Re: [Freedreno] [PATCH v10 06/13] iommu/arm-smmu-qcom: Get and set the pagetable config for split pagetables

[Rob Clark <robdclark@gmail.com>]

On Mon, Jul 20, 2020 at 8:41 AM Jordan Crouse <jcrouse@codeaurora.org> wrote:
>
> The Adreno GPU has the capability to manage its own pagetables and switch
> them dynamically from the hardware. To do this the GPU uses TTBR1 for
> "global" GPU memory and creates local pagetables for each context and
> switches them dynamically with the GPU.
>
> Use DOMAIN_ATTR_PGTABLE_CFG to get the current configuration for the
> TTBR1 pagetable from the smmu driver so the leaf driver can create
> compatible pagetables for use with TTBR0.
>
> Because TTBR0 is disabled by default when TTBR1 is enabled the GPU
> driver can pass the configuration of one of the newly created pagetables
> back through DOMAIN_ATTR_PGTABLE_CFG as a trigger to enable translation on
> TTBR0.
>
> Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
> ---
>
>  drivers/iommu/arm-smmu-qcom.c | 47 +++++++++++++++++++++++++++++++++++
>  drivers/iommu/arm-smmu.c      | 32 ++++++++++++++++++------
>  drivers/iommu/arm-smmu.h      | 10 ++++++++
>  3 files changed, 81 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu-qcom.c b/drivers/iommu/arm-smmu-qcom.c
> index b9a5c5369e86..9a0c64ca9cb6 100644
> --- a/drivers/iommu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm-smmu-qcom.c
> @@ -34,6 +34,52 @@ static bool qcom_adreno_smmu_is_gpu_device(struct device *dev)
>         return false;
>  }
>
> +/*
> + * Local implementation to configure TTBR0 wil the specified pagetable config.
> + * The GPU driver will call this to enable TTBR0 when per-instance pagetables
> + * are active
> + */
> +static int qcom_adreno_smmu_set_pgtable_cfg(struct arm_smmu_domain *smmu_domain,
> +               struct io_pgtable_cfg *pgtbl_cfg)
> +{
> +       struct io_pgtable *pgtable = io_pgtable_ops_to_pgtable(smmu_domain->pgtbl_ops);
> +       struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
> +       struct arm_smmu_cb *cb = &smmu_domain->smmu->cbs[cfg->cbndx];
> +
> +       /* The domain must have split pagetables already enabled */
> +       if (cb->tcr[0] & ARM_SMMU_TCR_EPD1)
> +               return -EINVAL;
> +
> +       /* If the pagetable config is NULL, disable TTBR0 */
> +       if (!pgtbl_cfg) {
> +               /* Do nothing if it is already disabled */
> +               if ((cb->tcr[0] & ARM_SMMU_TCR_EPD0))
> +                       return -EINVAL;
> +
> +               /* Set TCR to the original configuration */
> +               cb->tcr[0] = arm_smmu_lpae_tcr(&pgtable->cfg);
> +               cb->ttbr[0] = FIELD_PREP(ARM_SMMU_TTBRn_ASID, cb->cfg->asid);
> +       } else {
> +               u32 tcr = cb->tcr[0];
> +
> +               /* FIXME: What sort of validation do we need to do here? */
> +
> +               /* Don't call this again if TTBR0 is already enabled */
> +               if (!(cb->tcr[0] & ARM_SMMU_TCR_EPD0))
> +                       return -EINVAL;
> +
> +               tcr |= arm_smmu_lpae_tcr(pgtbl_cfg);
> +               tcr &= ~(ARM_SMMU_TCR_EPD0 | ARM_SMMU_TCR_EPD1);
> +
> +               cb->tcr[0] = tcr;
> +               cb->ttbr[0] = pgtbl_cfg->arm_lpae_s1_cfg.ttbr;
> +               cb->ttbr[0] |= FIELD_PREP(ARM_SMMU_TTBRn_ASID, cb->cfg->asid);
> +       }
> +
> +       arm_smmu_write_context_bank(smmu_domain->smmu, cb->cfg->cbndx);
> +       return 0;
> +}
> +
>  static int qcom_adreno_smmu_alloc_context_bank(struct arm_smmu_domain *smmu_domain,
>                 struct device *dev, int start, int count)
>  {
> @@ -131,6 +177,7 @@ static const struct arm_smmu_impl qcom_adreno_smmu_impl = {
>         .def_domain_type = qcom_smmu_def_domain_type,
>         .reset = qcom_smmu500_reset,
>         .alloc_context_bank = qcom_adreno_smmu_alloc_context_bank,
> +       .set_pgtable_cfg = qcom_adreno_smmu_set_pgtable_cfg,
>  };
>
>  static struct arm_smmu_device *qcom_smmu_create(struct arm_smmu_device *smmu,
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index fff536a44faa..e1036ae54a8d 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -86,13 +86,6 @@ struct arm_smmu_smr {
>         bool                            valid;
>  };
>
> -struct arm_smmu_cb {
> -       u64                             ttbr[2];
> -       u32                             tcr[2];
> -       u32                             mair[2];
> -       struct arm_smmu_cfg             *cfg;
> -};
> -
>  static bool using_legacy_binding, using_generic_binding;
>
>  static inline int arm_smmu_rpm_get(struct arm_smmu_device *smmu)
> @@ -558,7 +551,7 @@ static void arm_smmu_init_context_bank(struct arm_smmu_domain *smmu_domain,
>         }
>  }
>
> -static void arm_smmu_write_context_bank(struct arm_smmu_device *smmu, int idx)
> +void arm_smmu_write_context_bank(struct arm_smmu_device *smmu, int idx)
>  {
>         u32 reg;
>         bool stage1;
> @@ -1515,6 +1508,18 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
>                 case DOMAIN_ATTR_NESTING:
>                         *(int *)data = (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED);
>                         return 0;
> +               case DOMAIN_ATTR_PGTABLE_CFG: {
> +                       struct io_pgtable *pgtable;
> +                       struct io_pgtable_cfg *dest = data;
> +
> +                       if (!smmu_domain->pgtbl_ops)
> +                               return -ENODEV;
> +
> +                       pgtable = io_pgtable_ops_to_pgtable(smmu_domain->pgtbl_ops);
> +
> +                       memcpy(dest, &pgtable->cfg, sizeof(*dest));
> +                       return 0;
> +               }

hmm, maybe it would make sense to have impl hooks for get/set_attr, so
we could handle DOMAIN_ATTR_PGTABLE_CFG inside the adreno_smmu_impl?

Having impl specific domain attrs would be useful for what I have in
mind to enable stall/resume support, so we can hook in devcoredump to
iova faults (which would be a huge improvement for debugability, right
now iova faults are somewhat harder to debug than needed).  My rough
idea was to add DOMAIN_ATTR_RESUME, which could be used with
set_attr() to (1) enable STALL and let drm/msm know whether the iommu
supports it, and (2) resume translation from wq context after
devcoredump snapshot is collected.

BR,
-R

>                 default:
>                         return -ENODEV;
>                 }
> @@ -1555,6 +1560,17 @@ static int arm_smmu_domain_set_attr(struct iommu_domain *domain,
>                         else
>                                 smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
>                         break;
> +               case DOMAIN_ATTR_PGTABLE_CFG: {
> +                       struct arm_smmu_device *smmu = smmu_domain->smmu;
> +
> +                       ret = -EPERM;
> +
> +                       if (smmu)
> +                               if (smmu->impl && smmu->impl->set_pgtable_cfg)
> +                                       ret = smmu->impl->set_pgtable_cfg(smmu_domain,
> +                                               data);
> +                       }
> +                       break;
>                 default:
>                         ret = -ENODEV;
>                 }
> diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
> index 9f81c1fffe1e..9325fc28d24a 100644
> --- a/drivers/iommu/arm-smmu.h
> +++ b/drivers/iommu/arm-smmu.h
> @@ -328,6 +328,13 @@ struct arm_smmu_cfg {
>  };
>  #define ARM_SMMU_INVALID_IRPTNDX       0xff
>
> +struct arm_smmu_cb {
> +       u64                             ttbr[2];
> +       u32                             tcr[2];
> +       u32                             mair[2];
> +       struct arm_smmu_cfg             *cfg;
> +};
> +
>  enum arm_smmu_domain_stage {
>         ARM_SMMU_DOMAIN_S1 = 0,
>         ARM_SMMU_DOMAIN_S2,
> @@ -408,6 +415,8 @@ struct arm_smmu_impl {
>         int (*def_domain_type)(struct device *dev);
>         int (*alloc_context_bank)(struct arm_smmu_domain *smmu_domain,
>                         struct device *dev, int start, int max);
> +       int (*set_pgtable_cfg)(struct arm_smmu_domain *smmu_domain,
> +                       struct io_pgtable_cfg *cfg);
>  };
>
>  #define INVALID_SMENDX                 -1
> @@ -493,6 +502,7 @@ struct arm_smmu_device *arm_smmu_impl_init(struct arm_smmu_device *smmu);
>  struct arm_smmu_device *qcom_smmu_impl_init(struct arm_smmu_device *smmu);
>  struct arm_smmu_device *qcom_adreno_smmu_impl_init(struct arm_smmu_device *smmu);
>
> +void arm_smmu_write_context_bank(struct arm_smmu_device *smmu, int idx);
>  int arm_mmu500_reset(struct arm_smmu_device *smmu);
>
>  #endif /* _ARM_SMMU_H */
> --
> 2.25.1
>
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