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

Guo Ren
2021-05-19T05:48:37Z

On Wed, May 19, 2021 at 1:20 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Wed, May 19, 2021 at 05:04:13AM +0000, guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > The RISC-V ISA doesn't yet specify how to query or modify PMAs, so let
> > vendors define the custom properties of memory regions in PTE.
>
> Err, hell no. The ISA needs to gets this fixed first. Then we can
> talk about alternatives patching things in or trapping in the SBI.
> But if the RISC-V ISA can't get these basic done after years we can't
> support it in Linux at all.

The patchset just leaves a configuration chance for vendors. Before
RISC-V ISA fixes it, we should give the chance to let vendor solve
their real chip issues.

--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/