Re: [PATCH 12/19] media: i2c: ov4689: Implement digital gain control

Laurent Pinchart
2023-12-11T22:15:28Z

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