From: Arnd Bergmann <arnd@arndb.de>
To: cbe-oss-dev@ozlabs.org
Cc: Olof Johansson <olof@lixom.net>, linuxppc-dev@ozlabs.org
Subject: Re: [Cbe-oss-dev] [PATCH 3/3] Cell IOMMU static mapping support
Date: Mon, 28 Jan 2008 12:41:48 +0100 [thread overview]
Message-ID: <200801281241.49059.arnd@arndb.de> (raw)
In-Reply-To: <20080126025117.GA28066@lixom.net>
On Saturday 26 January 2008, Olof Johansson wrote:
> >
> > So instead of having an IOMMU window that we use to temporarily map things
> > in and out of DMA'able space, at boot we create a 1:1 mapping for all of
> > memory. This obviously only works for devices that can do 64-bit DMA.
>
> I don't get it. Why not disable the iommu instead?
>
When you disable the iommu, the 32-bit devices stop working because
they can no longer access all of main memory.
The 1:1 mapping is in addition to the DMA window used for those devices,
not in place of it.
Arnd <><
next prev parent reply other threads:[~2008-01-28 11:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-25 10:45 [PATCH 1/3] Add set_dma_ops() to match get_dma_ops() Michael Ellerman
2008-01-25 10:45 ` [PATCH 3/3] Cell IOMMU static mapping support Michael Ellerman
2008-01-25 13:12 ` [Cbe-oss-dev] " Geert Uytterhoeven
2008-01-26 2:51 ` Olof Johansson
2008-01-28 11:41 ` Arnd Bergmann [this message]
2008-01-28 16:23 ` [Cbe-oss-dev] " Olof Johansson
2008-01-28 21:16 ` Benjamin Herrenschmidt
2008-01-28 21:48 ` Olof Johansson
2008-01-28 21:37 ` Benjamin Herrenschmidt
2008-01-28 21:18 ` Benjamin Herrenschmidt
2008-01-25 10:45 ` [PATCH 2/3] Allocate the hash table under 1G on cell Michael Ellerman
2008-02-05 0:23 ` Benjamin Herrenschmidt
2008-02-05 0:23 ` [PATCH 1/3] Add set_dma_ops() to match get_dma_ops() Benjamin Herrenschmidt
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