[v6,13/16] ipa: mali-c55: agc: Quantise the ISP Digital Gain

25920 diff mbox series

The Mali-C55 ISP has a digital gain block which allows setting gain in Q5.8
format, a range of 0.0 to (very nearly) 32.0.

Convert usage to the new UQ<5, 8> FixedPoint Quantised type which will
support the conversion, clamping and quantisation so that the metadata
and debug prints can now report the effective gain applied instead of
the potentially inaccurate float.

As the UQ<5, 8> type already clamps values, remove the explicit
clamping.  This removes the clamping to a minimum of 1.0 gain, so we
rely on calculateNewEv to provide a valid gain.

Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

---
v5:
 - Use UQ<5, 8> type directly.
 - Use operator<< to report the UQ<5, 8> value.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 src/ipa/mali-c55/algorithms/agc.cpp | 18 +++++++++---------
 src/ipa/mali-c55/ipa_context.h      |  6 +++---
 2 files changed, 12 insertions(+), 12 deletions(-)

Hi Kieran,

Quoting Kieran Bingham (2026-01-21 18:37:32)
> The Mali-C55 ISP has a digital gain block which allows setting gain in Q5.8
> format, a range of 0.0 to (very nearly) 32.0.
> 
> Convert usage to the new UQ<5, 8> FixedPoint Quantised type which will
> support the conversion, clamping and quantisation so that the metadata
> and debug prints can now report the effective gain applied instead of
> the potentially inaccurate float.
> 
> As the UQ<5, 8> type already clamps values, remove the explicit
> clamping.  This removes the clamping to a minimum of 1.0 gain, so we
> rely on calculateNewEv to provide a valid gain.
> 
> Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>
> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> 
> ---
> v5:
>  - Use UQ<5, 8> type directly.
>  - Use operator<< to report the UQ<5, 8> value.
> 
> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> ---
>  src/ipa/mali-c55/algorithms/agc.cpp | 18 +++++++++---------
>  src/ipa/mali-c55/ipa_context.h      |  6 +++---
>  2 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/src/ipa/mali-c55/algorithms/agc.cpp b/src/ipa/mali-c55/algorithms/agc.cpp
> index 014fd12452ac..075717f44ea6 100644
> --- a/src/ipa/mali-c55/algorithms/agc.cpp
> +++ b/src/ipa/mali-c55/algorithms/agc.cpp
> @@ -38,8 +38,8 @@ static constexpr unsigned int kNumHistogramBins = 256;
>   * format, a range of 0.0 to (very nearly) 32.0. We clamp from 1.0 to the actual
>   * max value which is 8191 * 2^-8.
>   */
> -static constexpr double kMinDigitalGain = 1.0;
> -static constexpr double kMaxDigitalGain = 31.99609375;
> +static constexpr float kMinDigitalGain = 1.0;
> +static constexpr float kMaxDigitalGain = UQ<5, 8>::TraitsType::max;
>  
>  uint32_t AgcStatistics::decodeBinValue(uint16_t binVal)
>  {
> @@ -245,7 +245,7 @@ void Agc::fillGainParamBlock(IPAContext &context, IPAFrameContext &frameContext,
>                              MaliC55Params *params)
>  {
>         IPAActiveState &activeState = context.activeState;
> -       double gain;
> +       UQ<5, 8> gain;

I think this could benefit from a "using DigitalGainQ=UQ<5, 8>;"
declaration in ipa_context.h.

Otherwise looks good to me.

Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>

Cheers,
Stefan

>  
>         if (activeState.agc.autoEnabled)
>                 gain = activeState.agc.automatic.ispGain;
> @@ -253,7 +253,7 @@ void Agc::fillGainParamBlock(IPAContext &context, IPAFrameContext &frameContext,
>                 gain = activeState.agc.manual.ispGain;
>  
>         auto block = params->block<MaliC55Blocks::Dgain>();
> -       block->gain = floatingToFixedPoint<5, 8, uint16_t, double>(gain);
> +       block->gain = gain.quantized();
>  
>         frameContext.agc.ispGain = gain;
>  }
> @@ -358,7 +358,7 @@ void Agc::process(IPAContext &context,
>          */
>         uint32_t exposure = frameContext.agc.exposure;
>         double analogueGain = frameContext.agc.sensorGain;
> -       double digitalGain = frameContext.agc.ispGain;
> +       double digitalGain = frameContext.agc.ispGain.value();
>         double totalGain = analogueGain * digitalGain;
>         utils::Duration currentShutter = exposure * configuration.sensor.lineDuration;
>         utils::Duration effectiveExposureValue = currentShutter * totalGain;
> @@ -370,19 +370,19 @@ void Agc::process(IPAContext &context,
>                                activeState.agc.exposureMode, statistics_.yHist,
>                                effectiveExposureValue);
>  
> -       dGain = std::clamp(dGain, kMinDigitalGain, kMaxDigitalGain);
> +       UQ<5, 8> dGainQ = static_cast<float>(dGain);
>  
>         LOG(MaliC55Agc, Debug)
>                 << "Divided up shutter, analogue gain and digital gain are "
> -               << shutterTime << ", " << aGain << " and " << dGain;
> +               << shutterTime << ", " << aGain << " and " << dGainQ;
>  
>         activeState.agc.automatic.exposure = shutterTime / configuration.sensor.lineDuration;
>         activeState.agc.automatic.sensorGain = aGain;
> -       activeState.agc.automatic.ispGain = dGain;
> +       activeState.agc.automatic.ispGain = dGainQ;
>  
>         metadata.set(controls::ExposureTime, currentShutter.get<std::micro>());
>         metadata.set(controls::AnalogueGain, frameContext.agc.sensorGain);
> -       metadata.set(controls::DigitalGain, frameContext.agc.ispGain);
> +       metadata.set(controls::DigitalGain, frameContext.agc.ispGain.value());
>         metadata.set(controls::ColourTemperature, context.activeState.agc.temperatureK);
>  }
>  
> diff --git a/src/ipa/mali-c55/ipa_context.h b/src/ipa/mali-c55/ipa_context.h
> index 08f78e4f74ce..ac4b83773803 100644
> --- a/src/ipa/mali-c55/ipa_context.h
> +++ b/src/ipa/mali-c55/ipa_context.h
> @@ -41,12 +41,12 @@ struct IPAActiveState {
>                 struct {
>                         uint32_t exposure;
>                         double sensorGain;
> -                       double ispGain;
> +                       UQ<5, 8> ispGain;
>                 } automatic;
>                 struct {
>                         uint32_t exposure;
>                         double sensorGain;
> -                       double ispGain;
> +                       UQ<5, 8> ispGain;
>                 } manual;
>                 bool autoEnabled;
>                 uint32_t constraintMode;
> @@ -64,7 +64,7 @@ struct IPAFrameContext : public FrameContext {
>         struct {
>                 uint32_t exposure;
>                 double sensorGain;
> -               double ispGain;
> +               UQ<5, 8> ispGain;
>         } agc;
>  
>         struct {
> -- 
> 2.52.0
>