ACPI/IORT: Introduce iort_iommu_configure

DT based systems have a generic kernel API to configure IOMMUs
for devices (ie of_iommu_configure()).

On ARM based ACPI systems, the of_iommu_configure() equivalent can
be implemented atop ACPI IORT kernel API, with the corresponding
functions to map device identifiers to IOMMUs and retrieve the
corresponding IOMMU operations necessary for DMA operations set-up.

By relying on the iommu_fwspec generic kernel infrastructure,
implement the IORT based IOMMU configuration for ARM ACPI systems
and hook it up in the ACPI kernel layer that implements DMA
configuration for a device.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> [ACPI core]
Reviewed-by: Tomasz Nowicki <tn@semihalf.com>
Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
Tested-by: Tomasz Nowicki <tn@semihalf.com>
Cc: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Tomasz Nowicki <tn@semihalf.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h
index 79ba1bb..dcb2b60 100644
--- a/include/linux/acpi_iort.h
+++ b/include/linux/acpi_iort.h
@@ -34,6 +34,8 @@
 bool iort_node_match(u8 type);
 u32 iort_msi_map_rid(struct device *dev, u32 req_id);
 struct irq_domain *iort_get_device_domain(struct device *dev, u32 req_id);
+/* IOMMU interface */
+const struct iommu_ops *iort_iommu_configure(struct device *dev);
 #else
 static inline void acpi_iort_init(void) { }
 static inline bool iort_node_match(u8 type) { return false; }
@@ -42,6 +44,10 @@
 static inline struct irq_domain *iort_get_device_domain(struct device *dev,
 							u32 req_id)
 { return NULL; }
+/* IOMMU interface */
+static inline
+const struct iommu_ops *iort_iommu_configure(struct device *dev)
+{ return NULL; }
 #endif
 
 #define IORT_ACPI_DECLARE(name, table_id, fn)		\