[PATCH 01/10] ARM: change ARM_DMA_ZONE_SIZE into a variable

[John Linn]

> -----Original Message-----
> From: linux-arm-kernel-bounces at lists.infradead.org [mailto:linux-arm-
> kernel-bounces at lists.infradead.org] On Behalf Of Arnd Bergmann
> Sent: Thursday, July 07, 2011 10:17 AM
> To: linux-arm-kernel at lists.infradead.org
> Cc: Nicolas Pitre; grant.likely at secretlab.ca; Russell King - ARM
Linux;
> Barry Song
> Subject: Re: [PATCH 01/10] ARM: change ARM_DMA_ZONE_SIZE into a
> variable
> 
> On Thursday 07 July 2011, Nicolas Pitre wrote:
> > > What is hardware specific is that the DMA devices can only address
> a
> > > limited range of memory.  IMHO it's that which should be described
> in
> > > DT, not that we'll have a DMA zone of X bytes in size.
> >
> > I think that we all agree on the principle.  I certainly never
> intended
> > to suggest that the DMA zone size be stored as is in the device
tree.
> 
> There is a way to specify DMA address ranges in the device tree,
though
> I forgot the exact format. It comes down to saying the device sees
> memory range XXX to YYY as its local address AAA to BBB. We could use
> that information at boot time to determine what the largest range
> of memory is that is visible by all devices (and hope that it's at
> the start of physical memory).

If I'm following this right....

We have a hole at the start of physical memory (when it's at 0) so that
DMA can't DMA into it.  Sounds like that won't work for us?

Thanks,
John

> 
> 	Arnd
> 
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