Re: [PATCHv2 2/2] iommu/arm-smmu-qcom: Move the adreno smmu specific impl earlier
From: Bjorn Andersson
Date: Fri Feb 26 2021 - 14:15:44 EST
On Fri 26 Feb 12:23 CST 2021, Rob Clark wrote:
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On Fri, Feb 26, 2021 at 9:24 AM Bjorn Andersson
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<bjorn.andersson@xxxxxxxxxx> wrote:
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> On Fri 26 Feb 03:55 CST 2021, Sai Prakash Ranjan wrote:
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> > Adreno(GPU) SMMU and APSS(Application Processor SubSystem) SMMU
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> > both implement "arm,mmu-500" in some QTI SoCs and to run through
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> > adreno smmu specific implementation such as enabling split pagetables
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> > support, we need to match the "qcom,adreno-smmu" compatible first
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> > before apss smmu or else we will be running apps smmu implementation
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> > for adreno smmu and the additional features for adreno smmu is never
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> > set. For ex: we have "qcom,sc7280-smmu-500" compatible for both apps
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> > and adreno smmu implementing "arm,mmu-500", so the adreno smmu
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> > implementation is never reached because the current sequence checks
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> > for apps smmu compatible(qcom,sc7280-smmu-500) first and runs that
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> > specific impl and we never reach adreno smmu specific implementation.
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> So you're saying that you have a single SMMU instance that's compatible
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> with both an entry in qcom_smmu_impl_of_match[] and "qcom,adreno-smmu"?
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> Per your proposed change we will pick the adreno ops _only_ for this
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> component, essentially disabling the non-Adreno quirks selected by the
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> qcom impl. As such keeping the non-adreno compatible in the
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> qcom_smmu_impl_init[] seems to only serve to obfuscate the situation.
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> Don't we somehow need the combined set of quirks? (At least if we're
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> running this with a standard UEFI based boot flow?)
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are you thinking of the apps-smmu handover of display context bank?
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That shouldn't change, the only thing that changes is that gpu-smmu
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becomes an mmu-500, whereas previously only apps-smmu was..
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The current logic picks one of:
1) is the compatible mentioned in qcom_smmu_impl_of_match[]
2) is the compatible an adreno
3) no quirks needed
The change flips the order of these, so the only way I can see this
change affecting things is if we expected a match on #2, but we got one
on #1.
Which implies that the instance that we want to act according to the
adreno impl was listed in qcom_smmu_impl_of_match[] - which either is
wrong, or there's a single instance that needs both behaviors.
(And I believe Jordan's answer confirms the latter - there's a single
SMMU instance that needs all them quirks at once)
Regards,
Bjorn