On 03/03/2020 16:40, Arnd Bergmann wrote:
On Tue, Mar 3, 2020 at 2:18 PM John Garry <john.garry@xxxxxxxxxx> wrote:
+ linux-arch
For background, see
https://lore.kernel.org/lkml/2e80d7bc-32a0-cc40-00a9-8a383a1966c2@xxxxxxxxxx/
So today only ARM64 uses it for this relevant code, above. But maybe
others in future will want to use it - any arch without native IO port
access is a candidate.
I'm looking at Arnd here for help.
As long as the expectations are set, I see no reason why it shouldn't
but, I'll let Arnd comment on it too.
ok, so it looks reasonable consider replicating your change for ***, above.
To be clear, I would make this change in lib/logic_pio.c since
__io_pbr() can be overridden per-arch:
#define BUILD_LOGIC_IO(bw, type)
type logic_in##bw(unsigned long addr)
{
type ret = (type)~0;
if (addr < MMIO_UPPER_LIMIT) {
- ret = read##bw(PCI_IOBASE + addr);
+ __io_pbr();
+ ret = __raw_read##bw(PCI_IOBASE + addr);
+ __io_pbr();
__io_par();
} else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {
struct logic_pio_hwaddr *entry = find_io_range(addr);
...
(forgetting leX_to_cpu for the moment)
Yes, I suppose this is required to get consistent behavior on arm64,
which overrides __io_par() but not __io_ar(), with the current code
the barrier after read is weaker when LOGIC_PIO is enabled than it
is otherwise.
Ok.
Apart from that, this code is somewhat hidden. I mean, most people would
consider generic IO port accessors come from asm-generic/io.h only,
which is not the case here. Maybe this can be better integrated into
asm-generic/io.h, the only hint today being the logic_pio.h include half
way through the file.
For other architectures, I suppose we would need another indirection
level, as those can also override the default inb() itself to do something
other than readb(PCI_IOBASE + addr), and that is not handled
here either. We can do that if we need LOGIC_PIO on a second
architecture.
Jiaxun Yang did mention that MIPS may want to move away from its own IO
space management.
Thanks,
John
