@@ -27,6 +27,7 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
{
unsigned int last_s2cr = ARM_SMMU_GR0_S2CR(smmu->num_mapping_groups - 1);
u32 reg;
+ int i;
/*
* With some firmware writes to S2CR of type FAULT are ignored, and
@@ -37,9 +38,24 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
FIELD_PREP(ARM_SMMU_S2CR_CBNDX, 0xff) |
FIELD_PREP(ARM_SMMU_S2CR_PRIVCFG, S2CR_PRIVCFG_DEFAULT));
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) {
smmu->qcom_bypass_quirk = 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> --- drivers/iommu/arm-smmu-qcom.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)