[PATCH v5] libcamera: debayer_cpu: Sync DMABUFs

[Kieran Bingham]

From: Robert Mader <robert.mader at collabora.com>

Using `DMA_BUF_IOCTL_SYNC` is required for DMABUFs in order to ensure
correct output. Not doing so currently results in occasional tearing
and/or backlashes in GL/VK clients that use the buffers directly for
rendering.

An alternative approach to have the sync code in `MappedFrameBuffer` was
considered but rejected for now, in order to allow clients more
flexibility.

While the new helper is added to an annoymous namespace, add
timeDiff to the same namespace and remove the static definition as a
drive by.

Signed-off-by: Robert Mader <robert.mader at collabora.com>
Tested-by: Milan Zamazal <mzamazal at redhat.com> # Debix
Tested-by: Hans de Goede <hdegoede at redhat.com> # IPU6 + ov2740
Tested-by: Kieran Bingham <kieran.bingham at ideasonboard.com> # Lenovo X13s + OV5675
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

---
v5: Kieran:
 - Remove static
 - Fix ret negation that I suggested incorrectly.

 src/libcamera/software_isp/debayer_cpu.cpp | 32 +++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/libcamera/software_isp/debayer_cpu.cpp b/src/libcamera/software_isp/debayer_cpu.cpp
index 077f7f4bc45b..8a757fe9e02d 100644
--- a/src/libcamera/software_isp/debayer_cpu.cpp
+++ b/src/libcamera/software_isp/debayer_cpu.cpp
@@ -12,8 +12,11 @@
 #include "debayer_cpu.h"
 
 #include <stdlib.h>
+#include <sys/ioctl.h>
 #include <time.h>
 
+#include <linux/dma-buf.h>
+
 #include <libcamera/formats.h>
 
 #include "libcamera/internal/bayer_format.h"
@@ -718,12 +721,33 @@ void DebayerCpu::process4(const uint8_t *src, uint8_t *dst)
 	}
 }
 
-static inline int64_t timeDiff(timespec &after, timespec &before)
+namespace {
+
+void syncBufferForCPU(FrameBuffer *buffer, uint64_t syncFlags)
+{
+	for (const FrameBuffer::Plane &plane : buffer->planes()) {
+		const int fd = plane.fd.get();
+		struct dma_buf_sync sync = { syncFlags };
+		int ret;
+
+		ret = ioctl(fd, DMA_BUF_IOCTL_SYNC, &sync);
+		if (ret < 0) {
+			ret = errno;
+			LOG(Debayer, Error)
+				<< "Syncing buffer FD " << fd << " with flags "
+				<< syncFlags << " failed: " << strerror(ret);
+		}
+	}
+}
+
+inline int64_t timeDiff(timespec &after, timespec &before)
 {
 	return (after.tv_sec - before.tv_sec) * 1000000000LL +
 	       (int64_t)after.tv_nsec - (int64_t)before.tv_nsec;
 }
 
+} /* namespace */
+
 void DebayerCpu::process(FrameBuffer *input, FrameBuffer *output, DebayerParams params)
 {
 	timespec frameStartTime;
@@ -733,6 +757,9 @@ void DebayerCpu::process(FrameBuffer *input, FrameBuffer *output, DebayerParams
 		clock_gettime(CLOCK_MONOTONIC_RAW, &frameStartTime);
 	}
 
+	syncBufferForCPU(input, DMA_BUF_SYNC_START | DMA_BUF_SYNC_READ);
+	syncBufferForCPU(output, DMA_BUF_SYNC_START | DMA_BUF_SYNC_WRITE);
+
 	green_ = params.green;
 	red_ = swapRedBlueGains_ ? params.blue : params.red;
 	blue_ = swapRedBlueGains_ ? params.red : params.blue;
@@ -760,6 +787,9 @@ void DebayerCpu::process(FrameBuffer *input, FrameBuffer *output, DebayerParams
 
 	metadata.planes()[0].bytesused = out.planes()[0].size();
 
+	syncBufferForCPU(output, DMA_BUF_SYNC_END | DMA_BUF_SYNC_WRITE);
+	syncBufferForCPU(input, DMA_BUF_SYNC_END | DMA_BUF_SYNC_READ);
+
 	/* Measure before emitting signals */
 	if (measuredFrames_ < DebayerCpu::kLastFrameToMeasure &&
 	    ++measuredFrames_ > DebayerCpu::kFramesToSkip) {
-- 
2.46.0