[PATCH] ipa: rkisp1: Allow exposure time to be shorter than minimum frame duration limit

[Kieran Bingham]

Quoting Stefan Klug (2025-02-26 15:59:26)
> The minimum FrameDurationLimit also limits the min exposure time and
> results in overly bright AE regulation. Remove the limit on the minimum
> exposure time as the vertical blanking ensures the minimum frame
> duration limit.
> 
> Fixes: f72c76eb6e06 ("rkisp1: Honor the FrameDurationLimits control")
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>

Thanks, this is this is /very/ noticible here and the fix is very clear
(espcially thanks to the live graphs in camshark!)

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

> ---
>  src/ipa/rkisp1/algorithms/agc.cpp | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
> index 4e0e3734117e..5a3ba0131cf1 100644
> --- a/src/ipa/rkisp1/algorithms/agc.cpp
> +++ b/src/ipa/rkisp1/algorithms/agc.cpp
> @@ -526,9 +526,7 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
>         double maxAnalogueGain;
>  
>         if (frameContext.agc.autoExposureEnabled) {
> -               minExposureTime = std::clamp(frameContext.agc.minFrameDuration,
> -                                            context.configuration.sensor.minExposureTime,
> -                                            context.configuration.sensor.maxExposureTime);
> +               minExposureTime = context.configuration.sensor.minExposureTime;
>                 maxExposureTime = std::clamp(frameContext.agc.maxFrameDuration,
>                                              context.configuration.sensor.minExposureTime,
>                                              context.configuration.sensor.maxExposureTime);
> -- 
> 2.43.0
>