Re: [PATCH v2 0/2] PCI: xgene: Restore working PCIe functionnality

[Robin Murphy]

On 2022-03-21 19:21, Marc Zyngier wrote:
> On Mon, 21 Mar 2022 18:03:27 +0000,
> Rob Herring <robh@xxxxxxxxxx> wrote:
> > On Mon, Mar 21, 2022 at 11:36 AM Marc Zyngier <maz@xxxxxxxxxx> wrote:
> > > On Mon, 21 Mar 2022 15:17:34 +0000,
> > > Rob Herring <robh@xxxxxxxxxx> wrote:
> > > > On Mon, Mar 21, 2022 at 5:49 AM Marc Zyngier <maz@xxxxxxxxxx> wrote:
> > > > >
> > > > For XGene-1, I'd still like to understand what the issue is. Reverting
> > > > the first fix and fixing 'dma-ranges' should have fixed it. I need a
> > > > dump of how the IB registers are initialized in both cases. I'm not
> > > > saying changing 'dma-ranges' in the firmware is going to be required
> > > > here. There's a couple of other ways we could fix that without a
> > > > firmware change, but first I need to understand why it broke.
> > >
> > > Reverting 6dce5aa59e0b was enough for me, without changing anything
> > > else.
> >
> > Meaning c7a75d07827a didn't matter for you. I'm not sure that it would.
> >
> > Can you tell me what 'dma-ranges' contains on your system?
>
> Each pcie node (all 5 of them) has:
>
> dma-ranges = <0x42000000 0x80 0x00 0x80 0x00 0x00 0x80000000
>                0x42000000 0x00 0x00 0x00 0x00 0x80 0x00>;

Hmm, is there anyone other than iommu-dma who actually depends on the 
resource list being sorted in ascending order of bus address? I recall 
at the time I pushed for creating the list in sorted order as it was the 
simplest and most efficient option, but there's no technical reason we 
couldn't create it in as-found order and defer the sorting until 
iova_reserve_pci_windows() (at worst that could even operate on a 
temporary copy if need be). It's just more code, which didn't need to 
exist without a good reason, but if this is one then exist it certainly may.

Cheers,
Robin.