RFC on writel and writel_relaxed

[Jason Gunthorpe]

On Tue, Mar 27, 2018 at 09:56:47AM +0200, Arnd Bergmann wrote:
> On Tue, Mar 27, 2018 at 12:27 AM, Jason Gunthorpe <jgg at ziepe.ca> wrote:
> > On Tue, Mar 27, 2018 at 09:01:57AM +1100, Benjamin Herrenschmidt wrote:
> >> On Mon, 2018-03-26 at 17:46 -0400, Sinan Kaya wrote:
> >
> > I even see patches adding wmb() based on actual observed memory
> > corruption during testing on Intel:
> >
> > https://patchwork.kernel.org/patch/10177207/
> >
> > So you think all of this is unnecessary and writel is totally strongly
> > ordered, even on multi-socket Intel?
> 
> This example adds a wmb() between two writes to a coherent DMA
> area, it is definitely required there.

Ah! So it is, too many things called 'db' in that driver.. One of the
'db' is also WC BAR memory..

Jason