[PATCH v2] iommu/arm-smmu-v3: Don't reserve implementation defined register space

Jean-Philippe Brucker jean-philippe at linaro.org
Wed May 13 11:02:57 UTC 2020


Some SMMUv3 implementation embed the Perf Monitor Group Registers (PMCG)
inside the first 64kB region of the SMMU. Since PMCG are managed by a
separate driver, this layout causes resource reservation conflicts
during boot.

To avoid this conflict, don't reserve the MMIO regions that are
implementation defined. Although devm_ioremap_resource() still works on
full pages under the hood, this way we benefit from resource conflict
checks.

Fixes: 7d839b4b9e00 ("perf/smmuv3: Add arm64 smmuv3 pmu driver")
Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
---
v1->v2: simplify following Robin's comments
https://lore.kernel.org/linux-iommu/20200506174629.1504153-1-jean-philippe@linaro.org/
---
 drivers/iommu/arm-smmu-v3.c | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 82508730feb7a1..af21d24a09e888 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -171,6 +171,8 @@
 #define ARM_SMMU_PRIQ_IRQ_CFG1		0xd8
 #define ARM_SMMU_PRIQ_IRQ_CFG2		0xdc
 
+#define ARM_SMMU_REG_SZ			0xe00
+
 /* Common MSI config fields */
 #define MSI_CFG0_ADDR_MASK		GENMASK_ULL(51, 2)
 #define MSI_CFG2_SH			GENMASK(5, 4)
@@ -628,6 +630,7 @@ struct arm_smmu_strtab_cfg {
 struct arm_smmu_device {
 	struct device			*dev;
 	void __iomem			*base;
+	void __iomem			*page1;
 
 #define ARM_SMMU_FEAT_2_LVL_STRTAB	(1 << 0)
 #define ARM_SMMU_FEAT_2_LVL_CDTAB	(1 << 1)
@@ -733,9 +736,8 @@ static struct arm_smmu_option_prop arm_smmu_options[] = {
 static inline void __iomem *arm_smmu_page1_fixup(unsigned long offset,
 						 struct arm_smmu_device *smmu)
 {
-	if ((offset > SZ_64K) &&
-	    (smmu->options & ARM_SMMU_OPT_PAGE0_REGS_ONLY))
-		offset -= SZ_64K;
+	if (offset > SZ_64K)
+		return smmu->page1 + offset - SZ_64K;
 
 	return smmu->base + offset;
 }
@@ -4021,6 +4023,18 @@ err_reset_pci_ops: __maybe_unused;
 	return err;
 }
 
+static void __iomem *arm_smmu_ioremap(struct device *dev, resource_size_t start,
+				      resource_size_t size)
+{
+	struct resource res = {
+		.flags = IORESOURCE_MEM,
+		.start = start,
+		.end = start + size - 1,
+	};
+
+	return devm_ioremap_resource(dev, &res);
+}
+
 static int arm_smmu_device_probe(struct platform_device *pdev)
 {
 	int irq, ret;
@@ -4056,10 +4070,23 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
 	}
 	ioaddr = res->start;
 
-	smmu->base = devm_ioremap_resource(dev, res);
+	/*
+	 * Don't map the IMPLEMENTATION DEFINED regions, since they may contain
+	 * the PMCG registers which are reserved by the PMU driver.
+	 */
+	smmu->base = arm_smmu_ioremap(dev, ioaddr, ARM_SMMU_REG_SZ);
 	if (IS_ERR(smmu->base))
 		return PTR_ERR(smmu->base);
 
+	if (arm_smmu_resource_size(smmu) > SZ_64K) {
+		smmu->page1 = arm_smmu_ioremap(dev, ioaddr + SZ_64K,
+					       ARM_SMMU_REG_SZ);
+		if (IS_ERR(smmu->page1))
+			return PTR_ERR(smmu->page1);
+	} else {
+		smmu->page1 = smmu->base;
+	}
+
 	/* Interrupt lines */
 
 	irq = platform_get_irq_byname_optional(pdev, "combined");
-- 
2.26.2



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