ipa: rkisp1: Introduce AGC

Now that we have IPAContext and Algorithm, we can implement a simple AGC
based on the IPU3 one. It is very similar, except that there is no
histogram used for an inter quantile mean. The RkISP1 is returning a 5x5
array (for V10) of luminance means. Estimating the relative luminance is
thus a simple mean of all the blocks already calculated by the ISP.

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

src/ipa/rkisp1/algorithms/agc.h

@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Ideas On Board
+ *
+ * agc.h - RkISP1 AGC/AEC mean-based control algorithm
+ */
+
+#pragma once
+
+#include <linux/rkisp1-config.h>
+
+#include <libcamera/base/utils.h>
+
+#include <libcamera/geometry.h>
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+struct IPACameraSensorInfo;
+
+namespace ipa::rkisp1::algorithms {
+
+class Agc : public Algorithm
+{
+public:
+	Agc();
+	~Agc() = default;
+
+	int configure(IPAContext &context, const IPACameraSensorInfo &configInfo) override;
+	void process(IPAContext &context, const rkisp1_stat_buffer *stats) override;
+
+private:
+	void computeExposure(IPAContext &Context, double yGain);
+	utils::Duration filterExposure(utils::Duration exposureValue);
+	double estimateLuminance(const rkisp1_cif_isp_ae_stat *ae, double gain);
+
+	uint64_t frameCount_;
+
+	uint32_t numCells_;
+
+	utils::Duration filteredExposure_;
+};
+
+} /* namespace ipa::rkisp1::algorithms */
+} /* namespace libcamera */