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

From: Vivek Gautam
Date: Tue Aug 14 2018 - 09:28:17 EST

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