pmaports-rtwo/temp/libcamera/0007-debayer_egl-Implement-dmabuf-import-for-input-buffer.patch

From 7f354e1d4fa942a7f79f1d34c0b8b2bc86a4c1c5 Mon Sep 17 00:00:00 2001
From: Robert Mader <robert.mader@collabora.com>
Date: Wed, 27 May 2026 10:15:34 +0200
Subject: [PATCH 07/13] debayer_egl: Implement dmabuf import for input buffers

In many cases we can import the GPU-ISP input buffers, dmabufs from v4l2,
directly into EGL instead of mapping and uploading - i.e. copying - them.

Doing so can have positive effects in multiple areas, including reducing
memory bandwidth and CPU usage, as well as avoiding expensive dmabuf syncs
and syscalls.

The main reason direct imports may not work are the more demanding stride
alignment requirements many GPUs have - often 128 or 256 bytes - compared
to ISPs - apparently often closer to 32 bytes.

Thus we first try to import buffers directly and - if that fails - fall back
to the previous upload path. Failing imports should come at low cost as
drivers know the limitations and can bail out early, without causing
additional IO or context switches.

In the future we might be able to request buffers with a matching stride
from v4l2 drivers in many cases, making direct import the norm instead
of a hit-or-miss. An optional kernel API for that exists, but doesn't
seem to be implemented by any driver tested so far.

Note that passing around MappedFrameBuffer and DmaSyncer variables ensures
we don't do unnecessary mappings and dmabuf syncs.

Below are some benchmark results. All where done using postmarketOS edge
with updates from 21th May 2026 (Mesa 26.1.1). The mentioned pipelines
where run five times each, with the mean value included here, which should
be quite representive as the variance was rather small. All devices
where using the powersave governor.

- FairPhone 5

-- Back camera
cam -c /base/soc@0/cci@ac4a000/i2c-bus@1/camera@29 -s width=1920,height=1080 --capture=60
Before: 14027 us/frame
After: 12122 us/frame

- OnePlus 6

-- Back camera (imx519)
cam -c /base/soc@0/cci@ac4a000/i2c-bus@0/camera@10 -s width=1920,height=1080 --capture=60
Before: 30091 us/frame
After: 19878 us/frame

- Librem 5

-- Back camera
cam -c /base/soc@0/bus@30800000/i2c@30a50000/camera@2d -s width=1280,height=720 --capture=60
Before: 69092 us/frame
After: 41250 us/frame

- PinePhone

-- Front Camera
cam -c /base/i2c-csi/front-camera@3c -s width=1280,height=720 --capture=60
Before: 173769 us/frame
After: 143274 us/frame

-- Back camera
cam -c /base/i2c-csi/rear-camera@4c -s width=1280,height=720 --capture=60
Before: 174833 us/frame
After: 144476 us/frame

There is one case where performance regresses:

- Pixel 3a

-- Back camera
cam -c /base/soc@0/cci@ac4a000/i2c-bus@1/camera@1a -s width=1920,height=1080 --capture=60
Before: 14257 us/frame
After: 15161 us/frame

To my knowledge this is likely caused by bad sampling performance from
linear buffers. IMO this is a driver issue - if a copy to tiled format
makes sampling faster, drivers should do so implicitly (like e.g. v3d
already does).

Signed-off-by: Robert Mader <robert.mader@collabora.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
(cherry picked from commit 93f0db167a8dfb9bc58cb6bbcf91ef6a23462b16)
---
 src/libcamera/software_isp/debayer_egl.cpp | 58 ++++++++++++++++------
 src/libcamera/software_isp/debayer_egl.h   |  2 +-
 2 files changed, 43 insertions(+), 17 deletions(-)

diff --git a/src/libcamera/software_isp/debayer_egl.cpp b/src/libcamera/software_isp/debayer_egl.cpp
index 067333c03..e0f6dc6da 100644
--- a/src/libcamera/software_isp/debayer_egl.cpp
+++ b/src/libcamera/software_isp/debayer_egl.cpp
@@ -10,6 +10,7 @@
 #include "debayer_egl.h"
 
 #include <cmath>
+#include <assert.h>
 #include <stdlib.h>
 #include <time.h>
 
@@ -495,16 +496,34 @@ void DebayerEGL::setShaderVariableValues(const DebayerParams &params)
 	return;
 }
 
-int DebayerEGL::debayerGPU(MappedFrameBuffer &in, int out_fd, const DebayerParams &params)
+int DebayerEGL::debayerGPU(FrameBuffer *input, FrameBuffer *output, const DebayerParams &params, std::optional<MappedFrameBuffer> *inMapped, std::optional<DmaSyncer> *inDmaSyncer)
 {
+	bool dmabuf_import_succeeded = false;
+
 	/* eGL context switch */
 	egl_.makeCurrent();
 
-	/* Create a standard texture input */
-	egl_.createTexture2D(*eglImageBayerIn_, in.planes()[0].data());
+	/* Try to create texture for input buffer via dmabuf import */
+	if (!eglImageBayerIn_->dmabuf_import_failed_) {
+		if (egl_.createInputDMABufTexture2D(*eglImageBayerIn_, input->planes()[0].fd.get()) == 0)
+			dmabuf_import_succeeded = true;
+		else
+			LOG(Debayer, Info) << "Importing input buffer with DMABuf import failed, falling back to upload";
+	}
+
+	/* Otherwise create texture for input buffer via upload from CPU */
+	if (!dmabuf_import_succeeded) {
+		inDmaSyncer->emplace(input->planes()[0].fd, DmaSyncer::SyncType::Read);
+		inMapped->emplace(input, MappedFrameBuffer::MapFlag::Read);
+		if (!inMapped->value().isValid()) {
+			LOG(Debayer, Error) << "mmap-ing buffer(s) failed";
+			return -ENODEV;
+		}
+		egl_.createTexture2D(*eglImageBayerIn_, inMapped->value().planes()[0].data());
+	}
 
 	/* Generate the output render framebuffer as render to texture */
-	egl_.createOutputDMABufTexture2D(*eglImageBayerOut_, out_fd);
+	egl_.createOutputDMABufTexture2D(*eglImageBayerOut_, output->planes()[0].fd.get());
 
 	setShaderVariableValues(params);
 	glViewport(0, 0, width_, height_);
@@ -526,23 +545,16 @@ void DebayerEGL::process(uint32_t frame, FrameBuffer *input, FrameBuffer *output
 {
 	bench_.startFrame();
 
-	std::vector<DmaSyncer> dmaSyncers;
-
-	dmaSyncBegin(dmaSyncers, input, nullptr);
-
 	/* Copy metadata from the input buffer */
 	FrameMetadata &metadata = output->_d()->metadata();
 	metadata.status = input->metadata().status;
 	metadata.sequence = input->metadata().sequence;
 	metadata.timestamp = input->metadata().timestamp;
 
-	MappedFrameBuffer in(input, MappedFrameBuffer::MapFlag::Read);
-	if (!in.isValid()) {
-		LOG(Debayer, Error) << "mmap-ing buffer(s) failed";
-		goto error;
-	}
+	std::optional<MappedFrameBuffer> inMapped;
+	std::optional<DmaSyncer> inDmaSyncer;
 
-	if (debayerGPU(in, output->planes()[0].fd.get(), params)) {
+	if (debayerGPU(input, output, params, &inMapped, &inDmaSyncer)) {
 		LOG(Debayer, Error) << "debayerGPU failed";
 		goto error;
 	}
@@ -550,8 +562,22 @@ void DebayerEGL::process(uint32_t frame, FrameBuffer *input, FrameBuffer *output
 	metadata.planes()[0].bytesused = output->planes()[0].length;
 
 	/* Calculate stats for the whole frame */
-	stats_->processFrame(frame, 0, in);
-	dmaSyncers.clear();
+	if (frame % SwStatsCpu::kStatPerNumFrames) {
+		stats_->finishFrame(frame, 0);
+	} else {
+		if (!inMapped) {
+			/*
+			 * The buffer was directly imported into EGL and thus
+			 * not mapped for texture upload. Do it now for the
+			 * CPU-based stats calculation.
+			 */
+			assert(!inDmaSyncer);
+			inDmaSyncer.emplace(input->planes()[0].fd, DmaSyncer::SyncType::Read);
+			inMapped.emplace(input, MappedFrameBuffer::MapFlag::Read);
+		}
+		stats_->processFrame(frame, 0, inMapped.value());
+	}
+	inDmaSyncer.reset();
 
 	egl_.syncOutput();
 	bench_.finishFrame();
diff --git a/src/libcamera/software_isp/debayer_egl.h b/src/libcamera/software_isp/debayer_egl.h
index fcd281f4c..f2a127b0d 100644
--- a/src/libcamera/software_isp/debayer_egl.h
+++ b/src/libcamera/software_isp/debayer_egl.h
@@ -66,7 +66,7 @@ private:
 	int initBayerShaders(PixelFormat inputFormat, PixelFormat outputFormat);
 	int getShaderVariableLocations();
 	void setShaderVariableValues(const DebayerParams &params);
-	int debayerGPU(MappedFrameBuffer &in, int out_fd, const DebayerParams &params);
+	int debayerGPU(FrameBuffer *input, FrameBuffer *output, const DebayerParams &params, std::optional<MappedFrameBuffer> *mappedInputBuffer, std::optional<DmaSyncer> *inputBufferDmaSyncer);
 
 	/* Shader program identifiers */
 	GLuint vertexShaderId_ = 0;
-- 
2.54.0