Re: [PATCH v3 2/2] media: i2c: Add Sony IMX908 image sensor driver

[Lachlan Michael <Lachlan.Michael@sony.com>]

Dear Laurent,

On 9/29/2026 10:26 AM, Laurent Pinchart wrote:
> On Mon, Sep 21, 2026 at 09: 58: 16PM +0530, Jai Luthra wrote: > Hi 
> Lachlan, > > Thank you for your patch. > > And thanks for fixing my 
> comments from v2. I have a few more, some I missed > the last time 
> around, but some are new. 
> 
> On Mon, Sep 21, 2026 at 09:58:16PM +0530, Jai Luthra wrote:
>> Hi Lachlan,
>> 
>> Thank you for your patch.
>> 
>> And thanks for fixing my comments from v2. I have a few more, some I missed
>> the last time around, but some are new.
> 
> I've added a few small comments and a couple of clarifications.

Thanks for the comments and clarifications.

>> Quoting Lachlan Michael (2026-08-28 12:18:43)
>> > The Sony IMX908 is an 8.39 megapixel (3856x2176) CMOS image sensor
>> > with a MIPI CSI-2 output interface, configurable as either 2 or 4
>> > data lanes.
>> > 
>> > Add a V4L2 sub-device driver for the sensor. The driver supports
>> > RAW10 and RAW12 output formats, exposure and analogue gain controls,
>> > horizontal and vertical flipping, horizontal and vertical blanking
>> > controls, window cropping and test pattern generation.
>> > 
>> > HDR modes and RAW16 output are not currently supported.
>> > 
>> > Signed-off-by: Lachlan Michael <lachlan.michael@sony.com>
>> > ---
>> > Changes in v3:
>> > - Correct link-frequency indexing mapping to match the sensor
>> >   DATARATE_SEL values and the frequency ordering
>> > - Changed the pixel_rate to 16-pixel-per-clocks based on datasheet
>> >   mode values
>> > - Clean up the constant names, register definitions and comments in
>> >   response to review feedback.
>> > - Remove various (uneeded) checks in code based on feedback
>> > - Remove cached vmax/hmax and recalculated where necessary
>> > - Drop pixel_rate and test_pattern pointers from struct
>> > - Remove read-only controls set_ctrl switch
>> > - Remove event handlers
>> > - Remove uneeded delays at startup 
>> > - Simplify runtime_resume/suspend functions
>> > - Remove the 4k recording-area in favour of larger active area
>> > - Use the same constraints for VMAX for crop and all pixel mode to
>> >   simplify the driver logic by removing branching
>> > - Rework HMAX based on the fact that the whole line is always read
>> >   even in crop mode. HMAX varies in all modes now, but not with 
>> >   horizontal crop.
>> > - Minor edits and bugfixes 
>> > ---
>> >  MAINTAINERS                |    1 +
>> >  drivers/media/i2c/Kconfig  |   11 +
>> >  drivers/media/i2c/Makefile |    1 +
>> >  drivers/media/i2c/imx908.c | 1367 ++++++++++++++++++++++++++++++++++++
>> >  4 files changed, 1380 insertions(+)
>> >  create mode 100644 drivers/media/i2c/imx908.c
>> > 
>> > diff --git a/MAINTAINERS b/MAINTAINERS
>> > index bb7adcfd4767..a17c31234ec7 100644
>> > --- a/MAINTAINERS
>> > +++ b/MAINTAINERS
>> > @@ -25542,6 +25542,7 @@ SONY IMX908 SENSOR DRIVER
>> >  M:     Lachlan Michael <lachlan.michael@sony.com>
>> >  S:     Maintained
>> >  F:     Documentation/devicetree/bindings/media/i2c/sony,imx908.yaml
>> > +F:     drivers/media/i2c/imx908.c
>> >  
>> >  SONY MEMORYSTICK SUBSYSTEM
>> >  M:     Maxim Levitsky <maximlevitsky@gmail.com>
>> > diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
>> > index 5c52007f9cbe..cfa1359d8c7d 100644
>> > --- a/drivers/media/i2c/Kconfig
>> > +++ b/drivers/media/i2c/Kconfig
>> > @@ -310,6 +310,17 @@ config VIDEO_IMX678
>> >           To compile this driver as a module, choose M here: the
>> >           module will be called imx678.
>> >  
>> > +config VIDEO_IMX908
>> > +        tristate "Sony IMX908 sensor support"
>> > +        depends on GPIOLIB
>> > +        select V4L2_CCI_I2C
>> > +        help
>> > +          This is a Video4Linux2 sensor driver for the Sony
>> > +          IMX908 CMOS image sensor.
>> > +
>> > +          To compile this driver as a module, choose M here: the
>> > +          module will be called imx908.
>> > +
>> >  config VIDEO_MAX9271_LIB
>> >         tristate
>> >  
>> > diff --git a/drivers/media/i2c/Makefile b/drivers/media/i2c/Makefile
>> > index d04bd5724552..d91ed1bc6427 100644
>> > --- a/drivers/media/i2c/Makefile
>> > +++ b/drivers/media/i2c/Makefile
>> > @@ -63,6 +63,7 @@ obj-$(CONFIG_VIDEO_IMX412) += imx412.o
>> >  obj-$(CONFIG_VIDEO_IMX415) += imx415.o
>> >  obj-$(CONFIG_VIDEO_IMX678) += imx678.o
>> >  obj-$(CONFIG_VIDEO_IMX471) += imx471.o
>> > +obj-$(CONFIG_VIDEO_IMX908) += imx908.o
>> >  obj-$(CONFIG_VIDEO_IR_I2C) += ir-kbd-i2c.o
>> >  obj-$(CONFIG_VIDEO_ISL7998X) += isl7998x.o
>> >  obj-$(CONFIG_VIDEO_KS0127) += ks0127.o
>> > diff --git a/drivers/media/i2c/imx908.c b/drivers/media/i2c/imx908.c
>> > new file mode 100644
>> > index 000000000000..ca85a5cd058a
>> > --- /dev/null
>> > +++ b/drivers/media/i2c/imx908.c
>> > @@ -0,0 +1,1367 @@
>> > +// SPDX-License-Identifier: GPL-2.0
>> > +/*
>> > + * V4L2 driver for Sony IMX908
>> > + *
>> > + * Diagonal 6.42 mm (Type 1/2.8) CMOS image sensor with 8.39 M pixels.
>> > + *
>> > + * Copyright 2026 Sony Semiconductor Solutions Corporation
>> > + *
>> > + */
>> > +
>> > +#include <linux/align.h>
>> > +#include <linux/array_size.h>
>> > +#include <linux/bitops.h>
>> > +#include <linux/clk.h>
>> > +#include <linux/container_of.h>
>> > +#include <linux/delay.h>
>> > +#include <linux/err.h>
>> > +#include <linux/gpio/consumer.h>
>> > +#include <linux/i2c.h>
>> > +#include <linux/math.h>                /* DIV_ROUND_UP */
>> > +#include <linux/math64.h>      /* DIV64_U64_ROUND_UP */
>> > +#include <linux/minmax.h>
>> > +#include <linux/module.h>
>> > +#include <linux/pm_runtime.h>
>> > +#include <linux/property.h>
>> > +#include <linux/regulator/consumer.h>
>> > +
>> > +#include <media/media-entity.h>
>> > +#include <media/v4l2-cci.h>
>> > +#include <media/v4l2-ctrls.h>
>> > +#include <media/v4l2-fwnode.h>
>> > +#include <media/v4l2-mediabus.h>
>> > +#include <media/v4l2-rect.h>
>> > +#include <media/v4l2-subdev.h>
>> > +
>> > +/* ---- IMX908 Registers --------- */
>> > +#define IMX908_REG_STANDBY     CCI_REG8(0x3000)
>> > +#define IMX908_STANDBY_EN      BIT(0)          /* Standby mode */
>> > +#define IMX908_STANDBY_CANCEL  0x00            /* Operating mode */
>> > +#define IMX908_REG_XMSTA       CCI_REG8(0x3002)        /* [0] Init 1h */
>> > +#define IMX908_XMSTA_START     0x00
>> > +#define IMX908_XMSTA_STOP      0x01
>> > +#define IMX908_REG_XMASTER     CCI_REG8(0x3003)        /* [0] Init 0h */
>> > +#define IMX908_CONTROLLER_MODE 0x00
>> > +#define IMX908_REG_INCK_SEL    CCI_REG8(0x3014)        /* 0:74.25 1:37.125 2:72 3:27 4:24 */
>> > +#define IMX908_REG_DATARATE_SEL        CCI_REG8(0x3015)
>> > +
>> > +/* ---- Crop */
>> > +#define IMX908_REG_WINMODE     CCI_REG8(0x3018)        /* [3:0] */
>> > +#define IMX908_WINMODE_ALLPIX  0x00    /* All-pixel readout mode */
>> > +#define IMX908_WINMODE_CROP    0x04    /* Window cropping mode */
>> > +
>> > +/* ---- Flip */
>> > +#define IMX908_REG_HREVERSE    CCI_REG8(0x3020)
>> > +#define IMX908_HREVERSE_NORMAL 0x00
>> > +#define IMX908_HREVERSE_INV    0x01
>> > +#define IMX908_REG_VREVERSE    CCI_REG8(0x3021)
>> > +#define IMX908_VREVERSE_NORMAL 0x00
>> > +#define IMX908_VREVERSE_INV    0x01
>> > +
>> > +/* ---- Internal Analog to Digital conversion bit width */
>> > +#define IMX908_REG_ADBIT       CCI_REG8(0x3022)
>> > +#define IMX908_ADBIT_10BIT     0x00    /* 10-bit */
>> > +#define IMX908_ADBIT_12BIT     0x01    /* 11-bit + digital dither */
>> > +
>> > +#define IMX908_REG_MDBIT       CCI_REG8(0x3023)
>> > +#define IMX908_MDBIT_RAW10     0x00
>> > +#define IMX908_MDBIT_RAW12     0x01
>> > +
>> > +/* ---- VMAX  Frame length in lines */
>> > +#define IMX908_REG_VMAX                CCI_REG24_LE(0x3028)    /* [19:0] */
>> > +#define IMX908_VMAX_MAX                0xfffff
>> > +#define IMX908_VMAX_DEFAULT    2250
>> > +/*
>> > + * VMAX restrictions, documented for window cropping mode:
>> > + * VMAX >= PIX_VWIDTH + 70
>> > + * VMAX >= 1206
>> > + */
>> > +#define IMX908_VMAX_MARGIN     70
>> > +#define IMX908_VMAX_MIN                1206
>> > +
>> > +/* ---- HMAX Line length in clocks */
>> > +#define IMX908_REG_HMAX                CCI_REG16_LE(0x302c)    /* [15:0] */
>> > +#define IMX908_HMAX_MAX                0xffff
>> > +#define IMX908_HMAX_DEFAULT    1100
>> > +
>> > +/* ---- Cropping related */
>> > +#define IMX908_REG_PIX_HST     CCI_REG16_LE(0x303c)    /* [12:0] Init 0h */
>> > +#define IMX908_REG_PIX_HWIDTH  CCI_REG16_LE(0x303e)    /* [12:0] Init 0F10h */
>> > +#define IMX908_REG_LANEMODE    CCI_REG8(0x3040)
>> > +#define IMX908_LANEMODE_2LANE  0x01
>> > +#define IMX908_LANEMODE_4LANE  0x03
>> > +#define IMX908_REG_PIX_VST     CCI_REG16_LE(0x3044)    /* [12:0] Init 0h */
>> > +#define IMX908_REG_PIX_VWIDTH  CCI_REG16_LE(0x3046)    /* [12:0] Init 0884h */
>> > +#define IMX908_CROP_ALIGN_VSTART       4
>> > +#define IMX908_CROP_ALIGN_VWIDTH       4
>> > +#define IMX908_CROP_ALIGN_HSTART       4
>> > +#define IMX908_CROP_ALIGN_HWIDTH       16
>> > +#define IMX908_CROP_MIN_HEIGHT         1136
>> > +#define IMX908_CROP_MIN_WIDTH          1040
>> > +
>> > +/* ---- Shutter */
>> > +#define IMX908_REG_SHR0                CCI_REG24_LE(0x3050)    /* [19:0] */
>> > +#define IMX908_MIN_SHR0                7
>> > +
>> > +/*
>> > + * Analogue gain control
>> > + * Range is from 0 to 100 (0dB - 30dB) with 0.3dB step size
>> > + * Values from 101 to 240 are valid but correspond to additional digital gain
>> > + * (0.3dB - 42dB) so don't expose it to userspace
>> > + */
>> > +#define IMX908_REG_GAIN                CCI_REG16_LE(0x3070)    /* [10:0] */
>> > +#define IMX908_ANA_GAIN_MAX    100
>> > +#define IMX908_ANA_GAIN_MIN    0
>> > +#define IMX908_ANA_GAIN_STEP   1
>> > +#define IMX908_ANA_GAIN_DEFAULT        0
>> > +
>> > +/* ---- XVS/XHS output mode */
>> > +#define IMX908_XXS_DRV         CCI_REG8(0x30a6)        /* [1:0] XVS_DRV [3:2] XHS_DRV */
>> > +
>> > +#define IMX908_REG_BLKLEVEL    CCI_REG16_LE(0x30dc)    /* [15:0] black level */
>> > +
>> > +/* ---- Test Pattern Generator (TPG) registers */
>> > +#define IMX908_REG_TPG_EN      CCI_REG8(0x30e0)
>> > +#define IMX908_TPG_EN_BIT      BIT(0)
>> > +#define IMX908_REG_TPG_PATSEL  CCI_REG8(0x30e2)        /* [4:0] pattern idx */
>> > +#define IMX908_REG_TESTCLKEN   CCI_REG8(0x4900)
>> > +#define IMX908_TESTCLKEN_BIT   BIT(3)
>> > +
>> > +#define IMX908_REG_TYPE_ID     CCI_REG16_LE(0x4c0c)
>> > +#define IMX908_CHIP_ID         0x038c
>> > +
>> > +/* ---- IMX908 Common Register List ---- */
>> > +static const struct cci_reg_sequence imx908_common_regs[] = {
>> > +       { IMX908_XXS_DRV, IMX908_CONTROLLER_MODE },
>> > +       { CCI_REG8(0x039c), 0x03 },
>> > +       { CCI_REG8(0x3416), 0x20 },
>> > +       { CCI_REG8(0x3417), 0x00 },
>> > +       { CCI_REG8(0x3456), 0xf4 },
>> > +       { CCI_REG8(0x345d), 0x01 },
>> > +       { CCI_REG8(0x3460), 0x00 },
>> > +       { CCI_REG8(0x3461), 0x0b },
>> > +       { CCI_REG8(0x3471), 0x00 },
>> > +       { CCI_REG8(0x3472), 0x23 },
>> > +       { CCI_REG8(0x347b), 0x02 },
>> > +       { CCI_REG8(0x3481), 0x01 },
>> > +       { CCI_REG8(0x380c), 0x00 },
>> > +       { CCI_REG8(0x380f), 0x0c },
>> > +       { CCI_REG8(0x381c), 0x11 },
>> > +       { CCI_REG8(0x3820), 0x22 },
>> > +       { CCI_REG8(0x3824), 0x33 },
>> > +       { CCI_REG8(0x3828), 0x22 },
>> > +       { CCI_REG8(0x382c), 0x33 },
>> > +       { CCI_REG8(0x3830), 0x33 },
>> > +       { CCI_REG8(0x3838), 0x05 },
>> > +       { CCI_REG8(0x383c), 0x07 },
>> > +       { CCI_REG8(0x3840), 0x06 },
>> > +       { CCI_REG8(0x3848), 0x17 },
>> > +       { CCI_REG8(0x384c), 0x0b },
>> > +       { CCI_REG8(0x3850), 0x10 },
>> > +       { CCI_REG8(0x3854), 0x12 },
>> > +       { CCI_REG8(0x385c), 0x20 },
>> > +       { CCI_REG8(0x38c4), 0x64 },
>> > +       { CCI_REG8(0x38c5), 0x64 },
>> > +       { CCI_REG8(0x38c6), 0x64 },
>> > +       { CCI_REG8(0x3c4a), 0x15 },
>> > +       { CCI_REG8(0x3c4c), 0x13 },
>> > +       { CCI_REG8(0x3c4d), 0x13 },
>> > +       { CCI_REG8(0x3c4e), 0x13 },
>> > +       { CCI_REG8(0x3c50), 0x77 },
>> > +       { CCI_REG8(0x3c51), 0x07 },
>> > +       { CCI_REG8(0x3db4), 0x00 },
>> > +       { CCI_REG8(0x4419), 0x06 },
>> > +       { CCI_REG8(0x441c), 0x00 },
>> > +       { CCI_REG8(0x4426), 0x00 },
>> > +       { CCI_REG8(0x4538), 0x20 },
>> > +       { CCI_REG8(0x4539), 0x19 },
>> > +       { CCI_REG8(0x453a), 0x19 },
>> > +       { CCI_REG8(0x453b), 0x19 },
>> > +       { CCI_REG8(0x453c), 0x19 },
>> > +       { CCI_REG8(0x453d), 0x19 },
>> > +       { CCI_REG8(0x453e), 0x19 },
>> > +       { CCI_REG8(0x453f), 0x19 },
>> > +       { CCI_REG8(0x4540), 0x19 },
>> > +       { CCI_REG8(0x4544), 0x11 },
>> > +       { CCI_REG8(0x4545), 0x11 },
>> > +       { CCI_REG8(0x4546), 0x11 },
>> > +       { CCI_REG8(0x463c), 0x20 },
>> > +       { CCI_REG8(0x465e), 0xcf },
>> > +       { CCI_REG8(0x4684), 0x20 },
>> > +       { CCI_REG8(0x46a6), 0xcf },
>> > +       { CCI_REG8(0x46e2), 0xf3 },
>> > +};
>> > +
>> > +static const u32 imx908_bit_depth_regs[] = {
>> > +       CCI_REG8(0x3d78),
>> > +       CCI_REG8(0x3d79),
>> > +       CCI_REG8(0x3d80),
>> > +       CCI_REG8(0x3d81),
>> > +       CCI_REG8(0x3d88),
>> > +       CCI_REG8(0x3d89),
>> > +       CCI_REG8(0x3d90),
>> > +       CCI_REG8(0x3d91),
>> > +};
>> > +
>> > +#define IMX908_EXPOSURE_MIN    1
>> > +#define IMX908_EXPOSURE_STEP   1
>> > +
>> > +/* ---- Internal image-data interface clock */
>> > +#define IMX908_VTPXCK_HZ       74250000ULL
>> > +
>> > +/* Fixed pixel rate: 16 pixels per video timing pixel clock cycle */
>> > +#define IMX908_PIX_PER_CLK     16
>> > +#define IMX908_PIXEL_RATE      (IMX908_VTPXCK_HZ * IMX908_PIX_PER_CLK)
>> > +
>> > +/* ---- Subdev Pads */
>> > +#define IMX908_SOURCE_PAD      0
>> > +
>> > +#define IMX908_DEFAULT_MBUS_CODE MEDIA_BUS_FMT_SRGGB10_1X10
>> > +
>> > +/*
>> > + * IMX908 total area includes active area height plus
>> > + *  4 pixels effective pixel ignored area
>> > + * 10 pixels vertical direction effective OB
>> > + * 10 pixels OB side ignored area
>> > + */
>> > +static const struct v4l2_rect imx908_total_area = {
>> > +       .top = 0,
>> > +       .left = 0,
>> > +       .width = 3856,
>> > +       .height = 2200,
>> > +};
>> > +
>> 
>> The "Pixel Arrangement" section in the datasheet for IMX678 (Starvis 2,
>> same resolution) mentioned a horizontal margin of 8 and 9, and vertical
>> margin of 10 + 10 + 4 + 8 and 9, thus the total came out to be 3857x2201
>> 
>> Which also explained why the CFA readout stays R->G->G->B irrespective of
>> VFLIP and HFLIP, the extra pixel allowed shifting the readout start.
>> 
>> > +static const struct v4l2_rect imx908_active_area = {
>> > +       .top = 0,
>> > +       .left = 0,
>> > +       .width = 3856,
>> > +       .height = 2176,
>> 
>> Shouldn't this have .top = 24 (10 + 10 + 4)?
>> 
>> At least on IMX678, while the diagram shows the OB area at bottom, that's
>> where the scan starts from (N12 pin) when HREVERSE/VREVERSE are 0.
>> 
>> It would be good to confirm if IMX908 is indeed different in its behaviour
>> from Starvis2 sensors.
>> 
>> > +};
>> > +
>> > +static const char *const imx908_supply_names[] = {
>> > +       "avdd",  /* Analog (3.3V) supply */
>> > +       "dvdd",  /* Digital Core (1.1V) supply */
>> > +       "ovdd",  /* IF (1.8V) supply */
>> > +};
>> > +
>> > +static const u32 imx908_mbus_codes[] = {
>> > +       MEDIA_BUS_FMT_SRGGB10_1X10, /* RAW10 */
>> > +       MEDIA_BUS_FMT_SRGGB12_1X12, /* RAW12 */
>> > +};
>> > +
>> > +/*
>> > + * Link frequency indices, ordered so that the index is also the
>> > + * DATARATE_SEL register value. Keep in descending frequency order.
>> > + */
>> > +enum {
>> > +       IMX908_LINK_FREQ_1188MHZ = 0x00,
>> > +       IMX908_LINK_FREQ_1039MHZ = 0x01,
>> > +       IMX908_LINK_FREQ_891MHZ  = 0x02,
>> > +       IMX908_LINK_FREQ_720MHZ  = 0x03,
>> > +       IMX908_LINK_FREQ_594MHZ  = 0x04,
>> > +       IMX908_LINK_FREQ_445MHZ  = 0x05,
>> > +       IMX908_LINK_FREQ_360MHZ  = 0x06,
>> > +       IMX908_LINK_FREQ_297MHZ  = 0x07,
>> > +};
>> > +
>> > +static const s64 imx908_link_freqs[] = {
>> > +       [IMX908_LINK_FREQ_1188MHZ] = 1188000000LL,
>> > +       [IMX908_LINK_FREQ_1039MHZ] = 1039500000LL,
>> > +       [IMX908_LINK_FREQ_891MHZ]  =  891000000LL,
>> > +       [IMX908_LINK_FREQ_720MHZ]  =  720000000LL,
>> > +       [IMX908_LINK_FREQ_594MHZ]  =  594000000LL,
>> > +       [IMX908_LINK_FREQ_445MHZ]  =  445500000LL,
>> > +       [IMX908_LINK_FREQ_360MHZ]  =  360000000LL,
>> > +       [IMX908_LINK_FREQ_297MHZ]  =  297000000LL,
>> > +};
>> > +
>> > +/* Allowed clock values in Hz */
>> > +static const u32 imx908_inck_table[] = {
>> > +       74250000,
>> > +       37125000,
>> > +       72000000,
>> > +       27000000,
>> > +       24000000,
>> > +};
>> > +
>> > +struct imx908 {
>> > +       struct v4l2_subdev sd;
>> > +       struct media_pad pad;
>> > +       struct device *dev;
>> > +
>> > +       struct regmap *cci;
>> > +
>> > +       struct clk *xclk;
>> > +       struct gpio_desc *reset_gpio;
>> > +       struct regulator_bulk_data supplies[ARRAY_SIZE(imx908_supply_names)];
>> > +
>> > +       u8 inck_sel;
>> > +
>> > +       u8 num_lanes;
>> > +       unsigned long link_freq_bitmap;
>> > +       unsigned int link_freq_idx;
>> > +
>> > +       struct {
>> > +               struct v4l2_ctrl_handler handler;
>> > +
>> > +               struct v4l2_ctrl *exposure;
>> > +               struct v4l2_ctrl *vblank;
>> > +               struct v4l2_ctrl *hblank;
>> > +       } ctrls;
>> > +};
>> > +
>> > +static inline struct imx908 *to_imx908(struct v4l2_subdev *_sd)
>> > +{
>> > +       return container_of(_sd, struct imx908, sd);
>> > +}
>> > +
>> > +/* ----------------------- Basic Helper Functions --------------------------- */
>> > +static bool imx908_mbus_code_supported(struct imx908 *imx, u32 code)
>> > +{
>> > +       for (unsigned int i = 0; i < ARRAY_SIZE(imx908_mbus_codes); i++) {
>> > +               if (imx908_mbus_codes[i] == code)
>> > +                       return true;
>> > +       }
>> > +
>> > +       return false;
>> > +}
>> > +
>> > +static u16 imx908_calc_hmax(u32 width, u32 hblank)
>> > +{
>> > +       u32 hmax = DIV_ROUND_UP(width + hblank, IMX908_PIX_PER_CLK);
>> > +
>> > +       return min_t(u32, hmax, IMX908_HMAX_MAX);
>> > +}
>> > +
>> > +/* Horizontal cropping is digital, so the full width is always read out */
>> > +static u16 imx908_calc_min_hmax(struct imx908 *imx, u8 bpp)
>> > +{
>> > +       u64 link_hz = imx908_link_freqs[imx->link_freq_idx];
>> > +       u64 num = (u64)imx908_active_area.width * bpp * IMX908_VTPXCK_HZ;
>> > +       u64 den = (u64)imx->num_lanes * link_hz * 2; /* DDR */
>> > +
>> > +       /*
>> > +        * den can exceed 32 bits (e.g. 4 lanes * 720 MHz * 2 = 5.76 GHz), so
> 
> I think the first line of the comment is missing .

I don't think that is the case, but the comment maybe reads a bit 
strange since it starts with the variable name den. I'll rewrite in v4.

> 
>> > +        * DIV_ROUND_UP_ULL / do_div would truncate the divisor to u32. Use a
>> > +        * full 64/64 division.
>> > +        */
>> > +       return DIV64_U64_ROUND_UP(num, den);
>> > +}
>> > +
>> > +static u32 imx908_calc_min_vblank(const struct v4l2_rect *crop)
>> > +{
>> > +       u32 min_vmax = max_t(u32, crop->height + IMX908_VMAX_MARGIN,
>> > +                        IMX908_VMAX_MIN);
>> > +
>> > +       return min_vmax - crop->height;
>> > +}
>> > +
>> > +static int imx908_set_exposure_lines(struct imx908 *imx, u32 exposure_lines)
>> > +{
>> > +       const struct v4l2_mbus_framefmt *format;
>> > +       struct v4l2_subdev_state *state;
>> > +       u32 vmax, max_lines;
>> > +
>> > +       state = v4l2_subdev_get_locked_active_state(&imx->sd);
>> > +       format = v4l2_subdev_state_get_format(state, IMX908_SOURCE_PAD);
>> > +
>> > +       vmax = format->height + imx->ctrls.vblank->val;
>> > +       max_lines = vmax - IMX908_MIN_SHR0;
>> > +
>> > +       /* Guards SHR0 underflow when VBLANK+EXPOSURE are set together */
>> > +       exposure_lines = clamp_t(u32, exposure_lines, 1, max_lines);
>> > +
>> > +       u32 shr0 = vmax - exposure_lines;
>> > +
>> > +       return cci_write(imx->cci, IMX908_REG_SHR0, shr0, NULL);
>> > +}
>> > +
>> > +static u8 imx908_bits_per_pixel(u32 code)
>> > +{
>> > +       switch (code) {
>> > +       case MEDIA_BUS_FMT_SRGGB12_1X12:
>> > +               return 12;
>> > +       case MEDIA_BUS_FMT_SRGGB10_1X10:
>> > +       default:
>> > +               return 10;
>> > +       }
>> > +}
>> > +
>> > +static u32 imx908_hmax_to_hblank(u16 hmax, u32 width)
>> > +{
>> > +       return hmax * IMX908_PIX_PER_CLK - width;
>> > +}
>> > +
>> > +static int imx908_update_hblank_limits(struct imx908 *imx, u32 old_width,
>> > +                                      u32 width, u8 bpp)
>> > +{
>> > +       u16 min_hmax = imx908_calc_min_hmax(imx, bpp);
>> > +       u32 max_hblank = imx908_hmax_to_hblank(IMX908_HMAX_MAX, width);
>> > +       u32 min_hblank = imx908_hmax_to_hblank(min_hmax, width);
>> > +       /* Re-derive the line period at the old width to preserve line time */
> 
> I wonder if this is worth the extra complexity. Changing the output size
> is only allowed when the sensor is stopped, and I think we can expect
> userspace to set the hblank and vblank controls when reconfiguring the
> sensor. Dropping this would simplify the code. Up to you.
> 
> Same comment for vblank.

Agreed. In v4 I dropped the logic to preserve line length and frame 
duration across size changes and simplified 
imx908_update_hblank_limits(), imx908_update_vblank_limits(), and 
imx908_update_framing_limits().

>> > +       u16 hmax = imx908_calc_hmax(old_width, imx->ctrls.hblank->val);
>> > +       u32 hblank = imx908_hmax_to_hblank(hmax, width);
>> > +       int ret;
>> > +
>> > +       hblank = clamp_t(u32, hblank, min_hblank, max_hblank);
>> > +
>> > +       ret = __v4l2_ctrl_modify_range(imx->ctrls.hblank, min_hblank,
>> > +                                      max_hblank, IMX908_PIX_PER_CLK, hblank);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       if (imx->ctrls.hblank->val != hblank)
>> > +               __v4l2_ctrl_s_ctrl(imx->ctrls.hblank, hblank);
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static int imx908_update_vblank_limits(struct imx908 *imx,
>> > +                                      const struct v4l2_rect *crop,
>> > +                                      u32 old_height)
>> > +{
>> > +       u32 min_vblank = imx908_calc_min_vblank(crop);
>> > +       u32 max_vblank = IMX908_VMAX_MAX - crop->height;
>> > +       /* Preserve frame length across height changes when possible. */
>> > +       u32 vmax = old_height + imx->ctrls.vblank->val;
>> > +       u32 vblank = clamp_t(u32, vmax - crop->height,
>> > +                            min_vblank, max_vblank);
>> > +       int ret;
>> > +
>> > +       ret = __v4l2_ctrl_modify_range(imx->ctrls.vblank, min_vblank,
>> > +                                      max_vblank, 1, vblank);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       if (imx->ctrls.vblank->val != vblank)
>> > +               __v4l2_ctrl_s_ctrl(imx->ctrls.vblank, vblank);
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +/* ------------------ Pattern Generator (TPG) ----------------------- */
>> > +static const char * const imx908_tpg_menu[] = {
>> > +       "Disabled",
>> > +       "All 000h",
>> > +       "All FFFh",
>> > +       "All 555h",
>> > +       "All AAAh",
>> > +       "555h / AAAh Toggle",
>> > +       "AAAh / 555h Toggle",
>> > +       "000h / 555h Toggle",
>> > +       "555h / 000h Toggle",
>> > +       "000h / FFFh Toggle",
>> > +       "FFFh / 000h Toggle",
>> > +       "Horiz Color Bars",
>> > +       "Vert Color Bars",
>> > +};
>> > +
>> > +static int imx908_update_test_pattern(struct imx908 *imx, u32 index)
>> > +{
>> > +       int ret = 0;
>> > +
>> > +       if (index == 0) {
>> > +               /* Picture (not TPG) output setting */
>> > +               cci_update_bits(imx->cci, IMX908_REG_TPG_EN, IMX908_TPG_EN_BIT,
>> > +                               0x00, &ret);
>> > +
>> > +               /* Disable TESTCLKEN (write-only register) */
>> > +               cci_write(imx->cci, IMX908_REG_TESTCLKEN, 0x00, &ret);
>> > +
>> > +               return ret;
>> > +       }
>> > +
>> > +       cci_write(imx->cci, IMX908_REG_TESTCLKEN, IMX908_TESTCLKEN_BIT, &ret);
>> > +       cci_write(imx->cci, IMX908_REG_TPG_PATSEL, index - 1, &ret);
>> > +       cci_update_bits(imx->cci, IMX908_REG_TPG_EN, IMX908_TPG_EN_BIT,
>> > +                       IMX908_TPG_EN_BIT, &ret);
>> > +
>> > +       return ret;
>> > +}
>> > +
>> > +static int imx908_update_framing_limits(struct imx908 *imx,
>> > +                                       struct v4l2_subdev_state *state,
>> > +                                       u32 old_width,
>> > +                                       u32 old_height)
>> > +{
>> > +       const struct v4l2_mbus_framefmt *fmt;
>> > +       const struct v4l2_rect *crop;
>> > +       int ret;
>> > +
>> > +       fmt = v4l2_subdev_state_get_format(state, IMX908_SOURCE_PAD);
>> > +       crop = v4l2_subdev_state_get_crop(state, IMX908_SOURCE_PAD);
>> > +       u8 bpp = imx908_bits_per_pixel(fmt->code);
>> > +
>> > +       ret = imx908_update_hblank_limits(imx, old_width, fmt->width, bpp);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       ret = imx908_update_vblank_limits(imx, crop, old_height);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       u32 vmax = fmt->height + clamp_t(u32, imx->ctrls.vblank->val,
>> > +                                        imx908_calc_min_vblank(crop),
>> > +                                        IMX908_VMAX_MAX - fmt->height);
>> > +
>> > +       return __v4l2_ctrl_modify_range(imx->ctrls.exposure,
>> > +                                       IMX908_EXPOSURE_MIN,
>> > +                                       vmax - IMX908_MIN_SHR0,
>> > +                                       IMX908_EXPOSURE_STEP,
>> > +                                       imx->ctrls.exposure->default_value);
>> > +}
>> > +
>> > +/* ----------------------- HW Programming ---------------------- */
>> > +static int imx908_set_mode(struct imx908 *imx,
>> > +                          const struct v4l2_mbus_framefmt *fmt)
>> > +{
>> > +       u8 adbit, mdbit, value;
>> > +       u16 blklevel;
>> > +       int ret = 0;
>> > +
>> > +       switch (fmt->code) {
>> > +       case MEDIA_BUS_FMT_SRGGB10_1X10:
>> > +               adbit = IMX908_ADBIT_10BIT;
>> > +               mdbit = IMX908_MDBIT_RAW10;
>> > +               blklevel = 50; /* datasheet recommended value for 10-bit */
>> > +               value = 0x0c;  /* register map value for 10-bit */
>> > +               break;
>> > +       case MEDIA_BUS_FMT_SRGGB12_1X12:
>> > +       default:
>> > +               adbit = IMX908_ADBIT_12BIT;
>> > +               mdbit = IMX908_MDBIT_RAW12;
>> > +               blklevel = 200; /* datasheet recommended value for 12-bit */
>> > +               value = 0x05;   /* register map value for 12-bit */
>> > +               break;
>> > +       }
>> > +
>> > +       cci_write(imx->cci, IMX908_REG_XMASTER, IMX908_CONTROLLER_MODE, &ret);
>> > +       cci_write(imx->cci, IMX908_REG_ADBIT, adbit, &ret);
>> > +       cci_write(imx->cci, IMX908_REG_MDBIT, mdbit, &ret);
>> > +
>> > +       for (unsigned int i = 0; i < ARRAY_SIZE(imx908_bit_depth_regs); ++i)
>> > +               cci_write(imx->cci, imx908_bit_depth_regs[i], value, &ret);
>> > +
>> > +       cci_write(imx->cci, IMX908_REG_INCK_SEL, imx->inck_sel, &ret);
>> > +       cci_write(imx->cci, IMX908_REG_DATARATE_SEL, imx->link_freq_idx, &ret);
>> > +       cci_write(imx->cci, IMX908_REG_LANEMODE, imx->num_lanes == 2 ?
>> > +                 IMX908_LANEMODE_2LANE : IMX908_LANEMODE_4LANE, &ret);
>> > +       cci_write(imx->cci, IMX908_REG_BLKLEVEL, blklevel, &ret);
>> 
>> Has the BLKLEVEL register handling changed from Starvis2 -> Starvis3?
>> 
>> For IMX678 the default value recommended by datasheet were the same, 50 and
>> 200, but with a note that increasing register by 1 in 12-bit mode meant an
>> increase of 4 in the output. Thus the register always reads 50 (or 0x32) by
>> default.
>> 
>> > +
>> > +       if (ret)
>> > +               dev_err(imx->dev, " register write failed: %d\n", ret);
> 
> cci_write() logs a message on error already, so I would drop this.

Ok, dropped.
>> > +
>> > +       return ret;
>> > +}
>> > +
>> > +static int imx908_program_window(struct imx908 *imx,
>> > +                                const struct v4l2_rect *crop)
>> > +{
>> > +       bool all_pixel_mode = v4l2_rect_equal(crop, &imx908_active_area);
>> > +       int ret = 0;
>> > +
>> > +       cci_write(imx->cci, IMX908_REG_WINMODE,
>> > +                 all_pixel_mode ? IMX908_WINMODE_ALLPIX : IMX908_WINMODE_CROP,
>> > +                 &ret);
>> > +
>> > +       if (!all_pixel_mode) {
>> > +               cci_write(imx->cci, IMX908_REG_PIX_HST,    crop->left,   &ret);
>> > +               cci_write(imx->cci, IMX908_REG_PIX_HWIDTH, crop->width,  &ret);
>> > +               cci_write(imx->cci, IMX908_REG_PIX_VST,    crop->top,    &ret);
>> > +               cci_write(imx->cci, IMX908_REG_PIX_VWIDTH, crop->height, &ret);
>> > +       }
>> > +
>> > +       return ret;
>> > +}
>> > +
>> > +/* ----------------------- Start/Stop streaming ---------------------- */
>> > +static int imx908_start_streaming(struct imx908 *imx,
>> > +                                 struct v4l2_subdev_state *sd_state)
>> > +{
>> > +       const struct v4l2_mbus_framefmt *format;
>> > +       const struct v4l2_rect *crop;
>> > +       int ret = 0;
>> > +
>> > +       crop = v4l2_subdev_state_get_crop(sd_state, IMX908_SOURCE_PAD);
>> > +       format = v4l2_subdev_state_get_format(sd_state, IMX908_SOURCE_PAD);
>> > +
>> > +       cci_multi_reg_write(imx->cci, imx908_common_regs,
>> > +                           ARRAY_SIZE(imx908_common_regs), &ret);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       ret = imx908_set_mode(imx, format);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       ret = imx908_program_window(imx, crop);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       ret = __v4l2_ctrl_handler_setup(imx->sd.ctrl_handler);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       cci_write(imx->cci, IMX908_REG_STANDBY, IMX908_STANDBY_CANCEL, &ret);
>> > +       fsleep(24 * USEC_PER_MSEC); /* >=24 ms stabilization after standby cancel */
>> > +
>> > +       cci_write(imx->cci, IMX908_REG_XMSTA, IMX908_XMSTA_START, &ret);
>> > +
>> > +       return ret;
>> > +}
>> > +
>> > +static int imx908_stop_streaming(struct imx908 *imx)
>> > +{
>> > +       int ret = 0;
>> > +
>> > +       cci_write(imx->cci, IMX908_REG_STANDBY, IMX908_STANDBY_EN, &ret);
>> > +       cci_write(imx->cci, IMX908_REG_XMSTA, IMX908_XMSTA_STOP, &ret);
>> > +
>> > +       return ret;
>> > +}
>> > +
>> > +/* --------------------------- V4L2 controls ------------------------------ */
>> > +static int imx908_set_ctrl(struct v4l2_ctrl *ctrl)
>> > +{
>> > +       struct imx908 *imx = container_of(ctrl->handler, struct imx908,
>> > +                                         ctrls.handler);
>> > +       const struct v4l2_mbus_framefmt *format;
>> > +       struct v4l2_subdev_state *state;
>> > +       int ret = 0;
>> > +
>> > +       state = v4l2_subdev_get_locked_active_state(&imx->sd);
>> > +       format = v4l2_subdev_state_get_format(state, IMX908_SOURCE_PAD);
>> > +
>> > +       /* Update exposure control limits even if the sensor is not streaming */
>> > +       if (ctrl->id == V4L2_CID_VBLANK) {
>> > +               const struct v4l2_rect *crop;
>> > +
>> > +               crop = v4l2_subdev_state_get_crop(state, IMX908_SOURCE_PAD);
>> > +
>> > +               u32 min_vblank = imx908_calc_min_vblank(crop);
>> > +               u32 max_vblank = IMX908_VMAX_MAX - format->height;
>> > +               u32 vblank = clamp_t(u32, ctrl->val, min_vblank, max_vblank);
>> 
>> The above 3 lines are redundant for simple VBLANK control updates. V4L2
>> control framework would ensure new values are within the defined min/max
>> range before the drivers .s_ctrl is triggered.
> 
> That's right.

Understood. I've removed not only the three lines but the crop as well 
since it is now longer needed.
>> > +
>> > +               u32 vmax = format->height + vblank;
>> > +               u32 max_exposure = vmax - IMX908_MIN_SHR0;
>> > +               u32 current_exposure = clamp_t(u32, imx->ctrls.exposure->cur.val,
>> > +                                       IMX908_EXPOSURE_MIN, max_exposure);
>> 
>> Same here. No reason the exposure->cur.val would be out of bounds when user
>> requests an update to VBLANK value. So this should be:
> 
> But this isn't I think. The control framework will indeed ensure that
> the exposure value is within the min/max bounds, but here we're updating
> the max value *for exposure* based on the new current value *for
> vblank*.

I agree with you (Laurent) here, and this needs to be kept.

> 
>>     u32 current_exposure = imx->ctrls.exposure->cur.val
>> 
>> > +
>> > +               ret = __v4l2_ctrl_modify_range(imx->ctrls.exposure,
>> > +                                              IMX908_EXPOSURE_MIN,
>> > +                                              max_exposure,
>> > +                                              IMX908_EXPOSURE_STEP,
>> > +                                              current_exposure);
>> > +               if (ret)
>> > +                       return ret;
>> > +       }
>> > +
>> > +       /* Hardware writes only when powered; cached ctrls applied on resume */
>> > +       if (!pm_runtime_get_if_active(imx->dev))
>> > +               return 0;
>> > +
>> > +       switch (ctrl->id) {
>> > +       case V4L2_CID_EXPOSURE:
>> > +               ret = imx908_set_exposure_lines(imx, ctrl->val);
>> > +               break;
>> > +
>> > +       case V4L2_CID_ANALOGUE_GAIN:
>> > +               cci_write(imx->cci, IMX908_REG_GAIN, ctrl->val, &ret);
>> > +               break;
>> > +
>> > +       case V4L2_CID_VBLANK: {
>> > +               u32 vmax = format->height + ctrl->val;
>> > +
>> > +               ret = cci_write(imx->cci, IMX908_REG_VMAX, vmax, NULL);
>> > +               /* SHR0 derived from VMAX, re-apply exposure after changes */
>> > +               if (!ret)
>> > +                       ret = imx908_set_exposure_lines(imx,
>> > +                                                       imx->ctrls.exposure->val);
>> > +               break;
>> > +       }
>> > +
>> > +       case V4L2_CID_HBLANK: {
>> > +               u16 hmax = imx908_calc_hmax(format->width, ctrl->val);
>> > +
>> > +               cci_write(imx->cci, IMX908_REG_HMAX, hmax, &ret);
>> > +               break;
>> > +       }
>> > +
>> > +       case V4L2_CID_TEST_PATTERN:
>> > +               ret = imx908_update_test_pattern(imx, ctrl->val);
>> > +               break;
>> > +
>> > +       case V4L2_CID_HFLIP:
>> > +               cci_write(imx->cci, IMX908_REG_HREVERSE,
>> > +                         ctrl->val ? IMX908_HREVERSE_INV
>> > +                         : IMX908_HREVERSE_NORMAL, &ret);
>> > +               break;
>> > +
>> > +       case V4L2_CID_VFLIP:
>> > +               cci_write(imx->cci, IMX908_REG_VREVERSE,
>> > +                         ctrl->val ? IMX908_VREVERSE_INV
>> > +                         : IMX908_VREVERSE_NORMAL, &ret);
>> > +               break;
>> > +
>> 
>> Any reason the register values for HREVERSE/VREVERSE are inverted now w.r.t
>> the userspace HFLIP/VFLIP settings?
> 
> Are they inverted ? As far as I can see, the register is written with
> 0x01 (IMX908_VREVERSE_INV) when val is true and 0x00
> (IMX908_VREVERSE_NORMAL) when val is false. This should be the same
> behaviour as in v2, the change in the code seems to be there to avoid
> depending on the true value of the boolean control being 1. I don't mind
> either way, I think I would have kept v2, but this seems OK too.
> 
>> Ah, and is this why imx908_active_area.top was 0 and not 24 ?
>> 
>> What v2 did (writing ctrl->val directly to the registers) seemed okay to
>> me. It's usually a good idea to mention functional changes in the
>> changelog. If there is a valid reason for the swap, maybe also add a code
>> comment here explaining why.

There was no functional change from v2 to v3. Macro names were added, 
and this may have caused confusion. In the IMX908 datasheet, bit 0 of 
HREVERSE/VREVERSE sets normal readout (0x00) while bit 1 sets inverted 
readout (0x01, named _INV). When ctrl->val is true (flip requested), the 
register is set to 0x01, exactly as in v2.

I added a comment here for v4 so that other readers don't get confused.
/* Hardware REVERSE registers: NORMAL (0) = no flip, INV (1) = flip */

>> 
>> > +       default:
>> > +               dev_warn(imx->dev,
>> > +                        "ctrl(id:0x%x,val:0x%x) is not handled\n",
>> > +                        ctrl->id, ctrl->val);
>> > +               break;
>> > +       }
>> > +
>> > +       pm_runtime_put(imx->dev);
>> > +
>> > +       return ret;
>> > +}
>> > +
>> > +static const struct v4l2_ctrl_ops imx908_ctrl_ops = {
>> > +       .s_ctrl = imx908_set_ctrl,
>> > +};
>> > +
>> > +/* ------------------------ Pad/video ops ------------------ */
>> > +static int imx908_enum_mbus_code(struct v4l2_subdev *sd,
>> > +                                struct v4l2_subdev_state *sd_state,
>> > +                                struct v4l2_subdev_mbus_code_enum *code)
>> > +{
>> > +       if (code->index >= ARRAY_SIZE(imx908_mbus_codes))
>> > +               return -EINVAL;
>> > +       code->code = imx908_mbus_codes[code->index];
>> > +       return 0;
>> > +}
>> > +
>> > +static int imx908_enum_frame_size(struct v4l2_subdev *sd,
>> > +                                 struct v4l2_subdev_state *sd_state,
>> > +                                 struct v4l2_subdev_frame_size_enum *fse)
>> > +{
>> > +       struct imx908 *imx = to_imx908(sd);
>> > +       const struct v4l2_rect *crop;
>> > +
>> > +       if (fse->index > 0)
>> > +               return -EINVAL;
>> > +
>> > +       if (!imx908_mbus_code_supported(imx, fse->code))
>> > +               return -EINVAL;
>> > +
>> > +       crop = v4l2_subdev_state_get_crop(sd_state, IMX908_SOURCE_PAD);
>> > +
>> > +       fse->min_width  = crop->width;
>> > +       fse->max_width  = crop->width;
>> > +       fse->min_height = crop->height;
>> > +       fse->max_height = crop->height;
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static int imx908_set_pad_format(struct v4l2_subdev *sd,
>> > +                                struct v4l2_subdev_state *sd_state,
>> > +                                struct v4l2_subdev_format *fmt)
>> > +{
>> > +       struct imx908 *imx = to_imx908(sd);
>> > +       struct v4l2_mbus_framefmt *format;
>> > +
>> > +       if (fmt->which == V4L2_SUBDEV_FORMAT_ACTIVE &&
>> > +           v4l2_subdev_is_streaming(sd))
>> > +               return -EBUSY;
>> > +
>> > +       format = v4l2_subdev_state_get_format(sd_state, fmt->pad);
>> > +
>> > +       if (imx908_mbus_code_supported(imx, fmt->format.code))
>> > +               format->code = fmt->format.code;
>> > +       else
>> > +               format->code = IMX908_DEFAULT_MBUS_CODE;
>> > +
>> > +       /* Fully define metadata */
>> > +       format->field        = V4L2_FIELD_NONE;
>> > +       format->colorspace   = V4L2_COLORSPACE_RAW;
>> > +       format->ycbcr_enc    = V4L2_YCBCR_ENC_DEFAULT;
>> > +       format->quantization = V4L2_QUANTIZATION_FULL_RANGE;
>> > +       format->xfer_func    = V4L2_XFER_FUNC_NONE;
>> > +
>> > +       /* Limits track the real controls only for the ACTIVE state, not TRY */
>> > +       if (fmt->which == V4L2_SUBDEV_FORMAT_ACTIVE) {
>> > +               /* set_pad_format() never changes width, so old == new here */
>> > +               u32 old_width = format->width;
>> > +               u32 old_height = format->height;
>> > +               int ret = imx908_update_framing_limits(imx, sd_state,
>> > +                                              old_width, old_height);
>> > +
>> > +               if (ret)
>> > +                       return ret;
>> > +       }
>> 
>> I see program_window() only looks at crop size, so changing format
>> width/height to something else using S_FMT will not change anything on the
>> CSI-2 bus.
>> 
>> For freely-configurable sensor drivers like these, I think the usual
>> pattern is to allow S_SELECTION to configure the window size, and S_FMT
>> always snaps format->width = crop->width (same for height).
> 
> Unless I'm mistaken, that's what this function does. format->width and
> format->height are propagated from imx908_set_selection() and they are
> not modified here. Am I misunderstanding your comment, or missing
> something ?
> 
> This being said, the imx908_update_framing_limits() is a bit overkill,
> as the old and new width and height are guaranteed to be the same here.
> What can change is the format though, and therefore the bpp, so hblank
> has to be recalculated, but vblank doesn't need an update. I'm however
> fine keeping the full imx908_update_framing_limits() call for
> simplicity.

As you noted, format width and height are directly locked to the crop 
rectangle set in imx908_set_selection(). imx908_set_pad_format() only 
allows changing the mbus code (bit depth), returning the crop-propagated 
width and height back in fmt->format. I've kept the 
imx908_update_framing_limits() call here for simplicity to handle the 
HBLANK range recalculation required by the bpp change.

>> > +
>> > +       fmt->format = *format;
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static int imx908_set_selection(struct v4l2_subdev *sd,
>> > +                               struct v4l2_subdev_state *sd_state,
>> > +                               struct v4l2_subdev_selection *sel)
>> > +{
>> > +       struct imx908 *imx = to_imx908(sd);
>> > +       struct v4l2_mbus_framefmt *format;
>> > +       struct v4l2_rect *r = &sel->r;
>> > +       struct v4l2_rect *crop;
>> > +
>> > +       if (sel->target != V4L2_SEL_TGT_CROP)
>> > +               return -EINVAL;
>> > +
>> > +       if (sel->which == V4L2_SUBDEV_FORMAT_ACTIVE &&
>> > +           v4l2_subdev_is_streaming(sd))
>> > +               return -EBUSY;
>> > +
>> > +       crop = v4l2_subdev_state_get_crop(sd_state, sel->pad);
>> > +       format = v4l2_subdev_state_get_format(sd_state, sel->pad);
>> > +
>> > +       /*
>> > +        * Round the crop rectangle size down to the hardware alignment
>> > +        * constraints, then clamp it to the supported size range.
>> > +        */
>> > +       r->width = clamp_t(s32, ALIGN_DOWN(r->width, IMX908_CROP_ALIGN_HWIDTH),
>> > +                          IMX908_CROP_MIN_WIDTH, imx908_active_area.width);
>> > +       r->height = clamp_t(s32, ALIGN_DOWN(r->height, IMX908_CROP_ALIGN_VWIDTH),
>> > +                           IMX908_CROP_MIN_HEIGHT, imx908_active_area.height);
>> > +
>> > +       /*
>> > +        * Round and clamp the crop position similarly, with the maximum value
>> > +        * chosen so that the crop rectangle remains fully inside the active
>> > +        * pixel array.
>> > +        */
>> > +       r->left = clamp_t(s32, ALIGN_DOWN(r->left, IMX908_CROP_ALIGN_HSTART), 0,
>> > +                         imx908_active_area.width - r->width);
>> > +       r->top = clamp_t(s32, ALIGN_DOWN(r->top, IMX908_CROP_ALIGN_VSTART), 0,
>> > +                        imx908_active_area.height - r->height);
>> > +
>> > +       u32 old_width = crop->width;
>> > +       u32 old_height = crop->height;
>> > +
>> > +       *crop = *r;
>> > +
>> > +       /* IMX908 has no binning, so the output size matches the crop 1:1 */
>> > +       format->width  = crop->width;
>> > +       format->height = crop->height;
>> > +
>> > +       if (sel->which == V4L2_SUBDEV_FORMAT_ACTIVE) {
>> > +               int ret = imx908_update_framing_limits(imx, sd_state,
>> > +                                              old_width, old_height);
>> > +
>> > +               if (ret)
>> > +                       return ret;
>> > +       }
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static int imx908_get_selection(struct v4l2_subdev *sd,
>> > +                               struct v4l2_subdev_state *sd_state,
>> > +                               struct v4l2_subdev_selection *sel)
>> > +{
>> > +       switch (sel->target) {
>> > +       case V4L2_SEL_TGT_CROP:
>> > +               sel->r = *v4l2_subdev_state_get_crop(sd_state,
>> > +                                                    IMX908_SOURCE_PAD);
>> > +               return 0;
>> > +
>> > +       case V4L2_SEL_TGT_NATIVE_SIZE:
>> > +               sel->r = imx908_total_area;
>> > +               return 0;
>> > +
>> > +       case V4L2_SEL_TGT_CROP_DEFAULT:
>> > +               sel->r = imx908_active_area;
>> > +               return 0;
>> > +
>> > +       case V4L2_SEL_TGT_CROP_BOUNDS:
>> > +               sel->r = imx908_active_area;
>> > +               return 0;
>> 
>> nitpick: can be simplified as
>> 
>>        case V4L2_SEL_TGT_CROP_DEFAULT:
>>        case V4L2_SEL_TGT_CROP_BOUNDS:
>>                sel->r = imx908_active_area;
>>                return 0;>>>> > +       default:
>> > +               return -EINVAL;
>> > +       }
>> > +}
>> > +
>> > +static int imx908_enable_streams(struct v4l2_subdev *sd,
>> > +                                struct v4l2_subdev_state *sd_state,
>> > +                                u32 pad,
>> > +                                u64 streams_mask)
>> > +{
>> > +       struct imx908 *imx = to_imx908(sd);
>> > +       int ret;
>> > +
>> > +       ret = pm_runtime_resume_and_get(imx->dev);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       ret = imx908_start_streaming(imx, sd_state);
>> > +       if (ret) {
>> > +               pm_runtime_put_autosuspend(imx->dev);
>> > +               return ret;
>> > +       }
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static int imx908_disable_streams(struct v4l2_subdev *sd,
>> > +                                 struct v4l2_subdev_state *sd_state,
>> > +                                 u32 pad,
>> > +                                 u64 streams_mask)
>> > +{
>> > +       struct imx908 *imx = to_imx908(sd);
>> > +       int ret;
>> > +
>> > +       ret = imx908_stop_streaming(imx);
>> > +
>> > +       pm_runtime_put_autosuspend(imx->dev);
>> > +
>> > +       return ret;
>> > +}
>> > +
>> > +static int imx908_init_state(struct v4l2_subdev *sd,
>> > +                            struct v4l2_subdev_state *sd_state)
>> > +{
>> > +       struct v4l2_subdev_selection sel = {
>> > +               .which  = V4L2_SUBDEV_FORMAT_TRY,
>> > +               .pad    = IMX908_SOURCE_PAD,
>> > +               .target = V4L2_SEL_TGT_CROP,
>> > +               .r      = imx908_active_area,
>> > +       };
>> > +       struct v4l2_subdev_format fmt = {
>> > +               .which = V4L2_SUBDEV_FORMAT_TRY,
>> > +               .pad   = IMX908_SOURCE_PAD,
>> > +               .format = {
>> > +                       .code   = IMX908_DEFAULT_MBUS_CODE,
>> > +                       .width  = imx908_active_area.width,
>> > +                       .height = imx908_active_area.height,
>> > +               },
>> > +       };
>> > +
>> > +       imx908_set_selection(sd, sd_state, &sel);
>> > +       imx908_set_pad_format(sd, sd_state, &fmt);
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static const struct v4l2_subdev_video_ops imx908_video_ops = {
>> > +       .s_stream = v4l2_subdev_s_stream_helper,
>> > +};
>> > +
>> > +static const struct v4l2_subdev_pad_ops imx908_pad_ops = {
>> > +       .enum_mbus_code      = imx908_enum_mbus_code,
>> > +       .enum_frame_size     = imx908_enum_frame_size,
>> > +       .get_fmt             = v4l2_subdev_get_fmt,
>> > +       .set_fmt             = imx908_set_pad_format,
>> > +       .get_selection       = imx908_get_selection,
>> > +       .set_selection       = imx908_set_selection,
>> > +       .enable_streams      = imx908_enable_streams,
>> > +       .disable_streams     = imx908_disable_streams,
>> > +};
>> > +
>> > +static const struct v4l2_subdev_internal_ops imx908_internal_ops = {
>> > +       .init_state = imx908_init_state,
>> > +};
>> > +
>> > +static const struct v4l2_subdev_ops imx908_subdev_ops = {
>> > +       .video = &imx908_video_ops,
>> > +       .pad   = &imx908_pad_ops,
>> > +};
>> > +
>> > +/* ----------------------- Power management ---------------------- */
>> > +static int imx908_power_on(struct device *dev)
>> > +{
>> > +       struct v4l2_subdev *sd = dev_get_drvdata(dev);
>> > +       struct imx908 *imx = to_imx908(sd);
>> > +       int ret;
>> > +
>> > +       ret = regulator_bulk_enable(ARRAY_SIZE(imx908_supply_names),
>> > +                                   imx->supplies);
>> > +       if (ret) {
>> > +               dev_err(imx->dev, "failed to enable regulators\n");
>> > +               return ret;
>> > +       }
>> > +       /* XCLR already asserted by GPIOD_OUT_HIGH */
>> > +       udelay(1); /* >= 500ns T_low */
>> > +       gpiod_set_value_cansleep(imx->reset_gpio, 0); /* Sensor start */
>> > +
>> > +       ret = clk_prepare_enable(imx->xclk);
>> > +       if (ret) {
>> > +               dev_err(imx->dev, "failed to enable xclk: %d\n", ret);
>> > +               goto err_reset;
>> > +       }
>> > +
>> > +       fsleep(20); /* T_1 >= 20us before first SDA/SCL */
>> > +
>> > +       return 0;
>> > +
>> > +err_reset:
>> > +       gpiod_set_value_cansleep(imx->reset_gpio, 1); /* assert reset */
> 
> I'd drop this comment, the code is explicit.

Ok.

>> > +       regulator_bulk_disable(ARRAY_SIZE(imx908_supply_names), imx->supplies);
>> > +       return ret;
>> > +}
>> > +
>> > +static void imx908_power_off(struct device *dev)
>> > +{
>> > +       struct v4l2_subdev *sd = dev_get_drvdata(dev);
>> > +       struct imx908 *imx = to_imx908(sd);
>> > +
>> > +       clk_disable_unprepare(imx->xclk);
>> > +       gpiod_set_value_cansleep(imx->reset_gpio, 1);
>> > +       regulator_bulk_disable(ARRAY_SIZE(imx908_supply_names), imx->supplies);
>> > +}
>> > +
>> > +static int imx908_runtime_resume(struct device *dev)
>> > +{
>> > +       return imx908_power_on(dev);
>> > +}
>> > +
>> > +static int imx908_runtime_suspend(struct device *dev)
>> > +{
>> > +       imx908_power_off(dev);
>> > +       return 0;
>> > +}
>> > +
>> 
>> You could use imx908_power_off and imx908_power_on directly as the
>> RUNTIME_PM_OPS below.
> 
> I'd recommend pass the struct imx908 pointer to imx908_power_on() and
> imx908_power_off() and keeping imx908_runtime_resume() and
> imx908_runtime_suspend(), as done in v2. Sakari has requested the
> opposite though. I very strongly disagree with him on this, but I don't
> want to delay merging this driver because of that.

Keeping as-is following Sakari's earlier review comment.

>> > +static DEFINE_RUNTIME_DEV_PM_OPS(imx908_pm_ops,
>> > +                                imx908_runtime_suspend,
>> > +                                imx908_runtime_resume, NULL);
>> > +
>> > +/* ------------------------------- Probe/remove --------------------------- */
>> > +
>> > +static int imx908_get_inck_sel(struct imx908 *imx, u32 xclk_freq)
>> > +{
>> > +       for (unsigned int i = 0; i < ARRAY_SIZE(imx908_inck_table); i++) {
>> > +               if (imx908_inck_table[i] == xclk_freq) {
>> > +                       imx->inck_sel = i;
>> > +                       return 0;
>> > +               }
>> > +       }
>> > +
>> > +       return dev_err_probe(imx->dev, -EINVAL, "unsupported xclk %u Hz\n",
>> > +                            xclk_freq);
>> > +}
>> > +
>> > +static int imx908_get_regulators(struct imx908 *imx)
>> > +{
>> > +       for (unsigned int i = 0; i < ARRAY_SIZE(imx908_supply_names); i++)
>> > +               imx->supplies[i].supply = imx908_supply_names[i];
>> > +
>> > +       return devm_regulator_bulk_get(imx->dev,
>> > +                       ARRAY_SIZE(imx908_supply_names),
>> > +                       imx->supplies);
>> > +}
>> > +
>> > +static int imx908_parse_fwnode(struct imx908 *imx)
>> > +{
>> > +       struct v4l2_fwnode_endpoint bus_cfg = {
>> > +               .bus_type = V4L2_MBUS_CSI2_DPHY
>> > +       };
>> > +       struct fwnode_handle *ep;
>> > +       int ret = 0;
> 
> No need to initialize ret to 0.

Ok.

>> > +
>> > +       ep = fwnode_graph_get_next_endpoint(dev_fwnode(imx->dev), NULL);
>> > +
>> > +       /* Only data-lanes and link-frequencies are used from the endpoint */
>> > +       ret = v4l2_fwnode_endpoint_alloc_parse(ep, &bus_cfg);
>> > +       fwnode_handle_put(ep);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       imx->num_lanes = bus_cfg.bus.mipi_csi2.num_data_lanes;
>> > +
>> > +       if (imx->num_lanes != 2 && imx->num_lanes != 4) {
>> > +               dev_err(imx->dev,
>> > +                       "only 2 or 4 CSI-2 data lanes are supported (got %u)\n",
>> > +                       imx->num_lanes);
>> > +               ret = -EINVAL;
>> > +               goto out_free;
>> > +       }
>> > +
>> > +       ret = v4l2_link_freq_to_bitmap(imx->dev,
>> > +                                      bus_cfg.link_frequencies,
>> > +                                      bus_cfg.nr_of_link_frequencies,
>> > +                                      imx908_link_freqs,
>> > +                                      ARRAY_SIZE(imx908_link_freqs),
>> > +                                      &imx->link_freq_bitmap);
>> > +       if (ret)
>> > +               goto out_free;
>> 
>> The above two lines could be dropped.
> 
> That would result in a possibly weird value being printed in the debug
> message below, so I think keeping the goto would be better.

Keeping the check to prevent __ffs(0) and an out-of-bounds array access 
in the dev_dbg() message when v4l2_link_freq_to_bitmap() fails.

>> > +
>> > +       imx->link_freq_idx = __ffs(imx->link_freq_bitmap);
>> > +       dev_dbg(imx->dev, "using %u lanes at link freq %llu Hz\n",
>> > +               imx->num_lanes, imx908_link_freqs[imx->link_freq_idx]);
>> > +
>> > +out_free:
>> > +       v4l2_fwnode_endpoint_free(&bus_cfg);
>> > +       return ret;
>> > +}
>> > +
>> > +static int imx908_init_controls(struct imx908 *imx)
>> > +{
>> > +       struct v4l2_ctrl_handler *hdl = &imx->ctrls.handler;
>> > +       struct v4l2_fwnode_device_properties props;
>> > +       struct v4l2_ctrl *ctrl;
>> > +       int ret;
>> > +
>> > +       /* Read rotation and orientation properties from the firmware node */
>> > +       ret = v4l2_fwnode_device_parse(imx->dev, &props);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       ret = v4l2_ctrl_handler_init(hdl, 11);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       /* PIXEL_RATE is always read-only, so it needs no s_ctrl() handling */
>> > +       v4l2_ctrl_new_std(hdl, NULL, V4L2_CID_PIXEL_RATE,
>> > +                         IMX908_PIXEL_RATE, IMX908_PIXEL_RATE, 1,
>> > +                         IMX908_PIXEL_RATE);
>> > +
>> > +       /* LINK_FREQ is informational only and has no s_ctrl() handling */
> 
> Eventually we should make the link frequency selectable, but that can be
> done later.

Ok, we will consider to add support for runtime link frequency selection 
in a future update.

>> > +       ctrl = v4l2_ctrl_new_int_menu(hdl, NULL, V4L2_CID_LINK_FREQ,
>> > +                                     ARRAY_SIZE(imx908_link_freqs) - 1,
>> > +                                     imx->link_freq_idx, imx908_link_freqs);
>> > +       if (ctrl)
>> > +               ctrl->flags |= V4L2_CTRL_FLAG_READ_ONLY;
>> > +
>> > +       u32 min_vblank = imx908_calc_min_vblank(&imx908_active_area);
>> > +       u32 max_vblank = IMX908_VMAX_MAX - imx908_active_area.height;
>> > +       /* Default to the datasheet 30 fps operating point */
>> > +       u32 def_vblank = IMX908_VMAX_DEFAULT - imx908_active_area.height;
>> > +
>> > +       imx->ctrls.vblank = v4l2_ctrl_new_std(hdl, &imx908_ctrl_ops,
>> > +                                             V4L2_CID_VBLANK, min_vblank,
>> > +                                             max_vblank, 1, def_vblank);
>> > +
>> > +       u8 bpp = imx908_bits_per_pixel(IMX908_DEFAULT_MBUS_CODE);
>> > +       u16 min_hmax = imx908_calc_min_hmax(imx, bpp);
>> > +       u32 min_hblank = imx908_hmax_to_hblank(min_hmax,
>> > +                                              imx908_active_area.width);
>> > +       u32 max_hblank = imx908_hmax_to_hblank(IMX908_HMAX_MAX,
>> > +                                              imx908_active_area.width);
>> > +       u32 hblank = imx908_hmax_to_hblank(IMX908_HMAX_DEFAULT,
> 
> I would name this variable def_hblank to mimick def_vblank.

Ok.

>> > +                                          imx908_active_area.width);
>> > +
>> > +       /* Default HMAX can be infeasible at low link freqs; clamp into range */
>> > +       hblank = clamp_t(u32, hblank, min_hblank, max_hblank);
>> > +
>> > +       imx->ctrls.hblank = v4l2_ctrl_new_std(hdl, &imx908_ctrl_ops,
>> > +                                             V4L2_CID_HBLANK, min_hblank,
>> > +                                             max_hblank, IMX908_PIX_PER_CLK,
>> > +                                             hblank);
> 
> Add a blank line here to separate hblank from exposure.

Ok.
>> > +       u32 max_exp = IMX908_VMAX_DEFAULT - IMX908_MIN_SHR0;
>> > +
>> > +       imx->ctrls.exposure = v4l2_ctrl_new_std(hdl, &imx908_ctrl_ops,
>> > +                                               V4L2_CID_EXPOSURE,
>> > +                                               IMX908_EXPOSURE_MIN,
>> > +                                               max_exp,
>> > +                                               IMX908_EXPOSURE_STEP,
>> > +                                               max_exp / 2);
>> > +
>> > +       v4l2_ctrl_new_std(hdl, &imx908_ctrl_ops, V4L2_CID_ANALOGUE_GAIN,
>> > +                         IMX908_ANA_GAIN_MIN, IMX908_ANA_GAIN_MAX,
>> > +                         IMX908_ANA_GAIN_STEP, IMX908_ANA_GAIN_DEFAULT);
>> > +
>> > +       /* Set test pattern. Menu (13 entries: Disabled + 12 patterns) */
>> > +       v4l2_ctrl_new_std_menu_items(hdl, &imx908_ctrl_ops,
>> > +                                    V4L2_CID_TEST_PATTERN,
>> > +                                    ARRAY_SIZE(imx908_tpg_menu) - 1, 0, 0,
>> > +                                    imx908_tpg_menu);
>> > +
>> > +       v4l2_ctrl_new_std(hdl, &imx908_ctrl_ops, V4L2_CID_HFLIP, 0, 1, 1, 0);
>> > +       v4l2_ctrl_new_std(hdl, &imx908_ctrl_ops, V4L2_CID_VFLIP, 0, 1, 1, 0);
>> > +
>> > +       v4l2_ctrl_new_fwnode_properties(hdl, &imx908_ctrl_ops, &props);
>> > +       if (hdl->error) {
>> > +               ret = hdl->error;
>> > +               goto err_free;
>> 
>> Instead of the goto you could directly return here:
>> 
>>         v4l2_ctrl_handler_free(hdl);
>>         return ret;
> 
> Gotos are nice for error handling, but when the error path is reached
> from a single location, direct error handling is fine too.

Ok, changed to a direct return and dropped the label since it makes the 
code shorter.

>> > +       }
>> > +
>> > +       imx->sd.ctrl_handler = hdl;
>> > +
>> > +       return 0;
>> > +
>> > +err_free:
>> > +       v4l2_ctrl_handler_free(hdl);
>> > +       return ret;
>> > +}
>> > +
>> > +static int imx908_identify_model(struct imx908 *imx)
>> > +{
>> > +       u16 chip_id;
>> > +       u64 val;
>> > +       int ret;
>> > +
>> > +       /*
>> > +        * The TYPE_ID registers are not accessible after power-up while
>> > +        * the device remains in standby. Exit standby and wait for the
>> > +        * required stabilization period before reading the chip ID.
>> > +        */
>> > +       ret = cci_write(imx->cci, IMX908_REG_STANDBY, IMX908_STANDBY_CANCEL, NULL);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       fsleep(24 * USEC_PER_MSEC); /* >=24 ms stabilization after standby cancel */
>> > +
>> > +       ret = cci_read(imx->cci, IMX908_REG_TYPE_ID, &val, NULL);
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       chip_id = val;
>> > +       dev_dbg(imx->dev, "IMX908 chip ID: 0x%04x\n", chip_id);
>> > +
>> > +       if (chip_id != IMX908_CHIP_ID) {
>> > +               dev_err(imx->dev, "unexpected chip ID 0x%04x (expected 0x%04x)\n",
>> > +                       chip_id, IMX908_CHIP_ID);
>> > +               return -ENXIO;
>> > +       }
>> > +
>> > +       /* Set to standby mode to save power */
>> > +       ret = cci_write(imx->cci, IMX908_REG_STANDBY, IMX908_STANDBY_EN, NULL);
>> > +       if (ret) {
>> > +               dev_err(imx->dev, "failed to enter standby state: %d\n", ret);
>> > +               return ret;
>> > +       }
>> > +
>> > +       return 0;
>> > +}
>> > +
>> > +static int imx908_probe(struct i2c_client *client)
>> > +{
>> > +       struct imx908 *imx;
>> > +       int ret;
>> > +
>> > +       imx = devm_kzalloc(&client->dev, sizeof(*imx), GFP_KERNEL);
>> > +       if (!imx)
>> > +               return -ENOMEM;
>> > +       imx->dev = &client->dev;
>> > +
>> > +       v4l2_i2c_subdev_init(&imx->sd, client, &imx908_subdev_ops);
>> > +       imx->sd.internal_ops = &imx908_internal_ops;
>> > +
>> > +       imx->cci = devm_cci_regmap_init_i2c(client, 16);
>> > +       if (IS_ERR(imx->cci))
>> > +               return dev_err_probe(imx->dev, PTR_ERR(imx->cci),
>> > +                                    "CCI regmap init failed\n");
>> > +
>> > +       imx->xclk = devm_v4l2_sensor_clk_get(imx->dev, NULL);
>> > +       if (IS_ERR(imx->xclk))
>> > +               return dev_err_probe(imx->dev, PTR_ERR(imx->xclk),
>> > +                                    "failed to get clock\n");
>> > +
>> > +       ret = imx908_get_inck_sel(imx, clk_get_rate(imx->xclk));
>> > +       if (ret)
>> > +               return ret;
>> > +
>> > +       imx->reset_gpio = devm_gpiod_get_optional(imx->dev, "reset",
>> > +                                                 GPIOD_OUT_HIGH);
>> > +
> 
> You can drop this blank line.

Ok.

>> > +       if (IS_ERR(imx->reset_gpio))
>> > +               return dev_err_probe(imx->dev, PTR_ERR(imx->reset_gpio),
>> > +                                    "failed to get reset gpio\n");
>> > +
>> > +       ret = imx908_get_regulators(imx);
>> > +       if (ret)
>> > +               return dev_err_probe(imx->dev, ret, "failed to get regulators\n");
>> > +
>> > +       ret = imx908_parse_fwnode(imx);
>> > +       if (ret)
>> > +               return dev_err_probe(imx->dev, ret, "device tree parse failed\n");
>> > +
>> > +       ret = imx908_power_on(imx->dev);
>> > +       if (ret)
>> > +               return dev_err_probe(imx->dev, ret, "power-on failed\n");
>> > +
>> > +       ret = imx908_identify_model(imx);
>> > +       if (ret) {
>> > +               dev_err(imx->dev, "failed to identify model: %d\n", ret);
>> > +               goto err_power_off;
>> > +       }
>> > +
>> > +       /* Device is powered; keep it resumed across registration, release at end */
>> > +       pm_runtime_set_active(imx->dev);
>> > +       pm_runtime_get_noresume(imx->dev);
>> > +       ret = devm_pm_runtime_enable(imx->dev);
>> > +       if (ret)
>> > +               goto err_pm_put;
>> > +
>> > +       pm_runtime_set_autosuspend_delay(imx->dev, 1000);
>> > +       pm_runtime_use_autosuspend(imx->dev);
>> > +
>> > +       ret = imx908_init_controls(imx);
>> > +       if (ret)
>> > +               goto err_pm_put;
>> > +
>> > +       imx->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
>> > +       imx->sd.entity.function = MEDIA_ENT_F_CAM_SENSOR;
>> > +       imx->pad.flags = MEDIA_PAD_FL_SOURCE;
>> > +       ret = media_entity_pads_init(&imx->sd.entity, 1, &imx->pad);
>> > +       if (ret)
>> > +               goto err_hdl;
>> > +
>> > +       /* Share the ctrl handler lock so s_ctrl can access the locked state */
>> > +       imx->sd.state_lock = imx->ctrls.handler.lock;
>> > +
>> > +       ret = v4l2_subdev_init_finalize(&imx->sd);
>> > +       if (ret)
>> > +               goto err_entity;
>> > +
>> > +       ret = v4l2_async_register_subdev_sensor(&imx->sd);
>> > +       if (ret)
>> > +               goto err_subdev;
>> > +
>> > +       /* Balance get_noresume; allow the sensor to suspend after probe */
>> > +       pm_runtime_put_autosuspend(imx->dev);
>> > +
>> > +       return 0;
>> > +
>> > +err_subdev:
>> > +       v4l2_subdev_cleanup(&imx->sd);
>> > +
>> > +err_entity:
>> > +       media_entity_cleanup(&imx->sd.entity);
>> > +
>> > +err_hdl:
>> > +       v4l2_ctrl_handler_free(imx->sd.ctrl_handler);
>> > +
>> > +err_pm_put:
>> > +       pm_runtime_put_noidle(imx->dev);
>> > +
>> > +err_power_off:
>> > +       imx908_power_off(imx->dev);
>> > +
>> > +       return ret;
>> > +}
>> > +
>> > +static void imx908_remove(struct i2c_client *client)
>> > +{
>> > +       struct v4l2_subdev *sd = i2c_get_clientdata(client);
>> > +       struct imx908 *imx = to_imx908(sd);
>> > +
>> > +       v4l2_async_unregister_subdev(sd);
>> > +       v4l2_subdev_cleanup(sd);
>> > +       media_entity_cleanup(&sd->entity);
>> > +       v4l2_ctrl_handler_free(sd->ctrl_handler);
>> > +
>> > +       pm_runtime_disable(imx->dev);
>> 
>> This should be dropped given devm_pm_runtime_enable() was used in probe().
>> 
>> > +       if (!pm_runtime_status_suspended(imx->dev))
>> > +               imx908_power_off(imx->dev);
>> > +       pm_runtime_set_suspended(imx->dev);
>> > +}
>> > +
>> > +static const struct of_device_id imx908_of_ids[] = {
>> > +       { .compatible = "sony,imx908" },
>> > +       { /* sentinel */ }
>> > +};
>> > +MODULE_DEVICE_TABLE(of, imx908_of_ids);
>> > +
>> > +static struct i2c_driver imx908_i2c_driver = {
>> > +       .driver = {
>> > +               .name           = "imx908",
>> > +               .pm             = pm_ptr(&imx908_pm_ops),
>> > +               .of_match_table = imx908_of_ids,
>> > +       },
>> > +       .probe  = imx908_probe,
>> > +       .remove = imx908_remove,
>> > +};
>> > +module_i2c_driver(imx908_i2c_driver);
>> > +
>> > +MODULE_AUTHOR("Lachlan Michael <Lachlan.Michael@sony.com>");
>> > +MODULE_DESCRIPTION("Sony IMX908 Sensor Driver");
>> > +MODULE_LICENSE("GPL");
> 
> -- 
> Regards,
> 
> Laurent Pinchart
>