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Date: Fri, 17 Nov 2023 14:40:13 +0530
From: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
To: Robin Murphy <robin.murphy@....com>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: <will@...nel.org>, <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 11/16/2023 10:34 PM, Robin Murphy wrote:
> On 16/11/2023 3:24 pm, Dmitry Baryshkov wrote:
>> 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.
>
> There are still open errata #562869 and #1047329 which might need this
> workaround. I guess one could argue that we're not (knowingly) using
> nested translation at the moment, and also probably not running this in
> situations which would end up using short-descriptor format, however
> stuff like pKVM and IOMMUFD could potentially change those assumptions
> in future, so they still feel a bit sketchy to me.
>
Could you help provide some details on these two errata (#562869 and
#1047329).Both of these erratum are there for r2p4 revisions as well?
Thanks & regards,
Bibek
> Thanks,
> Robin.
>
>>
>>>
>>>>>
>>>>>>>
>>>>>>> /*
>>>>>>> * 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
>>
>>
>>
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