[PATCH kernel v4 0/4 repost] powerpc/ioda2: Yet another attempt to allow DMA masks between 32 and 59

[Christoph Hellwig]

On Fri, Jul 12, 2019 at 07:45:05PM +1000, Alexey Kardashevskiy wrote:
> This is an attempt to allow DMA masks between 32..59 which are not large
> enough to use either a PHB3 bypass mode or a sketchy bypass. Depending
> on the max order, up to 40 is usually available.

Can you elaborate what you man with supported in detail?  In the end
a DMA devices DMA capability is only really interesting as a lower
bound.

e.g. if you have a DMA that supports 40-bit DMA addressing we could
always treat it as if supports 32-bit addressing, and I thought the
powerpc code does that, as the DMA API now relies on that.  Did I miss
something and it explicitly rejected that (in which case I didn't spot
the fix in this series), or is this just an optimization to handle these
devices more optimally, in which case maybe the changelog could be
improved a bit.