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Re: ZONE_DMA on MIPS

To: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Subject: Re: ZONE_DMA on MIPS
From: Ralf Baechle <ralf@linux-mips.org>
Date: Mon, 19 Mar 2007 15:48:21 +0000
Cc: linux-mips@linux-mips.org
In-reply-to: <20070320.000947.88474417.anemo@mba.ocn.ne.jp>
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References: <20070320.000947.88474417.anemo@mba.ocn.ne.jp>
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On Tue, Mar 20, 2007 at 12:09:47AM +0900, Atsushi Nemoto wrote:

> Some ZONE_DMA patches were merged in 2.6.21.  On most MIPS, ZONE_DMA
> is not needed, isn't it?
> 
> Currently JAZZ, MALTA, QEMU, IP22, SNI_RM, RBTX4938 defines
> GENERIC_ISA_DMA so they may need ZONE_DMA (though I wonder QEMU or
> RBTX4938 really need it...)
> 
> Are there any other platforms requires special DMA zone?

Qemu supports more or less the full PC braind^Wheritage, including the
good old too-old floppy controller.  IP22 supports Indigo 2 systems
which have EISA support, so we only want ZONE_DMA if EISA is enabled.
For a bunch of other systems ZONE_DMA may be required to support b0rked
PCI cards that only support like 31-bit DMA addresses or even less.

  Ralf

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