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
