply);
> + }
> + sensor->supplies[cnt] = supply;
> + }

Using the regulator bulk api would simplify this.
See drivers/media/i2c/ccs/ccs-core.c

> +
> + mutex_init(&sensor->lock);
> +
> + ret = ar0521_init_controls(sensor);
> + if (ret)
> + goto entity_cleanup;
> +
> + ar0521_adj_fmt(&sensor->fmt);

Called already here above. Can anything in here change the format ?

> +
> + ret = v4l2_async_register_subdev(&sensor->sd);
> + if (ret)
> + goto free_ctrls;
> +
> + /* Turn on the device and enable runtime PM */
> + ret = ar0521_power_on(&client->dev);
> + if (ret)
> + goto disable;

Does the device stay powered all the time ?
Doesn't your resume callback call power_on() already ?

> + pm_runtime_set_active(&client->dev);
> + pm_runtime_enable(&client->dev);
> + dev_dbg(dev, "AR0521 driver initialized, master clock frequency: %u Hz, %u MIPI data lanes\n",
> + sensor->extclk_freq, sensor->lane_count);
> + return 0;
> +
> +disable:
> + v4l2_async_unregister_subdev(&sensor->sd);
> + media_entity_cleanup(&sensor->sd.entity);
> +free_ctrls:
> + v4l2_ctrl_handler_free(&sensor->ctrls.handler);
> +entity_cleanup:
> + media_entity_cleanup(&sensor->sd.entity);
> + mutex_destroy(&sensor->lock);
> + return ret;
> +}
> +
> +static int ar0521_remove(struct i2c_client *client)
> +{
> + struct v4l2_subdev *sd = i2c_get_clientdata(client);
> + struct ar0521_dev *sensor = to_ar0521_dev(sd);
> +
> + v4l2_async_unregister_subdev(&sensor->sd);
> + media_entity_cleanup(&sensor->sd.entity);
> + v4l2_ctrl_handler_free(&sensor->ctrls.handler);
> + pm_runtime_disable(&client->dev);
> + if (!pm_runtime_status_suspended(&client->dev))
> + ar0521_power_off(&client->dev);
> + pm_runtime_set_suspended(&client->dev);
> + mutex_destroy(&sensor->lock);
> + return 0;
> +}
> +
> +static const struct dev_pm_ops ar0521_pm_ops = {
> + SET_SYSTEM_SLEEP_PM_OPS(ar0521_suspend, ar0521_resume)
> + SET_RUNTIME_PM_OPS(ar0521_power_off, ar0521_power_on, NULL)
> +};
> +static const struct of_device_id ar0521_dt_ids[] = {
> + {.compatible = "onnn,ar0521"},
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, ar0521_dt_ids);
> +
> +static struct i2c_driver ar0521_i2c_driver = {
> + .driver = {
> + .name = "ar0521",
> + .pm = &ar0521_pm_ops,
> + .of_match_table = ar0521_dt_ids,
> + },
> + .probe = ar0521_probe,

You could use probe_new and drop the "const struct i2c_device_id *id"
argument to probe()

Thanks
j

> + .remove = ar0521_remove,
> +};
> +
> +module_i2c_driver(ar0521_i2c_driver);
> +
> +MODULE_DESCRIPTION("AR0521 MIPI Camera subdev driver");
> +MODULE_AUTHOR("Krzysztof Hałasa <khalasa@piap.pl>");
> +MODULE_LICENSE("GPL v2");