From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Frysinger <vapier.adi@gmail.com>
Subject: Re: [PATCH v3] ad7877: keep dma rx buffers in seperate cache lines
Date: Tue, 11 May 2010 16:43:25 -0400
Message-ID: <AANLkTinZe1N2NFOzU32PL2AIZi9TovHj5pQ2Y65eOc1T@mail.gmail.com>
References: <1273487642-2169-1-git-send-email-os@emlix.com>
	<AANLkTiktu7N5IXknkkJ9D5L4z5plhuGvD45IVqJm9zG1@mail.gmail.com>
	<20100511063309.GC9644@core.coreip.homeip.net> <y2k84144f021005102342m18bce930g53599c9112565f78@mail.gmail.com>
	<AANLkTinV79HZqS1cktHDsTsHDel-0Nti_Uk4i7mGaRiK@mail.gmail.com>
	<1273608441.15067.1002.camel@calx> <AANLkTimt-eRCt_HTq7OUwzG1dgRuzJHk1tlgOcq4ocL7@mail.gmail.com>
	<alpine.DEB.2.00.1005111520260.1500@router.home> <AANLkTilEfZLWYxPmCQ1KHIvUGIF_8Qchali66wHNf2gB@mail.gmail.com>
	<4BE9C033.2020106@cs.helsinki.fi>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: QUOTED-PRINTABLE
Return-path: <linux-input-owner@vger.kernel.org>
Received: from mail-gx0-f227.google.com ([209.85.217.227]:55948 "EHLO
	mail-gx0-f227.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754395Ab0EKUn4 convert rfc822-to-8bit (ORCPT
	<rfc822;linux-input@vger.kernel.org>);
	Tue, 11 May 2010 16:43:56 -0400
In-Reply-To: <4BE9C033.2020106@cs.helsinki.fi>
Sender: linux-input-owner@vger.kernel.org
List-Id: linux-input@vger.kernel.org
To: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Christoph Lameter <cl@linux.com>, Matt Mackall <mpm@selenic.com>, Dmitry Torokhov <dmitry.torokhov@gmail.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, =?UTF-8?Q?Daniel_Gl=C3=B6ckner?= <dg@emlix.com>, Oliver Schneidewind <osw@emlix.com>, Johannes Weiner <jw@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 16:38, Pekka Enberg wrote:
> Mike Frysinger wrote:
>> that is a question for David/Grant. =C2=A0i'm not the SPI core maint=
ainer,
>> i'm merely watching over some SPI drivers. =C2=A0however, this answe=
r also
>> doesnt sound like it's thinking big enough because what you're
>> proposing isnt specific to the SPI bus -- any time a DMA safe buffer
>> is needed dynamically, this function could be used.
>
> Well, we have dma_alloc_coherent(), shouldn't you be using that inste=
ad?

my understanding is that dma_alloc_coherent() gives you a buffer that
is always coherent.  the SPI layers take care of flushing and such on
the fly which means allocating coherent memory is overkill and bad for
performance.
-mike
--
To unsubscribe from this list: send the line "unsubscribe linux-input" =
in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html