libcamera: ipu3: Allow zero-copy RAW stream capture

With the refactored CIO2 interface it's now easy to add zero-copy for
buffers in the RAW stream. Use the internally allocated buffers inside
the CIO2Device if no buffer for the RAW stream is provided by the
application, or use the application-provided buffer if any.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

3 files changed, 60 insertions, 72 deletions

diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
index d698cd80..885e2ca0 100644
--- a/src/libcamera/pipeline/ipu3/cio2.cpp
+++ b/src/libcamera/pipeline/ipu3/cio2.cpp
@@ -213,31 +213,16 @@ int CIO2Device::exportBuffers(unsigned int count,
 	return output_->exportBuffers(count, buffers);
 }
 
-FrameBuffer *CIO2Device::getBuffer()
-{
-	if (availableBuffers_.empty()) {
-		LOG(IPU3, Error) << "CIO2 buffer underrun";
-		return nullptr;
-	}
-
-	FrameBuffer *buffer = availableBuffers_.front();
-
-	availableBuffers_.pop();
-
-	return buffer;
-}
-
-void CIO2Device::putBuffer(FrameBuffer *buffer)
-{
-	availableBuffers_.push(buffer);
-}
-
 int CIO2Device::start()
 {
-	int ret = output_->allocateBuffers(CIO2_BUFFER_COUNT, &buffers_);
+	int ret = output_->exportBuffers(CIO2_BUFFER_COUNT, &buffers_);
 	if (ret < 0)
 		return ret;
 
+	ret = output_->importBuffers(CIO2_BUFFER_COUNT);
+	if (ret)
+		LOG(IPU3, Error) << "Failed to import CIO2 buffers";
+
 	for (std::unique_ptr<FrameBuffer> &buffer : buffers_)
 		availableBuffers_.push(buffer.get());
 
@@ -257,11 +242,42 @@ int CIO2Device::stop()
 	return ret;
 }
 
-int CIO2Device::queueBuffer(FrameBuffer *buffer)
+int CIO2Device::queueBuffer(Request *request, FrameBuffer *rawBuffer)
 {
+	FrameBuffer *buffer = rawBuffer;
+
+	/* If no buffer is provided in the request, use an internal one. */
+	if (!buffer) {
+		if (availableBuffers_.empty()) {
+			LOG(IPU3, Error) << "CIO2 buffer underrun";
+			return -EINVAL;
+		}
+
+		buffer = availableBuffers_.front();
+		availableBuffers_.pop();
+	}
+
+	buffer->setRequest(request);
+
 	return output_->queueBuffer(buffer);
 }
 
+void CIO2Device::tryReturnBuffer(FrameBuffer *buffer)
+{
+	/*
+	 * \todo Once more pipelines deal with buffers that may be allocated
+	 * internally or externally this pattern might become a common need. At
+	 * that point this check should be moved to something clever in
+	 * FrameBuffer.
+	 */
+	for (const std::unique_ptr<FrameBuffer> &buf : buffers_) {
+		if (buf.get() == buffer) {
+			availableBuffers_.push(buffer);
+			break;
+		}
+	}
+}
+
 void CIO2Device::freeBuffers()
 {
 	/* The default std::queue constructor is explicit with gcc 5 and 6. */
diff --git a/src/libcamera/pipeline/ipu3/cio2.h b/src/libcamera/pipeline/ipu3/cio2.h
index 47c6f010..dc764b10 100644
--- a/src/libcamera/pipeline/ipu3/cio2.h
+++ b/src/libcamera/pipeline/ipu3/cio2.h
@@ -18,6 +18,7 @@ namespace libcamera {
 class CameraSensor;
 class FrameBuffer;
 class MediaDevice;
+class Request;
 class V4L2DeviceFormat;
 class V4L2Subdevice;
 class V4L2VideoDevice;
@@ -40,15 +41,13 @@ public:
 	int exportBuffers(unsigned int count,
 			  std::vector<std::unique_ptr<FrameBuffer>> *buffers);
 
-	FrameBuffer *getBuffer();
-	void putBuffer(FrameBuffer *buffer);
-
 	int start();
 	int stop();
 
 	CameraSensor *sensor() { return sensor_; }
 
-	int queueBuffer(FrameBuffer *buffer);
+	int queueBuffer(Request *request, FrameBuffer *rawBuffer);
+	void tryReturnBuffer(FrameBuffer *buffer);
 	Signal<FrameBuffer *> bufferReady;
 
 private:
diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
index 4818027e..6c43169e 100644
--- a/src/libcamera/pipeline/ipu3/ipu3.cpp
+++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
@@ -122,7 +122,6 @@ public:
 	}
 
 	void imguOutputBufferReady(FrameBuffer *buffer);
-	void imguInputBufferReady(FrameBuffer *buffer);
 	void cio2BufferReady(FrameBuffer *buffer);
 
 	CIO2Device cio2_;
@@ -737,25 +736,24 @@ void PipelineHandlerIPU3::stop(Camera *camera)
 int PipelineHandlerIPU3::queueRequestDevice(Camera *camera, Request *request)
 {
 	IPU3CameraData *data = cameraData(camera);
-	FrameBuffer *buffer;
 	int error = 0;
 
-	/* Get a CIO2 buffer, associate it with the request and queue it. */
-	buffer = data->cio2_.getBuffer();
-	if (!buffer)
-		return -EINVAL;
-
-	buffer->setRequest(request);
-	data->cio2_.queueBuffer(buffer);
+	/*
+	 * Queue a buffer on the CIO2, using the raw stream buffer provided in
+	 * the request, if any, or a CIO2 internal buffer otherwise.
+	 */
+	FrameBuffer *rawBuffer = request->findBuffer(&data->rawStream_);
+	error = data->cio2_.queueBuffer(request, rawBuffer);
+	if (error)
+		return error;
 
+	/* Queue all buffers from the request aimed for the ImgU. */
 	for (auto it : request->buffers()) {
 		IPU3Stream *stream = static_cast<IPU3Stream *>(it.first);
-		buffer = it.second;
-
-		/* Skip raw streams, they are copied from the CIO2 buffer. */
 		if (stream->raw_)
 			continue;
 
+		FrameBuffer *buffer = it.second;
 		int ret = stream->device_->dev->queueBuffer(buffer);
 		if (ret < 0)
 			error = ret;
@@ -885,8 +883,8 @@ int PipelineHandlerIPU3::registerCameras()
 		 */
 		data->cio2_.bufferReady.connect(data.get(),
 					&IPU3CameraData::cio2BufferReady);
-		data->imgu_->input_->bufferReady.connect(data.get(),
-					&IPU3CameraData::imguInputBufferReady);
+		data->imgu_->input_->bufferReady.connect(&data->cio2_,
+					&CIO2Device::tryReturnBuffer);
 		data->imgu_->output_.dev->bufferReady.connect(data.get(),
 					&IPU3CameraData::imguOutputBufferReady);
 		data->imgu_->viewfinder_.dev->bufferReady.connect(data.get(),
@@ -916,22 +914,6 @@ int PipelineHandlerIPU3::registerCameras()
  */
 
 /**
- * \brief Handle buffers completion at the ImgU input
- * \param[in] buffer The completed buffer
- *
- * Buffers completed from the ImgU input are immediately queued back to the
- * CIO2 unit to continue frame capture.
- */
-void IPU3CameraData::imguInputBufferReady(FrameBuffer *buffer)
-{
-	/* \todo Handle buffer failures when state is set to BufferError. */
-	if (buffer->metadata().status == FrameMetadata::FrameCancelled)
-		return;
-
-	cio2_.putBuffer(buffer);
-}
-
-/**
  * \brief Handle buffers completion at the ImgU output
  * \param[in] buffer The completed buffer
  *
@@ -963,27 +945,18 @@ void IPU3CameraData::cio2BufferReady(FrameBuffer *buffer)
 		return;
 
 	Request *request = buffer->request();
-	FrameBuffer *raw = request->findBuffer(&rawStream_);
 
-	if (!raw) {
-		/* No RAW buffers present, just queue to IMGU. */
-		imgu_->input_->queueBuffer(buffer);
+	/*
+	 * If the request contains a buffer for the RAW stream only, complete it
+	 * now as there's no need for ImgU processing.
+	 */
+	if (request->findBuffer(&rawStream_) &&
+	    pipe_->completeBuffer(camera_, request, buffer)) {
+		pipe_->completeRequest(camera_, request);
 		return;
 	}
 
-	/* RAW buffers present, special care is needed. */
-	if (request->buffers().size() > 1)
-		imgu_->input_->queueBuffer(buffer);
-
-	if (raw->copyFrom(buffer))
-		LOG(IPU3, Debug) << "Copy of FrameBuffer failed";
-
-	pipe_->completeBuffer(camera_, request, raw);
-
-	if (request->buffers().size() == 1) {
-		cio2_.putBuffer(buffer);
-		pipe_->completeRequest(camera_, request);
-	}
+	imgu_->input_->queueBuffer(buffer);
 }
 
 /* -----------------------------------------------------------------------------