[PATCH] ipa: rpi: Fix wrong frame integration difference value for OV9281

[Kieran Bingham]

Quoting Naushir Patuck (2024-12-09 10:47:23)
> The frameIntegrationDiff value should be 25, otherwise we see invalid
> frames when integration times are set to large values.
> 
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> ---
>  src/ipa/rpi/cam_helper/cam_helper_ov9281.cpp | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/ipa/rpi/cam_helper/cam_helper_ov9281.cpp b/src/ipa/rpi/cam_helper/cam_helper_ov9281.cpp
> index a65c8ac08c1c..96f7fff499f5 100644
> --- a/src/ipa/rpi/cam_helper/cam_helper_ov9281.cpp
> +++ b/src/ipa/rpi/cam_helper/cam_helper_ov9281.cpp
> @@ -25,7 +25,7 @@ private:
>          * Smallest difference between the frame length and integration time,
>          * in units of lines.
>          */
> -       static constexpr int frameIntegrationDiff = 4;
> +       static constexpr int frameIntegrationDiff = 25;

Aha, quite helpfully - Laurent just pointed out to me that this is
specified in the datasheet as

0x3502 EXPO 0x00 RW

Bit[7:0]: Exposure[7:0]
	Low 4 bits are fraction bits

Minimum exposure time is 1 row period.
Maximum exposure time is frame length -25 row
	periods, where frame length is set by registers
	{0x380E, 0x380F}

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


>  };
>  
>  /*
> -- 
> 2.43.0
>