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Re: aic7xxx (O2 scsi) DMA coherency (fwd)

To: linux-mips@oss.sgi.com
Subject: Re: aic7xxx (O2 scsi) DMA coherency (fwd)
From: Vivien Chappelier <vivien.chappelier@enst-bretagne.fr>
Date: Fri, 4 Jan 2002 20:46:07 +0100 (CET)
Sender: owner-linux-mips@oss.sgi.com
forgot the Cc to the list...
BTW sorry for the dual post.

---------- Forwarded message ----------
Date: Fri, 4 Jan 2002 20:33:48 +0100 (CET)
From: Vivien Chappelier <glaurung@melkor.maisel.enst-bretagne.fr>
To: Ilya Volynets <ilya@theilya.com>
Subject: Re: aic7xxx (O2 scsi) DMA coherency

> Are you sure GFP_DMA does what you think it does?

> I'm not. I thnk using pci_alloc_consistant is more appropriate for
> this purpose.

Neither am I, I'm just a new kernel hacker :)
Anyway, I think what we want is doing I/O using DMA with the scsi
controller, so I think we need DMA safe memory for this. Wether the arch
needs to ensure coherency for that is not really the concern. On the O2,
dma memory is uncacheable memory, but other archs might have other
concerns regarding dma memory (below 16Mb for example?), so I think
pci_alloc_consistent is not appropriate in this case.

regards,
Vivien Chappelier.



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