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[4/5] iommu/arm-smmu-qcom: Consstently initialize stream mappings

Message ID 20200709050145.3520931-5-bjorn.andersson@linaro.org (mailing list archive)
State New, archived
Headers show
Series iommu/arm-smmu: Support maintaining bootloader mappings | expand

Commit Message

Bjorn Andersson July 9, 2020, 5:01 a.m. UTC 
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(-)

Comments

Vinod Koul July 9, 2020, 7:32 a.m. UTC | #1 
On 08-07-20, 22:01, 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.

s/Consstently/Consistently in patch subject
diff mbox series

Patch

diff --git a/drivers/iommu/arm-smmu-qcom.c b/drivers/iommu/arm-smmu-qcom.c
index e8a36054e912..86b1917459a4 100644
--- a/drivers/iommu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm-smmu-qcom.c
@@ -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;
 }