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Subject: Re: [PATCH] Stop pci_set_dma_mask() from failing when RAM doesn't
	exceed the mask anyway
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: David Woodhouse <dwmw2@infradead.org>
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Date: Sat, 01 Aug 2009 18:00:56 +1000
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On Sat, 2009-08-01 at 08:54 +0100, David Woodhouse wrote:
> On Sat, 2009-08-01 at 08:25 +1000, Benjamin Herrenschmidt wrote:
> > On Fri, 2009-07-31 at 20:41 +0100, David Woodhouse wrote:
> > > On an iMac G5, the b43 driver is failing to initialise because trying to
> > > set the dma mask to 30-bit fails. Even though there's only 512MiB of RAM
> > > in the machine anyway:
> > > 	https://bugzilla.redhat.com/show_bug.cgi?id=514787
> > > 
> > > We should probably let it succeed if the available RAM in the system
> > > doesn't exceed the requested limit.
> > > 
> > > Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
> > 
> > Also, isn't our iommu code smart enough to clamp allocations to the DMA
> > mask nowadays ? In that case, we could probably just force iommu on
> > always...
> 
> We're not using the IOMMU on this box:
> 
> PowerMac motherboard: iMac G5
> DART: table not allocated, using direct DMA

I know, I was suggesting we do :-)

Cheers,
Ben.