ipa: ipu3: Introduce a modular tone mapping algorithm

Introduce a new algorithm to manage the tone mapping handling of the
IPU3.

The initial algorithm is chosen to configure the gamma contrast curve
which moves the implementation out of AWB for simplicity. As it is
initialised with a default gamma value of 1.1, there is no need to use
the default table at initialisation anymore.

This demonstrates the way to use process() call when the EventStatReady
comes in. The function calculates the LUT in the context of a frame, and
when prepare() is called, the parameters are filled with the updated
values.

AGC is modified to take the new process interface into account.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
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>

9 files changed, 116 insertions, 48 deletions

diff --git a/src/ipa/ipu3/algorithms/meson.build b/src/ipa/ipu3/algorithms/meson.build
index dc538b79..71eedfa4 100644
--- a/src/ipa/ipu3/algorithms/meson.build
+++ b/src/ipa/ipu3/algorithms/meson.build
@@ -2,4 +2,5 @@
 
 ipu3_ipa_algorithms = files([
     'algorithm.cpp',
+    'tone_mapping.cpp',
 ])
diff --git a/src/ipa/ipu3/algorithms/tone_mapping.cpp b/src/ipa/ipu3/algorithms/tone_mapping.cpp
new file mode 100644
index 00000000..3af96261
--- /dev/null
+++ b/src/ipa/ipu3/algorithms/tone_mapping.cpp
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Google inc.
+ *
+ * tone_mapping.cpp - IPU3 ToneMapping and Gamma control
+ */
+
+#include "tone_mapping.h"
+
+#include <cmath>
+#include <string.h>
+
+namespace libcamera {
+
+namespace ipa::ipu3::algorithms {
+
+ToneMapping::ToneMapping()
+	: gamma_(1.0)
+{
+}
+
+void ToneMapping::prepare([[maybe_unused]] IPAContext &context,
+			  ipu3_uapi_params *params)
+{
+	/* Copy the calculated LUT into the parameters buffer. */
+	memcpy(params->acc_param.gamma.gc_lut.lut,
+	       context.frameContext.toneMapping.gammaCorrection.lut,
+	       IPU3_UAPI_GAMMA_CORR_LUT_ENTRIES *
+	       sizeof(params->acc_param.gamma.gc_lut.lut[0]));
+
+	/* Enable the custom gamma table. */
+	params->use.acc_gamma = 1;
+	params->acc_param.gamma.gc_ctrl.enable = 1;
+}
+
+void ToneMapping::process([[maybe_unused]] IPAContext &context,
+			  [[maybe_unused]] const ipu3_uapi_stats_3a *stats)
+{
+	/*
+	 * Hardcode gamma to 1.1 as a default for now.
+	 *
+	 * \todo Expose gamma control setting through the libcamera control API
+	 */
+	gamma_ = 1.1;
+
+	struct ipu3_uapi_gamma_corr_lut &lut =
+		context.frameContext.toneMapping.gammaCorrection;
+
+	for (uint32_t i = 0; i < std::size(lut.lut); i++) {
+		double j = static_cast<double>(i) / (std::size(lut.lut) - 1);
+		double gamma = std::pow(j, 1.0 / gamma_);
+
+		/* The output value is expressed on 13 bits. */
+		lut.lut[i] = gamma * 8191;
+	}
+}
+
+} /* namespace ipa::ipu3::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/ipu3/algorithms/tone_mapping.h b/src/ipa/ipu3/algorithms/tone_mapping.h
new file mode 100644
index 00000000..1dae4f9a
--- /dev/null
+++ b/src/ipa/ipu3/algorithms/tone_mapping.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Google inc.
+ *
+ * tone_mapping.h - IPU3 ToneMapping and Gamma control
+ */
+#ifndef __LIBCAMERA_IPU3_ALGORITHMS_TONE_MAPPING_H__
+#define __LIBCAMERA_IPU3_ALGORITHMS_TONE_MAPPING_H__
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::ipu3::algorithms {
+
+class ToneMapping : public Algorithm
+{
+public:
+	ToneMapping();
+
+	void prepare(IPAContext &context, ipu3_uapi_params *params) override;
+	void process(IPAContext &context, const ipu3_uapi_stats_3a *stats) override;
+
+private:
+	double gamma_;
+};
+
+} /* namespace ipa::ipu3::algorithms */
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_IPU3_ALGORITHMS_TONE_MAPPING_H__ */
diff --git a/src/ipa/ipu3/ipa_context.h b/src/ipa/ipu3/ipa_context.h
index a031ab83..4b12f129 100644
--- a/src/ipa/ipu3/ipa_context.h
+++ b/src/ipa/ipu3/ipa_context.h
@@ -24,6 +24,9 @@ struct IPASessionConfiguration {
 };
 
 struct IPAFrameContext {
+	struct {
+		struct ipu3_uapi_gamma_corr_lut gammaCorrection;
+	} toneMapping;
 };
 
 struct IPAContext {
diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
index 4d5b0af1..3713b07b 100644
--- a/src/ipa/ipu3/ipu3.cpp
+++ b/src/ipa/ipu3/ipu3.cpp
@@ -30,6 +30,7 @@
 #include "libcamera/internal/mapped_framebuffer.h"
 
 #include "algorithms/algorithm.h"
+#include "algorithms/tone_mapping.h"
 #include "ipu3_agc.h"
 #include "ipu3_awb.h"
 #include "libipa/camera_sensor_helper.h"
@@ -91,6 +92,17 @@
  * \brief BDS output size configured by the pipeline handler
  */
 
+/**
+ * \struct IPAFrameContext::toneMapping
+ * \brief Context for ToneMapping and Gamma control
+ *
+ * \var IPAFrameContext::toneMapping::gammaCorrection
+ * \brief Per-pixel tone mapping implemented as a LUT
+ *
+ * The LUT structure is defined by the IPU3 kernel interface. See
+ * <linux/intel-ipu3.h> struct ipu3_uapi_gamma_corr_lut for further details.
+ */
+
 static constexpr uint32_t kMaxCellWidthPerSet = 160;
 static constexpr uint32_t kMaxCellHeightPerSet = 56;
 
@@ -225,6 +237,9 @@ int IPAIPU3::init(const IPASettings &settings,
 
 	*ipaControls = ControlInfoMap(std::move(controls), controls::controls);
 
+	/* Construct our Algorithms */
+	algorithms_.push_back(std::make_unique<algorithms::ToneMapping>());
+
 	return 0;
 }
 
@@ -423,7 +438,7 @@ void IPAIPU3::fillParams(unsigned int frame, ipu3_uapi_params *params)
 		algo->prepare(context_, &params_);
 
 	if (agcAlgo_->updateControls())
-		awbAlgo_->updateWbParameters(params_, agcAlgo_->gamma());
+		awbAlgo_->updateWbParameters(params_);
 
 	*params = params_;
 
diff --git a/src/ipa/ipu3/ipu3_agc.cpp b/src/ipa/ipu3/ipu3_agc.cpp
index 408eb849..20c2d3b4 100644
--- a/src/ipa/ipu3/ipu3_agc.cpp
+++ b/src/ipa/ipu3/ipu3_agc.cpp
@@ -52,7 +52,7 @@ static constexpr uint8_t kCellSize = 8;
 
 IPU3Agc::IPU3Agc()
 	: frameCount_(0), lastFrame_(0), converged_(false),
-	  updateControls_(false), iqMean_(0.0), gamma_(1.0),
+	  updateControls_(false), iqMean_(0.0),
 	  lineDuration_(0s), maxExposureTime_(0s),
 	  prevExposure_(0s), prevExposureNoDg_(0s),
 	  currentExposure_(0s), currentExposureNoDg_(0s)
@@ -104,9 +104,6 @@ void IPU3Agc::processBrightness(const ipu3_uapi_stats_3a *stats)
 		}
 	}
 
-	/* Limit the gamma effect for now */
-	gamma_ = 1.1;
-
 	/* Estimate the quantile mean of the top 2% of the histogram */
 	iqMean_ = Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0);
 }
diff --git a/src/ipa/ipu3/ipu3_agc.h b/src/ipa/ipu3/ipu3_agc.h
index f00b98d6..2d86127d 100644
--- a/src/ipa/ipu3/ipu3_agc.h
+++ b/src/ipa/ipu3/ipu3_agc.h
@@ -33,8 +33,6 @@ public:
 	void process(const ipu3_uapi_stats_3a *stats, uint32_t &exposure, double &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);
@@ -50,7 +48,6 @@ private:
 	bool updateControls_;
 
 	double iqMean_;
-	double gamma_;
 
 	Duration lineDuration_;
 	Duration maxExposureTime_;
diff --git a/src/ipa/ipu3/ipu3_awb.cpp b/src/ipa/ipu3/ipu3_awb.cpp
index 4bb321b3..c2d9e0c1 100644
--- a/src/ipa/ipu3/ipu3_awb.cpp
+++ b/src/ipa/ipu3/ipu3_awb.cpp
@@ -133,31 +133,6 @@ static const struct ipu3_uapi_ccm_mat_config imguCssCcmDefault = {
 	0, 0, 8191, 0
 };
 
-/* Default settings for Gamma correction */
-const struct ipu3_uapi_gamma_corr_lut imguCssGammaLut = { {
-	63, 79, 95, 111, 127, 143, 159, 175, 191, 207, 223, 239, 255, 271, 287,
-	303, 319, 335, 351, 367, 383, 399, 415, 431, 447, 463, 479, 495, 511,
-	527, 543, 559, 575, 591, 607, 623, 639, 655, 671, 687, 703, 719, 735,
-	751, 767, 783, 799, 815, 831, 847, 863, 879, 895, 911, 927, 943, 959,
-	975, 991, 1007, 1023, 1039, 1055, 1071, 1087, 1103, 1119, 1135, 1151,
-	1167, 1183, 1199, 1215, 1231, 1247, 1263, 1279, 1295, 1311, 1327, 1343,
-	1359, 1375, 1391, 1407, 1423, 1439, 1455, 1471, 1487, 1503, 1519, 1535,
-	1551, 1567, 1583, 1599, 1615, 1631, 1647, 1663, 1679, 1695, 1711, 1727,
-	1743, 1759, 1775, 1791, 1807, 1823, 1839, 1855, 1871, 1887, 1903, 1919,
-	1935, 1951, 1967, 1983, 1999, 2015, 2031, 2047, 2063, 2079, 2095, 2111,
-	2143, 2175, 2207, 2239, 2271, 2303, 2335, 2367, 2399, 2431, 2463, 2495,
-	2527, 2559, 2591, 2623, 2655, 2687, 2719, 2751, 2783, 2815, 2847, 2879,
-	2911, 2943, 2975, 3007, 3039, 3071, 3103, 3135, 3167, 3199, 3231, 3263,
-	3295, 3327, 3359, 3391, 3423, 3455, 3487, 3519, 3551, 3583, 3615, 3647,
-	3679, 3711, 3743, 3775, 3807, 3839, 3871, 3903, 3935, 3967, 3999, 4031,
-	4063, 4095, 4127, 4159, 4223, 4287, 4351, 4415, 4479, 4543, 4607, 4671,
-	4735, 4799, 4863, 4927, 4991, 5055, 5119, 5183, 5247, 5311, 5375, 5439,
-	5503, 5567, 5631, 5695, 5759, 5823, 5887, 5951, 6015, 6079, 6143, 6207,
-	6271, 6335, 6399, 6463, 6527, 6591, 6655, 6719, 6783, 6847, 6911, 6975,
-	7039, 7103, 7167, 7231, 7295, 7359, 7423, 7487, 7551, 7615, 7679, 7743,
-	7807, 7871, 7935, 7999, 8063, 8127, 8191
-} };
-
 IPU3Awb::IPU3Awb()
 	: Algorithm()
 {
@@ -197,10 +172,6 @@ void IPU3Awb::initialise(ipu3_uapi_params &params, const Size &bdsOutputSize, st
 	params.use.acc_ccm = 1;
 	params.acc_param.ccm = imguCssCcmDefault;
 
-	params.use.acc_gamma = 1;
-	params.acc_param.gamma.gc_lut = imguCssGammaLut;
-	params.acc_param.gamma.gc_ctrl.enable = 1;
-
 	zones_.reserve(kAwbStatsSizeX * kAwbStatsSizeY);
 }
 
@@ -350,7 +321,7 @@ void IPU3Awb::calculateWBGains(const ipu3_uapi_stats_3a *stats)
 	}
 }
 
-void IPU3Awb::updateWbParameters(ipu3_uapi_params &params, double agcGamma)
+void IPU3Awb::updateWbParameters(ipu3_uapi_params &params)
 {
 	/*
 	 * Green gains should not be touched and considered 1.
@@ -362,18 +333,10 @@ void IPU3Awb::updateWbParameters(ipu3_uapi_params &params, double agcGamma)
 	params.acc_param.bnr.wb_gains.b = 4096 * asyncResults_.blueGain;
 	params.acc_param.bnr.wb_gains.gb = 16;
 
-	LOG(IPU3Awb, Debug) << "Color temperature estimated: " << asyncResults_.temperatureK
-			    << " and gamma calculated: " << agcGamma;
+	LOG(IPU3Awb, Debug) << "Color temperature estimated: " << asyncResults_.temperatureK;
 
 	/* The CCM matrix may change when color temperature will be used */
 	params.acc_param.ccm = imguCssCcmDefault;
-
-	for (uint32_t i = 0; i < 256; i++) {
-		double j = i / 255.0;
-		double gamma = std::pow(j, 1.0 / agcGamma);
-		/* The maximum value 255 is represented on 13 bits in the IPU3 */
-		params.acc_param.gamma.gc_lut.lut[i] = gamma * 8191;
-	}
 }
 
 } /* namespace ipa::ipu3 */
diff --git a/src/ipa/ipu3/ipu3_awb.h b/src/ipa/ipu3/ipu3_awb.h
index ea2d4320..eeb2920b 100644
--- a/src/ipa/ipu3/ipu3_awb.h
+++ b/src/ipa/ipu3/ipu3_awb.h
@@ -31,7 +31,7 @@ public:
 
 	void initialise(ipu3_uapi_params &params, const Size &bdsOutputSize, struct ipu3_uapi_grid_config &bdsGrid);
 	void calculateWBGains(const ipu3_uapi_stats_3a *stats);
-	void updateWbParameters(ipu3_uapi_params &params, double agcGamma);
+	void updateWbParameters(ipu3_uapi_params &params);
 
 	struct Ipu3AwbCell {
 		unsigned char greenRedAvg;