Re: [PATCH 14/21] media: i2c: imx258: Add support for long exposure modes

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Hi Dave

On Tue, May 30, 2023 at 06:29:53PM +0100, Dave Stevenson wrote:
> The sensor has a register CIT_LSHIFT which extends the exposure
> and frame times by the specified power of 2 for longer
> exposure times.
>
> Add support for this by configuring this register via V4L2_CID_VBLANK
> and extending the V4L2_CID_EXPOSURE range accordingly.
>
> Signed-off-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
> ---
>  drivers/media/i2c/imx258.c | 38 ++++++++++++++++++++++++++++++++------
>  1 file changed, 32 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/media/i2c/imx258.c b/drivers/media/i2c/imx258.c
> index f5199e3243e8..1e424058fcb9 100644
> --- a/drivers/media/i2c/imx258.c
> +++ b/drivers/media/i2c/imx258.c
> @@ -69,6 +69,10 @@
>  #define IMX258_HDR_RATIO_STEP		1
>  #define IMX258_HDR_RATIO_DEFAULT	0x0
>
> +/* Long exposure multiplier */
> +#define IMX258_LONG_EXP_SHIFT_MAX	7
> +#define IMX258_LONG_EXP_SHIFT_REG	0x3002
> +
>  /* Test Pattern Control */
>  #define IMX258_REG_TEST_PATTERN		0x0600
>
> @@ -629,6 +633,8 @@ struct imx258 {
>  	struct v4l2_ctrl *vblank;
>  	struct v4l2_ctrl *hblank;
>  	struct v4l2_ctrl *exposure;
> +	/* Current long exposure factor in use. Set through V4L2_CID_VBLANK */
> +	unsigned int long_exp_shift;
>
>  	/* Current mode */
>  	const struct imx258_mode *cur_mode;
> @@ -793,6 +799,26 @@ static void imx258_adjust_exposure_range(struct imx258 *imx258)
>  				 exposure_def);
>  }
>
> +static int imx258_set_frame_length(struct imx258 *imx258, unsigned int val)
> +{
> +	int ret;
> +
> +	imx258->long_exp_shift = 0;
> +
> +	while (val > IMX258_VTS_MAX) {
> +		imx258->long_exp_shift++;
> +		val >>= 1;
> +	}
> +
> +	ret = imx258_write_reg(imx258, IMX258_REG_VTS,
> +			       IMX258_REG_VALUE_16BIT, val);
> +	if (ret)
> +		return ret;
> +
> +	return imx258_write_reg(imx258, IMX258_LONG_EXP_SHIFT_REG,
> +				IMX258_REG_VALUE_08BIT, imx258->long_exp_shift);
> +}
> +
>  static int imx258_set_ctrl(struct v4l2_ctrl *ctrl)
>  {
>  	struct imx258 *imx258 =
> @@ -823,7 +849,7 @@ static int imx258_set_ctrl(struct v4l2_ctrl *ctrl)
>  	case V4L2_CID_EXPOSURE:
>  		ret = imx258_write_reg(imx258, IMX258_REG_EXPOSURE,
>  				IMX258_REG_VALUE_16BIT,
> -				ctrl->val);
> +				ctrl->val >> imx258->long_exp_shift);

Shouldn't this be done only if vblank > VTS_MAX ?

>  		break;
>  	case V4L2_CID_DIGITAL_GAIN:
>  		ret = imx258_update_digital_gain(imx258, IMX258_REG_VALUE_16BIT,
> @@ -855,9 +881,8 @@ static int imx258_set_ctrl(struct v4l2_ctrl *ctrl)
>  		}
>  		break;
>  	case V4L2_CID_VBLANK:
> -		ret = imx258_write_reg(imx258, IMX258_REG_VTS,
> -				       IMX258_REG_VALUE_16BIT,
> -				       imx258->cur_mode->height + ctrl->val);
> +		ret = imx258_set_frame_length(imx258,
> +					      imx258->cur_mode->height + ctrl->val);
>  		break;
>  	default:
>  		dev_info(&client->dev,
> @@ -983,8 +1008,9 @@ static int imx258_set_pad_format(struct v4l2_subdev *sd,
>  			     imx258->cur_mode->height;
>  		__v4l2_ctrl_modify_range(
>  			imx258->vblank, vblank_min,
> -			IMX258_VTS_MAX - imx258->cur_mode->height, 1,
> -			vblank_def);
> +			((1 << IMX258_LONG_EXP_SHIFT_MAX) * IMX258_VTS_MAX) -
> +						imx258->cur_mode->height,
> +			1, vblank_def);
>  		__v4l2_ctrl_s_ctrl(imx258->vblank, vblank_def);
>  		h_blank =
>  			imx258->link_freq_configs[mode->link_freq_index].pixels_per_line
> --
> 2.25.1
>



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