[libcamera-devel] [PATCH] ipa: raspberrypi: Limit minimum exposure time for the IMX296

[Jacopo Mondi]

Hi Naush

On Mon, Sep 26, 2022 at 10:36:39AM +0100, Naushir Patuck via libcamera-devel wrote:
> Limit the minimum allowable exposure time to a single line in the IMX296 camera
> helper. This equates to approximately 30us.
>
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>

Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>

Thanks
  j

> ---
>  src/ipa/raspberrypi/cam_helper_imx296.cpp | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/src/ipa/raspberrypi/cam_helper_imx296.cpp b/src/ipa/raspberrypi/cam_helper_imx296.cpp
> index 09f828ea6249..66d21e36ecd0 100644
> --- a/src/ipa/raspberrypi/cam_helper_imx296.cpp
> +++ b/src/ipa/raspberrypi/cam_helper_imx296.cpp
> @@ -26,6 +26,7 @@ public:
>  	void getDelays(int &exposureDelay, int &gainDelay, int &vblankDelay) const override;
>
>  private:
> +	static constexpr uint32_t minExposureLines = 1;
>  	static constexpr uint32_t maxGainCode = 239;
>  	static constexpr Duration timePerLine = 550.0 / 37.125e6 * 1.0s;
>
> @@ -54,12 +55,12 @@ double CamHelperImx296::gain(uint32_t gainCode) const
>
>  uint32_t CamHelperImx296::exposureLines(Duration exposure) const
>  {
> -	return (exposure - 14.26us) / timePerLine;
> +	return std::max<uint32_t>(minExposureLines, (exposure - 14.26us) / timePerLine);
>  }
>
>  Duration CamHelperImx296::exposure(uint32_t exposureLines) const
>  {
> -	return exposureLines * timePerLine + 14.26us;
> +	return std::max<uint32_t>(minExposureLines, exposureLines) * timePerLine + 14.26us;
>  }
>
>  void CamHelperImx296::getDelays(int &exposureDelay, int &gainDelay,
> --
> 2.25.1
>