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Subject: Re: [RFC][PATCH 12/15] videobuf2: add begin/end cpu_access callbacks
 to dma-sg
To:     Sergey Senozhatsky <senozhatsky@chromium.org>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Tomasz Figa <tfiga@chromium.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>
Cc:     Sakari Ailus <sakari.ailus@iki.fi>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Pawel Osciak <posciak@chromium.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20191217032034.54897-1-senozhatsky@chromium.org>
 <20191217032034.54897-13-senozhatsky@chromium.org>
From:   Hans Verkuil <hverkuil@xs4all.nl>
Message-ID: <1c5198dc-db4e-47d6-0d8b-259fbbb6372f@xs4all.nl>
Date:   Fri, 10 Jan 2020 11:13:18 +0100
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On 12/17/19 4:20 AM, Sergey Senozhatsky wrote:
> Provide begin_cpu_access() and end_cpu_access() dma_buf_ops
> callbacks for cache synchronisation on exported buffers.
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  .../media/common/videobuf2/videobuf2-dma-sg.c | 22 +++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> index 6db60e9d5183..bfc99a0cb7b9 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> @@ -470,6 +470,26 @@ static void vb2_dma_sg_dmabuf_ops_release(struct dma_buf *dbuf)
>  	vb2_dma_sg_put(dbuf->priv);
>  }
>  

There is no corresponding vb2_sg_buffer_consistent function here.

Looking more closely I see that vb2_dma_sg_alloc doesn't pass the dma_attrs
argument to dma_map_sg_attrs, thus V4L2_FLAG_MEMORY_NON_CONSISTENT has no
effect on dma-sg buffers.

Is there a reason why dma_attrs isn't passed on to dma_map_sg_attrs()?

I suspect it was just laziness in the past, and that it should be wired
up, just as for dma-contig.

Regards,

	Hans

> +static int vb2_dma_sg_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf,
> +					enum dma_data_direction direction)
> +{
> +	struct vb2_dma_sg_buf *buf = dbuf->priv;
> +	struct sg_table *sgt = buf->dma_sgt;
> +
> +	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
> +	return 0;
> +}
> +
> +static int vb2_dma_sg_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf,
> +					enum dma_data_direction direction)
> +{
> +	struct vb2_dma_sg_buf *buf = dbuf->priv;
> +	struct sg_table *sgt = buf->dma_sgt;
> +
> +	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
> +	return 0;
> +}
> +
>  static void *vb2_dma_sg_dmabuf_ops_vmap(struct dma_buf *dbuf)
>  {
>  	struct vb2_dma_sg_buf *buf = dbuf->priv;
> @@ -488,6 +508,8 @@ static const struct dma_buf_ops vb2_dma_sg_dmabuf_ops = {
>  	.detach = vb2_dma_sg_dmabuf_ops_detach,
>  	.map_dma_buf = vb2_dma_sg_dmabuf_ops_map,
>  	.unmap_dma_buf = vb2_dma_sg_dmabuf_ops_unmap,
> +	.begin_cpu_access = vb2_dma_sg_dmabuf_ops_begin_cpu_access,
> +	.end_cpu_access = vb2_dma_sg_dmabuf_ops_end_cpu_access,
>  	.vmap = vb2_dma_sg_dmabuf_ops_vmap,
>  	.mmap = vb2_dma_sg_dmabuf_ops_mmap,
>  	.release = vb2_dma_sg_dmabuf_ops_release,
>