[PATCH v2 1/4] iommu/arm-smmu: Make instance lookup robust

[Robin Murphy]

Relying on the driver list was a cute idea for minimising the scope of
our SMMU device lookups, however it turns out to have a subtle flaw. The
SMMU device only gets added to that list after arm_smmu_device_probe()
returns success, so there's actually no way the iommu_device_register()
call from there could ever work as intended, even if it wasn't already
hampered by the fwspec setup not happening early enough.

Switch both arm_smmu_get_by_fwnode() implementations to use a platform
bus lookup instead, which *will* reliably work. Also make sure that we
don't register SMMUv2 instances until we've fully initialised them, to
avoid similar consequences of the lookup now finding a device with no
drvdata. Moving the error returns is also a perfect excuse to streamline
them with dev_err_probe() in the process.

Signed-off-by: Robin Murphy <robin.murphy at arm.com>
---

v2: Tweak commit message

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c |  4 +--
 drivers/iommu/arm/arm-smmu/arm-smmu.c       | 31 ++++++++++-----------
 2 files changed, 16 insertions(+), 19 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index a5c7002ff75b..e1eae4ecfa02 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3237,8 +3237,8 @@ static struct platform_driver arm_smmu_driver;
 static
 struct arm_smmu_device *arm_smmu_get_by_fwnode(struct fwnode_handle *fwnode)
 {
-	struct device *dev = driver_find_device_by_fwnode(&arm_smmu_driver.driver,
-							  fwnode);
+	struct device *dev = bus_find_device_by_fwnode(&platform_bus_type, fwnode);
+
 	put_device(dev);
 	return dev ? dev_get_drvdata(dev) : NULL;
 }
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 650664e0f6e3..0949f2734e5d 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1411,8 +1411,8 @@ static bool arm_smmu_capable(struct device *dev, enum iommu_cap cap)
 static
 struct arm_smmu_device *arm_smmu_get_by_fwnode(struct fwnode_handle *fwnode)
 {
-	struct device *dev = driver_find_device_by_fwnode(&arm_smmu_driver.driver,
-							  fwnode);
+	struct device *dev = bus_find_device_by_fwnode(&platform_bus_type, fwnode);
+
 	put_device(dev);
 	return dev ? dev_get_drvdata(dev) : NULL;
 }
@@ -2227,21 +2227,6 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
 					i, irq);
 	}
 
-	err = iommu_device_sysfs_add(&smmu->iommu, smmu->dev, NULL,
-				     "smmu.%pa", &smmu->ioaddr);
-	if (err) {
-		dev_err(dev, "Failed to register iommu in sysfs\n");
-		return err;
-	}
-
-	err = iommu_device_register(&smmu->iommu, &arm_smmu_ops,
-				    using_legacy_binding ? NULL : dev);
-	if (err) {
-		dev_err(dev, "Failed to register iommu\n");
-		iommu_device_sysfs_remove(&smmu->iommu);
-		return err;
-	}
-
 	platform_set_drvdata(pdev, smmu);
 
 	/* Check for RMRs and install bypass SMRs if any */
@@ -2250,6 +2235,18 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
 	arm_smmu_device_reset(smmu);
 	arm_smmu_test_smr_masks(smmu);
 
+	err = iommu_device_sysfs_add(&smmu->iommu, smmu->dev, NULL,
+				     "smmu.%pa", &smmu->ioaddr);
+	if (err)
+		return dev_err_probe(dev, err, "Failed to register iommu in sysfs\n");
+
+	err = iommu_device_register(&smmu->iommu, &arm_smmu_ops,
+				    using_legacy_binding ? NULL : dev);
+	if (err) {
+		iommu_device_sysfs_remove(&smmu->iommu);
+		return dev_err_probe(dev, err, "Failed to register iommu\n");
+	}
+
 	/*
 	 * We want to avoid touching dev->power.lock in fastpaths unless
 	 * it's really going to do something useful - pm_runtime_enabled()
-- 
2.39.2.101.g768bb238c484.dirty