Re: [PATCH v2 6/8] media: i2c: ov9282: recalculate strobe span on HBLANK change

[Dave Stevenson]

On Wed, 14 Oct 2026 at 07:49, Richard Leitner <richard.leitner@xxxxxxxxx> wrote:
>
> When HBLANK changes the line time changes. This means the time base for
> the strobe duration calculation changed. This results in the v4l2
> strobe_duration control value and the strobe_span register value being
> out of sync.
>
> Fix this by recalculating the strobe_span register value on HBLANK
> writes using the currently configured strobe_duration. This results in
> the strobe_duration configured by userspace being kept, but the
> underlying register value being changed. To ensure the values are
> applied on the same frame guard the writes with OV9282_REG_HOLD.

Group hold will do what is intended, but if control updates from
userspace for eg gain and exposure generally get too widely spread
then, we've got much bigger problems.

Reviewed-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>

> Fixes: 84ec7597ae1af ("media: i2c: ov9282: add strobe_duration v4l2 control")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Richard Leitner <richard.leitner@xxxxxxxxx>
> ---
>  drivers/media/i2c/ov9282.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> index b48c959b9c908..5114fbf28a26c 100644
> --- a/drivers/media/i2c/ov9282.c
> +++ b/drivers/media/i2c/ov9282.c
> @@ -625,6 +625,7 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
>         u32 exposure;
>         u32 lpfr;
>         int ret;
> +       int ret_hold;
>
>         switch (ctrl->id) {
>         case V4L2_CID_VBLANK:
> @@ -677,8 +678,14 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
>                                       OV9282_FLIP_BIT, ctrl->val ? OV9282_FLIP_BIT : 0, NULL);
>                 break;
>         case V4L2_CID_HBLANK:
> -               ret = cci_write(ov9282->regmap, OV9282_REG_TIMING_HTS,
> -                               (ctrl->val + ov9282->cur_mode->width) >> 1, NULL);
> +               ret = cci_write(ov9282->regmap, OV9282_REG_HOLD, 0x01, NULL);
> +               cci_write(ov9282->regmap, OV9282_REG_TIMING_HTS,
> +                         (ctrl->val + ov9282->cur_mode->width) >> 1, &ret);
> +               cci_write(ov9282->regmap, OV9282_REG_STROBE_FRAME_SPAN,
> +                         ov9282_us_to_lines(ov9282, ov9282->flash_duration->cur.val),
> +                         &ret);
> +               ret_hold = cci_write(ov9282->regmap, OV9282_REG_HOLD, 0, NULL);
> +               ret = ret ? ret : ret_hold;
>                 break;
>         case V4L2_CID_FLASH_STROBE_OE:
>                 ret = cci_update_bits(ov9282->regmap, OV9282_REG_OUTPUT_ENABLE6,
>
> --
> 2.53.0
>
>