diff --git a/plat/mediatek/common/custom/oem_svc.c b/plat/mediatek/common/custom/oem_svc.c
index 49e7571..c396e2d 100644
--- a/plat/mediatek/common/custom/oem_svc.c
+++ b/plat/mediatek/common/custom/oem_svc.c
@@ -32,14 +32,14 @@
 /*******************************************************************************
  * OEM top level handler for servicing SMCs.
  ******************************************************************************/
-uint64_t oem_smc_handler(uint32_t smc_fid,
-			uint64_t x1,
-			uint64_t x2,
-			uint64_t x3,
-			uint64_t x4,
+uintptr_t oem_smc_handler(uint32_t smc_fid,
+			u_register_t x1,
+			u_register_t x2,
+			u_register_t x3,
+			u_register_t x4,
 			void *cookie,
 			void *handle,
-			uint64_t flags)
+			u_register_t flags)
 {
 	WARN("Unimplemented OEM Call: 0x%x\n", smc_fid);
 	SMC_RET1(handle, SMC_UNK);
@@ -49,14 +49,14 @@
  * Top-level OEM Service SMC handler. This handler will in turn dispatch
  * calls to related SMC handler
  */
-uint64_t oem_svc_smc_handler(uint32_t smc_fid,
-			 uint64_t x1,
-			 uint64_t x2,
-			 uint64_t x3,
-			 uint64_t x4,
+uintptr_t oem_svc_smc_handler(uint32_t smc_fid,
+			 u_register_t x1,
+			 u_register_t x2,
+			 u_register_t x3,
+			 u_register_t x4,
 			 void *cookie,
 			 void *handle,
-			 uint64_t flags)
+			 u_register_t flags)
 {
 	/*
 	 * Dispatch OEM calls to OEM Common handler and return its return value
diff --git a/plat/mediatek/common/mtk_plat_common.c b/plat/mediatek/common/mtk_plat_common.c
index 6a13192..a15131d 100644
--- a/plat/mediatek/common/mtk_plat_common.c
+++ b/plat/mediatek/common/mtk_plat_common.c
@@ -19,10 +19,10 @@
 struct atf_arg_t gteearg;
 
 void clean_top_32b_of_param(uint32_t smc_fid,
-				uint64_t *px1,
-				uint64_t *px2,
-				uint64_t *px3,
-				uint64_t *px4)
+				u_register_t *px1,
+				u_register_t *px2,
+				u_register_t *px3,
+				u_register_t *px4)
 {
 	/* if parameters from SMC32. Clean top 32 bits */
 	if (0 == (smc_fid & SMC_AARCH64_BIT)) {
diff --git a/plat/mediatek/common/mtk_plat_common.h b/plat/mediatek/common/mtk_plat_common.h
index 7513bc7..501c339 100644
--- a/plat/mediatek/common/mtk_plat_common.h
+++ b/plat/mediatek/common/mtk_plat_common.h
@@ -48,10 +48,10 @@
 /* Declarations for mtk_plat_common.c */
 uint32_t plat_get_spsr_for_bl32_entry(void);
 uint32_t plat_get_spsr_for_bl33_entry(void);
-void clean_top_32b_of_param(uint32_t smc_fid, uint64_t *x1,
-				uint64_t *x2,
-				uint64_t *x3,
-				uint64_t *x4);
+void clean_top_32b_of_param(uint32_t smc_fid, u_register_t *x1,
+				u_register_t *x2,
+				u_register_t *x3,
+				u_register_t *x4);
 void bl31_prepare_kernel_entry(uint64_t k32_64);
 void enable_ns_access_to_cpuectlr(void);
 void boot_to_kernel(uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4);
diff --git a/plat/mediatek/common/mtk_sip_svc.c b/plat/mediatek/common/mtk_sip_svc.c
index 869a959..ea8cea0 100644
--- a/plat/mediatek/common/mtk_sip_svc.c
+++ b/plat/mediatek/common/mtk_sip_svc.c
@@ -19,14 +19,14 @@
 		0x8f, 0x95, 0x05, 0x00, 0x0f, 0x3d);
 
 #pragma weak mediatek_plat_sip_handler
-uint64_t mediatek_plat_sip_handler(uint32_t smc_fid,
-				uint64_t x1,
-				uint64_t x2,
-				uint64_t x3,
-				uint64_t x4,
+uintptr_t mediatek_plat_sip_handler(uint32_t smc_fid,
+				u_register_t x1,
+				u_register_t x2,
+				u_register_t x3,
+				u_register_t x4,
 				void *cookie,
 				void *handle,
-				uint64_t flags)
+				u_register_t flags)
 {
 	ERROR("%s: unhandled SMC (0x%x)\n", __func__, smc_fid);
 	SMC_RET1(handle, SMC_UNK);
@@ -34,14 +34,14 @@
 
 /*
  * This function handles Mediatek defined SiP Calls */
-uint64_t mediatek_sip_handler(uint32_t smc_fid,
-			uint64_t x1,
-			uint64_t x2,
-			uint64_t x3,
-			uint64_t x4,
+uintptr_t mediatek_sip_handler(uint32_t smc_fid,
+			u_register_t x1,
+			u_register_t x2,
+			u_register_t x3,
+			u_register_t x4,
 			void *cookie,
 			void *handle,
-			uint64_t flags)
+			u_register_t flags)
 {
 	uint32_t ns;
 
@@ -85,14 +85,14 @@
 /*
  * This function is responsible for handling all SiP calls from the NS world
  */
-uint64_t sip_smc_handler(uint32_t smc_fid,
-			 uint64_t x1,
-			 uint64_t x2,
-			 uint64_t x3,
-			 uint64_t x4,
+uintptr_t sip_smc_handler(uint32_t smc_fid,
+			 u_register_t x1,
+			 u_register_t x2,
+			 u_register_t x3,
+			 u_register_t x4,
 			 void *cookie,
 			 void *handle,
-			 uint64_t flags)
+			 u_register_t flags)
 {
 	switch (smc_fid) {
 	case SIP_SVC_CALL_COUNT:
diff --git a/plat/nvidia/tegra/common/tegra_sip_calls.c b/plat/nvidia/tegra/common/tegra_sip_calls.c
index d96ce7a..a818453 100644
--- a/plat/nvidia/tegra/common/tegra_sip_calls.c
+++ b/plat/nvidia/tegra/common/tegra_sip_calls.c
@@ -49,14 +49,14 @@
 /*******************************************************************************
  * This function is responsible for handling all SiP calls
  ******************************************************************************/
-uint64_t tegra_sip_handler(uint32_t smc_fid,
-			   uint64_t x1,
-			   uint64_t x2,
-			   uint64_t x3,
-			   uint64_t x4,
-			   void *cookie,
-			   void *handle,
-			   uint64_t flags)
+uintptr_t tegra_sip_handler(uint32_t smc_fid,
+			    u_register_t x1,
+			    u_register_t x2,
+			    u_register_t x3,
+			    u_register_t x4,
+			    void *cookie,
+			    void *handle,
+			    u_register_t flags)
 {
 	uint32_t regval;
 	int err;
diff --git a/plat/rockchip/common/rockchip_sip_svc.c b/plat/rockchip/common/rockchip_sip_svc.c
index eca4f99..2480599 100644
--- a/plat/rockchip/common/rockchip_sip_svc.c
+++ b/plat/rockchip/common/rockchip_sip_svc.c
@@ -18,14 +18,14 @@
 		0x8f, 0x88, 0xee, 0x74, 0x7b, 0x72);
 
 #pragma weak rockchip_plat_sip_handler
-uint64_t rockchip_plat_sip_handler(uint32_t smc_fid,
-				   uint64_t x1,
-				   uint64_t x2,
-				   uint64_t x3,
-				   uint64_t x4,
-				   void *cookie,
-				   void *handle,
-				   uint64_t flags)
+uintptr_t rockchip_plat_sip_handler(uint32_t smc_fid,
+				    u_register_t x1,
+				    u_register_t x2,
+				    u_register_t x3,
+				    u_register_t x4,
+				    void *cookie,
+				    void *handle,
+				    u_register_t flags)
 {
 	ERROR("%s: unhandled SMC (0x%x)\n", __func__, smc_fid);
 	SMC_RET1(handle, SMC_UNK);
@@ -34,14 +34,14 @@
 /*
  * This function is responsible for handling all SiP calls from the NS world
  */
-uint64_t sip_smc_handler(uint32_t smc_fid,
-			 uint64_t x1,
-			 uint64_t x2,
-			 uint64_t x3,
-			 uint64_t x4,
-			 void *cookie,
-			 void *handle,
-			 uint64_t flags)
+uintptr_t sip_smc_handler(uint32_t smc_fid,
+			  u_register_t x1,
+			  u_register_t x2,
+			  u_register_t x3,
+			  u_register_t x4,
+			  void *cookie,
+			  void *handle,
+			  u_register_t flags)
 {
 	uint32_t ns;
 
diff --git a/plat/rockchip/rk3368/plat_sip_calls.c b/plat/rockchip/rk3368/plat_sip_calls.c
index 03fee88..c0f43db 100644
--- a/plat/rockchip/rk3368/plat_sip_calls.c
+++ b/plat/rockchip/rk3368/plat_sip_calls.c
@@ -10,14 +10,14 @@
 #include <rockchip_sip_svc.h>
 #include <runtime_svc.h>
 
-uint64_t rockchip_plat_sip_handler(uint32_t smc_fid,
-				   uint64_t x1,
-				   uint64_t x2,
-				   uint64_t x3,
-				   uint64_t x4,
+uintptr_t rockchip_plat_sip_handler(uint32_t smc_fid,
+				   u_register_t x1,
+				   u_register_t x2,
+				   u_register_t x3,
+				   u_register_t x4,
 				   void *cookie,
 				   void *handle,
-				   uint64_t flags)
+				   u_register_t flags)
 {
 	ERROR("%s: unhandled SMC (0x%x)\n", __func__, smc_fid);
 	SMC_RET1(handle, SMC_UNK);
diff --git a/plat/rockchip/rk3399/plat_sip_calls.c b/plat/rockchip/rk3399/plat_sip_calls.c
index 2fbda67..ae74c9c 100644
--- a/plat/rockchip/rk3399/plat_sip_calls.c
+++ b/plat/rockchip/rk3399/plat_sip_calls.c
@@ -47,14 +47,14 @@
 	return 0;
 }
 
-uint64_t rockchip_plat_sip_handler(uint32_t smc_fid,
-				   uint64_t x1,
-				   uint64_t x2,
-				   uint64_t x3,
-				   uint64_t x4,
-				   void *cookie,
-				   void *handle,
-				   uint64_t flags)
+uintptr_t rockchip_plat_sip_handler(uint32_t smc_fid,
+				    u_register_t x1,
+				    u_register_t x2,
+				    u_register_t x3,
+				    u_register_t x4,
+				    void *cookie,
+				    void *handle,
+				    u_register_t flags)
 {
 	uint64_t x5, x6;
 
diff --git a/plat/xilinx/zynqmp/sip_svc_setup.c b/plat/xilinx/zynqmp/sip_svc_setup.c
index 8b44eaa..c7996ce 100644
--- a/plat/xilinx/zynqmp/sip_svc_setup.c
+++ b/plat/xilinx/zynqmp/sip_svc_setup.c
@@ -52,14 +52,14 @@
  * Handler for all SiP SMC calls. Handles standard SIP requests
  * and calls PM SMC handler if the call is for a PM-API function.
  */
-uint64_t sip_svc_smc_handler(uint32_t smc_fid,
-			     uint64_t x1,
-			     uint64_t x2,
-			     uint64_t x3,
-			     uint64_t x4,
-			     void *cookie,
-			     void *handle,
-			     uint64_t flags)
+uintptr_t sip_svc_smc_handler(uint32_t smc_fid,
+			      u_register_t x1,
+			      u_register_t x2,
+			      u_register_t x3,
+			      u_register_t x4,
+			      void *cookie,
+			      void *handle,
+			      u_register_t flags)
 {
 	/* Let PM SMC handler deal with PM-related requests */
 	if (is_pm_fid(smc_fid)) {