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

[Sai Prakash Ranjan]

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@xxxxxxxxx>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
---
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)
-- 
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