diff options
| author | Xu Yang <xu.yang_2@nxp.com> | 2026-01-13 17:53:10 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-01-14 16:03:18 +0100 |
| commit | 9bcb4c4c330ca36ba7ab398c03d75c15b769d59d (patch) | |
| tree | 31da1a5688aa0bc4b38b4a0147b96d02501101d1 | |
| parent | 0bce8f19bba16277257a915e4fb94e1cfe99d760 (diff) | |
usb: gadget: uvc: retry vb2_reqbufs() with vb_vmalloc_memops if use_sg fail
Based on the reality[1][2] that vb2_dma_sg_alloc() can't alloc buffer with
device DMA limits, those device will always get below error: "swiotlb
buffer is full (sz: 393216 bytes), total 65536 (slots), used 2358 (slots)"
and the uvc gadget function can't work at all.
The videobuf2-dma-sg.c driver doesn't has a formal improve about this issue
till now. For UVC gadget, the videobuf2 subsystem doesn't do dma_map() on
vmalloc returned big buffer when allocate the video buffers, however, it do
it for dma_sg returned buffer. So the issue happens for vb2_dma_sg_alloc().
To workaround the issue, lets retry vb2_reqbufs() with
vb_vmalloc_memops if it fails to allocate buffer with vb2_dma_sg_memops.
If use vmalloced buffer, UVC gadget will allocate some small buffers for
each usb_request to do dma transfer, then uvc driver will memcopy data
from big buffer to small buffer.
Link[1]: https://lore.kernel.org/linux-media/20230828075420.2009568-1-anle.pan@nxp.com/
Link[2]: https://lore.kernel.org/linux-media/20230914145812.12851-1-hui.fang@nxp.com/
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260113-uvc-gadget-fix-patch-v2-4-62950ef5bcb5@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/gadget/function/uvc_queue.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c index 21d80322cb61..586e5524c171 100644 --- a/drivers/usb/gadget/function/uvc_queue.c +++ b/drivers/usb/gadget/function/uvc_queue.c @@ -182,7 +182,15 @@ int uvcg_alloc_buffers(struct uvc_video_queue *queue, { int ret; +retry: ret = vb2_reqbufs(&queue->queue, rb); + if (ret < 0 && queue->use_sg) { + uvc_trace(UVC_TRACE_IOCTL, + "failed to alloc buffer with sg enabled, try non-sg mode\n"); + queue->use_sg = 0; + queue->queue.mem_ops = &vb2_vmalloc_memops; + goto retry; + } return ret ? ret : rb->count; } |