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Date:   Tue, 12 Dec 2023 00:15:33 +0200
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Mikhail Rudenko <mike.rudenko@gmail.com>
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Jacopo Mondi <jacopo@jmondi.org>,
        Tommaso Merciai <tommaso.merciai@amarulasolutions.com>,
        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
Message-ID: <20231211221533.GK27535@pendragon.ideasonboard.com>
References: <20231211175023.1680247-1-mike.rudenko@gmail.com>
 <20231211175023.1680247-13-mike.rudenko@gmail.com>
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In-Reply-To: <20231211175023.1680247-13-mike.rudenko@gmail.com>
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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);

-- 
Regards,

Laurent Pinchart