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From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: remove ixp2000 platform
Date: Wed, 7 Mar 2012 09:14:09 +0000	[thread overview]
Message-ID: <20120307091409.GL17370@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CACRpkdYQpnSMVWUizEYHTjx_AK5Ai7dos0SBd208Wf5ZJLdrCw@mail.gmail.com>

On Wed, Mar 07, 2012 at 09:40:31AM +0100, Linus Walleij wrote:
> Network equipment seems to like using BE.
> 
> I have some vague idea that this is beacuse IP packets are big
> endian, and thus you can process them quickly by just casting fields
> to e.g. u32 pointers and read them.
> 
> I don't know if this is true, but seems to much of a correlation to
> be pure coincidence. Thus a pretty interesting subject in
> embedded ARM not used for tablets/mobile/generic computing
> kind of stuff.

ISTR Nicolas explained this to me as being an established thing in the
comms sector.  They expect BE and only understand BE.

I did point out that you end up with many more endian conversions by
going to BE, mainly because PCI is LE and all your PCI accesses have
to be endian-swapped.  So in terms of bandwidth, I'd expect an ARM
PCI platform running in BE mode to have worse throughput than a LE
PCI platform.

But... if BE allows the comms people to keep their warm fuzzy feeling
who are we to argue.

  reply	other threads:[~2012-03-07  9:14 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1330450426-14639-1-git-send-email-robherring2@gmail.com>
2012-02-28 19:45 ` [PATCH] ARM: remove ixp2000 platform Arnd Bergmann
2012-03-06  1:41   ` Nicolas Pitre
2012-03-06  2:44     ` Rob Herring
2012-03-06  9:16       ` Russell King - ARM Linux
2012-03-06 14:11     ` Arnd Bergmann
2012-03-06 16:51       ` Nicolas Pitre
2012-03-06 17:10         ` Arnd Bergmann
2012-03-06 17:38           ` Richard Cochran
2012-03-07  8:40         ` Linus Walleij
2012-03-07  9:14           ` Russell King - ARM Linux [this message]
2012-03-07 11:54             ` Greg Ungerer
2012-03-11 12:31               ` Krzysztof Halasa
2012-03-11 23:48                 ` Greg Ungerer
2012-03-13 21:15                   ` Krzysztof Halasa
2012-03-07 17:09       ` Imre Kaloz

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