Hi Sergey,
On 09/06/2020 08:04, Sergey Senozhatsky wrote:
> We need a combination of two factors in order to permit modification
> of queue's memory consistency attribute in set_queue_consistency():
> (1) queue should allow user-space cache hints
> (2) queue should be used for MMAP-ed I/O
>
> Therefore the code in videobuf2 core looks as follows:
>
> q->memory = req->memory;
> set_queue_consistency(q, consistent);
>
> This works when we do something like this (suppose that queue allows
> cache hints)
>
> reqbufs.memory = V4L2_MEMORY_DMABUF;
> reqbufs.flags = 0;
> doioctl(node, VIDIOC_REQBUFS, &reqbufs);
>
> reqbufs.memory = V4L2_MEMORY_MMAP;
> reqbufs.flags = V4L2_FLAG_MEMORY_NON_CONSISTENT;
> doioctl(node, VIDIOC_REQBUFS, &reqbufs);
>
> However, this doesn't work the other way around
>
> reqbufs.memory = V4L2_MEMORY_MMAP;
> reqbufs.flags = V4L2_FLAG_MEMORY_NON_CONSISTENT;
> doioctl(node, VIDIOC_REQBUFS, &reqbufs);
>
> reqbufs.memory = V4L2_MEMORY_DMABUF;
> reqbufs.flags = 0;
> doioctl(node, VIDIOC_REQBUFS, &reqbufs);
>
> because __vb2_queue_free() doesn't clear queue's ->dma_attrs
> once its don't freeing queue buffers, and by the time we call
> set_queue_consistency() the queue is DMABUF so (2) is false
> and we never clear the stale consistency attribute.
>
> Re-implement set_queue_consistency() - it must always clear
> queue's non-consistency attr and set it only if (1) and (2).
>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
> ---
> drivers/media/common/videobuf2/videobuf2-core.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 7e081716b8da..37d0186ba330 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -704,12 +704,11 @@ EXPORT_SYMBOL(vb2_verify_memory_type);
>
> static void set_queue_consistency(struct vb2_queue *q, bool consistent_mem)
> {
> + q->dma_attrs &= ~DMA_ATTR_NON_CONSISTENT;
> +
> if (!vb2_queue_allows_cache_hints(q))
> return;
> -
> - if (consistent_mem)
> - q->dma_attrs &= ~DMA_ATTR_NON_CONSISTENT;
> - else
> + if (!consistent_mem)
> q->dma_attrs |= DMA_ATTR_NON_CONSISTENT;
> }
>
>
Is it OK with you if I fold this patch into the original patch series and make a
new PR for it? I prefer to have a series merged without a bug, rather than fixing
it in a final patch.
Regards,
Hans
