iommu: Tidy up io-pgtable dependencies

Some io-pgtable implementations, and thus their users too, carry a
slightly odd dependency to get around the GENERIC_ATOMIC64 version of
cmpxchg64() often failing to compile. Since this is a functional
dependency, it's a bit misleading and untidy to tie it explicitly to
COMPILE_TEST while assuming that it's also implied by the other
platform/architecture options. Make things clearer by separating these
functional dependencies into distinct statements from those controlling
visibility, and since they do look a bit non-obvious to the uninitiated,
also commenting them for good measure.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/51d8c78e2ecc6696ac5907526580209ea6da167f.1673553587.git.robin.murphy@arm.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/Kconfig

@@ -32,7 +32,8 @@ config IOMMU_IO_PGTABLE
 config IOMMU_IO_PGTABLE_LPAE
 	bool "ARMv7/v8 Long Descriptor Format"
 	select IOMMU_IO_PGTABLE
-	depends on ARM || ARM64 || (COMPILE_TEST && !GENERIC_ATOMIC64)
+	depends on ARM || ARM64 || COMPILE_TEST
+	depends on !GENERIC_ATOMIC64	# for cpmxchg64()
 	help
 	  Enable support for the ARM long descriptor pagetable format.
 	  This allocator supports 4K/2M/1G, 16K/32M and 64K/512M page
@@ -70,7 +71,8 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
 config IOMMU_IO_PGTABLE_DART
 	bool "Apple DART Formats"
 	select IOMMU_IO_PGTABLE
-	depends on ARM64 || (COMPILE_TEST && !GENERIC_ATOMIC64)
+	depends on ARM64 || COMPILE_TEST
+	depends on !GENERIC_ATOMIC64	# for cpmxchg64()
 	help
 	  Enable support for the Apple DART pagetable formats. These include
 	  the t8020 and t6000/t8110 DART formats used in Apple M1/M2 family
@@ -284,7 +286,8 @@ config EXYNOS_IOMMU_DEBUG
 
 config IPMMU_VMSA
 	bool "Renesas VMSA-compatible IPMMU"
-	depends on ARCH_RENESAS || (COMPILE_TEST && !GENERIC_ATOMIC64)
+	depends on ARCH_RENESAS || COMPILE_TEST
+	depends on !GENERIC_ATOMIC64	# for IOMMU_IO_PGTABLE_LPAE
 	select IOMMU_API
 	select IOMMU_IO_PGTABLE_LPAE
 	select ARM_DMA_USE_IOMMU
@@ -304,7 +307,8 @@ config SPAPR_TCE_IOMMU
 
 config APPLE_DART
 	tristate "Apple DART IOMMU Support"
-	depends on ARCH_APPLE || (COMPILE_TEST && !GENERIC_ATOMIC64)
+	depends on ARCH_APPLE || COMPILE_TEST
+	depends on !GENERIC_ATOMIC64	# for IOMMU_IO_PGTABLE_DART
 	select IOMMU_API
 	select IOMMU_IO_PGTABLE_DART
 	default ARCH_APPLE
@@ -319,7 +323,8 @@ config APPLE_DART
 # ARM IOMMU support
 config ARM_SMMU
 	tristate "ARM Ltd. System MMU (SMMU) Support"
-	depends on ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)
+	depends on ARM64 || ARM || COMPILE_TEST
+	depends on !GENERIC_ATOMIC64	# for IOMMU_IO_PGTABLE_LPAE
 	select IOMMU_API
 	select IOMMU_IO_PGTABLE_LPAE
 	select ARM_DMA_USE_IOMMU if ARM
@@ -466,7 +471,8 @@ config MTK_IOMMU_V1
 config QCOM_IOMMU
 	# Note: iommu drivers cannot (yet?) be built as modules
 	bool "Qualcomm IOMMU Support"
-	depends on ARCH_QCOM || (COMPILE_TEST && !GENERIC_ATOMIC64)
+	depends on ARCH_QCOM || COMPILE_TEST
+	depends on !GENERIC_ATOMIC64	# for IOMMU_IO_PGTABLE_LPAE
 	select QCOM_SCM
 	select IOMMU_API
 	select IOMMU_IO_PGTABLE_LPAE