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Re: aic7xxx (O2 scsi) DMA coherency

To: Ralf Baechle <>
Subject: Re: aic7xxx (O2 scsi) DMA coherency
From: Vivien Chappelier <>
Date: Fri, 4 Jan 2002 18:32:52 +0100 (CET)
Cc: Alan Cox <>,
In-reply-to: <>
On Thu, 3 Jan 2002, Ralf Baechle wrote:

> On Thu, Jan 03, 2002 at 10:51:51PM +0100, Vivien Chappelier 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?
> Indeed, it is.  I thought this one died ages ago.

Here is a patch to fix that then. It forces allocation of DMA safe
memory in any case. I've not looked at the PPC64 patch however.

Vivien Chappelier.

Attachment: linux-scsi_scan.diff
Description: Text document

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