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

Tomasz Figa
2023-09-12T07:52:25Z

On Tue, Sep 12, 2023 at 4:43 PM Hui Fang <hui.fang@nxp.com> wrote:
>
> On Tue, Sep 12, 2023 at 4:11 PM Tomasz Figa <tfiga@chromium.org> wrote:
> > Is your DMA device restricted only to the bottom-most 4 GB (32-bit DMA
> > address)? If yes, would it make sense to also allocate from that area rather
> > than bouncing the memory?
>
> The DMA device use 32-bit DMA address.
> From user space, can't control the v4l2 buffer address, may still change the
> code of vb2_dma_sg_alloc().

Right. You may want to try modifying vb2_dma_sg_alloc_compacted() to
use dma_alloc_pages() instead of alloc_pages().

Best regards,
Tomasz