[PATCH v2 1/3] ipa: rkisp1: agc: Read histogram weights from tuning file

[Paul Elder]

Add support to the rkisp1 AGC to read histogram weights from the tuning
file. As controls for selecting the metering mode are not yet supported,
for now hardcode the matrix metering mode, which is the same as what the
AGC previously hardcoded.

Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>

---
Changes in v2:
- add default metering mode if none are read successfully from the
  tuning file
- compute the predivider instead of using a table
---
 src/ipa/rkisp1/algorithms/agc.cpp | 99 ++++++++++++++++++++++++++++++-
 src/ipa/rkisp1/algorithms/agc.h   |  6 ++
 2 files changed, 102 insertions(+), 3 deletions(-)

diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
index 5aad5c7c..4fc06277 100644
--- a/src/ipa/rkisp1/algorithms/agc.cpp
+++ b/src/ipa/rkisp1/algorithms/agc.cpp
@@ -17,6 +17,8 @@
 #include <libcamera/control_ids.h>
 #include <libcamera/ipa/core_ipa_interface.h>
 
+#include "libcamera/internal/yaml_parser.h"
+
 #include "libipa/histogram.h"
 
 /**
@@ -36,6 +38,81 @@ namespace ipa::rkisp1::algorithms {
 
 LOG_DEFINE_CATEGORY(RkISP1Agc)
 
+int Agc::parseMeteringModes(IPAContext &context, const YamlObject &tuningData,
+			    const char *prop)
+{
+	const YamlObject &yamlMeteringModes = tuningData[prop];
+	if (!yamlMeteringModes.isDictionary()) {
+		LOG(RkISP1Agc, Error)
+			<< "'" << prop << "' parameter not found in tuning file";
+		return -EINVAL;
+	}
+
+	for (const auto &[key, value] : yamlMeteringModes.asDict()) {
+		if (controls::AeMeteringModeNameValueMap.find(key) ==
+		    controls::AeMeteringModeNameValueMap.end()) {
+			LOG(RkISP1Agc, Warning)
+				<< "Skipping unknown metering mode '" << key << "'";
+			continue;
+		}
+
+		std::vector<uint8_t> weights =
+			value.getList<uint8_t>().value_or(std::vector<uint8_t>{});
+		if (weights.size() != context.hw->numHistogramWeights) {
+			LOG(RkISP1Agc, Error)
+				<< "Invalid '" << key << "' values: expected "
+				<< context.hw->numHistogramWeights
+				<< " elements, got " << weights.size();
+			return -ENODATA;
+		}
+
+		meteringModes_[controls::AeMeteringModeNameValueMap.at(key)] = weights;
+	}
+
+	if (meteringModes_.empty()) {
+		int32_t meteringModeId = controls::AeMeteringModeNameValueMap.at("MeteringMatrix");
+		std::vector<uint8_t> weights = {
+			1, 1, 1, 1, 1,
+			1, 1, 1, 1, 1,
+			1, 1, 1, 1, 1,
+			1, 1, 1, 1, 1,
+			1, 1, 1, 1, 1,
+		};
+
+		meteringModes_[meteringModeId] = weights;
+	}
+
+	return 0;
+}
+
+uint8_t Agc::predivider(Size &size)
+{
+	/*
+	 * The maximum number of pixels that could potentially be in one bin is
+	 * if all the pixels of the image are in it, multiplied by 3 for the
+	 * three color channels. The counter for each bin is 16 bits wide, so
+	 * `factor` thus contains the number of times we'd wrap around. This is
+	 * obviously the number of pixels that we need to skip to make sure
+	 * that we don't wrap around, but we compute the square root of it
+	 * instead, as the skip that we need to program is for both the x and y
+	 * directions.
+	 *
+	 * There's a bit of extra rounding math to make sure the rounding goes
+	 * the correct direction so that the square of the step is big enough
+	 * to encompass the `factor` number of pixels that we need to skip.
+	 */
+	double factor = size.width * size.height * 3 / 65535.0;
+	double root = std::sqrt(factor);
+	uint8_t ret;
+
+	if (std::pow(std::floor(root), 2) + 0.01 < factor)
+		ret = static_cast<uint8_t>(std::ceil(root));
+	else
+		ret = static_cast<uint8_t>(std::floor(root));
+
+	return std::clamp<uint8_t>(ret, 3, 127);
+}
+
 Agc::Agc()
 {
 	supportsRaw_ = true;
@@ -59,6 +136,10 @@ int Agc::init(IPAContext &context, const YamlObject &tuningData)
 	if (ret)
 		return ret;
 
+	ret = parseMeteringModes(context, tuningData, "AeMeteringMode");
+	if (ret)
+		return ret;
+
 	context.ctrlMap.merge(controls());
 
 	return 0;
@@ -160,6 +241,7 @@ void Agc::prepare(IPAContext &context, const uint32_t frame,
 		frameContext.agc.gain = context.activeState.agc.automatic.gain;
 	}
 
+	/* \todo Remove this when we can set the below with controls */
 	if (frame > 0)
 		return;
 
@@ -178,14 +260,25 @@ void Agc::prepare(IPAContext &context, const uint32_t frame,
 	params->meas.hst_config.meas_window = context.configuration.agc.measureWindow;
 	/* Produce the luminance histogram. */
 	params->meas.hst_config.mode = RKISP1_CIF_ISP_HISTOGRAM_MODE_Y_HISTOGRAM;
+
 	/* Set an average weighted histogram. */
 	Span<uint8_t> weights{
 		params->meas.hst_config.hist_weight,
 		context.hw->numHistogramWeights
 	};
-	std::fill(weights.begin(), weights.end(), 1);
-	/* Step size can't be less than 3. */
-	params->meas.hst_config.histogram_predivider = 4;
+	/* \todo Get this from control */
+	std::vector<uint8_t> &modeWeights = meteringModes_.at(controls::MeteringMatrix);
+	std::copy(modeWeights.begin(), modeWeights.end(), weights.begin());
+
+	std::stringstream str;
+	str << "Histogram weights : ";
+	for (size_t i = 0; i < context.hw->numHistogramWeights; i++)
+		str << (int)params->meas.hst_config.hist_weight[i] << " ";
+	LOG(RkISP1Agc, Debug) << str.str();
+
+	/* \todo Add a control for this? */
+	params->meas.hst_config.histogram_predivider =
+		predivider(context.configuration.sensor.size);
 
 	/* Update the configuration for histogram. */
 	params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_HST;
diff --git a/src/ipa/rkisp1/algorithms/agc.h b/src/ipa/rkisp1/algorithms/agc.h
index f2f5b59d..77d94423 100644
--- a/src/ipa/rkisp1/algorithms/agc.h
+++ b/src/ipa/rkisp1/algorithms/agc.h
@@ -44,11 +44,17 @@ public:
 		     ControlList &metadata) override;
 
 private:
+	int parseMeteringModes(IPAContext &context, const YamlObject &tuningData,
+			       const char *prop);
+	uint8_t predivider(Size &size);
+
 	void fillMetadata(IPAContext &context, IPAFrameContext &frameContext,
 			  ControlList &metadata);
 	double estimateLuminance(double gain) const override;
 
 	Span<const uint8_t> expMeans_;
+
+	std::map<int32_t, std::vector<uint8_t>> meteringModes_;
 };
 
 } /* namespace ipa::rkisp1::algorithms */
-- 
2.39.2