From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mundt Date: Mon, 18 Sep 2006 15:22:43 +0000 Subject: Re: [PATCH 2/6] Introduce CONFIG_ZONE_DMA Message-Id: <20060918152243.GA4320@localhost.na.rta> List-Id: References: <20060911222729.4849.69497.sendpatchset@schroedinger.engr.sgi.com> <20060911222739.4849.79915.sendpatchset@schroedinger.engr.sgi.com> <20060918135559.GB15096@infradead.org> In-Reply-To: <20060918135559.GB15096@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christoph Hellwig Cc: Christoph Lameter , linux-mm@vger.kernel.org, Nick Piggin , linux-ia64@vger.kernel.org, Marcelo Tosatti , Arjan van de Ven , Martin Bligh , KAMEZAWA Hiroyuki , Andi Kleen , linux-arch@vger.kernel.org On Mon, Sep 18, 2006 at 02:55:59PM +0100, Christoph Hellwig wrote: > On Mon, Sep 11, 2006 at 03:27:39PM -0700, Christoph Lameter wrote: > > Second, arches may use ZONE_DMA in an unknown way. We set CONFIG_ZONE_DMA > > for all arches that do not set CONFIG_GENERIC_ISA_DMA in order to insure > > backwards compatibility. The arches may later undefine ZONE_DMA > > if their arch code has been verified to not depend on ZONE_DMA. > > Let's pass this on to linux-arch so that the arch maintainers can give input > whether they need ZONE_DMA or not. If this just sneaks in unseen I'd bet > various architectures will just keept it around despite not needing it. > sh and sh64 have no use for ZONE_DMA, it's effectively ZONE_DMA = ZONE_NORMAL anyways, so it can be safely switched off (though arch/sh/mm/init.c should then be changed to use ZONE_NORMAL if ZONE_DMA goes away, as we currently place all lowmem in ZONE_DMA, likewise for sh64). None of our DMA controllers have any particular limitations where ZONE_DMA would be useful at least.