Re: [PATCH RFC 0/3] riscv: Add DMA_COHERENT support

Christoph Hellwig
2021-05-20T05:48:26Z

On Thu, May 20, 2021 at 09:45:45AM +0800, Guo Ren wrote:
> It's a very big MIPS smell. What's the attribute of the uncached
> window? (uncached + strong-order/ uncached + weak, most vendors still
> use AXI interconnect, how to deal with a bufferable attribute?) In
> fact, customers' drivers use different ways to deal with DMA memory in
> non-coherent SOC. Most riscv SOC vendors are from ARM, so giving them
> the same way in DMA memory is a smart choice. So using PTE attributes
> is more suitable.

I'm not saying it is a good idea. Just that apparently this exists in
the ASICs.