Re: [RFC PATCH 0/4] Stop losing firmware-set DMA masks

[Robin Murphy]

On 10/07/18 19:02, Christoph Hellwig wrote:
> > These patches attempt to deal with this in the simplest way possible by
> > generalising the specific quirk for 32-bit bridges into an arbitrary
> > mask which can then also be plumbed into the firmware code. In the
> > interest of being minimally invasive, I've only included a point fix
> > for the IOMMU issue as seen on arm64 - there may be further tweaks
> > needed in DMA ops to catch all possible incarnations of this problem,
> > but this initial RFC is mostly about the impact beyond the dma-mapping
> > subsystem itself.
>
> Thanks, this looks very nice to me.
>
> In fact it probably solves the RISC-V/Xiling problem as well if we can
> just add the dma-ranges property to the device tree for the affected
> systems.  Palmer, do you know how easily the DT could be updated for
> that case?

That would indeed be nice, but beware that the way PCI devices are 
bodged through of_dma_configure() only actually works for dma-coherent 
and is busted WRT parsing dma-ranges correctly. Fixing that is my next 
step after getting these basics done ;)

Robin.