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

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Date:   Thu, 16 Nov 2023 18:14:36 +0530
From:   Bibek Kumar Patro <quic_bibekkum@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
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 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?

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