From: Paul Mackerras <paulus@samba.org>
To: Christoph Lameter <clameter@sgi.com>
Cc: Russell King <rmk+lkml@arm.linux.org.uk>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
jens.axboe@oracle.com
Subject: Re: Define CONFIG_BOUNCE to avoid useless inclusion of bounce buffer logic.
Date: Thu, 24 May 2007 13:47:06 +1000 [thread overview]
Message-ID: <18005.2746.374990.29287@cargo.ozlabs.ibm.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0705231011000.19822@schroedinger.engr.sgi.com>
Christoph Lameter writes:
> > The DMA zone is for memory allocations _for_ _DMA_. If all your memory
> > is DMA-able then it belongs in the DMA zone.
>
> Nope. The DMA zone is for crappy DMA devices that can only use a portion
> of memory.
That is (presumably) true today, but is in fact a redefinition of what
ZONE_DMA historically was for.
Also there is the problem that some drivers use ZONE_DMA allocations
because their device can only generate addresses below some limit, but
on a platform with an IOMMU there is in fact no restriction on what
memory the device can access.
Paul.
next prev parent reply other threads:[~2007-05-24 3:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-22 4:03 Christoph Lameter
2007-05-22 4:39 ` KAMEZAWA Hiroyuki
2007-05-22 5:27 ` Christoph Lameter
2007-05-23 14:07 ` Russell King
2007-05-23 17:15 ` Christoph Lameter
2007-05-23 22:58 ` Russell King
2007-05-23 23:07 ` Christoph Lameter
2007-05-24 7:50 ` Russell King
2007-05-24 3:47 ` Paul Mackerras [this message]
2007-05-24 4:03 ` Christoph Lameter
2007-06-03 22:24 ` Russell King
2007-05-24 9:57 ` Alan Cox
2007-05-22 7:08 ` Jens Axboe
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