From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Subject: Re: [PATCH v3] ad7877: keep dma rx buffers in seperate cache lines
Date: Tue, 11 May 2010 14:53:59 -0700
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To: Johannes Weiner <jw@emlix.com>
Cc: Mike Frysinger <vapier.adi@gmail.com>, Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@cs.helsinki.fi>, Matt Mackall <mpm@selenic.com>, Andrew Morton <akpm@linux-foundation.org>, Oskar Schirmer <os@emlix.com>, Michael Hennerich <Michael.Hennerich@analog.com>, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Daniel =?iso-8859-1?Q?Gl=F6ckner?= <dg@emlix.com>, Oliver Schneidewind <osw@emlix.com>, Nick Piggin <npiggin@suse.de>, David Rientjes <rientjes@google.com>, David Brownell <dbrownell@users.sourceforge.net>, Grant Likely <grant.likely@secretlab.ca>

On Tue, May 11, 2010 at 11:48:36PM +0200, Johannes Weiner wrote:
> On Tue, May 11, 2010 at 04:54:41PM -0400, Mike Frysinger wrote:
> > does the phrase "DMA safe buffer" imply cache alignment ?
> 
> I guess that depends on the architectural requirements.  On x86,
> apparently, not so much.  On ARM, probably yes, as it's the
> requirement to properly maintain coherency.

It looks liek ARM (and a few others) do this:

[dtor@hammer work]$ grep -r ARCH_KMALLOC_MINALIGN arch/
arch/sh/include/asm/page.h:#define ARCH_KMALLOC_MINALIGN        L1_CACHE_BYTES
arch/frv/include/asm/mem-layout.h:#define       ARCH_KMALLOC_MINALIGN           8
arch/powerpc/include/asm/page_32.h:#define ARCH_KMALLOC_MINALIGN        L1_CACHE_BYTES
arch/arm/include/asm/cache.h:#define ARCH_KMALLOC_MINALIGN      L1_CACHE_BYTES
arch/microblaze/include/asm/page.h:#define ARCH_KMALLOC_MINALIGN        L1_CACHE_BYTES
arch/mips/include/asm/mach-tx49xx/kmalloc.h: * All happy, no need to define ARCH_KMALLOC_MINALIGN
arch/mips/include/asm/mach-ip27/kmalloc.h: * All happy, no need to define ARCH_KMALLOC_MINALIGN
arch/mips/include/asm/mach-ip32/kmalloc.h:#define ARCH_KMALLOC_MINALIGN 32
arch/mips/include/asm/mach-ip32/kmalloc.h:#define ARCH_KMALLOC_MINALIGN 128
arch/mips/include/asm/mach-generic/kmalloc.h:#define ARCH_KMALLOC_MINALIGN      128
arch/avr32/include/asm/cache.h:#define ARCH_KMALLOC_MINALIGN    L1_CACHE_BYTES

-- 
Dmitry