Re: [PATCH 1/4] powerpc: Dynamic DMA zone limits

[Scott Wood <scottwood@freescale.com>]

On Tue, 2014-10-14 at 18:57 +1100, Benjamin Herrenschmidt wrote:
> On Tue, 2014-10-14 at 09:39 +0200, Scott Wood wrote:
> > For a short-term workaround, I'd rather leave CONFIG_ZONE_DMA32 where
> > it
> > is and put #ifdef CONFIG_FSL_SOC (with a comment) around the whole
> > thing.
> 
> I'd like to not enable CONFIG_ZONE_DMA32 when we don't need it, ie,
> on !BOOKE 64-bit

How does 64-bit powermac deal with it, with random PCI cards?  Does it
use an IOMMU for coherent allocations?

In any case, CONFIG_ZONE_DMA32 should be harmless if the zone isn't
dynamically created, but we can limit it to booke if you want.  The
current breakage has nothing to do with ZONE_DMA32, but rather to the
fact that we now check zones at all.  This is why I'd rather have the
short term workaround be a new ifdef, rather than moving ifdef
CONFIG_ZONE_DMA32 (moving it also obscures the way the code should look
if and when the workaround can be removed).

-Scott