Re: [PATCH 2/2] iommu/arm-smmu: add support for iova_to_phys through ATS1PR

[Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

On Wed, Sep 24 2014 at 09:37:12 AM, Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org> wrote:
> On Wed, Sep 24, 2014 at 02:12:00AM +0100, Mitchel Humpherys wrote:
>> On Mon, Sep 22 2014 at 08:26:14 AM, Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org> wrote:
>> > On Thu, Sep 11, 2014 at 07:30:44PM +0100, Mitchel Humpherys wrote:
>> >> +		return arm_smmu_iova_to_phys_soft(domain, iova);
>> >> +	}
>> >> +
>> >> +	phys = readl_relaxed(cb_base + ARM_SMMU_CB_PAR_LO);
>> >> +	phys |= ((u64) readl_relaxed(cb_base + ARM_SMMU_CB_PAR_HI)) << 32;
>> >> +
>> >> +	if (phys & CB_PAR_F) {
>> >> +		dev_err(dev, "translation fault on %s!\n", dev_name(dev));
>> >> +		dev_err(dev, "PAR = 0x%llx\n", phys);
>> >> +	}
>> >> +	phys = (phys & 0xFFFFFFF000ULL) | (iova & 0x00000FFF);
>> >
>> > How does this work for 64k pages?
>> 
>> So at the moment we're always assuming that we're using v7/v8 long
>> descriptor format, right?  All I see in the spec (14.5.15 SMMU_CBn_PAR)
>> is that bits[47:12]=>PA[47:12]...  Or am I missing something completely?
>
> I think you've got 64k pages confused with the short-descriptor format.
>
> When we use 64k pages with long descriptors, you're masked off bits 15-12 of
> the iova above, so you'll have a hole in the physical address afaict.

Even with long descriptors the spec says bits 15-12 should come from
CB_PAR...  It makes no mention of reinterpreting those bits depending on
the programmed page granule.  The only thing I can conclude from the
spec is that hardware should be smart enough to do the right thing with
bits 15-12 when the page granule is 64k.  Although even if hardware is
smart enough I guess CB_PAR[15:12] should be the same as iova[15:12] for
the 64k case?


-Mitch

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