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

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Message-ID: <CAA8EJprHppoN6rg8-rS1F+4kynQqmV1L3OiHFnJ0HyrshywFig@mail.gmail.com>
Date:   Thu, 16 Nov 2023 17:24:59 +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 Thu, 16 Nov 2023 at 14:45, Bibek Kumar Patro
<quic_bibekkum@...cinc.com> wrote:
>
>
>
> On 11/15/2023 4:33 PM, Dmitry Baryshkov wrote:
> > 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?
> >
>
> Just checked all these SoCs are using r2p4 revision.
> So CPRE needs to be enabled back here then?

can be enabled, yes.

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



-- 
With best wishes
Dmitry