linux-kernel - [RFC 2/2] iommu: arm-smmu: Don't blindly use first SMR to calculate mask

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Message-Id: <20190605210856.20677-3-bjorn.andersson@linaro.org>
Date:   Wed,  5 Jun 2019 14:08:56 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Joerg Roedel <joro@...tes.org>, Will Deacon <will.deacon@....com>,
        Robin Murphy <robin.murphy@....com>
Cc:     Vivek Gautam <vivek.gautam@...eaurora.org>,
        Jeffrey Hugo <jhugo@...eaurora.org>,
        Patrick Daly <pdaly@...eaurora.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org
Subject: [RFC 2/2] iommu: arm-smmu: Don't blindly use first SMR to calculate mask

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@...aro.org>
---
 drivers/iommu/arm-smmu.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index c8629a656b42..0c6f5fe6f382 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1084,23 +1084,35 @@ static void arm_smmu_test_smr_masks(struct arm_smmu_device *smmu)
 {
 	void __iomem *gr0_base = ARM_SMMU_GR0(smmu);
 	u32 smr;
+	int idx;
 
 	if (!smmu->smrs)
 		return;
 
+	for (idx = 0; idx < smmu->num_mapping_groups; idx++) {
+		smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(idx));
+		if (!(smr & SMR_VALID))
+			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 = smmu->streamid_mask << SMR_ID_SHIFT;
-	writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(0));
-	smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(0));
+	writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(idx));
+	smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(idx));
 	smmu->streamid_mask = smr >> SMR_ID_SHIFT;
 
 	smr = smmu->streamid_mask << SMR_MASK_SHIFT;
-	writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(0));
-	smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(0));
+	writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(idx));
+	smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(idx));
 	smmu->smr_mask_mask = smr >> SMR_MASK_SHIFT;
 }
 
-- 
2.18.0