ipa: ipu3: Add support for IPU3 AEC/AGC algorithm

Implement basic auto-exposure (AE) and auto-gain (AG) correction functions.
The functions computeTargetExposure() and computeGain() are adapted from
the Raspberry Pi AGC implementation to suit the IPU3 structures, and
filtering is added to reduce visible stepsize when there are large
exposure changes.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 62 insertions, 0 deletions

diff --git a/src/ipa/ipu3/ipu3_agc.h b/src/ipa/ipu3/ipu3_agc.h
new file mode 100644
index 00000000..bfdf45d1
--- /dev/null
+++ b/src/ipa/ipu3/ipu3_agc.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Ideas On Board
+ *
+ * ipu3_agc.h - IPU3 AGC/AEC control algorithm
+ */
+#ifndef __LIBCAMERA_IPU3_AGC_H__
+#define __LIBCAMERA_IPU3_AGC_H__
+
+#include <array>
+#include <unordered_map>
+
+#include <linux/intel-ipu3.h>
+
+#include <libcamera/geometry.h>
+
+#include "libipa/algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::ipu3 {
+
+class IPU3Agc : public Algorithm
+{
+public:
+	IPU3Agc();
+	~IPU3Agc() = default;
+
+	void initialise(struct ipu3_uapi_grid_config &bdsGrid);
+	void process(const ipu3_uapi_stats_3a *stats, uint32_t &exposure, uint32_t &gain);
+	bool converged() { return converged_; }
+	bool updateControls() { return updateControls_; }
+	/* \todo Use a metadata exchange between IPAs */
+	double gamma() { return gamma_; }
+
+private:
+	void processBrightness(const ipu3_uapi_stats_3a *stats);
+	void filterExposure();
+	void lockExposureGain(uint32_t &exposure, uint32_t &gain);
+
+	struct ipu3_uapi_grid_config aeGrid_;
+
+	uint64_t frameCount_;
+	uint64_t lastFrame_;
+
+	bool converged_;
+	bool updateControls_;
+
+	double iqMean_;
+	double gamma_;
+
+	double prevExposure_;
+	double prevExposureNoDg_;
+	double currentExposure_;
+	double currentExposureNoDg_;
+};
+
+} /* namespace ipa::ipu3 */
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_IPU3_AGC_H__ */