[libcamera-devel] [RFC 5/6] libcamera: ipu3: Do not unconditionally queue buffers to CIO2

[Niklas Söderlund]

Instead of unconditionally cycling buffers between the CIO2 and IMGU
pick a buffer when a request is queued to the pipeline. This is needed
if operations are the be applied to the buffer coming from CIO2 with
parameters coming from a Request.

The approach to pick a CIO2 buffer when a request is queued is similar
to other pipelines, where parameters and statistic buffers are picked
this way.

Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
---
 src/libcamera/pipeline/ipu3/ipu3.cpp | 69 +++++++++++++++++++++++-----
 1 file changed, 58 insertions(+), 11 deletions(-)

diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
index 0c2a217c9ea8f6ba..dbb0c4328aa0efe5 100644
--- a/src/libcamera/pipeline/ipu3/ipu3.cpp
+++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
@@ -8,6 +8,7 @@
 #include <algorithm>
 #include <iomanip>
 #include <memory>
+#include <queue>
 #include <vector>
 
 #include <linux/drm_fourcc.h>
@@ -119,6 +120,10 @@ public:
 	int allocateBuffers();
 	void freeBuffers();
 
+	FrameBuffer *getBuffer();
+	void putBuffer(FrameBuffer *buffer);
+	int queueBuffer(FrameBuffer *buffer);
+
 	int start();
 	int stop();
 
@@ -130,6 +135,7 @@ public:
 
 private:
 	std::vector<std::unique_ptr<FrameBuffer>> buffers_;
+	std::queue<FrameBuffer *> availableBuffers_;
 };
 
 class IPU3Stream : public Stream
@@ -157,6 +163,8 @@ public:
 	void imguInputBufferReady(FrameBuffer *buffer);
 	void cio2BufferReady(FrameBuffer *buffer);
 
+	std::map<FrameBuffer *, Request *> cio2ToRequest_;
+
 	CIO2Device cio2_;
 	ImgUDevice *imgu_;
 
@@ -717,11 +725,20 @@ 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 and track it it's used for this request. */
+	buffer = data->cio2_.getBuffer();
+	if (!buffer)
+		return -EINVAL;
+	data->cio2ToRequest_[buffer] = request;
+	data->cio2_.queueBuffer(buffer);
+
 	for (auto it : request->buffers()) {
 		IPU3Stream *stream = static_cast<IPU3Stream *>(it.first);
-		FrameBuffer *buffer = it.second;
+		buffer = it.second;
 
 		int ret = stream->device_->dev->queueBuffer(buffer);
 		if (ret < 0)
@@ -893,7 +910,9 @@ void IPU3CameraData::imguInputBufferReady(FrameBuffer *buffer)
 	if (buffer->metadata().status == FrameMetadata::FrameCancelled)
 		return;
 
-	cio2_.output_->queueBuffer(buffer);
+	/* Remove association between CIO2 buffer an Request. */
+	cio2ToRequest_.erase(buffer);
+	cio2_.putBuffer(buffer);
 }
 
 /**
@@ -1416,30 +1435,58 @@ int CIO2Device::configure(const Size &size,
 int CIO2Device::allocateBuffers()
 {
 	int ret = output_->allocateBuffers(CIO2_BUFFER_COUNT, &buffers_);
-	if (ret < 0)
+	if (ret < 0) {
 		LOG(IPU3, Error) << "Failed to allocate CIO2 buffers";
+		return ret;
+	}
+
+	for (std::unique_ptr<FrameBuffer> &buffer : buffers_)
+		availableBuffers_.push(buffer.get());
 
 	return ret;
 }
 
 void CIO2Device::freeBuffers()
 {
+	while (!availableBuffers_.empty())
+		availableBuffers_.pop();
+
 	buffers_.clear();
 
 	if (output_->releaseBuffers())
 		LOG(IPU3, Error) << "Failed to release CIO2 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::queueBuffer(FrameBuffer *buffer)
+{
+	int ret = output_->queueBuffer(buffer);
+	if (ret)
+		LOG(IPU3, Error) << "Failed to queue CIO2 buffer";
+
+	return ret;
+}
+
 int CIO2Device::start()
 {
-	for (const std::unique_ptr<FrameBuffer> &buffer : buffers_) {
-		int ret = output_->queueBuffer(buffer.get());
-		if (ret) {
-			LOG(IPU3, Error) << "Failed to queue CIO2 buffer";
-			return ret;
-		}
-	}
-
 	return output_->streamOn();
 }
 
-- 
2.25.1