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