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Re: aic7xxx (O2 scsi) DMA coherency

To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: aic7xxx (O2 scsi) DMA coherency
From: Vivien Chappelier <vivien.chappelier@enst-bretagne.fr>
Date: Fri, 4 Jan 2002 13:30:55 +0100 (CET)
Cc: Ralf Baechle <ralf@oss.sgi.com>, linux-mips@oss.sgi.com
In-reply-to: <E16MFrP-00018Z-00@the-village.bc.nu>
Sender: owner-linux-mips@oss.sgi.com
Hello,

On Thu, 3 Jan 2002, Alan Cox wrote:

> >     This tells the aic7xxx to use DMA safe memory for I/O.
> 
> That seems totally inappropriate. The unchecked dma option is for
> ancient ISA DMA controllers that didnt do the 16Mb check.
> 

Maybe this is more appropriate then :)
It tells the scsi scanner to always use DMA safe memory when doing its
INQUIRY commands...
On the O2, kernel is running in cacheable, non-coherent memory. kmalloc,
with GFP_DMA flag will return a piece of uncacheable memory which is safe
for I/O with devices.

regards,
Vivien Chappelier

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