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References: <20231211175023.1680247-1-mike.rudenko@gmail.com>
 <20231211175023.1680247-13-mike.rudenko@gmail.com>
 <20231211221533.GK27535@pendragon.ideasonboard.com>
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From:   Mikhail Rudenko <mike.rudenko@gmail.com>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Jacopo Mondi <jacopo@jmondi.org>,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        Dave Stevenson <dave.stevenson@raspberrypi.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>
Subject: Re: [PATCH 12/19] media: i2c: ov4689: Implement digital gain control
Date:   Tue, 12 Dec 2023 15:52:19 +0300
In-reply-to: <20231211221533.GK27535@pendragon.ideasonboard.com>
Message-ID: <87cyvbpoqb.fsf@gmail.com>
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On 2023-12-12 at 00:15 +02, Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote:

> Hi Mikhail,
>
> Thank you for the patch.
>
> On Mon, Dec 11, 2023 at 08:50:15PM +0300, Mikhail Rudenko wrote:
>> The OV4689 sensor supports digital gain up to 16x. Implement
>> corresponding control in the driver. Default digital gain value is not
>> modified by this patch.
>>
>> Signed-off-by: Mikhail Rudenko <mike.rudenko@gmail.com>
>> ---
>>  drivers/media/i2c/ov4689.c | 16 ++++++++++++++--
>>  1 file changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/media/i2c/ov4689.c b/drivers/media/i2c/ov4689.c
>> index 62aeae43d749..ed0ce1b9e55b 100644
>> --- a/drivers/media/i2c/ov4689.c
>> +++ b/drivers/media/i2c/ov4689.c
>> @@ -35,6 +35,12 @@
>>  #define OV4689_GAIN_STEP		1
>>  #define OV4689_GAIN_DEFAULT		0x80
>>
>> +#define OV4689_REG_DIG_GAIN		CCI_REG16(0x352A)
>
> Lowercase for hex constatns please.
>
>> +#define OV4689_DIG_GAIN_MIN		1
>> +#define OV4689_DIG_GAIN_MAX		0x7fff
>> +#define OV4689_DIG_GAIN_STEP		1
>> +#define OV4689_DIG_GAIN_DEFAULT		0x800
>> +
>>  #define OV4689_REG_TEST_PATTERN		CCI_REG8(0x5040)
>>  #define OV4689_TEST_PATTERN_ENABLE	0x80
>>  #define OV4689_TEST_PATTERN_DISABLE	0x0
>> @@ -131,7 +137,6 @@ static const struct cci_reg_sequence ov4689_2688x1520_regs[] = {
>>
>>  	/* AEC PK */
>>  	{CCI_REG8(0x3503), 0x04}, /* AEC_MANUAL gain_input_as_sensor_gain_format = 1 */
>> -	{CCI_REG8(0x352a), 0x08}, /* DIG_GAIN_FRAC_LONG dig_gain_long[14:8] = 0x08 (2x) */
>
> Is the default value really x2 ? That's not very nice :-S
>
> It would be much nicer if the default value of the control mapped to x1,
> otherwise it's impossible for userspace to interpret the scale of the
> digital gain value in a generic way. I suppose that could break existing
> applications though, which isn't great.
>
> Out of curiosity, can you tell what SoC(s) you're using this sensor with
> ?
>
>>
>>  	/* ADC and analog control*/
>>  	{CCI_REG8(0x3603), 0x40},
>> @@ -622,6 +627,9 @@ static int ov4689_set_ctrl(struct v4l2_ctrl *ctrl)
>>  				OV4689_TIMING_FLIP_MASK,
>>  				val ? 0 : OV4689_TIMING_FLIP_BOTH, &ret);
>>  		break;
>> +	case V4L2_CID_DIGITAL_GAIN:
>> +		cci_write(regmap, OV4689_REG_DIG_GAIN, val, &ret);
>> +		break;
>>  	default:
>>  		dev_warn(dev, "%s Unhandled id:0x%x, val:0x%x\n",
>>  			 __func__, ctrl->id, val);
>> @@ -650,7 +658,7 @@ static int ov4689_initialize_controls(struct ov4689 *ov4689)
>>
>>  	handler = &ov4689->ctrl_handler;
>>  	mode = ov4689->cur_mode;
>> -	ret = v4l2_ctrl_handler_init(handler, 13);
>> +	ret = v4l2_ctrl_handler_init(handler, 14);
>>  	if (ret)
>>  		return ret;
>>
>> @@ -693,6 +701,10 @@ static int ov4689_initialize_controls(struct ov4689 *ov4689)
>>  	v4l2_ctrl_new_std(handler, &ov4689_ctrl_ops, V4L2_CID_VFLIP, 0, 1, 1, 0);
>>  	v4l2_ctrl_new_std(handler, &ov4689_ctrl_ops, V4L2_CID_HFLIP, 0, 1, 1, 0);
>>
>> +	v4l2_ctrl_new_std(handler, &ov4689_ctrl_ops, V4L2_CID_DIGITAL_GAIN,
>> +			  OV4689_DIG_GAIN_MIN, OV4689_DIG_GAIN_MAX,
>> +			  OV4689_DIG_GAIN_STEP, OV4689_DIG_GAIN_DEFAULT);
>> +
>>  	if (handler->error) {
>>  		ret = handler->error;
>>  		dev_err(ov4689->dev, "Failed to init controls(%d)\n", ret);


--
Best regards,
Mikhail Rudenko