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Subject: Re: [PATCH v2 04/18] media/v4l2-core: set pages dirty upon releasing
 DMA buffers
To: Hans Verkuil <hverkuil@xs4all.nl>, Andrew Morton
 <akpm@linux-foundation.org>
References: <20191103211813.213227-1-jhubbard@nvidia.com>
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On 11/10/19 2:10 AM, Hans Verkuil wrote:
> On 11/3/19 10:17 PM, John Hubbard wrote:
>> After DMA is complete, and the device and CPU caches are synchronized,
>> it's still required to mark the CPU pages as dirty, if the data was
>> coming from the device. However, this driver was just issuing a
>> bare put_page() call, without any set_page_dirty*() call.
>>
>> Fix the problem, by calling set_page_dirty_lock() if the CPU pages
>> were potentially receiving data from the device.
>>
>> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
>> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> 
> Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> 
> Looks good, thanks!
> 

Hi Hans, it's great that you could take a look at this and the other v4l2 
patch, much appreciated.


thanks,
-- 
John Hubbard
NVIDIA
>> ---
>>  drivers/media/v4l2-core/videobuf-dma-sg.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c
>> index 66a6c6c236a7..28262190c3ab 100644
>> --- a/drivers/media/v4l2-core/videobuf-dma-sg.c
>> +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c
>> @@ -349,8 +349,11 @@ int videobuf_dma_free(struct videobuf_dmabuf *dma)
>>  	BUG_ON(dma->sglen);
>>  
>>  	if (dma->pages) {
>> -		for (i = 0; i < dma->nr_pages; i++)
>> +		for (i = 0; i < dma->nr_pages; i++) {
>> +			if (dma->direction == DMA_FROM_DEVICE)
>> +				set_page_dirty_lock(dma->pages[i]);
>>  			put_page(dma->pages[i]);
>> +		}
>>  		kfree(dma->pages);
>>  		dma->pages = NULL;
>>  	}
>>
>