Re: [PATCH 11/13] dtb: amd: Add PCIe SMMU device tree node

From: Will Deacon
Date: Wed Mar 30 2016 - 11:45:25 EST

Hi Eric,

On Wed, Mar 30, 2016 at 05:37:27PM +0200, Eric Auger wrote:
> On 01/28/2016 03:27 PM, Will Deacon wrote:
> > On Thu, Jan 28, 2016 at 03:17:33PM +0100, Arnd Bergmann wrote:
> >> On Thursday 28 January 2016 12:20:58 Robin Murphy wrote:
> >>>>
> >>> Any IDs specified here would only apply to DMA by the "platform device"
> >>> side of the host controller itself (as would an equivalent "iommus"
> >>> property on pcie0 once I finish the SMMUv2 generic binding support I'm
> >>> working on). In terms of PCI devices, the "mmu-masters" property is
> >>> overloaded such that only its existence matters, to identify that there
> >>> _is_ a relationship between the SMMU and the PCI bus(es) behind that
> >>> host controller.
> >>
> >> I wasn't aware that this was actually still specified. I had hoped
> >> we were getting rid of mmu-masters before anyone actually started
> >> using it, but now I see it in ns2.dtsi and fsl-ls2080a.dtsi.
> >>
> >> Does anyone know what happened to the plan to use the iommu DT binding
> >> for the ARM SMMU instead? Do we now have to support both ways indefinitely?
> >
> > We always did -- Seattle used the mmu-masters binding before the generic
> > binding even existed. Robin has been working on patches to get of_xlate
> > up and running, but it got held up by Laurent's series which didn't end
> > up going anywhere.
> >
> Up to now I have used the PCI smmu description as described in Suravee's
> patch and this does not work anymore with 4.6-rc1 since the default
> domain was introduced. So now I see 2 SMRs matching a single streamid
> (in my case 256, one steming from the "platform device" side of the host
> controller and one steming from the PCI device) and this causes SMCF
> (stream match conflict fault). So PCIe PF does not work.

Sorry about that, it wasn't intentional. In fact, I wrote commit
cbf8277ef456 ("iommu/arm-smmu: Treat IOMMU_DOMAIN_DMA as bypass for now")
specifically to avoid this breakage, after seeing it myself with VFIO
and an S2CR-based configuration. It looks like the check just needs moving
higher up (i.e. before we initialise the SMRs).

Does that fix it for you?