From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] fb.h: ARM uses __raw_{read/write}
Date: Mon, 13 Jun 2011 15:37:10 +0200
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Cc: Catalin Marinas <catalin.marinas@arm.com>,
        Paul Mundt <lethal@linux-sh.org>,
        H Hartley Sweeten <hartleys@visionengravers.com>,
        Russell King <linux@arm.linux.org.uk>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        linux-fbdev@vger.kernel.org
References: <201106101731.08578.hartleys@visionengravers.com> <20110613040003.GA29731@linux-sh.org> <20110613100819.GA26914@1n450.cable.virginmedia.net>
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On Monday 13 June 2011 12:08:19 Catalin Marinas wrote:
> The change proposed by Hartley wouldn't make much difference from the
> current volatile accesses (__raw_* accessors are implemented as volatile
> on ARM).

I guess it would mainly make a difference if we get a platform where
the PCI bus window is not in the same address space as the regular
physical memory and the accessors actually need to do a computation
on the address. AFAICT, ARM does not currently have any such platform
and I would hope that it says that way.

> I think the memcpy_(from|to)io could be optimised on ARM to only add a
> barrier before or after he copying loop.

Agreed, good idea.

	Arnd
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