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

[Jean-Philippe Brucker]

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, only reserve the MMIO region we actually use:
the first 0xe0 bytes of page 0 and the first 0xd0 bytes of page 1.
Although devm_ioremap() still works on full pages under the hood, this
way we benefit from resource conflict checks.

Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
---
A nicer (and hopefully working) solution to the problem dicussed here:
https://lore.kernel.org/linux-iommu/20200421155745.19815-1-jean-philippe@linaro.org/
---
 drivers/iommu/arm-smmu-v3.c | 50 +++++++++++++++++++++++++++++++++----
 1 file changed, 45 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 82508730feb7a1..fc85cdd5b62cca 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -171,6 +171,9 @@
 #define ARM_SMMU_PRIQ_IRQ_CFG1		0xd8
 #define ARM_SMMU_PRIQ_IRQ_CFG2		0xdc
 
+#define ARM_SMMU_PAGE0_REG_SZ		0xe0
+#define ARM_SMMU_PAGE1_REG_SZ		0xd0
+
 /* Common MSI config fields */
 #define MSI_CFG0_ADDR_MASK		GENMASK_ULL(51, 2)
 #define MSI_CFG2_SH			GENMASK(5, 4)
@@ -628,6 +631,7 @@ 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)
@@ -733,11 +737,14 @@ 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;
+	void __iomem *base = smmu->base;
 
-	return smmu->base + offset;
+	if (offset > SZ_64K) {
+		offset -= SZ_64K;
+		if (smmu->page1)
+			base = smmu->page1;
+	}
+	return base + offset;
 }
 
 static struct arm_smmu_domain *to_smmu_domain(struct iommu_domain *dom)
@@ -4021,6 +4028,28 @@ 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)
+{
+	void __iomem *dest_ptr;
+	struct resource *res;
+
+	res = devm_request_mem_region(dev, start, size, dev_name(dev));
+	if (!res) {
+		dev_err(dev, "can't request SMMU region %pa\n", &start);
+		return IOMEM_ERR_PTR(-EINVAL);
+	}
+
+	dest_ptr = devm_ioremap(dev, start, size);
+	if (!dest_ptr) {
+		dev_err(dev, "ioremap failed for SMMU region %pR\n", res);
+		devm_release_mem_region(dev, start, size);
+		dest_ptr = IOMEM_ERR_PTR(-ENOMEM);
+	}
+	return dest_ptr;
+}
+
 static int arm_smmu_device_probe(struct platform_device *pdev)
 {
 	int irq, ret;
@@ -4056,10 +4085,21 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
 	}
 	ioaddr = res->start;
 
-	smmu->base = devm_ioremap_resource(dev, res);
+	/*
+	 * Only map what we need, because the IMPLEMENTATION DEFINED registers
+	 * may be used for the PMCGs, which are reserved by the PMU driver.
+	 */
+	smmu->base = arm_smmu_ioremap(dev, ioaddr, ARM_SMMU_PAGE0_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_PAGE1_REG_SZ);
+		if (IS_ERR(smmu->page1))
+			return PTR_ERR(smmu->page1);
+	}
+
 	/* Interrupt lines */
 
 	irq = platform_get_irq_byname_optional(pdev, "combined");
-- 
2.26.2