Re: [PATCH v5 4/5] iommu/arm-smmu-qcom: Add stall support

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Thu 10 Jun 16:44 CDT 2021, Rob Clark wrote:

> From: Rob Clark <robdclark@chromium.org>
> 
> Add, via the adreno-smmu-priv interface, a way for the GPU to request
> the SMMU to stall translation on faults, and then later resume the
> translation, either retrying or terminating the current translation.
> 
> This will be used on the GPU side to "freeze" the GPU while we snapshot
> useful state for devcoredump.
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Regards,
Bjorn

> ---
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 33 ++++++++++++++++++++++
>  include/linux/adreno-smmu-priv.h           |  7 +++++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index b2e31ea84128..61fc645c1325 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -13,6 +13,7 @@ struct qcom_smmu {
>  	struct arm_smmu_device smmu;
>  	bool bypass_quirk;
>  	u8 bypass_cbndx;
> +	u32 stall_enabled;
>  };
>  
>  static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
> @@ -23,12 +24,17 @@ static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
>  static void qcom_adreno_smmu_write_sctlr(struct arm_smmu_device *smmu, int idx,
>  		u32 reg)
>  {
> +	struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
> +
>  	/*
>  	 * On the GPU device we want to process subsequent transactions after a
>  	 * fault to keep the GPU from hanging
>  	 */
>  	reg |= ARM_SMMU_SCTLR_HUPCF;
>  
> +	if (qsmmu->stall_enabled & BIT(idx))
> +		reg |= ARM_SMMU_SCTLR_CFCFG;
> +
>  	arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, reg);
>  }
>  
> @@ -48,6 +54,31 @@ static void qcom_adreno_smmu_get_fault_info(const void *cookie,
>  	info->contextidr = arm_smmu_cb_read(smmu, cfg->cbndx, ARM_SMMU_CB_CONTEXTIDR);
>  }
>  
> +static void qcom_adreno_smmu_set_stall(const void *cookie, bool enabled)
> +{
> +	struct arm_smmu_domain *smmu_domain = (void *)cookie;
> +	struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
> +	struct qcom_smmu *qsmmu = to_qcom_smmu(smmu_domain->smmu);
> +
> +	if (enabled)
> +		qsmmu->stall_enabled |= BIT(cfg->cbndx);
> +	else
> +		qsmmu->stall_enabled &= ~BIT(cfg->cbndx);
> +}
> +
> +static void qcom_adreno_smmu_resume_translation(const void *cookie, bool terminate)
> +{
> +	struct arm_smmu_domain *smmu_domain = (void *)cookie;
> +	struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
> +	struct arm_smmu_device *smmu = smmu_domain->smmu;
> +	u32 reg = 0;
> +
> +	if (terminate)
> +		reg |= ARM_SMMU_RESUME_TERMINATE;
> +
> +	arm_smmu_cb_write(smmu, cfg->cbndx, ARM_SMMU_CB_RESUME, reg);
> +}
> +
>  #define QCOM_ADRENO_SMMU_GPU_SID 0
>  
>  static bool qcom_adreno_smmu_is_gpu_device(struct device *dev)
> @@ -173,6 +204,8 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *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;
> +	priv->set_stall = qcom_adreno_smmu_set_stall;
> +	priv->resume_translation = qcom_adreno_smmu_resume_translation;
>  
>  	return 0;
>  }
> diff --git a/include/linux/adreno-smmu-priv.h b/include/linux/adreno-smmu-priv.h
> index 53fe32fb9214..c637e0997f6d 100644
> --- a/include/linux/adreno-smmu-priv.h
> +++ b/include/linux/adreno-smmu-priv.h
> @@ -45,6 +45,11 @@ struct adreno_smmu_fault_info {
>   *                 TTBR0 translation is enabled with the specified cfg
>   * @get_fault_info: Called by the GPU fault handler to get information about
>   *                  the fault
> + * @set_stall:     Configure whether stall on fault (CFCFG) is enabled.  Call
> + *                 before set_ttbr0_cfg().  If stalling on fault is enabled,
> + *                 the GPU driver must call resume_translation()
> + * @resume_translation: Resume translation after a fault
> + *
>   *
>   * 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
> @@ -60,6 +65,8 @@ struct adreno_smmu_priv {
>      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);
> +    void (*set_stall)(const void *cookie, bool enabled);
> +    void (*resume_translation)(const void *cookie, bool terminate);
>  };
>  
>  #endif /* __ADRENO_SMMU_PRIV_H */
> -- 
> 2.31.1
>