diff --git a/secure_fw/spm/CMakeLists.txt b/secure_fw/spm/CMakeLists.txt
index fc8df28..06787ee 100755
--- a/secure_fw/spm/CMakeLists.txt
+++ b/secure_fw/spm/CMakeLists.txt
@@ -51,7 +51,8 @@
         $<$<BOOL:${CONFIG_TFM_PSA_API_CROSS_CALL}>:cmsis_psa/spm_cross_call.c>
         $<$<BOOL:${TFM_PSA_API}>:cmsis_psa/static_load.c>
         $<$<BOOL:${TFM_PSA_API}>:ffm/psa_api.c>
-        $<$<BOOL:${TFM_PSA_API}>:ffm/backend.c>
+        $<$<BOOL:${CONFIG_TFM_SPM_BACKEND_IPC}>:ffm/backend_ipc.c>
+        $<$<BOOL:${CONFIG_TFM_SPM_BACKEND_SFN}>:ffm/backend_sfn.c>
         $<$<BOOL:${TFM_PSA_API}>:ffm/interrupt.c>
         $<$<BOOL:${TFM_PSA_API}>:cmsis_psa/tfm_core_svcalls_ipc.c>
         $<$<BOOL:${TFM_PSA_API}>:cmsis_psa/tfm_pools.c>
@@ -92,10 +93,7 @@
         $<$<AND:$<BOOL:${BL2}>,$<BOOL:${MCUBOOT_MEASURED_BOOT}>>:BOOT_DATA_AVAILABLE>
         $<$<BOOL:${TFM_EXCEPTION_INFO_DUMP}>:TFM_EXCEPTION_INFO_DUMP>
         $<$<BOOL:${TFM_NS_MANAGE_NSID}>:TFM_NS_MANAGE_NSID>
-        $<$<BOOL:${CONFIG_TFM_SPM_BACKEND_IPC}>:CONFIG_TFM_SPM_BACKEND_IPC>
-        $<$<BOOL:${CONFIG_TFM_SPM_BACKEND_SFN}>:CONFIG_TFM_SPM_BACKEND_SFN>
         $<$<BOOL:${TFM_PSA_API}>:CONFIG_TFM_CONN_HANDLE_MAX_NUM=${CONFIG_TFM_CONN_HANDLE_MAX_NUM}>
-
         # CONFIG_TFM_FP
         $<$<STREQUAL:${CONFIG_TFM_FP},hard>:CONFIG_TFM_FP=2>
         $<$<STREQUAL:${CONFIG_TFM_FP},soft>:CONFIG_TFM_FP=0>
diff --git a/secure_fw/spm/cmsis_psa/arch/tfm_arch_v6m_v7m.c b/secure_fw/spm/cmsis_psa/arch/tfm_arch_v6m_v7m.c
index 4f9e647..0493f61 100644
--- a/secure_fw/spm/cmsis_psa/arch/tfm_arch_v6m_v7m.c
+++ b/secure_fw/spm/cmsis_psa/arch/tfm_arch_v6m_v7m.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2021, Arm Limited. All rights reserved.
+ * Copyright (c) 2019-2022, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
@@ -30,15 +30,15 @@
 #pragma required = scheduler_lock
 #pragma required = tfm_core_svc_handler
 
-#ifdef CONFIG_TFM_PSA_API_CROSS_CALL
+#if CONFIG_TFM_PSA_API_CROSS_CALL == 1
 
 #pragma required = cross_call_execute_c
 
-#endif /* CONFIG_TFM_PSA_API_CROSS_CALL */
+#endif /* CONFIG_TFM_PSA_API_CROSS_CALL == 1*/
 
 #endif
 
-#ifdef CONFIG_TFM_PSA_API_CROSS_CALL
+#if CONFIG_TFM_PSA_API_CROSS_CALL == 1
 
 __naked uint32_t arch_non_preempt_call(uintptr_t fn_addr, uintptr_t frame_addr,
                                        uint32_t stk_base, uint32_t stk_limit)
@@ -75,7 +75,7 @@
     );
 }
 
-#endif /* CONFIG_TFM_PSA_API_CROSS_CALL */
+#endif /* CONFIG_TFM_PSA_API_CROSS_CALL == 1*/
 
 __attribute__((naked)) void PendSV_Handler(void)
 {
diff --git a/secure_fw/spm/cmsis_psa/arch/tfm_arch_v8m_base.c b/secure_fw/spm/cmsis_psa/arch/tfm_arch_v8m_base.c
index 52ba185..d95af8f 100644
--- a/secure_fw/spm/cmsis_psa/arch/tfm_arch_v8m_base.c
+++ b/secure_fw/spm/cmsis_psa/arch/tfm_arch_v8m_base.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2021, Arm Limited. All rights reserved.
+ * Copyright (c) 2018-2022, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
@@ -31,15 +31,15 @@
 #pragma required = scheduler_lock
 #pragma required = tfm_core_svc_handler
 
-#ifdef CONFIG_TFM_PSA_API_CROSS_CALL
+#if CONFIG_TFM_PSA_API_CROSS_CALL == 1
 
 #pragma required = cross_call_execute_c
 
-#endif /* CONFIG_TFM_PSA_API_CROSS_CALL */
+#endif /* CONFIG_TFM_PSA_API_CROSS_CALL == 1 */
 
 #endif
 
-#ifdef CONFIG_TFM_PSA_API_CROSS_CALL
+#if CONFIG_TFM_PSA_API_CROSS_CALL == 1
 
 __naked uint32_t arch_non_preempt_call(uintptr_t fn_addr, uintptr_t frame_addr,
                                        uint32_t stk_base, uint32_t stk_limit)
@@ -81,7 +81,7 @@
     );
 }
 
-#endif /* CONFIG_TFM_PSA_API_CROSS_CALL */
+#endif /* CONFIG_TFM_PSA_API_CROSS_CALL == 1 */
 
 __attribute__((naked)) void PendSV_Handler(void)
 {
diff --git a/secure_fw/spm/cmsis_psa/arch/tfm_arch_v8m_main.c b/secure_fw/spm/cmsis_psa/arch/tfm_arch_v8m_main.c
index cfc4e7e..aff6a78 100644
--- a/secure_fw/spm/cmsis_psa/arch/tfm_arch_v8m_main.c
+++ b/secure_fw/spm/cmsis_psa/arch/tfm_arch_v8m_main.c
@@ -36,15 +36,15 @@
 #pragma required = scheduler_lock
 #pragma required = tfm_core_svc_handler
 
-#ifdef CONFIG_TFM_PSA_API_CROSS_CALL
+#if CONFIG_TFM_PSA_API_CROSS_CALL == 1
 
 #pragma required = cross_call_execute_c
 
-#endif /* CONFIG_TFM_PSA_API_CROSS_CALL */
+#endif /* CONFIG_TFM_PSA_API_CROSS_CALL == 1*/
 
 #endif
 
-#ifdef CONFIG_TFM_PSA_API_CROSS_CALL
+#if CONFIG_TFM_PSA_API_CROSS_CALL == 1
 
 __naked uint32_t arch_non_preempt_call(uintptr_t fn_addr, uintptr_t frame_addr,
                                        uint32_t stk_base, uint32_t stk_limit)
@@ -84,7 +84,7 @@
     );
 }
 
-#endif /* CONFIG_TFM_PSA_API_CROSS_CALL */
+#endif /* CONFIG_TFM_PSA_API_CROSS_CALL == 1*/
 
 __attribute__((naked)) void PendSV_Handler(void)
 {
diff --git a/secure_fw/spm/cmsis_psa/spm_ipc.h b/secure_fw/spm/cmsis_psa/spm_ipc.h
index 4f513b3..bf4b498 100644
--- a/secure_fw/spm/cmsis_psa/spm_ipc.h
+++ b/secure_fw/spm/cmsis_psa/spm_ipc.h
@@ -392,7 +392,7 @@
  */
 void spm_assert_signal(void *p_pt, psa_signal_t signal);
 
-#ifdef CONFIG_TFM_PSA_API_CROSS_CALL
+#if CONFIG_TFM_PSA_API_CROSS_CALL == 1
 
 /*
  * SPM dispatcher to handle the API call under non-privileged model.
diff --git a/secure_fw/spm/ffm/backend.c b/secure_fw/spm/ffm/backend.c
deleted file mode 100644
index 9df5de7..0000000
--- a/secure_fw/spm/ffm/backend.c
+++ /dev/null
@@ -1,15 +0,0 @@
-/*
- * Copyright (c) 2021, Arm Limited. All rights reserved.
- *
- * SPDX-License-Identifier: BSD-3-Clause
- *
- */
-#include "config_impl.h"
-
-#if CONFIG_TFM_SPM_BACKEND_SFN == 1
-#include "backend_sfn.c"
-#elif CONFIG_TFM_SPM_BACKEND_IPC == 1
-#include "backend_ipc.c"
-#else
-#error "Invalid configuration."
-#endif
diff --git a/secure_fw/spm/ffm/backend_ipc.c b/secure_fw/spm/ffm/backend_ipc.c
index 443c5da..543282a 100644
--- a/secure_fw/spm/ffm/backend_ipc.c
+++ b/secure_fw/spm/ffm/backend_ipc.c
@@ -23,7 +23,7 @@
 /* Declare the global component list */
 struct partition_head_t partition_listhead;
 
-#ifdef CONFIG_TFM_PSA_API_CROSS_CALL
+#if CONFIG_TFM_PSA_API_CROSS_CALL == 1
 
 #ifdef TFM_MULTI_CORE_TOPOLOGY
 /* TODO: To be checked when RPC design updates. */
@@ -115,7 +115,7 @@
     THRD_INIT(&p_pt->thrd, &p_pt->ctx_ctrl,
               TO_THREAD_PRIORITY(PARTITION_PRIORITY(p_pldi->flags)));
 
-#if defined(CONFIG_TFM_PSA_API_CROSS_CALL) && !defined(TFM_MULTI_CORE_TOPOLOGY)
+#if (CONFIG_TFM_PSA_API_CROSS_CALL == 1) && !defined(TFM_MULTI_CORE_TOPOLOGY)
     if (p_pldi->pid == TFM_SP_NON_SECURE_ID) {
         SPM_THREAD_CONTEXT = &p_pt->ctx_ctrl;
     }
@@ -132,7 +132,7 @@
     uint32_t control;
     struct partition_t *p_cur_pt;
 
-#ifdef CONFIG_TFM_PSA_API_THREAD_CALL
+#if CONFIG_TFM_PSA_API_THREAD_CALL == 1
     TFM_CORE_ASSERT(SPM_THREAD_CONTEXT);
 #endif