diff --git a/arch/mips/dec/prom/Makefile b/arch/mips/dec/prom/Makefile
index 064ae7a76bdc..ae73e42ac20b 100644
--- a/arch/mips/dec/prom/Makefile
+++ b/arch/mips/dec/prom/Makefile
@@ -6,4 +6,3 @@
 lib-y			+= init.o memory.o cmdline.o identify.o console.o
 
 lib-$(CONFIG_32BIT)	+= locore.o
-lib-$(CONFIG_64BIT)	+= call_o32.o
diff --git a/arch/mips/dec/prom/call_o32.S b/arch/mips/dec/prom/call_o32.S
deleted file mode 100644
index 8c8498159e43..000000000000
--- a/arch/mips/dec/prom/call_o32.S
+++ /dev/null
@@ -1,89 +0,0 @@
-/*
- *	O32 interface for the 64 (or N32) ABI.
- *
- *	Copyright (C) 2002  Maciej W. Rozycki
- *
- *	This program is free software; you can redistribute it and/or
- *	modify it under the terms of the GNU General Public License
- *	as published by the Free Software Foundation; either version
- *	2 of the License, or (at your option) any later version.
- */
-
-#include <asm/asm.h>
-#include <asm/regdef.h>
-
-/* Maximum number of arguments supported.  Must be even!  */
-#define O32_ARGC	32
-/* Number of static registers we save.  */
-#define O32_STATC	11
-/* Frame size for both of the above.  */
-#define O32_FRAMESZ	(4 * O32_ARGC + SZREG * O32_STATC)
-
-		.text
-
-/*
- * O32 function call dispatcher, for interfacing 32-bit ROM routines.
- *
- * The standard 64 (N32) calling sequence is supported, with a0
- * holding a function pointer, a1-a7 -- its first seven arguments
- * and the stack -- remaining ones (up to O32_ARGC, including a1-a7).
- * Static registers, gp and fp are preserved, v0 holds a result.
- * This code relies on the called o32 function for sp and ra
- * restoration and thus both this dispatcher and the current stack
- * have to be placed in a KSEGx (or KUSEG) address space.  Any
- * pointers passed have to point to addresses within one of these
- * spaces as well.
- */
-NESTED(call_o32, O32_FRAMESZ, ra)
-		REG_SUBU	sp,O32_FRAMESZ
-
-		REG_S		ra,O32_FRAMESZ-1*SZREG(sp)
-		REG_S		fp,O32_FRAMESZ-2*SZREG(sp)
-		REG_S		gp,O32_FRAMESZ-3*SZREG(sp)
-		REG_S		s7,O32_FRAMESZ-4*SZREG(sp)
-		REG_S		s6,O32_FRAMESZ-5*SZREG(sp)
-		REG_S		s5,O32_FRAMESZ-6*SZREG(sp)
-		REG_S		s4,O32_FRAMESZ-7*SZREG(sp)
-		REG_S		s3,O32_FRAMESZ-8*SZREG(sp)
-		REG_S		s2,O32_FRAMESZ-9*SZREG(sp)
-		REG_S		s1,O32_FRAMESZ-10*SZREG(sp)
-		REG_S		s0,O32_FRAMESZ-11*SZREG(sp)
-
-		move		jp,a0
-
-		sll		a0,a1,zero
-		sll		a1,a2,zero
-		sll		a2,a3,zero
-		sll		a3,a4,zero
-		sw		a5,0x10(sp)
-		sw		a6,0x14(sp)
-		sw		a7,0x18(sp)
-
-		PTR_LA		t0,O32_FRAMESZ(sp)
-		PTR_LA		t1,0x1c(sp)
-		li		t2,O32_ARGC-7
-1:
-		lw		t3,(t0)
-		REG_ADDU	t0,SZREG
-		sw		t3,(t1)
-		REG_SUBU	t2,1
-		REG_ADDU	t1,4
-		bnez		t2,1b
-
-		jalr		jp
-
-		REG_L		s0,O32_FRAMESZ-11*SZREG(sp)
-		REG_L		s1,O32_FRAMESZ-10*SZREG(sp)
-		REG_L		s2,O32_FRAMESZ-9*SZREG(sp)
-		REG_L		s3,O32_FRAMESZ-8*SZREG(sp)
-		REG_L		s4,O32_FRAMESZ-7*SZREG(sp)
-		REG_L		s5,O32_FRAMESZ-6*SZREG(sp)
-		REG_L		s6,O32_FRAMESZ-5*SZREG(sp)
-		REG_L		s7,O32_FRAMESZ-4*SZREG(sp)
-		REG_L		gp,O32_FRAMESZ-3*SZREG(sp)
-		REG_L		fp,O32_FRAMESZ-2*SZREG(sp)
-		REG_L		ra,O32_FRAMESZ-1*SZREG(sp)
-
-		REG_ADDU	sp,O32_FRAMESZ
-		jr		ra
-END(call_o32)
diff --git a/arch/mips/fw/lib/call_o32.S b/arch/mips/fw/lib/call_o32.S
index b308b2a0613e..4703fe4dbd9a 100644
--- a/arch/mips/fw/lib/call_o32.S
+++ b/arch/mips/fw/lib/call_o32.S
@@ -1,7 +1,7 @@
 /*
  *	O32 interface for the 64 (or N32) ABI.
  *
- *	Copyright (C) 2002  Maciej W. Rozycki
+ *	Copyright (C) 2002, 2014  Maciej W. Rozycki
  *
  *	This program is free software; you can redistribute it and/or
  *	modify it under the terms of the GNU General Public License
@@ -12,28 +12,37 @@
 #include <asm/asm.h>
 #include <asm/regdef.h>
 
+/* O32 register size.  */
+#define O32_SZREG	4
 /* Maximum number of arguments supported.  Must be even!  */
 #define O32_ARGC	32
-/* Number of static registers we save.	*/
+/* Number of static registers we save.  */
 #define O32_STATC	11
-/* Frame size for static register  */
-#define O32_FRAMESZ	(SZREG * O32_STATC)
-/* Frame size on new stack */
-#define O32_FRAMESZ_NEW (SZREG + 4 * O32_ARGC)
+/* Argument area frame size.  */
+#define O32_ARGSZ	(O32_SZREG * O32_ARGC)
+/* Static register save area frame size.  */
+#define O32_STATSZ	(SZREG * O32_STATC)
+/* Stack pointer register save area frame size.  */
+#define O32_SPSZ	SZREG
+/* Combined area frame size.  */
+#define O32_FRAMESZ	(O32_ARGSZ + O32_SPSZ + O32_STATSZ)
+/* Switched stack frame size.  */
+#define O32_NFRAMESZ	(O32_ARGSZ + O32_SPSZ)
 
 		.text
 
 /*
  * O32 function call dispatcher, for interfacing 32-bit ROM routines.
  *
- * The standard 64 (N32) calling sequence is supported, with a0
- * holding a function pointer, a1 a new stack pointer, a2-a7 -- its
- * first six arguments and the stack -- remaining ones (up to O32_ARGC,
- * including a2-a7). Static registers, gp and fp are preserved, v0 holds
- * a result. This code relies on the called o32 function for sp and ra
- * restoration and this dispatcher has to be placed in a KSEGx (or KUSEG)
- * address space.  Any pointers passed have to point to addresses within
- * one of these spaces as well.
+ * The standard 64 (N32) calling sequence is supported, with a0 holding
+ * a function pointer, a1 a pointer to the new stack to call the
+ * function with or 0 if no stack switching is requested, a2-a7 -- the
+ * function call's first six arguments, and the stack -- the remaining
+ * arguments (up to O32_ARGC, including a2-a7).  Static registers, gp
+ * and fp are preserved, v0 holds the result.  This code relies on the
+ * called o32 function for sp and ra restoration and this dispatcher has
+ * to be placed in a KSEGx (or KUSEG) address space.  Any pointers
+ * passed have to point to addresses within one of these spaces as well.
  */
 NESTED(call_o32, O32_FRAMESZ, ra)
 		REG_SUBU	sp,O32_FRAMESZ
@@ -51,32 +60,36 @@ NESTED(call_o32, O32_FRAMESZ, ra)
 		REG_S		s0,O32_FRAMESZ-11*SZREG(sp)
 
 		move		jp,a0
-		REG_SUBU	s0,a1,O32_FRAMESZ_NEW
-		REG_S		sp,O32_FRAMESZ_NEW-1*SZREG(s0)
+
+		move		fp,sp
+		beqz		a1,0f
+		REG_SUBU	fp,a1,O32_NFRAMESZ
+0:
+		REG_S		sp,O32_NFRAMESZ-1*SZREG(fp)
 
 		sll		a0,a2,zero
 		sll		a1,a3,zero
 		sll		a2,a4,zero
 		sll		a3,a5,zero
-		sw		a6,0x10(s0)
-		sw		a7,0x14(s0)
+		sw		a6,4*O32_SZREG(fp)
+		sw		a7,5*O32_SZREG(fp)
 
 		PTR_LA		t0,O32_FRAMESZ(sp)
-		PTR_LA		t1,0x18(s0)
+		PTR_LA		t1,6*O32_SZREG(fp)
 		li		t2,O32_ARGC-6
 1:
 		lw		t3,(t0)
 		REG_ADDU	t0,SZREG
 		sw		t3,(t1)
 		REG_SUBU	t2,1
-		REG_ADDU	t1,4
+		REG_ADDU	t1,O32_SZREG
 		bnez		t2,1b
 
-		move		sp,s0
+		move		sp,fp
 
 		jalr		jp
 
-		REG_L		sp,O32_FRAMESZ_NEW-1*SZREG(sp)
+		REG_L		sp,O32_NFRAMESZ-1*SZREG(sp)
 
 		REG_L		s0,O32_FRAMESZ-11*SZREG(sp)
 		REG_L		s1,O32_FRAMESZ-10*SZREG(sp)
diff --git a/arch/mips/fw/sni/sniprom.c b/arch/mips/fw/sni/sniprom.c
index 2c2cb182af4e..6aa264b9856a 100644
--- a/arch/mips/fw/sni/sniprom.c
+++ b/arch/mips/fw/sni/sniprom.c
@@ -40,7 +40,8 @@
 
 #ifdef CONFIG_64BIT
 
-static u8 o32_stk[16384];
+/* O32 stack has to be 8-byte aligned. */
+static u64 o32_stk[4096];
 #define O32_STK	  &o32_stk[sizeof(o32_stk)]
 
 #define __PROM_O32(fun, arg) fun arg __asm__(#fun); \
diff --git a/arch/mips/include/asm/dec/prom.h b/arch/mips/include/asm/dec/prom.h
index c0ead6313845..b59a2103b61a 100644
--- a/arch/mips/include/asm/dec/prom.h
+++ b/arch/mips/include/asm/dec/prom.h
@@ -113,31 +113,31 @@ extern int (*__pmax_close)(int);
 #define __DEC_PROM_O32(fun, arg) fun arg __asm__(#fun); \
 				 __asm__(#fun " = call_o32")
 
-int __DEC_PROM_O32(_rex_bootinit, (int (*)(void)));
-int __DEC_PROM_O32(_rex_bootread, (int (*)(void)));
-int __DEC_PROM_O32(_rex_getbitmap, (int (*)(memmap *), memmap *));
+int __DEC_PROM_O32(_rex_bootinit, (int (*)(void), void *));
+int __DEC_PROM_O32(_rex_bootread, (int (*)(void), void *));
+int __DEC_PROM_O32(_rex_getbitmap, (int (*)(memmap *), void *, memmap *));
 unsigned long *__DEC_PROM_O32(_rex_slot_address,
-			     (unsigned long *(*)(int), int));
-void *__DEC_PROM_O32(_rex_gettcinfo, (void *(*)(void)));
-int __DEC_PROM_O32(_rex_getsysid, (int (*)(void)));
-void __DEC_PROM_O32(_rex_clear_cache, (void (*)(void)));
+			     (unsigned long *(*)(int), void *, int));
+void *__DEC_PROM_O32(_rex_gettcinfo, (void *(*)(void), void *));
+int __DEC_PROM_O32(_rex_getsysid, (int (*)(void), void *));
+void __DEC_PROM_O32(_rex_clear_cache, (void (*)(void), void *));
 
-int __DEC_PROM_O32(_prom_getchar, (int (*)(void)));
-char *__DEC_PROM_O32(_prom_getenv, (char *(*)(char *), char *));
-int __DEC_PROM_O32(_prom_printf, (int (*)(char *, ...), char *, ...));
+int __DEC_PROM_O32(_prom_getchar, (int (*)(void), void *));
+char *__DEC_PROM_O32(_prom_getenv, (char *(*)(char *), void *, char *));
+int __DEC_PROM_O32(_prom_printf, (int (*)(char *, ...), void *, char *, ...));
 
 
-#define rex_bootinit()		_rex_bootinit(__rex_bootinit)
-#define rex_bootread()		_rex_bootread(__rex_bootread)
-#define rex_getbitmap(x)	_rex_getbitmap(__rex_getbitmap, x)
-#define rex_slot_address(x)	_rex_slot_address(__rex_slot_address, x)
-#define rex_gettcinfo()		_rex_gettcinfo(__rex_gettcinfo)
-#define rex_getsysid()		_rex_getsysid(__rex_getsysid)
-#define rex_clear_cache()	_rex_clear_cache(__rex_clear_cache)
+#define rex_bootinit()		_rex_bootinit(__rex_bootinit, NULL)
+#define rex_bootread()		_rex_bootread(__rex_bootread, NULL)
+#define rex_getbitmap(x)	_rex_getbitmap(__rex_getbitmap, NULL, x)
+#define rex_slot_address(x)	_rex_slot_address(__rex_slot_address, NULL, x)
+#define rex_gettcinfo()		_rex_gettcinfo(__rex_gettcinfo, NULL)
+#define rex_getsysid()		_rex_getsysid(__rex_getsysid, NULL)
+#define rex_clear_cache()	_rex_clear_cache(__rex_clear_cache, NULL)
 
-#define prom_getchar()		_prom_getchar(__prom_getchar)
-#define prom_getenv(x)		_prom_getenv(__prom_getenv, x)
-#define prom_printf(x...)	_prom_printf(__prom_printf, x)
+#define prom_getchar()		_prom_getchar(__prom_getchar, NULL)
+#define prom_getenv(x)		_prom_getenv(__prom_getenv, NULL, x)
+#define prom_printf(x...)	_prom_printf(__prom_printf, NULL, x)
 
 #else /* !CONFIG_64BIT */