[PATCH v3] libcamera: debayer_cpu: Sync DMABUFs

[Robert Mader]

On 16.09.24 17:10, Kieran Bingham wrote:
> Quoting Robert Mader (2024-09-16 15:11:25)
>> 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.
>>
>> Signed-off-by: Robert Mader <robert.mader at collabora.com>
>>
>> ---
>>
>> Changes in v3:
>>   - add syncBufferForCPU() helper function
>>
>> Changes in v2:
>>   - sync input buffer as well
>>   - update commit title accordingly
>>   - small changes to the commit message
>>   - linting fixes, should pass now
>> ---
>>   src/libcamera/software_isp/debayer_cpu.cpp | 20 ++++++++++++++++++++
>>   1 file changed, 20 insertions(+)
>>
>> diff --git a/src/libcamera/software_isp/debayer_cpu.cpp b/src/libcamera/software_isp/debayer_cpu.cpp
>> index 077f7f4b..3748bd7c 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"
>> @@ -718,6 +721,17 @@ void DebayerCpu::process4(const uint8_t *src, uint8_t *dst)
>>          }
>>   }
>>   
>> +static void syncBufferForCPU(FrameBuffer *buffer, uint64_t syncFlags)
> I think these functions (including timeDiff below) should be wrapped in
> an annoymous namespace for the libcamera code style.
>
> But as the timeDiff is already in this form - they can both be converted
> after. (or before if you want to do the fix up)
>
>> +{
>> +       for (const FrameBuffer::Plane &plane : buffer->planes()) {
>> +               const int fd = plane.fd.get();
>> +               struct dma_buf_sync sync = { syncFlags };
>> +
>> +               if (ioctl(fd, DMA_BUF_IOCTL_SYNC, &sync) < 0)
>> +                       LOG(Debayer, Error) << "Syncing buffer FD " << fd << "failed: " << errno;
> This could be rewrapped easily
>
> 			LOG(Debayer, Error)
> 				<< "Syncing buffer FD " << fd << "failed: " << errno;
>
> But we can't reference errno directly from LOG() either, as mentioned in
> the previous version:
>
> Easiest cleanup is probably:
>
> 		int ret;
>
> 		ret = ioctl(fd, DMA_BUF_IOCTL_SYNC, &sync);
> 		if (ret < 0) {
> 			ret = errno;
> 			LOG(Debayer, Error)
> 				<< "Syncing buffer FD " << fd << "failed: "
> 				<< strerror(-ret);
>
> 		}
>
> Could also print the sync flags too to know which one has failed?
>
> With that handled:
>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

Thanks, addressed in v4, hopefully correctly (not quite sure about how 
to best print the flags, therefore didn't add the R-b).

>
>> +       }
>> +}
>> +
>>   static inline int64_t timeDiff(timespec &after, timespec &before)
>>   {
>>          return (after.tv_sec - before.tv_sec) * 1000000000LL +
>> @@ -733,6 +747,9 @@ 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 +777,9 @@ 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
>>
-- 
Robert Mader
Consultant Software Developer

Collabora Ltd.
Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK
Registered in England & Wales, no. 5513718