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

Drew Fustini
2021-05-19T06:54:34Z

On Wed, May 19, 2021 at 08:06:17AM +0200, Christoph Hellwig wrote:
> On Wed, May 19, 2021 at 02:05:00PM +0800, Guo Ren wrote:
> > Since the existing RISC-V ISA cannot solve this problem, it is better
> > to provide some configuration for the SOC vendor to customize.
>
> We've been talking about this problem for close to five years. So no,
> if you don't manage to get the feature into the ISA it can't be
> supported.

Isn't it a good goal for Linux to support the capabilities present in
the SoC that a currently being fab'd?

I believe the CMO group only started last year [1] so the RV64GC SoCs
that are going into mass production this year would not have had the
opporuntiy of utilizing any RISC-V ISA extension for handling cache
management.

Thanks,
Drew

[1] https://github.com/riscv/riscv-CMOs