iommu/amd: Add several helper functions

Move single iommu enabling codes into a wrapper function early_enable_iommu().
This can make later kdump change easier.

And also add iommu_disable_command_buffer and iommu_disable_event_buffer
for later usage.
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/amd_iommu_init.c

@@ -634,6 +634,14 @@ static void iommu_enable_command_buffer(struct amd_iommu *iommu)
 	amd_iommu_reset_cmd_buffer(iommu);
 }
 
+/*
+ * This function disables the command buffer
+ */
+static void iommu_disable_command_buffer(struct amd_iommu *iommu)
+{
+	iommu_feature_disable(iommu, CONTROL_CMDBUF_EN);
+}
+
 static void __init free_command_buffer(struct amd_iommu *iommu)
 {
 	free_pages((unsigned long)iommu->cmd_buf, get_order(CMD_BUFFER_SIZE));
@@ -666,6 +674,14 @@ static void iommu_enable_event_buffer(struct amd_iommu *iommu)
 	iommu_feature_enable(iommu, CONTROL_EVT_LOG_EN);
 }
 
+/*
+ * This function disables the event log buffer
+ */
+static void iommu_disable_event_buffer(struct amd_iommu *iommu)
+{
+	iommu_feature_disable(iommu, CONTROL_EVT_LOG_EN);
+}
+
 static void __init free_event_buffer(struct amd_iommu *iommu)
 {
 	free_pages((unsigned long)iommu->evt_buf, get_order(EVT_BUFFER_SIZE));
@@ -2046,15 +2062,8 @@ static void iommu_enable_ga(struct amd_iommu *iommu)
 #endif
 }
 
-/*
- * This function finally enables all IOMMUs found in the system after
- * they have been initialized
- */
-static void early_enable_iommus(void)
+static void early_enable_iommu(struct amd_iommu *iommu)
 {
-	struct amd_iommu *iommu;
-
-	for_each_iommu(iommu) {
 	iommu_disable(iommu);
 	iommu_init_flags(iommu);
 	iommu_set_device_table(iommu);
@@ -2064,7 +2073,18 @@ static void early_enable_iommus(void)
 	iommu_enable_ga(iommu);
 	iommu_enable(iommu);
 	iommu_flush_all_caches(iommu);
-	}
+}
+
+/*
+ * This function finally enables all IOMMUs found in the system after
+ * they have been initialized
+ */
+static void early_enable_iommus(void)
+{
+	struct amd_iommu *iommu;
+
+	for_each_iommu(iommu)
+		early_enable_iommu(iommu);
 
 #ifdef CONFIG_IRQ_REMAP
 	if (AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir))