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

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Date:   Wed, 15 Nov 2023 15:15:17 +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 11/14/2023 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.

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