Re: [PATCH 0/5] Qcom smmu-500 TLB invalidation errata for sdm845

[Vivek Gautam]

Hi Will,


On 8/14/2018 5:10 PM, Will Deacon wrote:
> Hi Vivek,
>
> On Tue, Aug 14, 2018 at 04:25:23PM +0530, Vivek Gautam wrote:
> > Qcom's implementation of arm,mmu-500 on sdm845 has a functional/performance
> > errata [1] because of which the TCU cache look ups are stalled during
> > invalidation cycle. This is mitigated by serializing all the invalidation
> > requests coming to the smmu.
> How does this implementation differ from the one supported by qcom_iommu.c?
> I notice you're adding firmware hooks here, which we avoided by having the
> extra driver. Please help me understand which devices exist, how they
> differ, and which drivers are intended to support them!

IIRC, the qcom_iommu driver was intended to support the static context 
bank - SID
mapping, and is very specific to the smmu-v2 version present on msm8916 soc.
However, this is the qcom's mmu-500 implementation specific errata. 
qcom_iommu
will not be able to support mmu-500 configurations.
Rob Clark can add more.
Let you know what you suggest.

> Also -- you didn't CC all the maintainers for the firmware bits, so adding
> Andy here for that, and Rob for the previous question.

I added Andy to the series, would you want me to add Rob H also?

Best regards
Vivek

> Thanks,
>
> Will