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

Mikhail Rudenko
2023-12-12T12:52:31Z

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