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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: Thu, 3 Jan 2002 22:51:51 +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
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. If you
> find you need it debug your pci remapper

This is used when scaning for devices (drivers/scsi/scsi_scan.c) . When
this flag is not set, the code uses memory from the stack (unsigned char
scsi_result0[256]; in scan_scsis) instead of kmallocating it DMA safe as
it should on non-coherent systems. Maybe this is the thing to change?

regards,
Vivien Chappelier.


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