iommu: Export intel_iommu_enabled to signal when iommu is in use

In i915 driver, we do not enable either rc6 or semaphores on SNB when dmar
is enabled. The new 'intel_iommu_enabled' variable signals when the
iommu code is in operation.

Cc: Ted Phelps <phelps@gnusto.com>
Cc: Peter <pab1612@gmail.com>
Cc: Lukas Hejtmanek <xhejtman@fi.muni.cz>
Cc: Andrew Lutomirski <luto@mit.edu>
CC: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

drivers/iommu/intel-iommu.c

@@ -405,6 +405,9 @@ int dmar_disabled = 0;
 int dmar_disabled = 1;
 #endif /*CONFIG_INTEL_IOMMU_DEFAULT_ON*/
 
+int intel_iommu_enabled = 0;
+EXPORT_SYMBOL_GPL(intel_iommu_enabled);
+
 static int dmar_map_gfx = 1;
 static int dmar_forcedac;
 static int intel_iommu_strict;
@@ -3647,6 +3650,8 @@ int __init intel_iommu_init(void)
 
 	bus_register_notifier(&pci_bus_type, &device_nb);
 
+	intel_iommu_enabled = 1;
+
 	return 0;
 }
 

include/linux/dma_remapping.h

@@ -31,6 +31,7 @@ extern void free_dmar_iommu(struct intel_iommu *iommu);
 extern int iommu_calculate_agaw(struct intel_iommu *iommu);
 extern int iommu_calculate_max_sagaw(struct intel_iommu *iommu);
 extern int dmar_disabled;
+extern int intel_iommu_enabled;
 #else
 static inline int iommu_calculate_agaw(struct intel_iommu *iommu)
 {
@@ -44,6 +45,7 @@ static inline void free_dmar_iommu(struct intel_iommu *iommu)
 {
 }
 #define dmar_disabled	(1)
+#define intel_iommu_enabled (0)
 #endif