linux-kernel - Re: [PATCH v2 3/3] iommu/arm-smmu: re-enable context caching in smmu reset operation

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Date:   Tue, 14 Nov 2023 16:15:23 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Bibek Kumar Patro <quic_bibekkum@...cinc.com>
Cc:     will@...nel.org, robin.murphy@....com, joro@...tes.org,
        a39.skl@...il.com, konrad.dybcio@...aro.org,
        quic_pkondeti@...cinc.com, quic_molvera@...cinc.com,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, qipl.kernel.upstream@...cinc.com
Subject: Re: [PATCH v2 3/3] iommu/arm-smmu: re-enable context caching in smmu
 reset operation

On Tue, 14 Nov 2023 at 15:57, Bibek Kumar Patro
<quic_bibekkum@...cinc.com> wrote:
>
> Context caching is re-enabled in the prefetch buffer for Qualcomm SoCs
> through SoC specific reset ops, which is disabled in the default MMU-500
> reset ops, but is expected for context banks using ACTLR register to
> retain the prefetch value during reset and runtime suspend.

Please refer to Documentation/process/submitting-patches.rst and
rephrase this following the rules there.

>
> Signed-off-by: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
> ---
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 25 ++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index 0eaf6f2a2e49..fa867b1d9d16 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -478,11 +478,28 @@ static int qcom_smmu_def_domain_type(struct device *dev)
>         return match ? IOMMU_DOMAIN_IDENTITY : 0;
>  }
>
> +static int qcom_smmu500_reset(struct arm_smmu_device *smmu)
> +{
> +       int i;
> +       u32 reg;
> +
> +       arm_mmu500_reset(smmu);
> +
> +       /* Re-enable context caching after reset */
> +       for (i = 0; i < smmu->num_context_banks; ++i) {
> +               reg = arm_smmu_cb_read(smmu, i, ARM_SMMU_CB_ACTLR);
> +               reg |= CPRE;
> +               arm_smmu_cb_write(smmu, i, ARM_SMMU_CB_ACTLR, reg);
> +       }
> +
> +       return 0;
> +}
> +
>  static int qcom_sdm845_smmu500_reset(struct arm_smmu_device *smmu)
>  {
>         int ret;
>
> -       arm_mmu500_reset(smmu);
> +       qcom_smmu500_reset(smmu);

Is this applicable for sdm845? For all other platforms supported by
qcom_smmu_500 implementation?

>
>         /*
>          * To address performance degradation in non-real time clients,
> @@ -509,7 +526,7 @@ static const struct arm_smmu_impl qcom_smmu_500_impl = {
>         .init_context = qcom_smmu_init_context,
>         .cfg_probe = qcom_smmu_cfg_probe,
>         .def_domain_type = qcom_smmu_def_domain_type,
> -       .reset = arm_mmu500_reset,
> +       .reset = qcom_smmu500_reset,
>         .write_s2cr = qcom_smmu_write_s2cr,
>         .tlb_sync = qcom_smmu_tlb_sync,
>  };
> @@ -528,7 +545,7 @@ static const struct arm_smmu_impl sm8550_smmu_500_impl = {
>         .init_context = qcom_smmu_init_context,
>         .cfg_probe = qcom_smmu_cfg_probe,
>         .def_domain_type = qcom_smmu_def_domain_type,
> -       .reset = arm_mmu500_reset,
> +       .reset = qcom_smmu500_reset,
>         .write_s2cr = qcom_smmu_write_s2cr,
>         .tlb_sync = qcom_smmu_tlb_sync,
>  };
> @@ -544,7 +561,7 @@ static const struct arm_smmu_impl qcom_adreno_smmu_v2_impl = {
>  static const struct arm_smmu_impl qcom_adreno_smmu_500_impl = {
>         .init_context = qcom_adreno_smmu_init_context,
>         .def_domain_type = qcom_smmu_def_domain_type,
> -       .reset = arm_mmu500_reset,
> +       .reset = qcom_smmu500_reset,
>         .alloc_context_bank = qcom_adreno_smmu_alloc_context_bank,
>         .write_sctlr = qcom_adreno_smmu_write_sctlr,
>         .tlb_sync = qcom_smmu_tlb_sync,
> --
> 2.17.1
>


-- 
With best wishes
Dmitry