Hi Rui,

On Thu, Feb 22, 2018 at 10:23:38AM +0000, Rui Miguel Silva wrote:
> This patch adds V4L2 sub-device driver for OV2680 image sensor.
> The OV2680 is a 1/5" CMOS color sensor from Omnivision.
> Supports output format: 10-bit Raw RGB.
> The OV2680 has a single lane MIPI interface.
> 
> The driver exposes following V4L2 controls:
> - auto/manual exposure,
> - exposure,
> - auto/manual gain,
> - gain,
> - horizontal/vertical flip,
> - test pattern menu.
> Supported resolution are only: QUXGA, 720P, UXGA.
> 
> Signed-off-by: Rui Miguel Silva <rui.si...@linaro.org>
> ---
>  drivers/media/i2c/Kconfig  |   13 +
>  drivers/media/i2c/Makefile |    1 +
>  drivers/media/i2c/ov2680.c | 1189 
> ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 1203 insertions(+)
>  create mode 100644 drivers/media/i2c/ov2680.c
> 
> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
> index 9f18cd296841..089103d29171 100644
> --- a/drivers/media/i2c/Kconfig
> +++ b/drivers/media/i2c/Kconfig
> @@ -586,6 +586,19 @@ config VIDEO_OV2659
>         To compile this driver as a module, choose M here: the
>         module will be called ov2659.
>  
> +config VIDEO_OV2680
> +     tristate "OmniVision OV2680 sensor support"
> +     depends on OF

I think you can drop OF dependency here.

> +     depends on GPIOLIB && VIDEO_V4L2 && I2C && VIDEO_V4L2_SUBDEV_API
> +     depends on MEDIA_CAMERA_SUPPORT
> +     select V4L2_FWNODE
> +     ---help---
> +       This is a Video4Linux2 sensor-level driver for the OmniVision
> +       OV2680 camera sensor with a MIPI CSI-2 interface.
> +
> +       To compile this driver as a module, choose M here: the
> +       module will be called ov2680.
> +
>  config VIDEO_OV5640
>       tristate "OmniVision OV5640 sensor support"
>       depends on OF
> diff --git a/drivers/media/i2c/Makefile b/drivers/media/i2c/Makefile
> index c0f94cd8d56d..d0aba4d37b8d 100644
> --- a/drivers/media/i2c/Makefile
> +++ b/drivers/media/i2c/Makefile
> @@ -61,6 +61,7 @@ obj-$(CONFIG_VIDEO_SONY_BTF_MPX) += sony-btf-mpx.o
>  obj-$(CONFIG_VIDEO_UPD64031A) += upd64031a.o
>  obj-$(CONFIG_VIDEO_UPD64083) += upd64083.o
>  obj-$(CONFIG_VIDEO_OV2640) += ov2640.o
> +obj-$(CONFIG_VIDEO_OV2680) += ov2680.o
>  obj-$(CONFIG_VIDEO_OV5640) += ov5640.o
>  obj-$(CONFIG_VIDEO_OV5645) += ov5645.o
>  obj-$(CONFIG_VIDEO_OV5647) += ov5647.o
> diff --git a/drivers/media/i2c/ov2680.c b/drivers/media/i2c/ov2680.c
> new file mode 100644
> index 000000000000..64c1c2b03f97
> --- /dev/null
> +++ b/drivers/media/i2c/ov2680.c
> @@ -0,0 +1,1189 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Omnivision OV2680 CMOS Image Sensor driver
> + *
> + * Copyright (C) 2018 Linaro Ltd
> + *
> + * Based on OV5640 Sensor Driver
> + * Copyright (C) 2011-2013 Freescale Semiconductor, Inc. All Rights Reserved.
> + * Copyright (C) 2014-2017 Mentor Graphics Inc.
> + *
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/of_gpio.h>

Do you need of_gpio.h?

> +
> +#include <media/v4l2-common.h>
> +#include <media/v4l2-ctrls.h>
> +#include <media/v4l2-device.h>
> +#include <media/v4l2-event.h>
> +#include <media/v4l2-fwnode.h>
> +#include <media/v4l2-image-sizes.h>
> +#include <media/v4l2-mediabus.h>
> +#include <media/v4l2-subdev.h>

Do you need all of these? At least v4l2-event.h and v4l2-image-sizes.h seem
redundant.

> +
> +#define OV2680_XVCLK_MIN     6000000
> +#define OV2680_XVCLK_MAX     24000000
> +
> +#define OV2680_CHIP_ID_HIGH  0x26
> +#define OV2680_CHIP_ID_LOW   0x80
> +
> +#define OV2680_REG_STREAM_CTRL               0x0100
> +#define OV2680_REG_SOFT_RESET                0x0103
> +
> +#define OV2680_REG_CHIP_ID_HIGH              0x300a
> +#define OV2680_REG_CHIP_ID_LOW               0x300b
> +
> +#define OV2680_REG_R_MANUAL          0x3503
> +#define OV2680_REG_GAIN_PK           0x350a
> +#define OV2680_REG_EXPOSURE_PK_HIGH  0x3500
> +#define OV2680_REG_EXPOSURE_PK_MED   0x3501
> +#define OV2680_REG_EXPOSURE_PK_LOW   0x3502
> +#define OV2680_REG_TIMING_HTS                0x380c
> +#define OV2680_REG_TIMING_VTS                0x380e
> +#define OV2680_REG_FORMAT1           0x3820
> +#define OV2680_REG_FORMAT2           0x3821
> +
> +#define OV2680_REG_ISP_CTRL00                0x5080
> +
> +enum ov2680_frame_rate {
> +     OV2680_30_FPS,
> +     OV2680_FRAMERATES_MAX,
> +};
> +
> +static const int ov2680_framerates[] = {
> +     [OV2680_30_FPS] = 30,
> +};
> +
> +enum ov2680_mode_id {
> +     OV2680_MODE_QUXGA_800_600,
> +     OV2680_MODE_720P_1280_720,
> +     OV2680_MODE_UXGA_1600_1200,
> +     OV2680_MODE_MAX,
> +};
> +
> +struct reg_value {
> +     u16 reg_addr;
> +     u8 val;
> +};
> +
> +struct ov2680_mode_info {
> +     const char *name;
> +     enum ov2680_mode_id id;
> +     u32 width;
> +     u32 height;
> +     const struct reg_value *reg_data;
> +     u32 reg_data_size;
> +};
> +
> +struct ov2680_ctrls {
> +     struct v4l2_ctrl_handler handler;
> +     struct {
> +             struct v4l2_ctrl *auto_exp;
> +             struct v4l2_ctrl *exposure;
> +     };
> +     struct {
> +             struct v4l2_ctrl *auto_gain;
> +             struct v4l2_ctrl *gain;
> +     };
> +
> +     struct v4l2_ctrl *hflip;
> +     struct v4l2_ctrl *vflip;
> +     struct v4l2_ctrl *test_pattern;
> +};
> +
> +struct ov2680_dev {
> +     struct i2c_client               *i2c_client;
> +     struct v4l2_subdev              sd;
> +
> +     struct media_pad                pad;
> +     struct v4l2_fwnode_endpoint     ep;
> +     struct clk                      *xvclk;
> +     u32                             xvclk_freq;
> +
> +     struct gpio_desc                *pwdn_gpio;
> +     struct mutex                    lock; /* protect members */
> +
> +     bool                            mode_pending_changes;
> +     bool                            is_enabled;
> +     bool                            is_streaming;
> +
> +     struct ov2680_ctrls             ctrls;
> +     struct v4l2_mbus_framefmt       fmt;
> +     struct v4l2_fract               frame_interval;
> +
> +     enum ov2680_frame_rate          current_fps;
> +     const struct ov2680_mode_info   *current_mode;
> +};
> +
> +static const char * const test_pattern_menu[] = {
> +     "Disabled",
> +     "Color bars",

"Color Bars",

> +     "Random Data",
> +     "Square",
> +     "Black Image",
> +};
> +
> +static const struct reg_value ov2680_setting_30fps_QUXGA_800_600[] = {
> +     {0x3086, 0x01}, {0x370a, 0x23}, {0x3808, 0x03}, {0x3809, 0x20},
> +     {0x380a, 0x02}, {0x380b, 0x58}, {0x380c, 0x06}, {0x380d, 0xac},
> +     {0x380e, 0x02}, {0x380f, 0x84}, {0x3811, 0x04}, {0x3813, 0x04},
> +     {0x3814, 0x31}, {0x3815, 0x31}, {0x3820, 0xc0}, {0x4008, 0x00},
> +     {0x4009, 0x03}, {0x4837, 0x1e}, {0x3501, 0x4e}, {0x3502, 0xe0},
> +};
> +
> +static const struct reg_value ov2680_setting_30fps_720P_1280_720[] = {
> +     {0x3086, 0x00}, {0x3808, 0x05}, {0x3809, 0x00}, {0x380a, 0x02},
> +     {0x380b, 0xd0}, {0x380c, 0x06}, {0x380d, 0xa8}, {0x380e, 0x05},
> +     {0x380f, 0x0e}, {0x3811, 0x08}, {0x3813, 0x06}, {0x3814, 0x11},
> +     {0x3815, 0x11}, {0x3820, 0xc0}, {0x4008, 0x00},
> +};
> +
> +static const struct reg_value ov2680_setting_30fps_UXGA_1600_1200[] = {
> +     {0x3086, 0x00}, {0x3501, 0x4e}, {0x3502, 0xe0}, {0x3808, 0x06},
> +     {0x3809, 0x40}, {0x380a, 0x04}, {0x380b, 0xb0}, {0x380c, 0x06},
> +     {0x380d, 0xa8}, {0x380e, 0x05}, {0x380f, 0x0e}, {0x3811, 0x00},
> +     {0x3813, 0x00}, {0x3814, 0x11}, {0x3815, 0x11}, {0x3820, 0xc0},
> +     {0x4008, 0x00}, {0x4837, 0x18}
> +};
> +
> +static const struct ov2680_mode_info ov2680_mode_init_data = {
> +     "mode_quxga_800_600", OV2680_MODE_QUXGA_800_600, 800, 600,
> +     ov2680_setting_30fps_QUXGA_800_600,
> +     ARRAY_SIZE(ov2680_setting_30fps_QUXGA_800_600),
> +};
> +
> +static const struct ov2680_mode_info
> +ov2680_mode_data[OV2680_FRAMERATES_MAX][OV2680_MODE_MAX] = {

You only have a single frame rate. Do you plan to support more?

As the frame rate is specific to a mode rather than the other way around, I
think you should probably swap the array dimensions. You could even remove
this as frame rate selection clearly isn't implemented in the driver.

> +     {
> +             {"mode_quxga_800_600", OV2680_MODE_QUXGA_800_600,
> +              800, 600, ov2680_setting_30fps_QUXGA_800_600,
> +              ARRAY_SIZE(ov2680_setting_30fps_QUXGA_800_600)},
> +             {"mode_720p_1280_720", OV2680_MODE_720P_1280_720,
> +              1280, 720, ov2680_setting_30fps_720P_1280_720,
> +              ARRAY_SIZE(ov2680_setting_30fps_720P_1280_720)},
> +             {"mode_uxga_1600_1200", OV2680_MODE_UXGA_1600_1200,
> +              1600, 1200, ov2680_setting_30fps_UXGA_1600_1200,
> +              ARRAY_SIZE(ov2680_setting_30fps_UXGA_1600_1200)},
> +     },
> +};
> +
> +static struct ov2680_dev *to_ov2680_dev(struct v4l2_subdev *sd)
> +{
> +     return container_of(sd, struct ov2680_dev, sd);
> +}
> +
> +static struct device *ov2680_to_dev(struct ov2680_dev *sensor)
> +{
> +     return &sensor->i2c_client->dev;
> +}
> +
> +static inline struct v4l2_subdev *ctrl_to_sd(struct v4l2_ctrl *ctrl)
> +{
> +     return &container_of(ctrl->handler, struct ov2680_dev,
> +                          ctrls.handler)->sd;
> +}
> +
> +static int ov2680_write_reg(struct ov2680_dev *sensor, u16 reg, u8 val)
> +{
> +     struct i2c_client *client = sensor->i2c_client;
> +     struct i2c_msg msg;
> +     u8 buf[3];
> +     int ret;
> +
> +     buf[0] = reg >> 8;
> +     buf[1] = reg & 0xff;
> +     buf[2] = val;
> +
> +     msg.addr = client->addr;
> +     msg.flags = client->flags;
> +     msg.buf = buf;
> +     msg.len = sizeof(buf);
> +
> +     ret = i2c_transfer(client->adapter, &msg, 1);
> +     if (ret < 0) {
> +             dev_err(&client->dev, "write error: reg=0x%4x: %d\n", reg, ret);
> +             return ret;
> +     }
> +
> +     return 0;
> +}
> +
> +static int ov2680_write_reg16(struct ov2680_dev *sensor, u16 reg, u16 val)
> +{
> +     int ret;
> +
> +     ret = ov2680_write_reg(sensor, reg, val >> 8);
> +     if (ret)
> +             return ret;
> +
> +     return ov2680_write_reg(sensor, reg + 1, val & 0xff);
> +}
> +
> +static int ov2680_read_reg(struct ov2680_dev *sensor, u16 reg, u8 *val)
> +{
> +     struct i2c_client *client = sensor->i2c_client;
> +     struct i2c_msg msg[2];
> +     u8 buf[2];
> +     int ret;
> +
> +     buf[0] = reg >> 8;
> +     buf[1] = reg & 0xff;
> +
> +     msg[0].addr = client->addr;
> +     msg[0].flags = client->flags;
> +     msg[0].buf = buf;
> +     msg[0].len = sizeof(buf);
> +
> +     msg[1].addr = client->addr;
> +     msg[1].flags = client->flags | I2C_M_RD;
> +     msg[1].buf = buf;
> +     msg[1].len = 1;
> +
> +     ret = i2c_transfer(client->adapter, msg, 2);
> +     if (ret < 0) {
> +             dev_err(&client->dev, "read error: reg=0x%4x: %d\n", reg, ret);
> +             return ret;
> +     }
> +
> +     *val = buf[0];
> +     return 0;
> +}
> +
> +static int ov2680_read_reg16(struct ov2680_dev *sensor, u16 reg, u16 *val)
> +{
> +     u8 hi, lo;
> +     int ret;
> +
> +     ret = ov2680_read_reg(sensor, reg, &hi);
> +     if (ret)
> +             return ret;
> +     ret = ov2680_read_reg(sensor, reg + 1, &lo);
> +     if (ret)
> +             return ret;

You shouldn't implement accessing 16-bit registers like this neither for
reading or writing unless there's a specific reason to do so. Just access
the high and low octet in the same transaction.

> +
> +     *val = ((u16)hi << 8) | (u16)lo;
> +
> +     return 0;
> +}
> +
> +static int ov2680_mod_reg(struct ov2680_dev *sensor, u16 reg, u8 mask, u8 
> val)
> +{
> +     u8 readval;
> +     int ret;
> +
> +     ret = ov2680_read_reg(sensor, reg, &readval);
> +     if (ret < 0)
> +             return ret;
> +
> +     readval &= ~mask;
> +     val &= mask;
> +     val |= readval;
> +
> +     return ov2680_write_reg(sensor, reg, val);
> +}
> +
> +static int ov2680_load_regs(struct ov2680_dev *sensor,
> +                         const struct ov2680_mode_info *mode)
> +{
> +     const struct reg_value *regs = mode->reg_data;
> +     unsigned int i;
> +     int ret = 0;
> +     u16 reg_addr;
> +     u8 val;
> +
> +     for (i = 0; i < mode->reg_data_size; ++i, ++regs) {
> +             reg_addr = regs->reg_addr;
> +             val = regs->val;
> +
> +             ret = ov2680_write_reg(sensor, reg_addr, val);
> +             if (ret)
> +                     break;
> +     }
> +
> +     return ret;
> +}
> +
> +static void ov2680_power_up(struct ov2680_dev *sensor)
> +{
> +     if (!sensor->pwdn_gpio)
> +             return;
> +
> +     gpiod_set_value(sensor->pwdn_gpio, 1);
> +     usleep_range(5000, 10000);
> +}

Even if you're using GPIO only right now, the power up and power down
may not be executed before the corresponding power up sequence.

> +
> +static void ov2680_power_down(struct ov2680_dev *sensor)
> +{
> +     if (!sensor->pwdn_gpio)
> +             return;
> +
> +     gpiod_set_value(sensor->pwdn_gpio, 0);
> +     usleep_range(5000, 10000);
> +}
> +
> +static int ov2680_soft_reset(struct ov2680_dev *sensor)
> +{
> +     struct device *dev = ov2680_to_dev(sensor);
> +     int ret;
> +
> +     ret = ov2680_write_reg(sensor, OV2680_REG_SOFT_RESET, 0x01);
> +     if (ret != 0) {
> +             dev_err(dev, "sensor soft reset failed\n");
> +             return ret;
> +     }
> +     usleep_range(1000, 2000);
> +     return 0;
> +}
> +
> +static void ov2680_reset(struct ov2680_dev *sensor)
> +{
> +     if (!sensor->pwdn_gpio) {
> +             ov2680_soft_reset(sensor);
> +             return;
> +     }
> +
> +     ov2680_power_down(sensor);
> +     ov2680_power_up(sensor);

Please merge the two above functions to ov2670_enable. That might be better
called e.g. ov2670_power_on. Likewise ov2670_disable could be
ov2670_power_off. These functions are implementing power on and power off
sequences after all.

> +}
> +
> +static int ov2680_vflip_enable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_mod_reg(sensor, OV2680_REG_FORMAT1, BIT(2), BIT(2));
> +}
> +
> +static int ov2680_vflip_disable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_mod_reg(sensor, OV2680_REG_FORMAT1, BIT(2), 0);
> +}
> +
> +static int ov2680_hflip_enable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_mod_reg(sensor, OV2680_REG_FORMAT2, BIT(2), BIT(2));
> +}
> +
> +static int ov2680_hflip_disable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_mod_reg(sensor, OV2680_REG_FORMAT2, BIT(2), 0);
> +}
> +
> +static int ov2680_test_pattern_set(struct ov2680_dev *sensor, int value)
> +{
> +     int ret;
> +
> +     if (!value)
> +             return ov2680_mod_reg(sensor, OV2680_REG_ISP_CTRL00, BIT(7), 0);
> +
> +     ret = ov2680_mod_reg(sensor, OV2680_REG_ISP_CTRL00, 0x03, value - 1);
> +     if (ret < 0)
> +             return ret;
> +
> +     ret = ov2680_mod_reg(sensor, OV2680_REG_ISP_CTRL00, BIT(7), BIT(7));
> +     if (ret < 0)
> +             return ret;
> +
> +     return 0;
> +}
> +
> +static int ov2680_gain_set(struct ov2680_dev *sensor, bool auto_gain)
> +{
> +     struct ov2680_ctrls *ctrls = &sensor->ctrls;
> +     u16 gain;
> +     int ret;
> +
> +     ret = ov2680_mod_reg(sensor, OV2680_REG_R_MANUAL, BIT(1),
> +                          auto_gain ? 0 : BIT(1));
> +     if (ret < 0)
> +             return ret;
> +
> +     if (auto_gain)
> +             return 0;
> +
> +     gain = (u16)ctrls->gain->val;
> +
> +     ret = ov2680_write_reg16(sensor, OV2680_REG_GAIN_PK, gain & 0x7ff);

I think you could just use ctrls->gain->val here.

> +
> +     return 0;
> +}
> +
> +static int ov2680_gain_get(struct ov2680_dev *sensor)
> +{
> +     u16 gain;
> +     int ret;
> +
> +     ret = ov2680_read_reg16(sensor, OV2680_REG_GAIN_PK, &gain);
> +     if (ret)
> +             return ret;
> +
> +     return gain & 0x3ff;

Why 3ff here but 7ff when setting the gain?

> +}
> +
> +static int ov2680_auto_gain_enable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_gain_set(sensor, true);
> +}
> +
> +static int ov2680_auto_gain_disable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_gain_set(sensor, false);
> +}

Could you use ov2680_gain_set() from the caller instead? Perhaps rename it
as ov2680_autogain_set()?

> +
> +static int ov2680_exposure_set(struct ov2680_dev *sensor, bool auto_exp)
> +{
> +     struct ov2680_ctrls *ctrls = &sensor->ctrls;
> +     u32 exp;
> +     int ret;
> +
> +     ret = ov2680_mod_reg(sensor, OV2680_REG_R_MANUAL, BIT(0),
> +                          auto_exp ? 0 : BIT(0));
> +     if (ret < 0)
> +             return ret;
> +
> +     if (auto_exp)
> +             return 0;
> +
> +     exp = (u32)ctrls->exposure->val;
> +     exp <<= 4;
> +
> +     ret = ov2680_write_reg(sensor, OV2680_REG_EXPOSURE_PK_LOW, exp & 0xf0);
> +     if (ret)
> +             return ret;
> +
> +     ret = ov2680_write_reg(sensor, OV2680_REG_EXPOSURE_PK_MED,
> +                            (exp >> 8) & 0xff);
> +     if (ret)
> +             return ret;
> +
> +     return ov2680_write_reg(sensor, OV2680_REG_EXPOSURE_PK_HIGH,
> +                             (exp >> 16) & 0x0f);

I'd suppose you'll get interesting effects if the exposure latching point
happens to be in between these updates.

A single read would avoid that. Or is there a particular reason to perform
a read of a single register in three transactions?

> +}
> +
> +static int ov2680_exposure_get(struct ov2680_dev *sensor)
> +{
> +     int exp, ret;
> +     u8 temp;
> +
> +     ret = ov2680_read_reg(sensor, OV2680_REG_EXPOSURE_PK_HIGH, &temp);
> +     if (ret)
> +             return ret;
> +     exp = ((int)temp & 0x0f) << 16;
> +
> +     ret = ov2680_read_reg(sensor, OV2680_REG_EXPOSURE_PK_MED, &temp);
> +     if (ret)
> +             return ret;
> +     exp |= ((int)temp & 0xff) << 8;
> +
> +     ret = ov2680_read_reg(sensor, OV2680_REG_EXPOSURE_PK_LOW, &temp);
> +     if (ret)
> +             return ret;
> +     exp |= ((int)temp & 0xf0);
> +
> +     return exp >> 4;
> +}
> +
> +static int ov2680_auto_exposure_enable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_exposure_set(sensor, true);
> +}
> +
> +static int ov2680_auto_exposure_disable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_exposure_set(sensor, false);
> +}

Same for exposure.

> +
> +static int ov2680_stream_enable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_write_reg(sensor, OV2680_REG_STREAM_CTRL, 1);
> +}
> +
> +static int ov2680_stream_disable(struct ov2680_dev *sensor)
> +{
> +     return ov2680_write_reg(sensor, OV2680_REG_STREAM_CTRL, 0);
> +}
> +
> +static int ov2680_mode_set_direct(struct ov2680_dev *sensor)
> +{
> +     int ret;
> +
> +     if (!sensor->current_mode->reg_data)
> +             return -EINVAL;
> +
> +     ret = ov2680_load_regs(sensor, sensor->current_mode);
> +     if (ret < 0)
> +             return ret;
> +
> +     return 0;
> +}
> +
> +static int ov2680_mode_set(struct ov2680_dev *sensor)
> +{
> +     int ret;
> +
> +     ret = ov2680_auto_gain_disable(sensor);
> +     if (ret < 0)
> +             return ret;
> +
> +     ret = ov2680_auto_exposure_disable(sensor);
> +     if (ret < 0)
> +             return ret;
> +
> +     ret = ov2680_mode_set_direct(sensor);

ov2680_mode_set_direct() is only used here. How about moving the contents
here?

> +     if (ret < 0)
> +             return ret;
> +
> +     ret = ov2680_auto_gain_enable(sensor);

This should be based on the control value, shouldn't it?

> +     if (ret < 0)
> +             return ret;
> +
> +     ret = ov2680_auto_exposure_enable(sensor);
> +     if (ret < 0)
> +             return ret;

As well as the exposure.

> +
> +     sensor->mode_pending_changes = false;
> +
> +     return 0;
> +}
> +
> +static int ov2680_mode_restore(struct ov2680_dev *sensor)
> +{
> +     int ret;
> +
> +     ret = ov2680_load_regs(sensor, &ov2680_mode_init_data);
> +     if (ret < 0)
> +             return ret;
> +
> +     return ov2680_mode_set(sensor);
> +}
> +
> +static int ov2680_disable(struct ov2680_dev *sensor)
> +{
> +     if (!sensor->is_enabled)
> +             return 0;
> +
> +     clk_disable_unprepare(sensor->xvclk);
> +     ov2680_power_down(sensor);
> +     sensor->is_enabled = false;
> +
> +     return 0;
> +}
> +
> +static int ov2680_enable(struct ov2680_dev *sensor)
> +{
> +     struct device *dev = ov2680_to_dev(sensor);
> +     int ret;
> +
> +     if (sensor->is_enabled)
> +             return 0;
> +
> +     ov2680_reset(sensor);
> +
> +     ret = clk_prepare_enable(sensor->xvclk);
> +     if (ret < 0)
> +             return ret;
> +
> +     ret = ov2680_mode_restore(sensor);
> +     if (ret < 0)
> +             goto disable;
> +
> +     sensor->is_enabled = true;
> +
> +     /* Set clock lane into LP-11 state */
> +     ov2680_stream_enable(sensor);
> +     usleep_range(1000, 2000);
> +     ov2680_stream_disable(sensor);
> +
> +     return 0;
> +
> +disable:
> +     dev_err(dev, "failed to enable sensor: %d\n", ret);
> +     ov2680_disable(sensor);
> +
> +     return ret;
> +}
> +
> +static int ov2680_s_power(struct v4l2_subdev *sd, int on)
> +{
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +     int ret = 0;
> +
> +     mutex_lock(&sensor->lock);
> +
> +     if (on)
> +             ret = ov2680_enable(sensor);
> +     else
> +             ret = ov2680_disable(sensor);
> +
> +     mutex_unlock(&sensor->lock);
> +
> +     if (on && ret == 0) {
> +             ret = v4l2_ctrl_handler_setup(&sensor->ctrls.handler);
> +             if (ret < 0)
> +                     return ret;
> +     }
> +
> +     return ret;
> +}
> +
> +static int ov2680_g_frame_interval(struct v4l2_subdev *sd,
> +                                struct v4l2_subdev_frame_interval *fi)
> +{
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +
> +     mutex_lock(&sensor->lock);
> +     fi->interval = sensor->frame_interval;
> +     mutex_unlock(&sensor->lock);
> +
> +     return 0;
> +}
> +
> +static int ov2680_s_frame_interval(struct v4l2_subdev *sd,
> +                                struct v4l2_subdev_frame_interval *fi)
> +{
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +
> +     if (fi->interval.denominator != sensor->frame_interval.denominator ||
> +         fi->interval.numerator != sensor->frame_interval.numerator)

You only support 30 frames per second. Even then, you need to modify the
request to match with what the driver supports, so the implementation can
be the same than for g_frame_interval.

> +             return -EINVAL;
> +
> +     return 0;
> +}
> +
> +static int ov2680_s_stream(struct v4l2_subdev *sd, int enable)
> +{
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +     int ret = 0;
> +
> +     mutex_lock(&sensor->lock);
> +
> +     if (sensor->is_streaming == !!enable)
> +             goto unlock;
> +
> +     if (enable && sensor->mode_pending_changes) {
> +             ret = ov2680_mode_set(sensor);
> +             if (ret < 0)
> +                     goto unlock;
> +     }
> +
> +     if (enable)
> +             ret = ov2680_stream_enable(sensor);
> +     else
> +             ret = ov2680_stream_disable(sensor);
> +
> +     sensor->is_streaming = !!enable;
> +
> +unlock:
> +     mutex_unlock(&sensor->lock);
> +
> +     return ret;
> +}
> +
> +static int ov2680_enum_mbus_code(struct v4l2_subdev *sd,
> +                              struct v4l2_subdev_pad_config *cfg,
> +                              struct v4l2_subdev_mbus_code_enum *code)
> +{
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +
> +     if (code->pad != 0 || code->index != 0)
> +             return -EINVAL;
> +
> +     code->code = sensor->fmt.code;
> +
> +     return 0;
> +}
> +
> +static int ov2680_get_fmt(struct v4l2_subdev *sd,
> +                       struct v4l2_subdev_pad_config *cfg,
> +                       struct v4l2_subdev_format *format)
> +{
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +     struct v4l2_mbus_framefmt *fmt;
> +
> +     if (format->pad != 0)
> +             return -EINVAL;
> +
> +     mutex_lock(&sensor->lock);
> +
> +     if (format->which == V4L2_SUBDEV_FORMAT_TRY)
> +             fmt = v4l2_subdev_get_try_format(&sensor->sd, cfg, format->pad);
> +     else
> +             fmt = &sensor->fmt;
> +
> +     format->format = *fmt;
> +
> +     mutex_unlock(&sensor->lock);
> +
> +     return 0;
> +}
> +
> +static const struct ov2680_mode_info *
> +ov2680_mode_find(struct ov2680_dev *sensor, enum ov2680_frame_rate fps,
> +              int width, int height)
> +{
> +     const struct ov2680_mode_info *mode = NULL;
> +     bool mode_found = false;
> +     int i;
> +
> +     for (i = OV2680_MODE_MAX - 1; i >= 0; i--) {
> +             mode = &ov2680_mode_data[fps][i];
> +
> +             if (!mode->reg_data)
> +                     continue;
> +
> +             if (mode->width == width && mode->height == height) {

The closest match would be better. Can you use this? I'm planning to send a
pull request on the set soon.

<URL:https://patchwork.linuxtv.org/patch/46975/>

> +                     mode_found = true;
> +                     break;
> +             }
> +     }
> +
> +     return mode_found ? mode : NULL;
> +}
> +
> +static int ov2680_set_fmt(struct v4l2_subdev *sd,
> +                       struct v4l2_subdev_pad_config *cfg,
> +                       struct v4l2_subdev_format *format)
> +{
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +     struct v4l2_mbus_framefmt *fmt = &format->format;
> +     const struct ov2680_mode_info *mode;
> +     int ret = 0;
> +
> +     if (format->pad != 0)
> +             return -EINVAL;
> +
> +     mutex_lock(&sensor->lock);
> +
> +     if (sensor->is_streaming) {
> +             ret = -EBUSY;
> +             goto unlock;
> +     }
> +
> +     mode = ov2680_mode_find(sensor, sensor->current_fps, fmt->width,
> +                             fmt->height);
> +     if (!mode) {
> +             ret = -EINVAL;
> +             goto unlock;
> +     }
> +
> +     if (format->which == V4L2_SUBDEV_FORMAT_TRY) {
> +             fmt = v4l2_subdev_get_try_format(sd, cfg, 0);
> +
> +             *fmt = format->format;
> +             goto unlock;
> +     }
> +
> +     fmt->width = mode->width;
> +     fmt->height = mode->height;
> +     fmt->code = sensor->fmt.code;
> +     fmt->colorspace = sensor->fmt.colorspace;
> +
> +     sensor->current_mode = mode;
> +     sensor->fmt = format->format;
> +     sensor->mode_pending_changes = true;
> +
> +unlock:
> +     mutex_unlock(&sensor->lock);
> +
> +     return ret;
> +}
> +
> +static int ov2680_enum_frame_size(struct v4l2_subdev *sd,
> +                               struct v4l2_subdev_pad_config *cfg,
> +                               struct v4l2_subdev_frame_size_enum *fse)
> +{
> +     int index = fse->index;
> +
> +     if (index >= OV2680_MODE_MAX)
> +             return -EINVAL;
> +
> +     fse->min_width = ov2680_mode_data[0][index].width;
> +     fse->min_height = ov2680_mode_data[0][index].height;
> +     fse->max_width = ov2680_mode_data[0][index].width;
> +     fse->max_height = ov2680_mode_data[0][index].height;
> +
> +     return 0;
> +}
> +
> +static int ov2680_enum_frame_interval(struct v4l2_subdev *sd,
> +                           struct v4l2_subdev_pad_config *cfg,
> +                           struct v4l2_subdev_frame_interval_enum *fie)
> +{
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +     const struct ov2680_mode_info *mode;
> +     struct v4l2_fract tpf;
> +
> +     if (fie->index >= OV2680_FRAMERATES_MAX)
> +             return -EINVAL;
> +
> +     tpf.denominator = ov2680_framerates[fie->index];
> +     tpf.numerator = 1;
> +
> +     fie->interval = tpf;
> +
> +     mode = ov2680_mode_find(sensor, sensor->current_fps, fie->width,
> +                             fie->height);
> +
> +     return mode ? 0 : -EINVAL;
> +}
> +
> +static int ov2680_g_volatile_ctrl(struct v4l2_ctrl *ctrl)
> +{
> +     struct v4l2_subdev *sd = ctrl_to_sd(ctrl);
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +     int val;
> +
> +     if (!sensor->is_enabled)
> +             return 0;
> +
> +     switch (ctrl->id) {
> +     case V4L2_CID_AUTOGAIN:
> +             if (!ctrl->val)
> +                     return 0;
> +             val = ov2680_gain_get(sensor);
> +             if (val < 0)
> +                     return val;
> +             sensor->ctrls.gain->val = val;
> +             break;
> +     case V4L2_CID_EXPOSURE_AUTO:
> +             if (ctrl->val == V4L2_EXPOSURE_MANUAL)
> +                     return 0;
> +             val = ov2680_exposure_get(sensor);
> +             if (val < 0)
> +                     return val;
> +             sensor->ctrls.exposure->val = val;
> +             break;
> +     }
> +
> +     return 0;
> +}
> +
> +static int ov2680_s_ctrl(struct v4l2_ctrl *ctrl)
> +{
> +     struct v4l2_subdev *sd = ctrl_to_sd(ctrl);
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +
> +     if (!sensor->is_enabled)
> +             return 0;
> +
> +     switch (ctrl->id) {
> +     case V4L2_CID_AUTOGAIN:
> +             return ov2680_gain_set(sensor, !!ctrl->val);
> +     case V4L2_CID_EXPOSURE_AUTO:
> +             return ov2680_exposure_set(sensor, !!ctrl->val);
> +     case V4L2_CID_VFLIP:
> +             if (ctrl->val)
> +                     return ov2680_vflip_enable(sensor);
> +             else
> +                     return ov2680_vflip_disable(sensor);
> +     case V4L2_CID_HFLIP:
> +             if (ctrl->val)
> +                     return ov2680_hflip_enable(sensor);
> +             else
> +                     return ov2680_hflip_disable(sensor);
> +     case V4L2_CID_TEST_PATTERN:
> +             return ov2680_test_pattern_set(sensor, ctrl->val);
> +     default:
> +             break;
> +     }
> +
> +     return -EINVAL;
> +}
> +
> +static const struct v4l2_ctrl_ops ov2680_ctrl_ops = {
> +     .g_volatile_ctrl = ov2680_g_volatile_ctrl,
> +     .s_ctrl = ov2680_s_ctrl,
> +};
> +
> +static const struct v4l2_subdev_core_ops ov2680_core_ops = {
> +     .s_power = ov2680_s_power,
> +};
> +
> +static const struct v4l2_subdev_video_ops ov2680_video_ops = {
> +     .g_frame_interval       = ov2680_g_frame_interval,
> +     .s_frame_interval       = ov2680_s_frame_interval,
> +     .s_stream               = ov2680_s_stream,
> +};
> +
> +static const struct v4l2_subdev_pad_ops ov2680_pad_ops = {
> +     .enum_mbus_code         = ov2680_enum_mbus_code,
> +     .get_fmt                = ov2680_get_fmt,
> +     .set_fmt                = ov2680_set_fmt,
> +     .enum_frame_size        = ov2680_enum_frame_size,
> +     .enum_frame_interval    = ov2680_enum_frame_interval,
> +};
> +
> +static const struct v4l2_subdev_ops ov2680_subdev_ops = {
> +     .core   = &ov2680_core_ops,
> +     .video  = &ov2680_video_ops,
> +     .pad    = &ov2680_pad_ops,
> +};
> +
> +static int ov2680_mode_init(struct ov2680_dev *sensor)
> +{
> +     const struct ov2680_mode_info *init_mode;
> +
> +     /* set initial mode */
> +     sensor->fmt.code = MEDIA_BUS_FMT_SBGGR10_1X10;
> +     sensor->fmt.width = 800;
> +     sensor->fmt.height = 600;
> +     sensor->fmt.field = V4L2_FIELD_NONE;
> +     sensor->fmt.colorspace = V4L2_COLORSPACE_SRGB;
> +
> +     sensor->frame_interval.denominator = ov2680_framerates[OV2680_30_FPS];
> +     sensor->frame_interval.numerator = 1;
> +
> +     sensor->current_fps = OV2680_30_FPS;
> +     init_mode = &ov2680_mode_data[OV2680_30_FPS][OV2680_MODE_QUXGA_800_600];
> +
> +     sensor->current_mode = init_mode;
> +
> +     sensor->mode_pending_changes = true;
> +
> +     return 0;
> +}
> +
> +static int ov2680_v4l2_init(struct ov2680_dev *sensor)
> +{
> +     const struct v4l2_ctrl_ops *ops = &ov2680_ctrl_ops;
> +     struct ov2680_ctrls *ctrls = &sensor->ctrls;
> +     struct v4l2_ctrl_handler *hdl = &ctrls->handler;
> +     int ret = 0;
> +
> +     v4l2_i2c_subdev_init(&sensor->sd, sensor->i2c_client,
> +                          &ov2680_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 < 0)
> +             return ret;
> +
> +     v4l2_ctrl_handler_init(hdl, 32);
> +
> +     hdl->lock = &sensor->lock;
> +
> +     ctrls->vflip = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_VFLIP, 0, 1, 1, 0);
> +     ctrls->hflip = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_HFLIP, 0, 1, 1, 0);
> +
> +     ctrls->test_pattern = v4l2_ctrl_new_std_menu_items(hdl,
> +                                     &ov2680_ctrl_ops,
> +                                     V4L2_CID_TEST_PATTERN,
> +                                     ARRAY_SIZE(test_pattern_menu) - 1,
> +                                     0, 0, test_pattern_menu);
> +
> +     ctrls->auto_exp = v4l2_ctrl_new_std_menu(hdl, ops,
> +                                              V4L2_CID_EXPOSURE_AUTO,
> +                                              V4L2_EXPOSURE_MANUAL, 0,
> +                                              V4L2_EXPOSURE_AUTO);
> +
> +     ctrls->exposure = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_EXPOSURE,
> +                                         0, 32767, 1, 0);
> +
> +     ctrls->auto_gain = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_AUTOGAIN,
> +                                          0, 1, 1, 1);
> +     ctrls->gain = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_GAIN, 0, 2047, 1, 0);
> +
> +     ctrls->gain->flags |= V4L2_CTRL_FLAG_VOLATILE;
> +     ctrls->exposure->flags |= V4L2_CTRL_FLAG_VOLATILE;

v4l2_ctrl_new_std() may return NULL. Please check gain and exposure are
non-NULL before dereferencing them. The error handling seems fine
otherwise.

> +
> +     v4l2_ctrl_auto_cluster(2, &ctrls->auto_gain, 1, true);
> +     v4l2_ctrl_auto_cluster(2, &ctrls->auto_exp, 1, true);
> +
> +     sensor->sd.ctrl_handler = hdl;
> +
> +     ret = v4l2_async_register_subdev(&sensor->sd);
> +     if (ret < 0) {
> +             media_entity_cleanup(&sensor->sd.entity);
> +             v4l2_ctrl_handler_free(hdl);
> +     }
> +
> +     return ret;
> +}
> +
> +static int ov2680_check_id(struct ov2680_dev *sensor)
> +{
> +     struct device *dev = ov2680_to_dev(sensor);
> +     u8 chip_id_high;
> +     u8 chip_id_low;
> +     int ret;
> +
> +     ov2680_reset(sensor);

I don't have the sensor datasheet, but practically everywhere you'll need
execute the power up sequence before accessing the sensor registers.

> +
> +     ret = ov2680_read_reg(sensor, OV2680_REG_CHIP_ID_HIGH, &chip_id_high);
> +     if (ret < 0) {
> +             dev_err(dev, "failed to read chip id high\n");
> +             return -ENODEV;
> +     }
> +
> +     ret = ov2680_read_reg(sensor, OV2680_REG_CHIP_ID_LOW, &chip_id_low);
> +     if (ret < 0) {
> +             dev_err(dev, "failed to read chip id low\n");
> +             return -ENODEV;
> +     }
> +
> +     if (chip_id_high != OV2680_CHIP_ID_HIGH ||
> +         chip_id_low != OV2680_CHIP_ID_LOW) {
> +             dev_err(dev, "chip id: 0x%02x%02x does not match expected: 
> 0x%02x%02x\n",
> +                     chip_id_high, chip_id_low, OV2680_CHIP_ID_HIGH,
> +                     OV2680_CHIP_ID_LOW);
> +             return -ENODEV;
> +     }
> +
> +     return 0;
> +}
> +
> +static int ov2860_parse_dt(struct ov2680_dev *sensor)
> +{
> +     struct device *dev = ov2680_to_dev(sensor);
> +     int ret;
> +
> +     sensor->pwdn_gpio = devm_gpiod_get_optional(dev, "powerdown",
> +                                                 GPIOD_OUT_HIGH);
> +     ret = PTR_ERR_OR_ZERO(sensor->pwdn_gpio);
> +     if (ret < 0) {
> +             dev_dbg(dev, "error while getting powerdown gpio: %d\n", ret);
> +             return ret;
> +     }
> +
> +     sensor->xvclk = devm_clk_get(dev, "xvclk");
> +     if (IS_ERR(sensor->xvclk)) {
> +             dev_err(dev, "xvclk clock missing or invalid\n");
> +             return PTR_ERR(sensor->xvclk);
> +     }
> +
> +     sensor->xvclk_freq = clk_get_rate(sensor->xvclk);
> +     if (sensor->xvclk_freq < OV2680_XVCLK_MIN ||
> +         sensor->xvclk_freq > OV2680_XVCLK_MAX) {

I believe the register lists are intended for a particular frequency and do
not work for others. What is this frequency?

> +             dev_err(dev, "xvclk frequency out of range: %d Hz\n",
> +                     sensor->xvclk_freq);
> +             return -EINVAL;
> +     }
> +
> +     return 0;
> +}
> +
> +static int ov2680_probe(struct i2c_client *client,
> +                     const struct i2c_device_id *id)
> +{
> +     struct device *dev = &client->dev;
> +     struct ov2680_dev *sensor;
> +     int ret;
> +
> +     sensor = devm_kzalloc(dev, sizeof(*sensor), GFP_KERNEL);
> +     if (!sensor)
> +             return -ENOMEM;
> +
> +     sensor->i2c_client = client;
> +
> +     ret = ov2860_parse_dt(sensor);
> +     if (ret < 0)
> +             return -EINVAL;
> +
> +     ret = ov2680_check_id(sensor);
> +     if (ret < 0)
> +             return ret;
> +
> +     ret = ov2680_mode_init(sensor);
> +     if (ret < 0)
> +             return ret;
> +
> +     mutex_init(&sensor->lock);
> +
> +     ret = ov2680_v4l2_init(sensor);
> +     if (ret < 0)
> +             goto lock_destroy;
> +
> +     dev_info(dev, "ov2680 init correctly\n");
> +
> +     return 0;
> +
> +lock_destroy:
> +     mutex_destroy(&sensor->lock);
> +
> +     return ret;
> +}
> +
> +static int ov2680_remove(struct i2c_client *client)
> +{
> +     struct v4l2_subdev *sd = i2c_get_clientdata(client);
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +
> +     v4l2_async_unregister_subdev(&sensor->sd);
> +     mutex_destroy(&sensor->lock);
> +     media_entity_cleanup(&sensor->sd.entity);
> +     v4l2_ctrl_handler_free(&sensor->ctrls.handler);
> +
> +     return 0;
> +}
> +
> +static int __maybe_unused ov2680_suspend(struct device *dev)
> +{
> +     struct i2c_client *client = to_i2c_client(dev);
> +     struct v4l2_subdev *sd = i2c_get_clientdata(client);
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +
> +     if (sensor->is_streaming)
> +             ov2680_stream_disable(sensor);
> +
> +     return 0;
> +}
> +
> +static int __maybe_unused ov2680_resume(struct device *dev)
> +{
> +     struct i2c_client *client = to_i2c_client(dev);
> +     struct v4l2_subdev *sd = i2c_get_clientdata(client);
> +     struct ov2680_dev *sensor = to_ov2680_dev(sd);
> +     int ret;
> +
> +     if (sensor->is_streaming) {
> +             ret = ov2680_stream_enable(sensor);
> +             if (ret < 0)
> +                     goto stream_disable;
> +     }
> +
> +     return 0;
> +
> +stream_disable:
> +     ov2680_stream_disable(sensor);
> +     sensor->is_streaming = false;
> +
> +     return ret;
> +}
> +
> +static const struct dev_pm_ops ov2680_pm_ops = {
> +     SET_SYSTEM_SLEEP_PM_OPS(ov2680_suspend, ov2680_resume)
> +};
> +
> +static const struct i2c_device_id ov2680_id[] = {
> +     {"ov2680", 0},
> +     { },
> +};
> +MODULE_DEVICE_TABLE(i2c, ov2680_id);
> +
> +static const struct of_device_id ov2680_dt_ids[] = {
> +     { .compatible = "ovti,ov2680" },
> +     { /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, ov2680_dt_ids);
> +
> +static struct i2c_driver ov2680_i2c_driver = {
> +     .driver = {
> +             .name  = "ovti,ov2680",
> +             .of_match_table = ov2680_dt_ids,
> +     },
> +     .id_table = ov2680_id,
> +     .probe    = ov2680_probe,
> +     .remove   = ov2680_remove,
> +};
> +module_i2c_driver(ov2680_i2c_driver);
> +
> +MODULE_AUTHOR("Rui Miguel Silva <rui.si...@linaro.org>");
> +MODULE_DESCRIPTION("OV2680 CMOS Image Sensor driver");
> +MODULE_LICENSE("GPL v2");

-- 
Regards,

Sakari Ailus
sakari.ai...@linux.intel.com

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