Hi Mikhail,
Le lundi 03 mars 2025 à 14:40 +0300, Mikhail Rudenko a écrit :
When support for V4L2_FLAG_MEMORY_NON_CONSISTENT was removed in commit 129134e5415d ("media: media/v4l2: remove V4L2_FLAG_MEMORY_NON_CONSISTENT flag"), vb2_dc_dmabuf_ops_{begin,end}_cpu_access() functions were made no-ops. Later, when support for V4L2_MEMORY_FLAG_NON_COHERENT was introduced in commit c0acf9cfeee0 ("media: videobuf2: handle V4L2_MEMORY_FLAG_NON_COHERENT flag"), the above functions remained no-ops, making cache maintenance for non-coherent dmabufs allocated by dma-contig impossible.
Fix this by reintroducing dma_sync_sgtable_for_{cpu,device} and {flush,invalidate}_kernel_vmap_range calls to vb2_dc_dmabuf_ops_{begin,end}_cpu_access() functions for non-coherent buffers.
Fixes: c0acf9cfeee0 ("media: videobuf2: handle V4L2_MEMORY_FLAG_NON_COHERENT flag") Cc: stable@vger.kernel.org Signed-off-by: Mikhail Rudenko mike.rudenko@gmail.com
.../media/common/videobuf2/videobuf2-dma-contig.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c index a13ec569c82f6da2d977222b94af32e74c6c6c82..d41095fe5bd21faf815d6b035d7 bc888a84a95d5 100644 --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c @@ -427,6 +427,17 @@ static int vb2_dc_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf, enum dma_data_direction direction) {
- struct vb2_dc_buf *buf = dbuf->priv;
- struct sg_table *sgt = buf->dma_sgt;
- if (!buf->non_coherent_mem)
return 0;- if (buf->vaddr)
invalidate_kernel_vmap_range(buf->vaddr, buf->size);
What would make me a lot more confortable with this change is if you enable kernel mappings for one test. This will ensure you cover the call to "invalidate" in your testing. I'd like to know about the performance impact. With this implementation it should be identical to the VB2 one.
What I was trying to say in previous comments, is that my impression is that we can skip this for CPU read access, since we don't guaranty concurrent access anyway. Both address space can keep their cache in that case. Though, I see RKISP does not use kernel mapping plus I'm not reporting a bug, but checking if we should leave a comment for possible users of kernel mapping in the future ?
- dma_sync_sgtable_for_cpu(buf->dev, sgt, direction);
return 0; } @@ -434,6 +445,17 @@ static int vb2_dc_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf, enum dma_data_direction direction) {
- struct vb2_dc_buf *buf = dbuf->priv;
- struct sg_table *sgt = buf->dma_sgt;
- if (!buf->non_coherent_mem)
return 0;- if (buf->vaddr)
flush_kernel_vmap_range(buf->vaddr, buf->size);- dma_sync_sgtable_for_device(buf->dev, sgt, direction);
return 0; }