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Subject: Re: SCSI breakage on non-cache coherent architectures
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reply-To: benh@kernel.crashing.org
To: David Miller <davem@davemloft.net>
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       linux-scsi@vger.kernel.org, rmk@arm.linux.org.uk
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Date: Tue, 20 Nov 2007 11:34:24 +1100
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On Mon, 2007-11-19 at 14:31 -0800, David Miller wrote:
> From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Date: Tue, 20 Nov 2007 06:51:14 +1100
> 
> > On Mon, 2007-11-19 at 00:38 -0800, David Miller wrote:
> > > From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > > Date: Mon, 19 Nov 2007 16:35:23 +1100
> > > 
> > > You could make a ____dma_cacheline_aligned and use that.
> > > It seems pretty reasonable.
> > 
> > I was thinking about that. What archs would need it ? arm, mips, what
> > else ?
> 
> The sparc32 port would need it too.

James preference seem to go for a revert of the patch that removed the
kmalloc of the buffer instead. Sounds definitely like an easier plan
for .24 (and maybe even backport to stable).

I'll produce a patch for that later today or tomorrow.

Do you still think we should introduce this __dma_cacheline_aligned ? Do
you see other cases of drivers where it would be useful ? It tend to
agree with your earlier statement that drivers doing that are broken and
should be using a separate allocator for DMA'ble objects (in fact, on
non-cache coherent archs, kmalloc is just fine).

Cheers,
Ben.