From: "H. Peter Anvin" <hpa@zytor.com>
To: Ben Hutchings <bhutchings@solarflare.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
David Miller <davem@davemloft.net>,
tglx@linutronix.de, mingo@redhat.com, netdev@vger.kernel.org,
linux-net-drivers@solarflare.com, x86@kernel.org
Subject: Re: [PATCH 2/3] x86_64: Define 128-bit memory-mapped I/O operations
Date: Wed, 22 Aug 2012 08:13:41 -0700 [thread overview]
Message-ID: <5034F725.2090802@zytor.com> (raw)
In-Reply-To: <1345647537.2709.0.camel@bwh-desktop.uk.solarflarecom.com>
On 08/22/2012 07:58 AM, Ben Hutchings wrote:
>
> Because reordering, and see the comment at the top of this file.
>
Your architecture sounds similar to one I once worked on (Orion
Microsystems CNIC/OPA-2). That architecture had a descriptor ring in
device memory, and a single trigger bit would move the head pointer.
We used write combining to write out a set of descriptors, and then used
a non-write-combining write to do the final write which bumps the head
pointer. The UC write flushes the write combiners ahead of it, so it
ends up with two transactions (one for the WC data and one for the UC
trigger) but it could frequently push quite a few descriptors in that
operation.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2012-08-22 15:13 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-22 1:17 [PATCH 0/3] x86_64, sfc: 128-bit memory-mapped I/O Ben Hutchings
2012-08-22 1:20 ` [PATCH 1/3] x86_64: Define 128-bit types for kernel code only Ben Hutchings
2012-08-22 1:23 ` [PATCH 2/3] x86_64: Define 128-bit memory-mapped I/O operations Ben Hutchings
2012-08-22 1:37 ` H. Peter Anvin
2012-08-22 2:04 ` Ben Hutchings
2012-08-22 2:34 ` David Miller
2012-08-22 3:24 ` H. Peter Anvin
2012-08-22 3:29 ` David Miller
2012-08-22 3:49 ` H. Peter Anvin
2012-08-22 3:52 ` Linus Torvalds
2012-08-22 3:59 ` H. Peter Anvin
2012-08-22 4:14 ` David Miller
2012-08-22 21:14 ` David Miller
2012-08-22 21:28 ` Linus Torvalds
2012-08-22 21:38 ` David Miller
2012-08-22 4:35 ` Linus Torvalds
2012-08-22 5:00 ` David Miller
2012-08-22 14:06 ` Linus Torvalds
2012-08-22 4:42 ` Linus Torvalds
2012-08-22 13:26 ` Ben Hutchings
2012-08-22 14:20 ` Linus Torvalds
2012-08-22 14:24 ` Ben Hutchings
2012-08-22 14:30 ` Benjamin LaHaise
2012-08-22 14:58 ` Ben Hutchings
2012-08-22 15:13 ` H. Peter Anvin [this message]
2012-08-22 15:27 ` David Laight
2012-08-22 15:49 ` H. Peter Anvin
2012-08-22 15:51 ` Ben Hutchings
2012-08-22 15:54 ` H. Peter Anvin
2012-08-22 16:44 ` Ben Hutchings
2012-08-22 16:49 ` H. Peter Anvin
2012-08-22 16:55 ` Linus Torvalds
2012-08-22 17:09 ` Ben Hutchings
2012-08-22 17:12 ` H. Peter Anvin
2012-08-22 17:27 ` Ben Hutchings
2012-08-22 17:54 ` Linus Torvalds
2012-08-22 18:11 ` Ben Hutchings
2012-08-22 18:18 ` H. Peter Anvin
2012-08-22 18:28 ` Linus Torvalds
2012-08-22 19:01 ` Ben Hutchings
2012-08-22 17:26 ` Linus Torvalds
2012-08-22 16:51 ` Linus Torvalds
2012-08-22 16:59 ` H. Peter Anvin
2012-08-22 15:51 ` H. Peter Anvin
2012-08-22 14:50 ` Linus Torvalds
2012-08-22 14:56 ` Linus Torvalds
2012-08-22 15:05 ` David Laight
2012-08-22 15:16 ` Linus Torvalds
2012-08-22 15:41 ` Ben Hutchings
2012-08-22 14:42 ` David Laight
2012-08-22 1:26 ` [PATCH 3/3] sfc: Use __raw_writeo() to perform TX descriptor push where possible Ben Hutchings
2012-08-22 1:38 ` [PATCH 0/3] x86_64, sfc: 128-bit memory-mapped I/O H. Peter Anvin
2012-08-22 1:43 ` Ben Hutchings
2012-08-22 1:59 ` H. Peter Anvin
2012-08-22 2:10 ` Ben Hutchings
2012-08-22 2:31 ` H. Peter Anvin
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