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Message-ID: <4db1b4d2-0aa9-4640-b7d7-7d18ab64569a@arm.com>
Date: Thu, 16 Nov 2023 17:04:13 +0000
From: Robin Murphy <robin.murphy@....com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
Bibek Kumar Patro <quic_bibekkum@...cinc.com>
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 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.
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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