Michael Barkowski wrote: > Kumar Gala wrote: > > > > On Oct 2, 2009, at 9:46 AM, Timur Tabi wrote: > > > >> Michael Barkowski wrote: > >>> Just wondering - is there a case where using volatile for UCC > >>> parameter RAM for example will not work, or is the use of I/O > >>> accessors everywhere an attempt to be portable to other architectures? > >> > >> 'volatile' just doesn't really do what you think it should do. The > >> PowerPC architecture is too complicated w.r.t. ordering of reads and > >> writes. In other words, you can't trust it. > >> > >> No one should be using 'volatile' to access I/O registers. > > > > See Documentation/volatile-considered-harmful.txt > > > > I'm happy to adopt your interpretation of it, and I appreciate the > explanation. > > from Documentation/volatile-considered-harmful.txt: > > - The above-mentioned accessor functions might use volatile on > > architectures where direct I/O memory access does work. Essentially, > > each accessor call becomes a little critical section on its own and > > ensures that the access happens as expected by the programmer. > > Part of it was that I wondered if this was one of those architectures. I > guess not.
I guess this could only work on architectures having a totally ordered memory model. Definitely not the case for Power. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
