MIPS: XPA: Standardise readx/writex accessors

Now that we are using assembler macros to implement XPA instructions on
toolchains which don't support them, pass Cop0 register names to the
__{readx,writex}_32bit_c0_register macros in $n format rather than
register numbers. Also pass a register select which may be useful in
future (for example for MemoryMapID field of WatchHi registers on
I6500).

This is to make them consistent with the normal Cop0 register access
macros which they were originally based on.

Signed-off-by: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17777/

arch/mips/include/asm/mipsregs.h

@@ -1516,7 +1516,7 @@ _ASM_MACRO_2R_1S(mthc0, rt, rd, sel,
 #define _ASM_SET_XPA ".set\txpa\n\t"
 #endif
 
-#define __readx_32bit_c0_register(source)				\
+#define __readx_32bit_c0_register(source, sel)				\
 ({									\
 	unsigned int __res;						\
 									\
@@ -1524,23 +1524,23 @@ _ASM_MACRO_2R_1S(mthc0, rt, rd, sel,
 	"	.set	push					\n"	\
 	"	.set	mips32r2				\n"	\
 	_ASM_SET_XPA							\
-	"	mfhc0	%0, $%1					\n"	\
+	"	mfhc0	%0, " #source ", %1			\n"	\
 	"	.set	pop					\n"	\
 	: "=r" (__res)							\
-	: "i" (source));						\
+	: "i" (sel));							\
 	__res;								\
 })
 
-#define __writex_32bit_c0_register(register, value)			\
+#define __writex_32bit_c0_register(register, sel, value)		\
 do {									\
 	__asm__ __volatile__(						\
 	"	.set	push					\n"	\
 	"	.set	mips32r2				\n"	\
 	_ASM_SET_XPA							\
-	"	mthc0	%z0, $%1				\n"	\
+	"	mthc0	%z0, " #register ", %1			\n"	\
 	"	.set	pop					\n"	\
 	:								\
-	: "Jr" (value), "i" (register));				\
+	: "Jr" (value), "i" (sel));					\
 } while (0)
 
 #define read_c0_index()		__read_32bit_c0_register($0, 0)
@@ -1552,14 +1552,14 @@ do {									\
 #define read_c0_entrylo0()	__read_ulong_c0_register($2, 0)
 #define write_c0_entrylo0(val)	__write_ulong_c0_register($2, 0, val)
 
-#define readx_c0_entrylo0()	__readx_32bit_c0_register(2)
-#define writex_c0_entrylo0(val)	__writex_32bit_c0_register(2, val)
+#define readx_c0_entrylo0()	__readx_32bit_c0_register($2, 0)
+#define writex_c0_entrylo0(val)	__writex_32bit_c0_register($2, 0, val)
 
 #define read_c0_entrylo1()	__read_ulong_c0_register($3, 0)
 #define write_c0_entrylo1(val)	__write_ulong_c0_register($3, 0, val)
 
-#define readx_c0_entrylo1()	__readx_32bit_c0_register(3)
-#define writex_c0_entrylo1(val)	__writex_32bit_c0_register(3, val)
+#define readx_c0_entrylo1()	__readx_32bit_c0_register($3, 0)
+#define writex_c0_entrylo1(val)	__writex_32bit_c0_register($3, 0, val)
 
 #define read_c0_conf()		__read_32bit_c0_register($3, 0)
 #define write_c0_conf(val)	__write_32bit_c0_register($3, 0, val)