Subject: Re: [V1, 2/2] media: i2c: Add more sensor mode for ov8856 camera sensor

From: Tomasz Figa <[email-masked]>
Date: Fri, 23 Aug 2019 19:01:26 +0900

Hi Dongchun,

On Thu, Aug 08, 2019 at 05:22:15PM +0800, [email-masked] wrote:
> From: Dongchun Zhu <[email-masked]>
> 
> This patch mainly adds two more sensor modes for OV8856 image sensor.
> The OV8856 driver currently supports output format: 10-bit Raw,
> the resolution of 1632*1224 and 3264*2448, and the bayer order of BGGR.
> The hardware version also differs in some OTP regiser,
> as well as PLL register setting.
> 
> Signed-off-by: Dongchun Zhu <[email-masked]>
> ---
>  drivers/media/i2c/ov8856.c | 624 ++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 621 insertions(+), 3 deletions(-)
> 

Thanks for the patch! Please see my comments inline.

> diff --git a/drivers/media/i2c/ov8856.c b/drivers/media/i2c/ov8856.c
> index cd347d6..e0610b6 100644
> --- a/drivers/media/i2c/ov8856.c
> +++ b/drivers/media/i2c/ov8856.c
> @@ -1,12 +1,15 @@
>  // SPDX-License-Identifier: GPL-2.0
>  // Copyright (c) 2019 Intel Corporation.
>  
> +#include <linux/clk.h>
>  #include <asm/unaligned.h>
>  #include <linux/acpi.h>
>  #include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/i2c.h>
>  #include <linux/module.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/regulator/consumer.h>
>  #include <media/v4l2-ctrls.h>
>  #include <media/v4l2-device.h>
>  #include <media/v4l2-fwnode.h>
> @@ -19,6 +22,7 @@
>  #define OV8856_LINK_FREQ_180MHZ		180000000ULL
>  #define OV8856_SCLK			144000000ULL
>  #define OV8856_MCLK			19200000
> +#define OV8856_XVCLK_FREQ		24000000
>  #define OV8856_DATA_LANES		4
>  #define OV8856_RGB_DEPTH		10
>  
> @@ -29,6 +33,18 @@
>  #define OV8856_MODE_STANDBY		0x00
>  #define OV8856_MODE_STREAMING		0x01
>  
> +/* define 1B module */
> +#define OV8856_1B_MODULE		0x02
> +
> +/* otp sram register */
> +#define OV8856_OTP_REG			0x700f

This isn't a register. I believe the OTP read-out buffer is at 0x7000 and
0xf is the offset of the byte in the OTP that means the module revision.

> +#define OV8856_OTP_REG_ONE		0x3d84
> +#define OV8856_OTP_REG_TWO		0x3d81

These registers are definitely not "ONE" and "TWO". Please use proper
names as per the datasheet.

> +
> +/* clock register */
> +#define OV8856_CLK_REG			0x3614
> +#define OV8856_CLK_REG_1B_VAL		0x20

Same here. These don't look like the real names of the register and bit
field.

> +
>  /* vertical-timings from sensor */
>  #define OV8856_REG_VTS			0x380e
>  #define OV8856_VTS_MAX			0x7fff
> @@ -64,6 +80,14 @@
>  
>  #define to_ov8856(_sd)			container_of(_sd, struct ov8856, sd)
>  
> +static const char * const ov8856_supply_names[] = {
> +	"dovdd",	/* Digital I/O power */
> +	"avdd",		/* Analog power */
> +	"dvdd",		/* Digital core power */
> +};
> +
> +#define OV8856_NUM_SUPPLIES ARRAY_SIZE(ov8856_supply_names)
> +
>  enum {
>  	OV8856_LINK_FREQ_720MBPS,
>  	OV8856_LINK_FREQ_360MBPS,
> @@ -316,6 +340,208 @@ static const struct ov8856_reg mode_3280x2464_regs[] = {
>  	{0x5e00, 0x00}
>  };
>  
> +static const struct ov8856_reg mode_3264x2448_regs[] = {
> +	{0x0103, 0x01},
> +	{0x0302, 0x3c},
> +	{0x0303, 0x01},
> +	{0x031e, 0x0c},
> +	{0x3000, 0x00},
> +	{0x300e, 0x00},
> +	{0x3010, 0x00},
> +	{0x3015, 0x84},
> +	{0x3018, 0x72},
> +	{0x3021, 0x23},
> +	{0x3033, 0x24},
> +	{0x3500, 0x00},
> +	{0x3501, 0x9a},
> +	{0x3502, 0x20},
> +	{0x3503, 0x08},
> +	{0x3505, 0x83},
> +	{0x3508, 0x01},
> +	{0x3509, 0x80},
> +	{0x350c, 0x00},
> +	{0x350d, 0x80},
> +	{0x350e, 0x04},
> +	{0x350f, 0x00},
> +	{0x3510, 0x00},
> +	{0x3511, 0x02},
> +	{0x3512, 0x00},
> +	{0x3600, 0x72},
> +	{0x3601, 0x40},
> +	{0x3602, 0x30},
> +	{0x3610, 0xc5},
> +	{0x3611, 0x58},
> +	{0x3612, 0x5c},
> +	{0x3613, 0xca},
> +	{0x3614, 0x60},
> +	{0x3628, 0xff},
> +	{0x3629, 0xff},
> +	{0x362a, 0xff},
> +	{0x3633, 0x10},
> +	{0x3634, 0x10},
> +	{0x3635, 0x10},
> +	{0x3636, 0x10},
> +	{0x3663, 0x08},
> +	{0x3669, 0x34},
> +	{0x366d, 0x00},
> +	{0x366e, 0x10},
> +	{0x3706, 0x86},
> +	{0x370b, 0x7e},
> +	{0x3714, 0x23},
> +	{0x3730, 0x12},
> +	{0x3733, 0x10},
> +	{0x3764, 0x00},
> +	{0x3765, 0x00},
> +	{0x3769, 0x62},
> +	{0x376a, 0x2a},
> +	{0x376b, 0x30},
> +	{0x3780, 0x00},
> +	{0x3781, 0x24},
> +	{0x3782, 0x00},
> +	{0x3783, 0x23},
> +	{0x3798, 0x2f},
> +	{0x37a1, 0x60},
> +	{0x37a8, 0x6a},
> +	{0x37ab, 0x3f},
> +	{0x37c2, 0x04},
> +	{0x37c3, 0xf1},
> +	{0x37c9, 0x80},
> +	{0x37cb, 0x16},
> +	{0x37cc, 0x16},
> +	{0x37cd, 0x16},
> +	{0x37ce, 0x16},
> +	{0x3800, 0x00},
> +	{0x3801, 0x00},
> +	{0x3802, 0x00},
> +	{0x3803, 0x0c},
> +	{0x3804, 0x0c},
> +	{0x3805, 0xdf},
> +	{0x3806, 0x09},
> +	{0x3807, 0xa3},
> +	{0x3808, 0x0c},
> +	{0x3809, 0xc0},
> +	{0x380a, 0x09},
> +	{0x380b, 0x90},
> +	{0x380c, 0x07},
> +	{0x380d, 0x8c},
> +	{0x380e, 0x09},
> +	{0x380f, 0xb2},
> +	{0x3810, 0x00},
> +	{0x3811, 0x04},
> +	{0x3812, 0x00},
> +	{0x3813, 0x02},
> +	{0x3814, 0x01},
> +	{0x3815, 0x01},
> +	{0x3816, 0x00},
> +	{0x3817, 0x00},
> +	{0x3818, 0x00},
> +	{0x3819, 0x00},
> +	{0x3820, 0x80},
> +	{0x3821, 0x46},
> +	{0x382a, 0x01},
> +	{0x382b, 0x01},
> +	{0x3830, 0x06},
> +	{0x3836, 0x02},
> +	{0x3862, 0x04},
> +	{0x3863, 0x08},
> +	{0x3cc0, 0x33},
> +	{0x3d85, 0x17},
> +	{0x3d8c, 0x73},
> +	{0x3d8d, 0xde},
> +	{0x4001, 0xe0},
> +	{0x4003, 0x40},
> +	{0x4008, 0x00},
> +	{0x4009, 0x0b},
> +	{0x400a, 0x00},
> +	{0x400b, 0x84},
> +	{0x400f, 0x80},
> +	{0x4010, 0xf0},
> +	{0x4011, 0xff},
> +	{0x4012, 0x02},
> +	{0x4013, 0x01},
> +	{0x4014, 0x01},
> +	{0x4015, 0x01},
> +	{0x4042, 0x00},
> +	{0x4043, 0x80},
> +	{0x4044, 0x00},
> +	{0x4045, 0x80},
> +	{0x4046, 0x00},
> +	{0x4047, 0x80},
> +	{0x4048, 0x00},
> +	{0x4049, 0x80},
> +	{0x4041, 0x03},
> +	{0x404c, 0x20},
> +	{0x404d, 0x00},
> +	{0x404e, 0x20},
> +	{0x4203, 0x80},
> +	{0x4307, 0x30},
> +	{0x4317, 0x00},
> +	{0x4502, 0x50},
> +	{0x4503, 0x08},
> +	{0x4601, 0x80},
> +	{0x4800, 0x44},
> +	{0x4816, 0x53},
> +	{0x481b, 0x50},
> +	{0x481f, 0x27},
> +	{0x4823, 0x3c},
> +	{0x482b, 0x00},
> +	{0x4831, 0x66},
> +	{0x4837, 0x16},
> +	{0x483c, 0x0f},
> +	{0x484b, 0x05},
> +	{0x5000, 0x77},
> +	{0x5001, 0x0a},
> +	{0x5003, 0xc8},
> +	{0x5004, 0x04},
> +	{0x5006, 0x00},
> +	{0x5007, 0x00},
> +	{0x502e, 0x03},
> +	{0x5030, 0x41},
> +	{0x5780, 0x14},
> +	{0x5781, 0x0f},
> +	{0x5782, 0x44},
> +	{0x5783, 0x02},
> +	{0x5784, 0x01},
> +	{0x5785, 0x01},
> +	{0x5786, 0x00},
> +	{0x5787, 0x04},
> +	{0x5788, 0x02},
> +	{0x5789, 0x0f},
> +	{0x578a, 0xfd},
> +	{0x578b, 0xf5},
> +	{0x578c, 0xf5},
> +	{0x578d, 0x03},
> +	{0x578e, 0x08},
> +	{0x578f, 0x0c},
> +	{0x5790, 0x08},
> +	{0x5791, 0x04},
> +	{0x5792, 0x00},
> +	{0x5793, 0x52},
> +	{0x5794, 0xa3},
> +	{0x5795, 0x02},
> +	{0x5796, 0x20},
> +	{0x5797, 0x20},
> +	{0x5798, 0xd5},
> +	{0x5799, 0xd5},
> +	{0x579a, 0x00},
> +	{0x579b, 0x50},
> +	{0x579c, 0x00},
> +	{0x579d, 0x2c},
> +	{0x579e, 0x0c},
> +	{0x579f, 0x40},
> +	{0x57a0, 0x09},
> +	{0x57a1, 0x40},
> +	{0x59f8, 0x3d},
> +	{0x5a08, 0x02},
> +	{0x5b00, 0x02},
> +	{0x5b01, 0x10},
> +	{0x5b02, 0x03},
> +	{0x5b03, 0xcf},
> +	{0x5b05, 0x6c},
> +	{0x5e00, 0x00},
> +	{0x5e10, 0xfc}
> +};
> +

It would be better if we could find the differences between the two arrays
and handle them incrementally.

[snip]

> +static int ov8856_update_otp_reg(struct ov8856 *ov8856)
> +{
> +	int ret;
> +
> +	ret = ov8856_write_reg(ov8856, OV8856_REG_MODE_SELECT,
> +			       OV8856_REG_VALUE_08BIT, OV8856_MODE_STREAMING);
> +	if (ret)
> +		return ret;
> +
> +	ret = ov8856_write_reg(ov8856, OV8856_OTP_REG_ONE,
> +			       OV8856_REG_VALUE_08BIT, OV8856_MODE_STANDBY);
> +	if (ret)
> +		return ret;
> +
> +	return ov8856_write_reg(ov8856, OV8856_OTP_REG_TWO,
> +				OV8856_REG_VALUE_08BIT, OV8856_MODE_STREAMING);

Hmm, this doesn't sound right. The OTP register doesn't have anything to do
with streaming. Also we should stop streaming at the end.

> +}
> +
>  static int ov8856_set_ctrl(struct v4l2_ctrl *ctrl)
>  {
>  	struct ov8856 *ov8856 = container_of(ctrl->handler,
> @@ -825,7 +1302,13 @@ static void ov8856_update_pad_format(const struct ov8856_mode *mode,
>  {
>  	fmt->width = mode->width;
>  	fmt->height = mode->height;
> -	fmt->code = MEDIA_BUS_FMT_SGRBG10_1X10;
> +
> +	/* Bayer Order is determined by image resolution */
> +	if (fmt->width == 3264 || fmt->width == 1632)

Could we instead set the bayer order in the mode struct?

> +		fmt->code = MEDIA_BUS_FMT_SBGGR10_1X10;
> +	else
> +		fmt->code = MEDIA_BUS_FMT_SGRBG10_1X10;
> +
>  	fmt->field = V4L2_FIELD_NONE;
>  }
>  
> @@ -850,6 +1333,17 @@ static int ov8856_start_streaming(struct ov8856 *ov8856)
>  		return ret;
>  	}
>  
> +	/* update R3614 for 1B module */

What's R3614?

> +	if (ov8856->is_1B_module) {
> +		ret = ov8856_write_reg(ov8856, OV8856_CLK_REG,
> +				       OV8856_REG_VALUE_08BIT,
> +				       OV8856_CLK_REG_1B_VAL);
> +		if (ret) {
> +			dev_err(&client->dev, "failed to set R3614");
> +			return ret;
> +		}
> +	}
> +
>  	ret = __v4l2_ctrl_handler_setup(ov8856->sd.ctrl_handler);
>  	if (ret)
>  		return ret;
> @@ -882,6 +1376,8 @@ static int ov8856_set_stream(struct v4l2_subdev *sd, int enable)
>  	if (ov8856->streaming == enable)
>  		return 0;
>  
> +	dev_dbg(&client->dev, "hardware version: (%d)\n", ov8856->is_1B_module);
> +
>  	mutex_lock(&ov8856->mutex);
>  	if (enable) {
>  		ret = pm_runtime_get_sync(&client->dev);
> @@ -908,6 +1404,54 @@ static int ov8856_set_stream(struct v4l2_subdev *sd, int enable)
>  	return ret;
>  }
>  
> +/* Calculate the delay in us by clock rate and clock cycles */
> +static inline u32 ov8856_cal_delay(u32 cycles)
> +{
> +	return DIV_ROUND_UP(cycles, OV8856_XVCLK_FREQ / 1000 / 1000);
> +}
> +
> +static int __ov8856_power_on(struct ov8856 *ov8856)
> +{
> +	int ret;
> +	u32 delay_us;
> +	struct i2c_client *client = v4l2_get_subdevdata(&ov8856->sd);
> +
> +	ret = clk_prepare_enable(ov8856->xvclk);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Failed to enable xvclk\n");
> +		return ret;
> +	}
> +
> +	gpiod_set_value_cansleep(ov8856->reset_gpio, 1);

According to my datasheet, this sensor doesn't have a reset pin. The one I
can see there is XSHUTDN, which I would call "n_shutdn" here.

> +
> +	ret = regulator_bulk_enable(OV8856_NUM_SUPPLIES, ov8856->supplies);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Failed to enable regulators\n");
> +		goto disable_clk;
> +	}
> +
> +	gpiod_set_value_cansleep(ov8856->reset_gpio, 0);

According to the datasheet, XSHUTDN should be 0 for shutdown and 1 for
running. Why is it the other way around here?

> +
> +	/* 8192 cycles prior to first SCCB transaction */
> +	delay_us = ov8856_cal_delay(8192);

If we pass a constant to the function and the function itself only uses
constants inside, could we just define a constant delay instead?

> +	usleep_range(delay_us  * 2, delay_us * 4);

Normally one one just give some small delta here, like +/- 100 us.

> +
> +	return 0;
> +
> +disable_clk:
> +	clk_disable_unprepare(ov8856->xvclk);
> +
> +	return ret;
> +}
> +
> +static void __ov8856_power_off(struct ov8856 *ov8856)
> +{
> +	clk_disable_unprepare(ov8856->xvclk);
> +	gpiod_set_value_cansleep(ov8856->reset_gpio, 1);
> +
> +	regulator_bulk_disable(OV8856_NUM_SUPPLIES, ov8856->supplies);
> +}
> +
>  static int __maybe_unused ov8856_suspend(struct device *dev)
>  {
>  	struct i2c_client *client = to_i2c_client(dev);
> @@ -915,8 +1459,8 @@ static int __maybe_unused ov8856_suspend(struct device *dev)
>  	struct ov8856 *ov8856 = to_ov8856(sd);
>  
>  	mutex_lock(&ov8856->mutex);
> -	if (ov8856->streaming)
> -		ov8856_stop_streaming(ov8856);
> +
> +	__ov8856_power_off(ov8856);

This change is incorrect because it will power off even if the device was
already powered off, causing reference count mismatch. The original code
was okay.

>  
>  	mutex_unlock(&ov8856->mutex);
>  
> @@ -1089,6 +1633,20 @@ static int ov8856_identify_module(struct ov8856 *ov8856)
>  		return -ENXIO;
>  	}
>  
> +	/* set R3614 to distinguish harward versions */

hardware

> +	ret = ov8856_update_otp_reg(ov8856);
> +	if (ret) {
> +		dev_err(&client->dev, "failed to set otp register");
> +		return ret;
> +	}
> +
> +	ret = ov8856_read_reg(ov8856, OV8856_OTP_REG,
> +			      OV8856_REG_VALUE_08BIT, &val);
> +	if (ret)
> +		return ret;
> +
> +	ov8856->is_1B_module = (val == OV8856_1B_MODULE) ? 1 : 0;

I'd rename ov8856_update_otp_reg() to ov8856_check_revision() and move the
few lines above to that function too.

> +
>  	return 0;
>  }
>  
> @@ -1164,11 +1722,27 @@ static int ov8856_remove(struct i2c_client *client)
>  	media_entity_cleanup(&sd->entity);
>  	v4l2_ctrl_handler_free(sd->ctrl_handler);
>  	pm_runtime_disable(&client->dev);
> +	if (!pm_runtime_status_suspended(&client->dev))
> +		__ov8856_power_off(ov8856);
> +	pm_runtime_set_suspended(&client->dev);
>  	mutex_destroy(&ov8856->mutex);
>  
>  	return 0;
>  }
>  
> +static int ov8856_configure_regulators(struct ov8856 *ov8856)
> +{
> +	struct i2c_client *client = v4l2_get_subdevdata(&ov8856->sd);
> +	int i;
> +
> +	for (i = 0; i < OV8856_NUM_SUPPLIES; i++)
> +		ov8856->supplies[i].supply = ov8856_supply_names[i];
> +
> +	return devm_regulator_bulk_get(&client->dev,
> +				       OV8856_NUM_SUPPLIES,
> +				       ov8856->supplies);
> +}

There is not much value in having a dedicated function just to call one
more function. Could you move back to the caller?

> +
>  static int ov8856_probe(struct i2c_client *client)
>  {
>  	struct ov8856 *ov8856;
> @@ -1186,6 +1760,40 @@ static int ov8856_probe(struct i2c_client *client)
>  		return -ENOMEM;
>  
>  	v4l2_i2c_subdev_init(&ov8856->sd, client, &ov8856_subdev_ops);
> +
> +	ov8856->xvclk = devm_clk_get(&client->dev, "xvclk");
> +	if (IS_ERR(ov8856->xvclk)) {
> +		dev_err(&client->dev, "Failed to get xvclk\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = clk_set_rate(ov8856->xvclk, OV8856_XVCLK_FREQ);

We should get the frequency from the DT bindings.

> +	if (ret < 0) {
> +		dev_err(&client->dev, "Failed to set xvclk rate (24MHz)\n");
> +		return ret;
> +	}
> +	if (clk_get_rate(ov8856->xvclk) != OV8856_XVCLK_FREQ)
> +		dev_warn(&client->dev,
> +			 "xvclk mismatched, modes are based on 24MHz\n");
> +
> +	ov8856->reset_gpio = devm_gpiod_get(&client->dev,
> +					    "reset",
> +					    GPIOD_OUT_LOW);
> +	if (IS_ERR(ov8856->reset_gpio)) {
> +		dev_err(&client->dev, "Failed to get reset-gpios\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = ov8856_configure_regulators(ov8856);
> +	if (ret) {
> +		dev_err(&client->dev, "Failed to get power regulators\n");
> +		return ret;
> +	}
> +
> +	ret = __ov8856_power_on(ov8856);
> +	if (ret)
> +		goto probe_error_v4l2_ctrl_handler_free;
> +
>  	ret = ov8856_identify_module(ov8856);
>  	if (ret) {
>  		dev_err(&client->dev, "failed to find sensor: %d", ret);
> @@ -1251,11 +1859,21 @@ static const struct acpi_device_id ov8856_acpi_ids[] = {
>  MODULE_DEVICE_TABLE(acpi, ov8856_acpi_ids);
>  #endif
>  
> +#if IS_ENABLED(CONFIG_OF)
> +static const struct of_device_id ov8856_of_match[] = {
> +	{ .compatible = "ovti,ov8856" },
> +	{},
> +};
> +

nit: Unnecessary blank line.

Best regards,
Tomasz

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