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

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Message-ID: <CAA8EJprPE=z2VN5LkaUyLyvYpx6i1eF9dyxOzN_L86pi5tmU-Q@mail.gmail.com>
Date:   Wed, 15 Nov 2023 13:03:58 +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 Wed, 15 Nov 2023 at 11:45, Bibek Kumar Patro
<quic_bibekkum@...cinc.com> wrote:
>
> On 11/14/2023 7:45 PM, Dmitry Baryshkov wrote:
> > 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.
> >
>
> Noted, will go through the description once and rephrase it
> in next version complying with rules.
>
> >>
> >> 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?
> >
>
> In arm_mmu500_reset operation drivers/iommu/arm/arm-smmu/arm-smmu-impl.c
> CPRE bit is reset for all SoC based on mmu500 platform, hence for all
> Qualcomm SoCs including sm845 we are setting back the CPRE bit.

The errata for the CoreLink MMU-500 requires CPRE to be disabled for
all revisions before r2p2. Do we know whether these SoC used CoreLink
MMU-500 and which version of it?

>
> >>
> >>          /*
> >>           * 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