linux-kernel - Re: [PATCH] of: set dma_mask to point to coherent_dma

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Date:	Tue, 12 Nov 2013 13:21:44 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robherring2@...il.com>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>
Subject: Re: [PATCH] of: set dma_mask to point to coherent_dma_mask

On Tue, 12 Nov 2013, Russell King - ARM Linux wrote:
> On Mon, Nov 11, 2013 at 04:59:14PM +0000, Stefano Stabellini wrote:
> > On Wed, 6 Nov 2013, Stefano Stabellini wrote:
> > > On Sat, 2 Nov 2013, Grant Likely wrote:
> > > > On Wed, 30 Oct 2013 00:05:22 -0500, Rob Herring <robherring2@...il.com> wrote:
> > > > > From: Rob Herring <rob.herring@...xeda.com>
> > > > > 
> > > > > Platform devices created by DT code don't initialize dma_mask pointer to
> > > > > anything. Set it to coherent_dma_mask by default if the architecture
> > > > > code has not set it.
> > > > > 
> > > > > Signed-off-by: Rob Herring <rob.herring@...xeda.com>
> > > > 
> > > > I believe this is okay. I haven't done any testing to back up that
> > > > opinion though.
> > > 
> > > Tested-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > 
> > BTW I hope you are planning on sending this upstream soon, because
> > without it I can very easily corrupt my root fs by simply booting the system.
> 
> What's the mechanism for that corruption?  Having the DMA mask not set
> should not cause DMA corruption - that hints at something else being
> wrong, and that needs to be investigated.

Russell, you are right.
I went through the swiotlb-xen code and I realized that I missed a
map_page call on one of the (usually unused) fallback paths.
Thanks!!
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