[PATCH] media: videobuf2-dma-sg: limit the sg segment size

Anle Pan
2023-08-27T23:58:31Z

When allocating from pages, the size of the sg segment is unlimited and
the default is UINT_MAX. This will cause the DMA stream mapping failed
later with a "swiotlb buffer full" error. The default maximum mapping
size is 128 slots x 2K = 256K, determined by "IO_TLB_SEGSIZE".
To fix the issue, limit the sg segment size according to
"dma_max_mapping_size" to match the mapping limit.

Signed-off-by: Anle Pan <anle.pan@nxp.com>
---
drivers/media/common/videobuf2/videobuf2-dma-sg.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
index fa69158a65b1..b608a7c5f240 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
@@ -105,6 +105,7 @@ static void *vb2_dma_sg_alloc(struct vb2_buffer *vb, struct device *dev,
struct sg_table *sgt;
int ret;
int num_pages;
+ size_t max_segment = 0;

if (WARN_ON(!dev) || WARN_ON(!size))
return ERR_PTR(-EINVAL);
@@ -134,8 +135,12 @@ static void *vb2_dma_sg_alloc(struct vb2_buffer *vb, struct device *dev,
if (ret)
goto fail_pages_alloc;

- ret = sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
- buf->num_pages, 0, size, GFP_KERNEL);
+ if (dev)
+ max_segment = dma_max_mapping_size(dev);
+ if (max_segment == 0)
+ max_segment = UINT_MAX;
+ ret = sg_alloc_table_from_pages_segment(buf->dma_sgt, buf->pages,
+ buf->num_pages, 0, size, max_segment, GFP_KERNEL);
if (ret)
goto fail_table_alloc;

--
2.25.1