amd-iommu: add function to disable all iommus

This function is required for suspend/resume support with AMD IOMMU
enabled.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

arch/x86/kernel/amd_iommu_init.c

@@ -252,6 +252,11 @@ static void __init iommu_enable(struct amd_iommu *iommu)
 	iommu_feature_enable(iommu, CONTROL_IOMMU_EN);
 }
 
+static void iommu_disable(struct amd_iommu *iommu)
+{
+	iommu_feature_disable(iommu, CONTROL_IOMMU_EN);
+}
+
 /*
  * mapping and unmapping functions for the IOMMU MMIO space. Each AMD IOMMU in
  * the system has one.
@@ -945,6 +950,14 @@ static void __init enable_iommus(void)
 	}
 }
 
+static void disable_iommus(void)
+{
+	struct amd_iommu *iommu;
+
+	for_each_iommu(iommu)
+		iommu_disable(iommu);
+}
+
 /*
  * Suspend/Resume support
  * disable suspend until real resume implemented