Re: [PATCH RFC 0/3] API for 128-bit IO access

Yury Norov
2018-01-26T09:05:42Z

On Wed, Jan 24, 2018 at 10:22:13AM +0000, Will Deacon wrote:
> On Wed, Jan 24, 2018 at 12:05:16PM +0300, Yury Norov wrote:
> > This series adds API for 128-bit memory IO access and enables it for ARM64.
> > The original motivation for 128-bit API came from new Cavium network device
> > driver. The hardware requires 128-bit access to make things work. See
> > description in patch 3 for details.
> >
> > Also, starting from ARMv8.4, stp and ldp instructions become atomic, and
> > API for 128-bit access would be helpful in core arm64 code.
>
> Only for normal, cacheable memory, so they're not suitable for IO accesses
> as you're proposing here.

Hi Will,

Thanks for clarification.

Could you elaborate, do you find 128-bit read/write API useless, or
you just correct my comment?

I think that ordered uniform 128-bit access API would be helpful, even
if not atomic.

Yury.