Re: [PATCH] add delay between port write and port read

[Mikulas Patocka]

On Tue, 19 Feb 2019, Maciej W. Rozycki wrote:

> On Tue, 19 Feb 2019, Mikulas Patocka wrote:
> 
> > >  As I say, shouldn't the barrier be in `iowriteX' instead?  I don't 
> > > suppose these are allowed to be weakly ordered.
> > > 
> > >   Maciej
> > 
> > iowriteX is for memory-mapped I/O, out[bwl] is for I/O ports.
> 
>  Well, actually `iowriteX' is generic and for MMIO you have `writeX'.  
> See lib/iomap.c, the comment at the top and e.g. `iowrite8' there for an 
> actual proof.  Alpha may have an oddball implementation, but there you go. 
> Drivers will assume they can do `iowriteX' to any kind of I/O resource, 
> and ordering must be respected as per Documentation/memory-barriers.txt.
> 
>   Maciej

So, do you think that the barrier whould be added to iowriteX and slow 
down every MMIO access?

Mikulas