Re: [PATCH] iomm/arm-smmu: Add stall implementation hook

[Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>]

Hi Will, Robin

On 2020-04-22 01:50, Sai Prakash Ranjan wrote:
> Add stall implementation hook to enable stalling
> faults on QCOM platforms which supports it without
> causing any kind of hardware mishaps. Without this
> on QCOM platforms, GPU faults can cause unrelated
> GPU memory accesses to return zeroes. This has the
> unfortunate result of command-stream reads from CP
> getting invalid data, causing a cascade of fail.
> 
> Suggested-by: Rob Clark <robdclark@gmail.com>
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> ---
> This has been attempted previously by Rob Clark in 2017, 2018.
> Hopefully we can get something concluded in 2020.
>  * https://patchwork.kernel.org/patch/9953803/
>  * https://patchwork.kernel.org/patch/10618713/
> ---
>  drivers/iommu/arm-smmu-qcom.c | 1 +
>  drivers/iommu/arm-smmu.c      | 7 +++++++
>  drivers/iommu/arm-smmu.h      | 1 +
>  3 files changed, 9 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu-qcom.c 
> b/drivers/iommu/arm-smmu-qcom.c
> index 24c071c1d8b0..a13b229389d4 100644
> --- a/drivers/iommu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm-smmu-qcom.c
> @@ -32,6 +32,7 @@ static int qcom_sdm845_smmu500_reset(struct
> arm_smmu_device *smmu)
> 
>  static const struct arm_smmu_impl qcom_smmu_impl = {
>  	.reset = qcom_sdm845_smmu500_reset,
> +	.stall = true,
>  };
> 
>  struct arm_smmu_device *qcom_smmu_impl_init(struct arm_smmu_device 
> *smmu)
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index e622f4e33379..16b03fca9966 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -488,6 +488,11 @@ static irqreturn_t arm_smmu_context_fault(int
> irq, void *dev)
>  			    fsr, iova, fsynr, cbfrsynra, idx);
> 
>  	arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr);
> +
> +	if (smmu->impl && smmu->impl->stall && (fsr & ARM_SMMU_FSR_SS))
> +		arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_RESUME,
> +				  ARM_SMMU_RESUME_TERMINATE);
> +
>  	return IRQ_HANDLED;
>  }
> 
> @@ -659,6 +664,8 @@ static void arm_smmu_write_context_bank(struct
> arm_smmu_device *smmu, int idx)
>  		reg |= ARM_SMMU_SCTLR_S1_ASIDPNE;
>  	if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
>  		reg |= ARM_SMMU_SCTLR_E;
> +	if (smmu->impl && smmu->impl->stall)
> +		reg |= ARM_SMMU_SCTLR_CFCFG;
> 
>  	arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, reg);
>  }
> diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
> index 8d1cd54d82a6..d5134e0d5cce 100644
> --- a/drivers/iommu/arm-smmu.h
> +++ b/drivers/iommu/arm-smmu.h
> @@ -386,6 +386,7 @@ struct arm_smmu_impl {
>  	int (*init_context)(struct arm_smmu_domain *smmu_domain);
>  	void (*tlb_sync)(struct arm_smmu_device *smmu, int page, int sync,
>  			 int status);
> +	bool stall;
>  };
> 
>  static inline void __iomem *arm_smmu_page(struct arm_smmu_device 
> *smmu, int n)

Any comments on this patch?

Thanks,
Sai

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