On Wed, Jun 05, 2024 at 04:40:35PM +0900, Yunke Cao wrote:
> When multiple planes use the same dma buf, each plane will have its own dma
> buf attachment and mapping. It is a waste of IOVA space.
>
> This patch adds a dbuf_duplicated boolean in vb2_plane. If a plane's dbuf
> is the same as an existing plane, do not create another attachment and
> mapping.
>
> Signed-off-by: Yunke Cao <yunkec@xxxxxxxxxxxx>
> ---
> v3
> - Adjust the patch according to the previous patches to resolve conflicts.
> - Add comment to explain the purpose of the change.
>
> v2
> - Separate out the refactor changes out to previous patches.
> - Fix mem_priv check.
> ---
> .../media/common/videobuf2/videobuf2-core.c | 29 ++++++++++++++++---
> include/media/videobuf2-core.h | 3 ++
> 2 files changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index cbc8928f0418..90b65bf6c463 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -304,10 +304,13 @@ static void __vb2_plane_dmabuf_put(struct vb2_buffer *vb, struct vb2_plane *p)
> if (!p->mem_priv)
> return;
>
> - if (p->dbuf_mapped)
> - call_void_memop(vb, unmap_dmabuf, p->mem_priv);
> + if (!p->dbuf_duplicated) {
> + if (p->dbuf_mapped)
> + call_void_memop(vb, unmap_dmabuf, p->mem_priv);
> +
> + call_void_memop(vb, detach_dmabuf, p->mem_priv);
> + }
>
> - call_void_memop(vb, detach_dmabuf, p->mem_priv);
> dma_buf_put(p->dbuf);
> p->mem_priv = NULL;
> p->dbuf = NULL;
> @@ -316,6 +319,7 @@ static void __vb2_plane_dmabuf_put(struct vb2_buffer *vb, struct vb2_plane *p)
> p->length = 0;
> p->m.fd = 0;
> p->data_offset = 0;
> + p->dbuf_duplicated = false;
> }
>
> /*
> @@ -1374,7 +1378,7 @@ static int __prepare_dmabuf(struct vb2_buffer *vb)
> struct vb2_plane planes[VB2_MAX_PLANES];
> struct vb2_queue *q = vb->vb2_queue;
> void *mem_priv;
> - unsigned int plane;
> + unsigned int plane, i;
> int ret = 0;
> bool reacquired = vb->planes[0].mem_priv == NULL;
>
> @@ -1427,6 +1431,23 @@ static int __prepare_dmabuf(struct vb2_buffer *vb)
> }
>
> for (plane = 0; plane < vb->num_planes; ++plane) {
> + /*
> + * This is an optimization to reduce dma_buf attachment/mapping.
> + * When the same dma_buf is used for multiple planes, there is no need
> + * to create duplicated attachments.
> + */
> + for (i = 0; i < plane; ++i) {
> + if (planes[plane].dbuf == vb->planes[i].dbuf) {
Oops, I just realized that we forgot about one thing. vb_queue has
alloc_devs[] array with per-plane struct device used for DMA mapping
API. If those are different, we can't reuse the attachment, so we need
to check them here too...
Best regards,
Tomasz
> + vb->planes[plane].dbuf_duplicated = true;
> + vb->planes[plane].dbuf = vb->planes[i].dbuf;
> + vb->planes[plane].mem_priv = vb->planes[i].mem_priv;
> + break;
> + }
> + }
> +
> + if (vb->planes[plane].dbuf_duplicated)
> + continue;
> +
> /* Acquire each plane's memory */
> mem_priv = call_ptr_memop(attach_dmabuf,
> vb,
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 955237ac503d..053ced60595f 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -154,6 +154,8 @@ struct vb2_mem_ops {
> * @mem_priv: private data with this plane.
> * @dbuf: dma_buf - shared buffer object.
> * @dbuf_mapped: flag to show whether dbuf is mapped or not
> + * @duplicated_dbuf: boolean to show whether dbuf is duplicated with a
> + * previous plane of the buffer.
> * @bytesused: number of bytes occupied by data in the plane (payload).
> * @length: size of this plane (NOT the payload) in bytes. The maximum
> * valid size is MAX_UINT - PAGE_SIZE.
> @@ -179,6 +181,7 @@ struct vb2_plane {
> void *mem_priv;
> struct dma_buf *dbuf;
> unsigned int dbuf_mapped;
> + bool dbuf_duplicated;
> unsigned int bytesused;
> unsigned int length;
> unsigned int min_length;
> --
> 2.45.1.288.g0e0cd299f1-goog
>
