ipa: rkisp1: agc: Read histogram weights from tuning file

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@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>

Author: Rahi374

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 +38,85 @@ namespace ipa::rkisp1::algorithms {
 
 LOG_DEFINE_CATEGORY(RkISP1Agc)
 
+int Agc::parseMeteringModes(IPAContext &context, const YamlObject &tuningData)
+{
+	if (!tuningData.isDictionary()) {
+		LOG(RkISP1Agc, Error)
+			<< "'AeMeteringMode' parameter not found in tuning file";
+		return -EINVAL;
+	}
+
+	for (const auto &[key, value] : tuningData.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, Warning)
+				<< "Failed to read metering mode'" << key << "'";
+			continue;
+		}
+
+		meteringModes_[controls::AeMeteringModeNameValueMap.at(key)] = weights;
+	}
+
+	if (meteringModes_.empty()) {
+		LOG(RkISP1Agc, Warning)
+			<< "No metering modes read from tuning file; defaulting to matrix";
+		int32_t meteringModeId = controls::AeMeteringModeNameValueMap.at("MeteringMatrix");
+		std::vector<uint8_t> weights(context.hw->numHistogramWeights, 1);
+
+		meteringModes_[meteringModeId] = weights;
+	}
+
+	return 0;
+}
+
+uint8_t Agc::computeHistogramPredivider(Size &size, enum rkisp1_cif_isp_histogram_mode mode)
+{
+	/*
+	 * 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.
+	 *
+	 * Even though it looks like dividing into a counter of 65536 would
+	 * overflow by 1, this is apparently fine according to the hardware
+	 * documentation, and this successfully gets the expected documented
+	 * predivider size for cases where:
+	 * (width / predivider) * (height / predivider) * 3 == 65536.
+	 *
+	 * 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.
+	 *
+	 * \todo Take into account weights. That is, if the weights are low
+	 * enough we can potentially reduce the predivider to increase
+	 * precision. This needs some investigation however, as this hardware
+	 * behavior is undocumented and is only an educated guess.
+	 */
+	int count = mode == RKISP1_CIF_ISP_HISTOGRAM_MODE_RGB_COMBINED ? 3 : 1;
+	double factor = size.width * size.height * count / 65536.0;
+	double root = std::sqrt(factor);
+	uint8_t predivider;
+
+	if (std::pow(std::floor(root), 2) < factor)
+		predivider = static_cast<uint8_t>(std::ceil(root));
+	else
+		predivider = static_cast<uint8_t>(std::floor(root));
+
+	return std::clamp<uint8_t>(predivider, 3, 127);
+}
+
 Agc::Agc()
 {
 	supportsRaw_ = true;
@@ -59,6 +140,11 @@ int Agc::init(IPAContext &context, const YamlObject &tuningData)
 	if (ret)
 		return ret;
 
+	const YamlObject &yamlMeteringModes = tuningData["AeMeteringMode"];
+	ret = parseMeteringModes(context, yamlMeteringModes);
+	if (ret)
+		return ret;
+
 	context.ctrlMap.merge(controls());
 
 	return 0;
@@ -160,6 +246,7 @@ 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 +265,21 @@ 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());
+
+	struct rkisp1_cif_isp_window window = params->meas.hst_config.meas_window;
+	Size windowSize = { window.h_size, window.v_size };
+	params->meas.hst_config.histogram_predivider =
+		computeHistogramPredivider(windowSize,
+					   static_cast<rkisp1_cif_isp_histogram_mode>(params->meas.hst_config.mode));
 
 	/* Update the configuration for histogram. */
 	params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_HST;

src/ipa/rkisp1/algorithms/agc.h

@@ -44,11 +44,17 @@ class Agc : public Algorithm, public AgcMeanLuminance
 		     ControlList &metadata) override;
 
 private:
+	int parseMeteringModes(IPAContext &context, const YamlObject &tuningData);
+	uint8_t computeHistogramPredivider(Size &size,
+					   enum rkisp1_cif_isp_histogram_mode mode);
+
 	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 */