[PATCH v2] asm-generic: introduce io_stop_wc() and add implementation for ARM64

[Catalin Marinas]

On Tue, Dec 21, 2021 at 10:17:27AM +0100, Arnd Bergmann wrote:
> On Tue, Dec 21, 2021 at 4:55 AM Xiongfeng Wang
> <wangxiongfeng2 at huawei.com> wrote:
> >
> > For memory accesses with write-combining attributes (e.g. those returned
> > by ioremap_wc()), the CPU may wait for prior accesses to be merged with
> > subsequent ones. But in some situation, such wait is bad for the
> > performance.
> >
> > We introduce io_stop_wc() to prevent the merging of write-combining
> > memory accesses before this macro with those after it.
> >
> > We add implementation for ARM64 using DGH instruction and provide NOP
> > implementation for other architectures.
> >
> > Signed-off-by: Xiongfeng Wang <wangxiongfeng2 at huawei.com>
> > Suggested-by: Will Deacon <will at kernel.org>
> > Suggested-by: Catalin Marinas <catalin.marinas at arm.com>
> > ---
> > v1->v2: change 'Normal-Non Cacheable' to 'write-combining'
> 
> For asm-generic:
> 
> Acked-by: Arnd Bergmann <arnd at arndb.de>
> 
> Will, Catalin: if you are happy with this version, please merge it through the
> arm64 tree.

Thanks for the ack Arnd. I'll queue this through the arm64 tree.

-- 
Catalin