iommu/dma: Clean up Kconfig

Although iommu-dma is a per-architecture chonce, that is currently
implemented in a rather haphazard way. Selecting from the arch Kconfig
was the original logical approach, but is complicated by having to
manage dependencies; conversely, selecting from drivers ends up hiding
the architecture dependency *too* well. Instead, let's just have it
enable itself automatically when IOMMU API support is enabled for the
relevant architectures. It can't get much clearer than that.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/2e33c8bc2b1bb478157b7964bfed976cb7466139.1660668998.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

arch/arm64/Kconfig

@@ -209,7 +209,6 @@ config ARM64
 	select HAVE_KPROBES
 	select HAVE_KRETPROBES
 	select HAVE_GENERIC_VDSO
-	select IOMMU_DMA if IOMMU_SUPPORT
 	select IRQ_DOMAIN
 	select IRQ_FORCED_THREADING
 	select KASAN_VMALLOC if KASAN

drivers/iommu/Kconfig

@@ -137,7 +137,7 @@ config OF_IOMMU
 
 # IOMMU-agnostic DMA-mapping layer
 config IOMMU_DMA
-	bool
+	def_bool ARM64 || IA64 || X86
 	select DMA_OPS
 	select IOMMU_API
 	select IOMMU_IOVA
@@ -476,7 +476,6 @@ config VIRTIO_IOMMU
 	depends on VIRTIO
 	depends on (ARM64 || X86)
 	select IOMMU_API
-	select IOMMU_DMA
 	select INTERVAL_TREE
 	select ACPI_VIOT if ACPI
 	help

drivers/iommu/amd/Kconfig

@@ -9,7 +9,6 @@ config AMD_IOMMU
 	select PCI_PASID
 	select IOMMU_API
 	select IOMMU_IOVA
-	select IOMMU_DMA
 	select IOMMU_IO_PGTABLE
 	depends on X86_64 && PCI && ACPI && HAVE_CMPXCHG_DOUBLE
 	help

drivers/iommu/intel/Kconfig

@@ -19,7 +19,6 @@ config INTEL_IOMMU
 	select DMAR_TABLE
 	select SWIOTLB
 	select IOASID
-	select IOMMU_DMA
 	select PCI_ATS
 	help
 	  DMA remapping (DMAR) devices support enables independent address