[PATCH 1/3] iommu/arm-smmu: Don't blindly use first SMR to calculate mask

[Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>]

With the SMRs inherited from the bootloader the first SMR might actually
be valid and in use. As such probing the SMR mask using the first SMR
might break a stream in use. Search for an unused stream and use this to
probe the SMR mask.

Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---

Changes since RFC:
- Deal with EXIDS
- Use arm_smmu_gr0_read/write()

 drivers/iommu/arm-smmu.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 4f1a350d9529..6ca6a4e072c8 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -945,24 +945,43 @@ static void arm_smmu_write_sme(struct arm_smmu_device *smmu, int idx)
  */
 static void arm_smmu_test_smr_masks(struct arm_smmu_device *smmu)
 {
+	u32 s2cr;
 	u32 smr;
+	int idx;
 
 	if (!smmu->smrs)
 		return;
 
+	for (idx = 0; idx < smmu->num_mapping_groups; idx++) {
+		if (smmu->features & ARM_SMMU_FEAT_EXIDS) {
+			s2cr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_S2CR(idx));
+			if (!FIELD_GET(S2CR_EXIDVALID, s2cr))
+				break;
+		} else {
+			smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(idx));
+			if (!FIELD_GET(SMR_VALID, smr))
+				break;
+		}
+	}
+
+	if (idx == smmu->num_mapping_groups) {
+		dev_err(smmu->dev, "Unable to compute streamid_mask\n");
+		return;
+	}
+
 	/*
 	 * SMR.ID bits may not be preserved if the corresponding MASK
 	 * bits are set, so check each one separately. We can reject
 	 * masters later if they try to claim IDs outside these masks.
 	 */
 	smr = FIELD_PREP(SMR_ID, smmu->streamid_mask);
-	arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_SMR(0), smr);
-	smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(0));
+	arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_SMR(idx), smr);
+	smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(idx));
 	smmu->streamid_mask = FIELD_GET(SMR_ID, smr);
 
 	smr = FIELD_PREP(SMR_MASK, smmu->streamid_mask);
-	arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_SMR(0), smr);
-	smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(0));
+	arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_SMR(idx), smr);
+	smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(idx));
 	smmu->smr_mask_mask = FIELD_GET(SMR_MASK, smr);
 }
 
-- 
2.24.0