Re: [PATCHv2 2/2] iommu/arm-smmu-qcom: Move the adreno smmu specific impl earlier

On Fri, Feb 26, 2021 at 9:24 AM Bjorn Andersson
[off-list ref] wrote:

On Fri 26 Feb 03:55 CST 2021, Sai Prakash Ranjan wrote:

quoted

Adreno(GPU) SMMU and APSS(Application Processor SubSystem) SMMU
both implement "arm,mmu-500" in some QTI SoCs and to run through
adreno smmu specific implementation such as enabling split pagetables
support, we need to match the "qcom,adreno-smmu" compatible first
before apss smmu or else we will be running apps smmu implementation
for adreno smmu and the additional features for adreno smmu is never
set. For ex: we have "qcom,sc7280-smmu-500" compatible for both apps
and adreno smmu implementing "arm,mmu-500", so the adreno smmu
implementation is never reached because the current sequence checks
for apps smmu compatible(qcom,sc7280-smmu-500) first and runs that
specific impl and we never reach adreno smmu specific implementation.

So you're saying that you have a single SMMU instance that's compatible
with both an entry in qcom_smmu_impl_of_match[] and "qcom,adreno-smmu"?

Per your proposed change we will pick the adreno ops _only_ for this
component, essentially disabling the non-Adreno quirks selected by the
qcom impl. As such keeping the non-adreno compatible in the
qcom_smmu_impl_init[] seems to only serve to obfuscate the situation.

Don't we somehow need the combined set of quirks? (At least if we're
running this with a standard UEFI based boot flow?)

are you thinking of the apps-smmu handover of display context bank?
That shouldn't change, the only thing that changes is that gpu-smmu
becomes an mmu-500, whereas previously only apps-smmu was..

BR,
-R

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