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

[Rob Clark <robdclark@gmail.com>]

On Fri, Feb 26, 2021 at 9:24 AM Bjorn Andersson
<bjorn.andersson@linaro.org> wrote:
>
> On Fri 26 Feb 03:55 CST 2021, Sai Prakash Ranjan wrote:
>
> > 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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