Re: [PATCH] iommu/dma: Explicitly sort PCI DMA windows

[dann frazier <dann.frazier@canonical.com>]

On Wed, Mar 23, 2022 at 07:55:23PM -0500, Rob Herring wrote:
> On Wed, Mar 23, 2022 at 5:15 PM dann frazier <dann.frazier@canonical.com> wrote:
> >
> > On Wed, Mar 23, 2022 at 09:49:04AM +0000, Marc Zyngier wrote:
> > > On Tue, 22 Mar 2022 17:27:36 +0000,
> > > Robin Murphy <robin.murphy@arm.com> wrote:
> > > >
> > > > Originally, creating the dma_ranges resource list in pre-sorted fashion
> > > > was the simplest and most efficient way to enforce the order required by
> > > > iova_reserve_pci_windows(). However since then at least one PCI host
> > > > driver is now re-sorting the list for its own probe-time processing,
> > > > which doesn't seem entirely unreasonable, so that basic assumption no
> > > > longer holds. Make iommu-dma robust and get the sort order it needs by
> > > > explicitly sorting, which means we can also save the effort at creation
> > > > time and just build the list in whatever natural order the DT had.
> > > >
> > > > Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> > > > ---
> > > >
> > > > Looking at this area off the back of the XGene thread[1] made me realise
> > > > that we need to do it anyway, regardless of whether it might also happen
> > > > to restore the previous XGene behaviour or not. Presumably nobody's
> > > > tried to use pcie-cadence-host behind an IOMMU yet...
> > >
> > > This definitely restores PCIe functionality on my Mustang (XGene-1).
> > > Hopefully dann can comment on whether this addresses his own issue, as
> > > his firmware is significantly different.
> >
> > Robin, Marc,
> >
> > Adding just this patch on top of v5.17 (w/ vendor dtb) isn't enough to
> > fix m400 networking:
> 
> I wouldn't expect it to given both the IB register selection changed
> and the 2nd dma-ranges entry is ignored.
> 
> Can you (and others) try out this branch:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git xgene-pci-fix
> 
> It should maintain the same IB register usage for both cases and
> handle the error in 'dma-ranges'.

Looks good Rob :)

https://paste.ubuntu.com/p/zJF9PKhQpS/


  -dann