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From: Arnd Bergmann <arnd@arndb.de>
To: linuxppc-dev@ozlabs.org
Cc: jbahr <jbahr@set-software-services.com>
Subject: Re: Discontiguous Memory
Date: Sat, 16 Sep 2006 11:51:40 +0200	[thread overview]
Message-ID: <200609161151.41294.arnd@arndb.de> (raw)
In-Reply-To: <1158368179.14473.203.camel@localhost.localdomain>

Am Saturday 16 September 2006 02:56 schrieb Benjamin Herrenschmidt:
> =A0- A more annoying one is support for DMA since a lot of devices cannot
> DMA above 32 bits. A lot of 'sane' platforms that provide more memory
> than can be DMA'ed in 32 bits also provide an IOMMU that does page
> translation of incoming DMAs. This isn't your case however, thus you
> would have to implement some of the alternate solutions used on x86_64
> (Intel 64 bits platforms also lack an iommu). This essentially consist
> of defining a ZONE_DMA32 and possibly also using swiotlb to do bounce
> buffering for drivers that don't deal with ZONE_DMA32 yet.

On 32 bit platforms, you normally have ZONE_NORMAL for up to 4G and
ZONE_HIGHMEM beyond, so you don't need an extra ZONE_DMA32.

	Arnd <><

  reply	other threads:[~2006-09-16  9:51 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-09-15 20:22 Discontiguous Memory jbahr
2006-09-15 23:24 ` Arnd Bergmann
2006-09-15 23:31   ` Jeffery Bahr
2006-09-16  0:56 ` Benjamin Herrenschmidt
2006-09-16  9:51   ` Arnd Bergmann [this message]
2006-09-16 22:50     ` Benjamin Herrenschmidt

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