Re: [PATCH RFC 07/11] arm64: dts: qcom: sm6350: Affirm IDR0.CCTW on apps_smmu

[Konrad Dybcio <konradybcio@kernel.org>]

On 24.09.2024 9:37 AM, Luca Weiss wrote:
> On Tue Sep 24, 2024 at 9:15 AM CEST, Luca Weiss wrote:
>> On Thu Sep 19, 2024 at 12:57 AM CEST, Konrad Dybcio wrote:
>>> From: Konrad Dybcio <quic_kdybcio@quicinc.com>
>>>
>>> On RPMh-based SoCs, the APPS SMMU advertizes support for cache-coherent
>>> pagetable walk via the IDR0 register. This however is not respected by
>>> the arm-smmu driver unless dma-coherent is set.
>>>
>>> Mark the node as dma-coherent to ensure this (and other) implementations
>>> take this coherency into account.
>>
>> Hi Konrad!
>>
>> Similar to [0] everything seems to look fine on SM7225 Fairphone 4.
>>
>> [    0.190433] arm-smmu 15000000.iommu: probing hardware configuration...
>> [    0.190459] arm-smmu 15000000.iommu: SMMUv2 with:
>> [    0.190499] arm-smmu 15000000.iommu:         stage 1 translation
>> [    0.190515] arm-smmu 15000000.iommu:         coherent table walk
>> [    0.190531] arm-smmu 15000000.iommu:         stream matching with 71 register groups
>> [    0.190560] arm-smmu 15000000.iommu:         63 context banks (0 stage-2 only)
>> [    0.191097] arm-smmu 15000000.iommu:         Supported page sizes: 0x61311000
>> [    0.191114] arm-smmu 15000000.iommu:         Stage-1: 36-bit VA -> 36-bit IPA
>> [    0.191299] arm-smmu 15000000.iommu:         preserved 0 boot mappings
>>
>> The Adreno SMMU still has non-coherent table walk.
>>
>> [    1.141215] arm-smmu 3d40000.iommu: probing hardware configuration...
>> [    1.141243] arm-smmu 3d40000.iommu: SMMUv2 with:
>> [    1.141270] arm-smmu 3d40000.iommu:  stage 1 translation
>> [    1.141279] arm-smmu 3d40000.iommu:  address translation ops
>> [    1.141288] arm-smmu 3d40000.iommu:  non-coherent table walk
>> [    1.141296] arm-smmu 3d40000.iommu:  (IDR0.CTTW overridden by FW configuration)
>> [    1.141307] arm-smmu 3d40000.iommu:  stream matching with 5 register groups
>> [    1.141326] arm-smmu 3d40000.iommu:  5 context banks (0 stage-2 only)
>> [    1.141347] arm-smmu 3d40000.iommu:  Supported page sizes: 0x63315000
>> [    1.141356] arm-smmu 3d40000.iommu:  Stage-1: 48-bit VA -> 36-bit IPA
>> [    1.141568] arm-smmu 3d40000.iommu:  preserved 0 boot mappings
>>
>>
>> Tested-by: Luca Weiss <luca.weiss@fairphone.com> # sm7225-fairphone-fp4
>>
>> [0] https://lore.kernel.org/linux-arm-msm/CAD=FV=Xrbe1NO+trk1SJ30gHm5jLFjd0bAeG3H46gD+vNFZa1w@mail.gmail.com/
> 
> FWIW adding 'dma-coherent;' to &adreno_smmu also doesn't seem to
> explode:
> 
> [    1.451965] arm-smmu 3d40000.iommu: probing hardware configuration...
> [    1.455547] arm-smmu 3d40000.iommu: SMMUv2 with:
> [    1.459041] arm-smmu 3d40000.iommu:  stage 1 translation
> [    1.462446] arm-smmu 3d40000.iommu:  address translation ops
> [    1.465843] arm-smmu 3d40000.iommu:  coherent table walk
> [    1.469216] arm-smmu 3d40000.iommu:  stream matching with 5 register groups
> [    1.472645] arm-smmu 3d40000.iommu:  5 context banks (0 stage-2 only)
> [    1.476067] arm-smmu 3d40000.iommu:  Supported page sizes: 0x63315000
> [    1.479458] arm-smmu 3d40000.iommu:  Stage-1: 48-bit VA -> 36-bit IPA
> [    1.483152] arm-smmu 3d40000.iommu:  preserved 0 boot mappings
> 
> And kmscube still runs as expected.

Thanks, I'll look into adreno separately

Konrad