| Message ID | 20200904155513.282067-6-bjorn.andersson@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | iommu/arm-smmu: Support maintaining bootloader mappings | expand |
On 2020-09-04 21:25, Bjorn Andersson wrote: > Firmware that traps writes to S2CR to translate BYPASS into FAULT also > ignores writes of type FAULT. As such booting with "disable_bypass" set > will result in all S2CR registers left as configured by the bootloader. > > This has been seen to result in indeterministic results, as these > mappings might linger and reference context banks that Linux is > reconfiguring. > > Use the fact that BYPASS writes result in FAULT type to force all > stream > mappings to FAULT. > > Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org> > --- Reviewed-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c index 284761a1cd8e..70a1eaa52e14 100644 --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c @@ -195,6 +195,7 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu) unsigned int last_s2cr = ARM_SMMU_GR0_S2CR(smmu->num_mapping_groups - 1); struct qcom_smmu *qsmmu = to_qcom_smmu(smmu); u32 reg; + int i; /* * With some firmware writes to S2CR of type FAULT are ignored, and @@ -206,9 +207,24 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu) FIELD_PREP(ARM_SMMU_S2CR_PRIVCFG, S2CR_PRIVCFG_DEFAULT); arm_smmu_gr0_write(smmu, last_s2cr, reg); reg = arm_smmu_gr0_read(smmu, last_s2cr); - if (FIELD_GET(ARM_SMMU_S2CR_TYPE, reg) != S2CR_TYPE_BYPASS) + if (FIELD_GET(ARM_SMMU_S2CR_TYPE, reg) != S2CR_TYPE_BYPASS) { qsmmu->bypass_broken = true; + /* + * With firmware ignoring writes of type FAULT, booting the + * Linux kernel with disable_bypass disabled (i.e. "enable + * bypass") the initialization during probe will leave mappings + * in an inconsistent state. Avoid this by configuring all + * S2CRs to BYPASS. + */ + for (i = 0; i < smmu->num_mapping_groups; i++) { + smmu->s2crs[i].type = S2CR_TYPE_BYPASS; + smmu->s2crs[i].privcfg = S2CR_PRIVCFG_DEFAULT; + smmu->s2crs[i].cbndx = 0xff; + smmu->s2crs[i].count = 0; + } + } + return 0; }
Firmware that traps writes to S2CR to translate BYPASS into FAULT also ignores writes of type FAULT. As such booting with "disable_bypass" set will result in all S2CR registers left as configured by the bootloader. This has been seen to result in indeterministic results, as these mappings might linger and reference context banks that Linux is reconfiguring. Use the fact that BYPASS writes result in FAULT type to force all stream mappings to FAULT. Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org> --- Changes since v2: - None drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) -- 2.28.0