[PATCH] iommu/arm-smmu-qcom: Initialize SCTLR of the bypass context

[PATCH] iommu/arm-smmu-qcom: Initialize SCTLR of the bypass context

[Bjorn Andersson]

On SM8150 it's occasionally observed that the boot hangs in between the
writing of SMEs and context banks in arm_smmu_device_reset().

The problem seems to coincide with a display refresh happening after
updating the stream mapping, but before clearing - and there by
disabling translation - the context bank picked to emulate translation
bypass.

Resolve this by explicitly disabling the bypass context already in
cfg_probe.

Fixes: f9081b8ff593 ("iommu/arm-smmu-qcom: Implement S2CR quirk")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---
 drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 5dff7ffbef11..1b83d140742f 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -196,6 +196,8 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
 
 		set_bit(qsmmu->bypass_cbndx, smmu->context_map);
 
+		arm_smmu_cb_write(smmu, qsmmu->bypass_cbndx, ARM_SMMU_CB_SCTLR, 0);
+
 		reg = FIELD_PREP(ARM_SMMU_CBAR_TYPE, CBAR_TYPE_S1_TRANS_S2_BYPASS);
 		arm_smmu_gr1_write(smmu, ARM_SMMU_GR1_CBAR(qsmmu->bypass_cbndx), reg);
 	}
-- 
2.29.2

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

Re: [PATCH] iommu/arm-smmu-qcom: Initialize SCTLR of the bypass context

[Will Deacon]

On Tue, 5 Jan 2021 16:50:38 -0800, Bjorn Andersson wrote:
> On SM8150 it's occasionally observed that the boot hangs in between the
> writing of SMEs and context banks in arm_smmu_device_reset().
> 
> The problem seems to coincide with a display refresh happening after
> updating the stream mapping, but before clearing - and there by
> disabling translation - the context bank picked to emulate translation
> bypass.
> 
> [...]

Applied to arm64 (for-next/iommu/fixes), thanks!

[1/1] iommu/arm-smmu-qcom: Initialize SCTLR of the bypass context
      https://git.kernel.org/arm64/c/aded8c7c2b72

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu