ipa: ipu3: Put IPAFrameContext(s) in a ring buffer

Instead of having one frame context constantly being updated,
this patch aims to introduce per-frame IPAFrameContext which
are stored in a ring buffer. Whenever a request is queued, a new
IPAFrameContext is created and inserted into the ring buffer.

The IPAFrameContext structure itself has been slightly extended
to store a frame id and a ControlList for incoming frame
controls (sent in by the application). The next step would be to
read and set these controls whenever the request is actually queued
to the hardware.

Since now we are working in multiples of IPAFrameContext, the
Algorithm::process() will actually take in a IPAFrameContext pointer
(as opposed to a nullptr while preparing for this change).

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

src/ipa/ipu3/algorithms/agc.cpp

@@ -183,14 +183,13 @@ utils::Duration Agc::filterExposure(utils::Duration exposureValue)
  * \param[in] yGain The gain calculated based on the relative luminance target
  * \param[in] iqMeanGain The gain calculated based on the relative luminance target
  */
-void Agc::computeExposure(IPAContext &context, double yGain,
-			  double iqMeanGain)
+void Agc::computeExposure(IPAContext &context, IPAFrameContext *frameContext,
+			  double yGain, double iqMeanGain)
 {
 	const IPASessionConfiguration &configuration = context.configuration;
-	IPAFrameContext &frameContext = context.frameContext;
 	/* Get the effective exposure and gain applied on the sensor. */
-	uint32_t exposure = frameContext.sensor.exposure;
-	double analogueGain = frameContext.sensor.gain;
+	uint32_t exposure = frameContext->sensor.exposure;
+	double analogueGain = frameContext->sensor.gain;
 
 	/* Use the highest of the two gain estimates. */
 	double evGain = std::max(yGain, iqMeanGain);
@@ -360,7 +359,7 @@ void Agc::process(IPAContext &context, [[maybe_unused]] IPAFrameContext *frameCo
 			break;
 	}
 
-	computeExposure(context, yGain, iqMeanGain);
+	computeExposure(context, frameContext, yGain, iqMeanGain);
 	frameCount_++;
 }
 

src/ipa/ipu3/algorithms/agc.h

@@ -35,8 +35,8 @@ private:
 	double measureBrightness(const ipu3_uapi_stats_3a *stats,
 				 const ipu3_uapi_grid_config &grid) const;
 	utils::Duration filterExposure(utils::Duration currentExposure);
-	void computeExposure(IPAContext &context, double yGain,
-			     double iqMeanGain);
+	void computeExposure(IPAContext &context, IPAFrameContext *frameContext,
+			     double yGain, double iqMeanGain);
 	double estimateLuminance(IPAActiveState &activeState,
 				 const ipu3_uapi_grid_config &grid,
 				 const ipu3_uapi_stats_3a *stats,

src/ipa/ipu3/ipa_context.cpp

@@ -58,13 +58,11 @@ namespace libcamera::ipa::ipu3 {
  * \var IPAContext::configuration
  * \brief The IPA session configuration, immutable during the session
  *
- * \var IPAContext::frameContext
- * \brief The frame context for the frame being processed
+ * \var IPAContext::frameContexts
+ * \brief Ring buffer of the IPAFrameContext(s)
  *
  * \var IPAContext::activeState
  * \brief The current state of IPA algorithms
- *
- * \todo The frame context needs to be turned into real per-frame data storage.
  */
 
 /**
@@ -183,6 +181,26 @@ namespace libcamera::ipa::ipu3 {
  */
 
 /**
+ * \brief Default constructor for IPAFrameContext
+ */
+IPAFrameContext::IPAFrameContext() = default;
+
+/**
+ * \brief Construct a IPAFrameContext instance
+ */
+IPAFrameContext::IPAFrameContext(uint32_t id, const ControlList &reqControls)
+	: frame(id), frameControls(reqControls)
+{
+	sensor = {};
+}
+
+/**
+ * \var IPAFrameContext::frame
+ * \brief The frame number
+ *
+ * \var IPAFrameContext::frameControls
+ * \brief Controls sent in by the application while queuing the request
+ *
  * \var IPAFrameContext::sensor
  * \brief Effective sensor values that were applied for the frame
  *

src/ipa/ipu3/ipa_context.h

@@ -8,16 +8,22 @@
 
 #pragma once
 
+#include <array>
+
 #include <linux/intel-ipu3.h>
 
 #include <libcamera/base/utils.h>
 
+#include <libcamera/controls.h>
 #include <libcamera/geometry.h>
 
 namespace libcamera {
 
 namespace ipa::ipu3 {
 
+/* Maximum number of frame contexts to be held */
+static constexpr uint32_t kMaxFrameContexts = 16;
+
 struct IPASessionConfiguration {
 	struct {
 		ipu3_uapi_grid_config bdsGrid;
@@ -71,17 +77,23 @@ struct IPAActiveState {
 };
 
 struct IPAFrameContext {
+	IPAFrameContext();
+	IPAFrameContext(uint32_t id, const ControlList &reqControls);
+
 	struct {
 		uint32_t exposure;
 		double gain;
 	} sensor;
+
+	uint32_t frame;
+	ControlList frameControls;
 };
 
 struct IPAContext {
 	IPASessionConfiguration configuration;
 	IPAActiveState activeState;
 
-	IPAFrameContext frameContext;
+	std::array<IPAFrameContext, kMaxFrameContexts> frameContexts;
 };
 
 } /* namespace ipa::ipu3 */

src/ipa/ipu3/ipu3.cpp

@@ -313,7 +313,7 @@ int IPAIPU3::init(const IPASettings &settings,
 	}
 
 	/* Clean context */
-	context_ = {};
+	context_.configuration = {};
 	context_.configuration.sensor.lineDuration = sensorInfo.lineLength * 1.0s / sensorInfo.pixelRate;
 
 	/* Construct our Algorithms */
@@ -456,7 +456,8 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
 
 	/* Clean IPAActiveState at each reconfiguration. */
 	context_.activeState = {};
-	context_.frameContext = {};
+	IPAFrameContext initFrameContext;
+	context_.frameContexts.fill(initFrameContext);
 
 	if (!validateSensorControls()) {
 		LOG(IPAIPU3, Error) << "Sensor control validation failed.";
@@ -568,15 +569,20 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
 	const ipu3_uapi_stats_3a *stats =
 		reinterpret_cast<ipu3_uapi_stats_3a *>(mem.data());
 
-	context_.frameContext.sensor.exposure = sensorControls.get(V4L2_CID_EXPOSURE).get<int32_t>();
-	context_.frameContext.sensor.gain = camHelper_->gain(sensorControls.get(V4L2_CID_ANALOGUE_GAIN).get<int32_t>());
+	IPAFrameContext &frameContext = context_.frameContexts[frame % kMaxFrameContexts];
+
+	if (frameContext.frame != frame)
+		LOG(IPAIPU3, Warning) << "Frame " << frame << " does not match its frame context";
+
+	frameContext.sensor.exposure = sensorControls.get(V4L2_CID_EXPOSURE).get<int32_t>();
+	frameContext.sensor.gain = camHelper_->gain(sensorControls.get(V4L2_CID_ANALOGUE_GAIN).get<int32_t>());
 
 	double lineDuration = context_.configuration.sensor.lineDuration.get<std::micro>();
 	int32_t vBlank = context_.configuration.sensor.defVBlank;
 	ControlList ctrls(controls::controls);
 
 	for (auto const &algo : algorithms_)
-		algo->process(context_, nullptr, stats);
+		algo->process(context_, &frameContext, stats);
 
 	setControls(frame);
 
@@ -584,11 +590,11 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
 	int64_t frameDuration = (vBlank + sensorInfo_.outputSize.height) * lineDuration;
 	ctrls.set(controls::FrameDuration, frameDuration);
 
-	ctrls.set(controls::AnalogueGain, context_.frameContext.sensor.gain);
+	ctrls.set(controls::AnalogueGain, frameContext.sensor.gain);
 
 	ctrls.set(controls::ColourTemperature, context_.activeState.awb.temperatureK);
 
-	ctrls.set(controls::ExposureTime, context_.frameContext.sensor.exposure * lineDuration);
+	ctrls.set(controls::ExposureTime, frameContext.sensor.exposure * lineDuration);
 
 	/*
 	 * \todo The Metadata provides a path to getting extended data
@@ -609,10 +615,10 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
  * Parse the request to handle any IPA-managed controls that were set from the
  * application such as manual sensor settings.
  */
-void IPAIPU3::queueRequest([[maybe_unused]] const uint32_t frame,
-			   [[maybe_unused]] const ControlList &controls)
+void IPAIPU3::queueRequest(const uint32_t frame, const ControlList &controls)
 {
 	/* \todo Start processing for 'frame' based on 'controls'. */
+	context_.frameContexts[frame % kMaxFrameContexts] = { frame, controls };
 }
 
 /**