iommu/arm-smmu: Support SMMU module probing from the IORT

Add support for SMMU drivers built as modules to the ACPI/IORT device
probing path, by deferring the probe of the master if the SMMU driver is
known to exist but has not been loaded yet. Given that the IORT code
registers a platform device for each SMMU that it discovers, we can
easily trigger the udev based autoloading of the SMMU drivers by making
the platform device identifier part of the module alias.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: John Garry <john.garry@huawei.com> # only manual smmu ko loading
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Tested-by: John Garry <john.garry@huawei.com> # smmu v3
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/acpi/arm64/iort.c

@@ -850,9 +850,9 @@ static inline bool iort_iommu_driver_enabled(u8 type)
 {
 	switch (type) {
 	case ACPI_IORT_NODE_SMMU_V3:
-		return IS_BUILTIN(CONFIG_ARM_SMMU_V3);
+		return IS_ENABLED(CONFIG_ARM_SMMU_V3);
 	case ACPI_IORT_NODE_SMMU:
-		return IS_BUILTIN(CONFIG_ARM_SMMU);
+		return IS_ENABLED(CONFIG_ARM_SMMU);
 	default:
 		pr_warn("IORT node type %u does not describe an SMMU\n", type);
 		return false;

drivers/iommu/arm-smmu-v3.c

@@ -3734,4 +3734,5 @@ module_platform_driver(arm_smmu_driver);
 
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMUv3 implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon@arm.com>");
+MODULE_ALIAS("platform:arm-smmu-v3");
 MODULE_LICENSE("GPL v2");

drivers/iommu/arm-smmu.c

@@ -2281,4 +2281,5 @@ module_platform_driver(arm_smmu_driver);
 
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMU implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon@arm.com>");
+MODULE_ALIAS("platform:arm-smmu");
 MODULE_LICENSE("GPL v2");