Re: [PATCH v4 1/5] io: define several IO & PIO barrier types for the asm-generic version

Arnd Bergmann
2018-04-06T13:20:44Z

On Fri, Apr 6, 2018 at 2:50 PM, <okaya@codeaurora.org> wrote:
> On 2018-04-06 06:19, Arnd Bergmann wrote:
>>
>> On Thu, Apr 5, 2018 at 3:09 PM, Sinan Kaya <okaya@codeaurora.org> wrote:
>>>
>>
>> I would guess that at least s390 doesn't need the barriers
>> (maintainers on Cc now), but there may be others that want to
>> override the new barriers with weaker ones where an MMIO
>> access is guaranteed to serialize against DMA, or where
>> a specialized barrier for this case exists.
>>
>> Looking over the asm-generic implementation once more now,
>> I wonder if we should change the relaxed accessors to not have
>> any barriers (back to the version before your series) rather than
>> defaulting them to having the same barriers as the regular
>> readl/writel.
>
>
> I can do a follow up patch. You want to map them to raw api without any
> barriers as before. Right?

Right, but of course with the byteswap.

Arnd