ipa: ipu3: agc: Refactor condition on exposure correction

Simplify the reading by removing one level of indentation to return
early when the change is small between two calls.

Reword the LOG() message when we are correctly exposed, and move the
lastFrame_ variable to update it even if the change is small.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 48 insertions, 45 deletions

diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index 43ef89df..feee7939 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -138,61 +138,64 @@ void Agc::lockExposureGain(uint32_t &exposure, double &analogueGain)
 	if ((frameCount_ < kInitialFrameMinAECount) || (frameCount_ - lastFrame_ < kFrameSkipCount))
 		return;
 
+	lastFrame_ = frameCount_;
+
 	/* Are we correctly exposed ? */
 	if (std::abs(iqMean_ - kEvGainTarget * knumHistogramBins) <= 1) {
-		LOG(IPU3Agc, Debug) << "!!! Good exposure with iqMean = " << iqMean_;
-	} else {
-		double evGain = kEvGainTarget * knumHistogramBins / iqMean_;
+		LOG(IPU3Agc, Debug) << "We are well exposed (iqMean = "
+				    << iqMean_ << ")";
+		return;
+	}
 
-		/* extracted from Rpi::Agc::computeTargetExposure */
-		utils::Duration currentShutter = exposure * lineDuration_;
-		currentExposureNoDg_ = currentShutter * analogueGain;
-		LOG(IPU3Agc, Debug) << "Actual total exposure " << currentExposureNoDg_
-				    << " Shutter speed " << currentShutter
-				    << " Gain " << analogueGain
-				    << " Needed ev gain " << evGain;
+	double evGain = kEvGainTarget * knumHistogramBins / iqMean_;
 
-		currentExposure_ = prevExposureValue_ * evGain;
-		utils::Duration minShutterSpeed = minExposureLines_ * lineDuration_;
-		utils::Duration maxShutterSpeed = maxExposureLines_ * lineDuration_;
+	/* extracted from Rpi::Agc::computeTargetExposure */
+	utils::Duration currentShutter = exposure * lineDuration_;
+	currentExposureNoDg_ = currentShutter * analogueGain;
+	LOG(IPU3Agc, Debug) << "Actual total exposure " << currentExposureNoDg_
+			    << " Shutter speed " << currentShutter
+			    << " Gain " << analogueGain
+			    << " Needed ev gain " << evGain;
 
-		utils::Duration maxTotalExposure = maxShutterSpeed * kMaxGain;
-		currentExposure_ = std::min(currentExposure_, maxTotalExposure);
-		LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
-				    << ", maximum is " << maxTotalExposure;
+	currentExposure_ = prevExposureValue_ * evGain;
+	utils::Duration minShutterSpeed = minExposureLines_ * lineDuration_;
+	utils::Duration maxShutterSpeed = maxExposureLines_ * lineDuration_;
 
-		/* \todo: estimate if we need to desaturate */
-		filterExposure();
+	utils::Duration maxTotalExposure = maxShutterSpeed * kMaxGain;
+	currentExposure_ = std::min(currentExposure_, maxTotalExposure);
+	LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
+			    << ", maximum is " << maxTotalExposure;
 
-		utils::Duration exposureValue = filteredExposure_;
-		utils::Duration shutterTime = minShutterSpeed;
+	/* \todo: estimate if we need to desaturate */
+	filterExposure();
 
-		/*
-		 * Push the shutter time up to the maximum first, and only then
-		 * increase the gain.
-		 */
-		shutterTime = std::clamp<utils::Duration>(exposureValue / kMinGain,
-							  minShutterSpeed, maxShutterSpeed);
-		double stepGain = std::clamp(exposureValue / shutterTime,
-					     kMinGain, kMaxGain);
-		LOG(IPU3Agc, Debug) << "Divided up shutter and gain are "
-				    << shutterTime << " and "
-				    << stepGain;
+	utils::Duration exposureValue = filteredExposure_;
+	utils::Duration shutterTime = minShutterSpeed;
 
-		exposure = shutterTime / lineDuration_;
-		analogueGain = stepGain;
+	/*
+	* Push the shutter time up to the maximum first, and only then
+	* increase the gain.
+	*/
+	shutterTime = std::clamp<utils::Duration>(exposureValue / kMinGain,
+						  minShutterSpeed, maxShutterSpeed);
+	double stepGain = std::clamp(exposureValue / shutterTime,
+				     kMinGain, kMaxGain);
+	LOG(IPU3Agc, Debug) << "Divided up shutter and gain are "
+			    << shutterTime << " and "
+			    << stepGain;
+
+	exposure = shutterTime / lineDuration_;
+	analogueGain = stepGain;
 
-		/*
-		 * Update the exposure value for the next process call.
-		 *
-		 * \todo Obtain the values of the exposure time and analog gain
-		 * that were actually used by the sensor, either from embedded
-		 * data when available, or from the delayed controls
-		 * infrastructure in case a slow down caused a mismatch.
-		 */
-		prevExposureValue_ = shutterTime * analogueGain;
-	}
-	lastFrame_ = frameCount_;
+	/*
+	 * Update the exposure value for the next process call.
+	 *
+	 * \todo Obtain the values of the exposure time and analog gain
+	 * that were actually used by the sensor, either from embedded
+	 * data when available, or from the delayed controls
+	 * infrastructure in case a slow down caused a mismatch.
+	 */
+	prevExposureValue_ = shutterTime * analogueGain;
 }
 
 void Agc::process(IPAContext &context, const ipu3_uapi_stats_3a *stats)