Re: [PATCH v6 3/5] iommu/arm-smmu: introduction of ACTLR for custom prefetcher settings

[Bibek Kumar Patro <quic_bibekkum@quicinc.com>]

On 12/21/2023 6:06 AM, Dmitry Baryshkov wrote:
> On Wed, 20 Dec 2023 at 15:39, Bibek Kumar Patro
> <quic_bibekkum@quicinc.com> wrote:
>>
>> Currently in Qualcomm  SoCs the default prefetch is set to 1 which allows
>> the TLB to fetch just the next page table. MMU-500 features ACTLR
>> register which is implementation defined and is used for Qualcomm SoCs
>> to have a custom prefetch setting enabling TLB to prefetch the next set
>> of page tables accordingly allowing for faster translations.
>>
>> ACTLR value is unique for each SMR (Stream matching register) and stored
>> in a pre-populated table. This value is set to the register during
>> context bank initialisation.
>>
>> Signed-off-by: Bibek Kumar Patro <quic_bibekkum@quicinc.com>
>> ---
>>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 45 ++++++++++++++++++++++
>>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h |  6 ++-
>>   drivers/iommu/arm/arm-smmu/arm-smmu.c      |  5 ++-
>>   drivers/iommu/arm/arm-smmu/arm-smmu.h      |  5 +++
>>   4 files changed, 58 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> index 20c9836d859b..1cefdd0ca110 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> @@ -24,6 +24,12 @@
>>   #define CPRE                   (1 << 1)
>>   #define CMTLB                  (1 << 0)
>>
>> +struct actlr_config {
>> +       u16 sid;
>> +       u16 mask;
>> +       u32 actlr;
>> +};
>> +
>>   static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
>>   {
>>          return container_of(smmu, struct qcom_smmu, smmu);
>> @@ -215,9 +221,38 @@ static bool qcom_adreno_can_do_ttbr1(struct arm_smmu_device *smmu)
>>          return true;
>>   }
>>
>> +static void qcom_smmu_set_actlr(struct device *dev, struct arm_smmu_device *smmu, int cbndx,
>> +               const struct actlr_config *actlrcfg)
>> +{
>> +       struct arm_smmu_master_cfg *cfg = dev_iommu_priv_get(dev);
>> +       struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>> +       struct arm_smmu_smr *smr;
>> +       u16 mask;
>> +       int idx;
>> +       u16 id;
>> +       int i;
>> +
>> +       for (; actlrcfg->sid || actlrcfg->mask || actlrcfg->actlr; actlrcfg++) {
>> +               id = actlrcfg->sid;
>> +               mask = actlrcfg->mask;
>> +
>> +               for_each_cfg_sme(cfg, fwspec, i, idx) {
>> +                       smr = &smmu->smrs[idx];
>> +                       if (smr_is_subset(smr, id, mask)) {
>> +                               arm_smmu_cb_write(smmu, cbndx, ARM_SMMU_CB_ACTLR,
>> +                                               actlrcfg->actlr);
>> +                               break;
>> +                       }
>> +               }
>> +       }
>> +}
>> +
>>   static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>>                  struct io_pgtable_cfg *pgtbl_cfg, struct device *dev)
>>   {
>> +       struct arm_smmu_device *smmu = smmu_domain->smmu;
>> +       struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
>> +       int cbndx = smmu_domain->cfg.cbndx;
>>          struct adreno_smmu_priv *priv;
>>
>>          smmu_domain->cfg.flush_walk_prefer_tlbiasid = true;
>> @@ -248,6 +283,9 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>>          priv->set_stall = qcom_adreno_smmu_set_stall;
>>          priv->resume_translation = qcom_adreno_smmu_resume_translation;
>>
>> +       if (qsmmu->data->actlrcfg_gfx)
>> +               qcom_smmu_set_actlr(dev, smmu, cbndx, qsmmu->data->actlrcfg_gfx);
> 
> There was a feedback point against v4 that there can be more than two
> (apps + gpu) SMMU devices. No, we can not use additional compat
> strings, the SMMU units are compatible with each other.

Just to understand better, did you mean if in the below check
[inside arm-smmu-qcom.c file during qcom_smmu_create()], "else" has two 
things? (Currently adreno_impl for gpu smmu, else for only
apps smmu)

          if (np && of_device_is_compatible(np, "qcom,adreno-smmu"))
                  impl = data->adreno_impl;
          else
                  impl = data->impl;

> Please add
> matching between the smmu and particular actlr table using the IO
> address of the SMMU block.
> 

The ACTLR table for each smmu will have A IO address attached, so based 
on IO address we can apply ACTLR.
Is this your proposal((IMO hardcoding IO in driver won't be viable, 
isn't it?), or in smmu DT we would need to set the IO?


Thanks & regards,
Bibek

>> +
>>          return 0;
>>   }
>>
>> @@ -274,6 +312,13 @@ static const struct of_device_id qcom_smmu_client_of_match[] __maybe_unused = {
>>   static int qcom_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>>                  struct io_pgtable_cfg *pgtbl_cfg, struct device *dev)
>>   {
>> +       struct arm_smmu_device *smmu = smmu_domain->smmu;
>> +       struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
>> +       int cbndx = smmu_domain->cfg.cbndx;
>> +
>> +       if (qsmmu->data->actlrcfg)
>> +               qcom_smmu_set_actlr(dev, smmu, cbndx, qsmmu->data->actlrcfg);
>> +
> 
> One issue occured to me, while I was reviewing the patchset. The ACTLR
> settings are related to the whole SMMU setup, but we are applying them
> each time there is an SMMU context init (in other words, one per each
> domain). Is that correct? Or it's just that there is no better place
> for initialising the global register set? Would it be better to
> reprogram the ACTLR registers which are related just to this
> particular domain?
> 
>>          smmu_domain->cfg.flush_walk_prefer_tlbiasid = true;
>>
>>          return 0;
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>> index f3b91963e234..cb4cb402c202 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>> @@ -1,6 +1,6 @@
>>   /* SPDX-License-Identifier: GPL-2.0-only */
>>   /*
>> - * Copyright (c) 2022, Qualcomm Innovation Center, Inc. All rights reserved.
>> + * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
>>    */
>>
>>   #ifndef _ARM_SMMU_QCOM_H
>> @@ -24,7 +24,11 @@ struct qcom_smmu_config {
>>          const u32 *reg_offset;
>>   };
>>
>> +struct actlr_config;
>> +
>>   struct qcom_smmu_match_data {
>> +       const struct actlr_config *actlrcfg;
>> +       const struct actlr_config *actlrcfg_gfx;
>>          const struct qcom_smmu_config *cfg;
>>          const struct arm_smmu_impl *impl;
>>          const struct arm_smmu_impl *adreno_impl;
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> index d6d1a2a55cc0..0c7f700b27dd 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> @@ -990,9 +990,10 @@ static int arm_smmu_find_sme(struct arm_smmu_device *smmu, u16 id, u16 mask)
>>                   * expect simply identical entries for this case, but there's
>>                   * no harm in accommodating the generalisation.
>>                   */
>> -               if ((mask & smrs[i].mask) == mask &&
>> -                   !((id ^ smrs[i].id) & ~smrs[i].mask))
>> +
>> +               if (smr_is_subset(&smrs[i], id, mask))
>>                          return i;
>> +
>>                  /*
>>                   * If the new entry has any other overlap with an existing one,
>>                   * though, then there always exists at least one stream ID
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
>> index 703fd5817ec1..2e4f65412c6b 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
>> @@ -501,6 +501,11 @@ static inline void arm_smmu_writeq(struct arm_smmu_device *smmu, int page,
>>                  writeq_relaxed(val, arm_smmu_page(smmu, page) + offset);
>>   }
>>
>> +static inline bool smr_is_subset(struct arm_smmu_smr *smrs, u16 id, u16 mask)
>> +{
>> +       return (mask & smrs->mask) == mask && !((id ^ smrs->id) & ~smrs->mask);
>> +}
>> +
>>   #define ARM_SMMU_GR0           0
>>   #define ARM_SMMU_GR1           1
>>   #define ARM_SMMU_CB(s, n)      ((s)->numpage + (n))
>> --
>> 2.17.1
>>
> 
>