From: Anton Blanchard <anton@samba.org>
To: davem@redhat.com, ralf@uni-koblenz.de, linux-kernel@vger.kernel.org
Subject: Re: memory-mapped i/o barrier
Date: Mon, 14 Jan 2002 17:24:54 +1100 [thread overview]
Message-ID: <20020114062454.GA18794@krispykreme> (raw)
In-Reply-To: <20020110134859.A729245@sgi.com>
In-Reply-To: <20020110134859.A729245@sgi.com>
Hi,
> Here's a copy of a patch I just got accepted into the 2.5 patch for
> ia64, and I'm wondering if you guys will accept something similar. On
> mips64, mmiob() could just be implemented as a 'sync', but I'm not
> sure how to do it (or if it's even necessary) on other platforms.
> Please let me know what you think. I wrote a small documentation file
> for the macro that appears at the top of the patch.
>
> Thanks,
> Jesse
>
>
> diff -Naur --exclude=*~ --exclude=TAGS linux-2.4.17-ia64/Documentation/mmio_barrier.txt linux-2.4.17-ia64-mmiob/Documentation/mmio_barrier.txt
> --- linux-2.4.17-ia64/Documentation/mmio_barrier.txt Wed Dec 31 16:00:00 1969
> +++ linux-2.4.17-ia64-mmiob/Documentation/mmio_barrier.txt Tue Jan 8 15:57:37 2002
> @@ -0,0 +1,15 @@
> +On some platforms, so-called memory-mapped I/O is weakly ordered. For
> +example, the following might occur:
> +
> +CPU A writes 0x1 to Device #1
> +CPU B writes 0x2 to Device #1
> +Device #1 sees 0x2
> +Device #1 sees 0x1
Can loads/stores also complete out of order to IO? (the example just shows
a store from one cpu passing one from another cpu)
On ppc32/ppc64 this can happen, it is fixed up in the low level pci
routines. Is there a case where you cant wrap it up in the low level
routines like ppc32/ppc64?
Anton
next prev parent reply other threads:[~2002-01-15 0:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-10 21:48 memory-mapped i/o barrier Jesse Barnes
2002-01-10 23:05 ` Alan Cox
2002-01-10 22:59 ` Jesse Barnes
2002-01-14 6:24 ` Anton Blanchard [this message]
2002-01-15 1:02 ` Jesse Barnes
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