[libcamera-devel] [PATCH 2/2] ipa: rkisp1: agc: Restore minimum analogue gain limit

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

On Mon, May 29, 2023 at 02:39:26PM +0200, Jacopo Mondi via libcamera-devel wrote:
> Commit a3178dd0391f ("ipa: rkisp1: agc: drop hard-coded analogue gain range")
> removed both minimum and maximum limits for the analogue gain value.
> 
> However, as some sensors can potentially have a minimum gain lower than
> 1.0, restore the check for the minimum limit.
> 
> Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> ---
>  src/ipa/rkisp1/algorithms/agc.cpp | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
> index a4e5500e72d6..e5aeb3426eff 100644
> --- a/src/ipa/rkisp1/algorithms/agc.cpp
> +++ b/src/ipa/rkisp1/algorithms/agc.cpp
> @@ -36,6 +36,9 @@ namespace ipa::rkisp1::algorithms {
> 
>  LOG_DEFINE_CATEGORY(RkISP1Agc)
> 
> +/* Minimum limit for analogue gain value */
> +static constexpr double kMinAnalogueGain = 1.0;
> +
>  /* \todo Honour the FrameDurationLimits control instead of hardcoding a limit */
>  static constexpr utils::Duration kMaxShutterSpeed = 60ms;
> 
> @@ -254,7 +257,8 @@ void Agc::computeExposure(IPAContext &context, IPAFrameContext &frameContext,
>  	utils::Duration maxShutterSpeed = std::min(configuration.sensor.maxShutterSpeed,
>  						   kMaxShutterSpeed);
> 
> -	double minAnalogueGain = configuration.sensor.minAnalogueGain;
> +	double minAnalogueGain = std::max(configuration.sensor.minAnalogueGain,
> +					  kMinAnalogueGain);
>  	double maxAnalogueGain = configuration.sensor.maxAnalogueGain;
> 
>  	/* Consider within 1% of the target as correctly exposed. */

-- 
Regards,

Laurent Pinchart