On 20/08/2024 15:27, Marc Gonzalez wrote:
On qcom msm8998, writing to the last context bank of lpass_q6_smmu
(base address 0x05100000) produces a system freeze & reboot.
The hardware/hypervisor reports 13 context banks for the LPASS SMMU
on msm8998, but only the first 12 are accessible...
Override the number of context banks
[ 2.546101] arm-smmu 5100000.iommu: probing hardware configuration...
[ 2.552439] arm-smmu 5100000.iommu: SMMUv2 with:
[ 2.558945] arm-smmu 5100000.iommu: stage 1 translation
[ 2.563627] arm-smmu 5100000.iommu: address translation ops
[ 2.568923] arm-smmu 5100000.iommu: non-coherent table walk
[ 2.574566] arm-smmu 5100000.iommu: (IDR0.CTTW overridden by FW configuration)
[ 2.580220] arm-smmu 5100000.iommu: stream matching with 12 register groups
[ 2.587263] arm-smmu 5100000.iommu: 13 context banks (0 stage-2 only)
[ 2.614447] arm-smmu 5100000.iommu: Supported page sizes: 0x63315000
[ 2.621358] arm-smmu 5100000.iommu: Stage-1: 36-bit VA -> 36-bit IPA
[ 2.627772] arm-smmu 5100000.iommu: preserved 0 boot mappings
Specifically, the crashes occur here:
qsmmu->bypass_cbndx = smmu->num_context_banks - 1;
arm_smmu_cb_write(smmu, qsmmu->bypass_cbndx, ARM_SMMU_CB_SCTLR, 0);
and here:
arm_smmu_write_context_bank(smmu, i);
arm_smmu_cb_write(smmu, i, ARM_SMMU_CB_FSR, ARM_SMMU_CB_FSR_FAULT);
It is likely that FW reserves the last context bank for its own use,
thus a simple work-around is: DON'T USE IT in Linux.
If we decrease the number of context banks, last one will be "hidden".
Signed-off-by: Marc Gonzalez <mgonzalez@xxxxxxxxxx>
Reviewed-by: Caleb Connolly <caleb.connolly@xxxxxxxxxx>
---
Changes in v3:
- Use very specific test (hack) to avoid changing the binding (Bjorn)
- Link to v2: https://lore.kernel.org/r/20240819-smmu-v1-0-bce6e4738825@xxxxxxxxxx
Changes in v2:
- Use the compatible prop instead of a specific prop to trigger work-around (Bjorn & Caleb)
- Add qcom,msm8998-lpass-smmu compatible string
- Link to v1: https://lore.kernel.org/r/20240814-smmu-v1-0-3d6c27027d5b@xxxxxxxxxx
On qcom msm8998, writing to the last context bank of lpass_q6_smmu
(base address 0x05100000) produces a system freeze & reboot.
The hardware/hypervisor reports 13 context banks for the LPASS SMMU
on msm8998, but only the first 12 are accessible...
Override the number of context banks
[ 2.546101] arm-smmu 5100000.iommu: probing hardware configuration...
[ 2.552439] arm-smmu 5100000.iommu: SMMUv2 with:
[ 2.558945] arm-smmu 5100000.iommu: stage 1 translation
[ 2.563627] arm-smmu 5100000.iommu: address translation ops
[ 2.568923] arm-smmu 5100000.iommu: non-coherent table walk
[ 2.574566] arm-smmu 5100000.iommu: (IDR0.CTTW overridden by FW configuration)
[ 2.580220] arm-smmu 5100000.iommu: stream matching with 12 register groups
[ 2.587263] arm-smmu 5100000.iommu: 13 context banks (0 stage-2 only)
[ 2.614447] arm-smmu 5100000.iommu: Supported page sizes: 0x63315000
[ 2.621358] arm-smmu 5100000.iommu: Stage-1: 36-bit VA -> 36-bit IPA
[ 2.627772] arm-smmu 5100000.iommu: preserved 0 boot mappings
Specifically, here:
qsmmu->bypass_cbndx = smmu->num_context_banks - 1;
arm_smmu_cb_write(smmu, qsmmu->bypass_cbndx, ARM_SMMU_CB_SCTLR, 0);
and here:
arm_smmu_write_context_bank(smmu, i);
arm_smmu_cb_write(smmu, i, ARM_SMMU_CB_FSR, ARM_SMMU_CB_FSR_FAULT);
It is likely that FW reserves the last context bank for its own use,
thus a simple work-around would be: DON'T USE IT in Linux.
For reference, the lpass_q6_smmu node looks like this:
lpass_q6_smmu: iommu@5100000 {
compatible = "qcom,msm8998-smmu-v2", "qcom,smmu-v2";
reg = <0x05100000 0x40000>;
clocks = <&gcc HLOS1_VOTE_LPASS_ADSP_SMMU_CLK>;
clock-names = "iface";
#global-interrupts = <0>;
#iommu-cells = <1>;
interrupts =
<GIC_SPI 226 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 393 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 394 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 395 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 396 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 397 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 398 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 399 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 400 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 401 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 402 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 403 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 137 IRQ_TYPE_LEVEL_HIGH>;
power-domains = <&gcc LPASS_ADSP_GDSC>;
status = "disabled";
};
---
drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 7e65189ca7b8c..625db1d00fe5e 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -282,6 +282,13 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
u32 smr;
int i;
+ /*
+ * MSM8998 LPASS SMMU reports 13 context banks, but accessing
+ * the last context bank crashes the system.
+ */
+ if (of_device_is_compatible(smmu->dev->of_node, "qcom,msm8998-smmu-v2") && smmu->num_context_banks == 13)
+ smmu->num_context_banks = 12;
+
/*
* Some platforms support more than the Arm SMMU architected maximum of
* 128 stream matching groups. For unknown reasons, the additional
---
base-commit: 96a96aed6bb75b5c212f233b6c059a9354cdeebe
change-id: 20240814-smmu-d572c1a16aac
Best regards,
--
// Caleb (they/them)
