On Sat, Aug 1, 2015 at 9:33 AM, Borislav Petkov <[email protected]> wrote:
>
> Well, it doesn't really make sense to write-combine IO memory, does it?
Quite the reverse.
It makes no sense to write-combine normal memory (RAM), because caches
work and sane memory is always cache-coherent. So marking regular
memory write-combining is a sign of crap hardware (which admittedly
exists all too much, but hopefully goes away).
In contrast, marking MMIO memory write-combining is not a sign of crap
hardware - it's just a sign of things like frame buffers on the card
etc. Which very much wants write combining. So WC for MMIO at least
makes sense.
Yes, yes, I realize that "crap hardware" may actually be the more
common case, but still..
Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
