Re: [PATCH 3/6] iommu/arm-smmu: add support for iova_to_phys through ATS1PR

Will Deacon
2014-09-01T16:15:09Z

On Tue, Aug 26, 2014 at 02:54:51PM +0100, Will Deacon wrote:
> On Tue, Aug 19, 2014 at 07:12:41PM +0100, Mitchel Humpherys wrote:
> > On Tue, Aug 19 2014 at 05:44:32 AM, Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org> wrote:
> > >> @@ -2005,6 +2073,11 @@ int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
> > >> return -ENODEV;
> > >> }
> > >>
> > >> + if (smmu->version == 1 || (!(id & ID0_ATOSNS) && (id & ID0_S1TS))) {
> > >
> > > Are you sure about this? The v2 spec says that is ATOSNS is clear then S1TS
> > > is also clear.
> >
> > I was looking at Section 4.1.1 of ARM IHI 0062C ID091613 which states:
> >
> > In SMMUv2, the address translation registers are OPTIONAL. The
> > address translation registers are implemented only when both:
> >
> > o The SMMU_IDR0.S1TS bit is set to 1.
> > o The SMMU_IDR0.ATOSNS bit is set to 0.
> >
> > I assume you're referring to section 9.6.1 of the same document:
> >
> > ATOSNS, bit[26]
> > Address Translation Operations Not Supported. The possible values of
> > this bit are:
> >
> > 0 Address translation operations are supported. Stage 1
> > translation is not supported, that is, the S1TS bit is set to 0.
> >
> > 1 Address translation operations are not supported. Stage 1
> > translation is supported, that is, the S1TS bit is set to 1.
> >
> > If that really means that S1TS and ATOSNS always have the same value
> > then Section 4.1.1 doesn't make any sense. Or am I missing something?
>
> I'll get this checked, as those two paragraphs don't make an awful lot of
> sense together.

Right, word from above says that ATOS is implemented iff:

IDR0.S1TS == 1 && IDR0.ATOSNS == 0

Basically, ATOS only works for stage-1 when it's present, so that explains
the dependency. Looking at the piece of diff at the top of this mail, I
think that means your code is correct

Will