Re: [RFC PATCH v1 2/3] drm/msm: Add an adreno-smmu-priv callback to get pagefault info

[Rob Clark]

On Mon, Nov 9, 2020 at 2:23 PM Jordan Crouse <jcrouse@xxxxxxxxxxxxxx> wrote:
>
> Add a callback in adreno-smmu-priv to read interesting SMMU
> registers to provide an opportunity for a richer debug experience
> in the GPU driver.
>
> Signed-off-by: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>
> ---
>
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 19 +++++++++++++
>  drivers/iommu/arm/arm-smmu/arm-smmu.h      |  2 ++
>  include/linux/adreno-smmu-priv.h           | 31 +++++++++++++++++++++-
>  3 files changed, 51 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index d0636c803a36..367a267324a2 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -32,6 +32,24 @@ static void qcom_adreno_smmu_write_sctlr(struct arm_smmu_device *smmu, int idx,
>         arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, reg);
>  }
>
> +static void qcom_adreno_smmu_get_fault_info(const void *cookie,
> +               struct adreno_smmu_fault_info *info)
> +{
> +       struct arm_smmu_domain *smmu_domain = (void *)cookie;
> +       struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
> +       struct arm_smmu_device *smmu = smmu_domain->smmu;
> +
> +       info->fsr = arm_smmu_cb_read(smmu, cfg->cbndx, ARM_SMMU_CB_FSR);
> +       /* FIXME: return error here if we aren't really in a fault? */
> +
> +       info->fsynr0 = arm_smmu_cb_read(smmu, cfg->cbndx, ARM_SMMU_CB_FSYNR0);
> +       info->fsynr1 = arm_smmu_cb_read(smmu, cfg->cbndx, ARM_SMMU_CB_FSYNR1);
> +       info->far = arm_smmu_cb_readq(smmu, cfg->cbndx, ARM_SMMU_CB_FAR);
> +       info->cbfrsynra = arm_smmu_gr1_read(smmu, ARM_SMMU_GR1_CBFRSYNRA(cfg->cbndx));
> +       info->ttbr0 = arm_smmu_cb_read(smmu, cfg->cbndx, ARM_SMMU_CB_TTBR0);
> +       info->contextidr = arm_smmu_cb_read(smmu, cfg->cbndx, ARM_SMMU_CB_CONTEXTIDR);
> +}
> +
>  #define QCOM_ADRENO_SMMU_GPU_SID 0
>
>  static bool qcom_adreno_smmu_is_gpu_device(struct device *dev)
> @@ -156,6 +174,7 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>         priv->cookie = smmu_domain;
>         priv->get_ttbr1_cfg = qcom_adreno_smmu_get_ttbr1_cfg;
>         priv->set_ttbr0_cfg = qcom_adreno_smmu_set_ttbr0_cfg;
> +       priv->get_fault_info = qcom_adreno_smmu_get_fault_info;
>
>         return 0;
>  }
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> index 04288b6fc619..fe511540a6bf 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> @@ -224,6 +224,8 @@ enum arm_smmu_cbar_type {
>  #define ARM_SMMU_CB_FSYNR0             0x68
>  #define ARM_SMMU_FSYNR0_WNR            BIT(4)
>
> +#define ARM_SMMU_CB_FSYNR1             0x6c
> +
>  #define ARM_SMMU_CB_S1_TLBIVA          0x600
>  #define ARM_SMMU_CB_S1_TLBIASID                0x610
>  #define ARM_SMMU_CB_S1_TLBIVAL         0x620
> diff --git a/include/linux/adreno-smmu-priv.h b/include/linux/adreno-smmu-priv.h
> index a889f28afb42..fc2592ebb9ba 100644
> --- a/include/linux/adreno-smmu-priv.h
> +++ b/include/linux/adreno-smmu-priv.h
> @@ -8,6 +8,32 @@
>
>  #include <linux/io-pgtable.h>
>
> +/**
> + * struct adreno_smmu_fault_info - container for key fault information
> + *
> + * @far: The faulting IOVA from ARM_SMMU_CB_FAR
> + * @ttbr0: The current TTBR0 pagetable from ARM_SMMU_CB_TTBR0
> + * @contextidr: The value of ARM_SMMU_CB_CONTEXTIDR
> + * @fsr: The fault status from ARM_SMMU_CB_FSR
> + * @fsynr0: The value of FSYNR0 from ARM_SMMU_CB_FSYNR0
> + * @fsynr1: The value of FSYNR1 from ARM_SMMU_CB_FSYNR0
> + * @cbfrsynra: The value of CBFRSYNRA from ARM_SMMU_GR1_CBFRSYNRA(idx)
> + *
> + * This struct passes back key page fault information to the GPU driver
> + * through the get_fault_info function pointer.
> + * The GPU driver can use this information to print informative
> + * log messages and provide deeper GPU specific insight into the fault.
> + */
> +struct adreno_smmu_fault_info {
> +       u64 far;
> +       u64 ttbr0;
> +       u32 contextidr;
> +       u32 fsr;
> +       u32 fsynr0;
> +       u32 fsynr1;
> +       u32 cbfrsynra;
> +};
> +
>  /**
>   * struct adreno_smmu_priv - private interface between adreno-smmu and GPU
>   *
> @@ -17,6 +43,8 @@
>   * @set_ttbr0_cfg: Set the TTBR0 config for the GPUs context bank.  A
>   *                 NULL config disables TTBR0 translation, otherwise
>   *                 TTBR0 translation is enabled with the specified cfg
> + * @get_fault_info: Call a helper function in the GPU driver to process a
> + *                 pagefault

This description isn't quite right, since it is call*ed* by the GPU
driver.  (And the helper aspect is irrelivant to the adreno/smmu
private interface).  Maybe something like:

"Called by the GPU driver fault handler to retrieve information about
a pagefault"

?

BR,
-R

>   *
>   * The GPU driver (drm/msm) and adreno-smmu work together for controlling
>   * the GPU's SMMU instance.  This is by necessity, as the GPU is directly
> @@ -31,6 +59,7 @@ struct adreno_smmu_priv {
>      const void *cookie;
>      const struct io_pgtable_cfg *(*get_ttbr1_cfg)(const void *cookie);
>      int (*set_ttbr0_cfg)(const void *cookie, const struct io_pgtable_cfg *cfg);
> +    void (*get_fault_info)(const void *cookie, struct adreno_smmu_fault_info *info);
>  };
>
> -#endif /* __ADRENO_SMMU_PRIV_H */
> \ No newline at end of file
> +#endif /* __ADRENO_SMMU_PRIV_H */
> --
> 2.25.1
>
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