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diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
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+++ b/src/ipa/ipu3/algorithms/agc.cpp
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+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Ideas On Board
+ *
+ * ipu3_agc.cpp - AGC/AEC control algorithm
+ */
+
+#include "agc.h"
+
+#include <algorithm>
+#include <chrono>
+#include <cmath>
+
+#include <libcamera/base/log.h>
+
+#include <libcamera/ipa/core_ipa_interface.h>
+
+#include "libipa/histogram.h"
+
+namespace libcamera {
+
+using namespace std::literals::chrono_literals;
+
+namespace ipa::ipu3::algorithms {
+
+LOG_DEFINE_CATEGORY(IPU3Agc)
+
+/* Number of frames to wait before calculating stats on minimum exposure */
+static constexpr uint32_t kInitialFrameMinAECount = 4;
+/* Number of frames to wait between new gain/exposure estimations */
+static constexpr uint32_t kFrameSkipCount = 6;
+
+/* Maximum ISO value for analogue gain */
+static constexpr uint32_t kMinISO = 100;
+static constexpr uint32_t kMaxISO = 1500;
+
+/* Maximum analogue gain value
+ * \todo grab it from a camera helper */
+static constexpr uint32_t kMinGain = kMinISO / 100;
+static constexpr uint32_t kMaxGain = kMaxISO / 100;
+
+/* \todo use calculated value based on sensor */
+static constexpr uint32_t kMinExposure = 1;
+static constexpr uint32_t kMaxExposure = 1976;
+
+/* Histogram constants */
+static constexpr uint32_t knumHistogramBins = 256;
+static constexpr double kEvGainTarget = 0.5;
+
+/* A cell is 8 bytes and contains averages for RGB values and saturation ratio */
+static constexpr uint8_t kCellSize = 8;
+
+Agc::Agc()
+	: frameCount_(0), lastFrame_(0), iqMean_(0.0), lineDuration_(0s),
+	  maxExposureTime_(0s), prevExposure_(0s), prevExposureNoDg_(0s),
+	  currentExposure_(0s), currentExposureNoDg_(0s)
+{
+}
+
+int Agc::configure(IPAContext &context, const IPAConfigInfo &configInfo)
+{
+	aeGrid_ = context.configuration.grid.bdsGrid;
+
+	lineDuration_ = configInfo.sensorInfo.lineLength * 1.0s
+		      / configInfo.sensorInfo.pixelRate;
+	maxExposureTime_ = kMaxExposure * lineDuration_;
+
+	return 0;
+}
+
+void Agc::processBrightness(const ipu3_uapi_stats_3a *stats)
+{
+	const struct ipu3_uapi_grid_config statsAeGrid = stats->stats_4a_config.awb_config.grid;
+	Rectangle aeRegion = { statsAeGrid.x_start,
+			       statsAeGrid.y_start,
+			       static_cast<unsigned int>(statsAeGrid.x_end - statsAeGrid.x_start) + 1,
+			       static_cast<unsigned int>(statsAeGrid.y_end - statsAeGrid.y_start) + 1 };
+	Point topleft = aeRegion.topLeft();
+	int topleftX = topleft.x >> aeGrid_.block_width_log2;
+	int topleftY = topleft.y >> aeGrid_.block_height_log2;
+
+	/* Align to the grid cell width and height */
+	uint32_t startX = topleftX << aeGrid_.block_width_log2;
+	uint32_t startY = topleftY * aeGrid_.width << aeGrid_.block_width_log2;
+	uint32_t endX = (startX + (aeRegion.size().width >> aeGrid_.block_width_log2)) << aeGrid_.block_width_log2;
+	uint32_t i, j;
+	uint32_t count = 0;
+
+	uint32_t hist[knumHistogramBins] = { 0 };
+	for (j = topleftY;
+	     j < topleftY + (aeRegion.size().height >> aeGrid_.block_height_log2);
+	     j++) {
+		for (i = startX + startY; i < endX + startY; i += kCellSize) {
+			/*
+			 * The grid width (and maybe height) is not reliable.
+			 * We observed a bit shift which makes the value 160 to be 32 in the stats grid.
+			 * Use the one passed at init time.
+			 */
+			if (stats->awb_raw_buffer.meta_data[i + 4 + j * aeGrid_.width] == 0) {
+				uint8_t Gr = stats->awb_raw_buffer.meta_data[i + 0 + j * aeGrid_.width];
+				uint8_t Gb = stats->awb_raw_buffer.meta_data[i + 3 + j * aeGrid_.width];
+				hist[(Gr + Gb) / 2]++;
+				count++;
+			}
+		}
+	}
+
+	/* Estimate the quantile mean of the top 2% of the histogram */
+	iqMean_ = Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0);
+}
+
+void Agc::filterExposure()
+{
+	double speed = 0.2;
+	if (prevExposure_ == 0s) {
+		/* DG stands for digital gain.*/
+		prevExposure_ = currentExposure_;
+		prevExposureNoDg_ = currentExposureNoDg_;
+	} else {
+		/*
+		 * If we are close to the desired result, go faster to avoid making
+		 * multiple micro-adjustments.
+		 * \ todo: Make this customisable?
+		 */
+		if (prevExposure_ < 1.2 * currentExposure_ &&
+		    prevExposure_ > 0.8 * currentExposure_)
+			speed = sqrt(speed);
+
+		prevExposure_ = speed * currentExposure_ +
+				prevExposure_ * (1.0 - speed);
+		prevExposureNoDg_ = speed * currentExposureNoDg_ +
+				prevExposureNoDg_ * (1.0 - speed);
+	}
+	/*
+	 * We can't let the no_dg exposure deviate too far below the
+	 * total exposure, as there might not be enough digital gain available
+	 * in the ISP to hide it (which will cause nasty oscillation).
+	 */
+	double fastReduceThreshold = 0.4;
+	if (prevExposureNoDg_ <
+	    prevExposure_ * fastReduceThreshold)
+		prevExposureNoDg_ = prevExposure_ * fastReduceThreshold;
+	LOG(IPU3Agc, Debug) << "After filtering, total_exposure " << prevExposure_;
+}
+
+void Agc::lockExposureGain(uint32_t &exposure, double &gain)
+{
+	/* Algorithm initialization should wait for first valid frames */
+	/* \todo - have a number of frames given by DelayedControls ?
+	 * - implement a function for IIR */
+	if ((frameCount_ < kInitialFrameMinAECount) || (frameCount_ - lastFrame_ < kFrameSkipCount))
+		return;
+
+	/* Are we correctly exposed ? */
+	if (std::abs(iqMean_ - kEvGainTarget * knumHistogramBins) <= 1) {
+		LOG(IPU3Agc, Debug) << "!!! Good exposure with iqMean = " << iqMean_;
+	} else {
+		double newGain = kEvGainTarget * knumHistogramBins / iqMean_;
+
+		/* extracted from Rpi::Agc::computeTargetExposure */
+		libcamera::utils::Duration currentShutter = exposure * lineDuration_;
+		currentExposureNoDg_ = currentShutter * gain;
+		LOG(IPU3Agc, Debug) << "Actual total exposure " << currentExposureNoDg_
+				    << " Shutter speed " << currentShutter
+				    << " Gain " << gain;
+		currentExposure_ = currentExposureNoDg_ * newGain;
+		libcamera::utils::Duration maxTotalExposure = maxExposureTime_ * kMaxGain;
+		currentExposure_ = std::min(currentExposure_, maxTotalExposure);
+		LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_;
+
+		/* \todo: estimate if we need to desaturate */
+		filterExposure();
+
+		libcamera::utils::Duration newExposure = 0.0s;
+		if (currentShutter < maxExposureTime_) {
+			exposure = std::clamp(static_cast<uint32_t>(exposure * currentExposure_ / currentExposureNoDg_), kMinExposure, kMaxExposure);
+			newExposure = currentExposure_ / exposure;
+			gain = std::clamp(static_cast<uint32_t>(gain * currentExposure_ / newExposure), kMinGain, kMaxGain);
+		} else if (currentShutter >= maxExposureTime_) {
+			gain = std::clamp(static_cast<uint32_t>(gain * currentExposure_ / currentExposureNoDg_), kMinGain, kMaxGain);
+			newExposure = currentExposure_ / gain;
+			exposure = std::clamp(static_cast<uint32_t>(exposure * currentExposure_ / newExposure), kMinExposure, kMaxExposure);
+		}
+		LOG(IPU3Agc, Debug) << "Adjust exposure " << exposure * lineDuration_ << " and gain " << gain;
+	}
+	lastFrame_ = frameCount_;
+}
+
+void Agc::process(IPAContext &context, const ipu3_uapi_stats_3a *stats)
+{
+	uint32_t &exposure = context.frameContext.agc.exposure;
+	double &gain = context.frameContext.agc.gain;
+	processBrightness(stats);
+	lockExposureGain(exposure, gain);
+	frameCount_++;
+}
+
+} /* namespace ipa::ipu3::algorithms */
+
+} /* namespace libcamera */