On Tue, Feb 12, 2019 at 12:55:17PM +0100, Arnd Bergmann wrote: > On Mon, Feb 11, 2019 at 6:45 PM Will Deacon <will.deacon@xxxxxxx> wrote: > > > > The inX() I/O accessors must enforce ordering against subsequent calls > > to the delay() routines, so that a read-back from a device can be used > > to postpone a subsequent write to the same device. > > > > On some architectures, including arm64, this ordering can only be > > achieved by creating a dependency on the value returned by the inX() > > operation, so we need to pass the value we read to the __io_par() > > macro in this case. > > > > Reported-by: Andrew Murray <andrew.murray@xxxxxxx> > > Signed-off-by: Will Deacon <will.deacon@xxxxxxx> > > --- > > include/asm-generic/io.h | 8 ++++---- > > For changing the asm-generic file in the arm64 tree, > > Acked-by: Arnd Bergmann <arnd@xxxxxxxx> Thanks, Arnd. > For all I can see, this should not conflict with the usage of the > same macros on RISC-V, though it does make add a significant > difference, so I'd like to see an Ack from the RISC-V folks as > well (added to Cc), or possibly a change to arch/riscv/include/asm/io.h > to do a corresponding change. There's already a comment in that header which says that the accesses are ordered wrt timer reads, so I don't think anything needs to change there. For consistency with the macro arguments, I could augment their __io_par to take the read value as an unused argument, if that's what you mean? Will
