MIPS: Avoid using .set mips0 to restore ISA

We currently have 2 commonly used methods for switching ISA within
assembly code, then restoring the original ISA.

  1) Using a pair of .set push & .set pop directives. For example:

     .set	push
     .set	mips32r2
     <some_insn>
     .set	pop

  2) Using .set mips0 to restore the ISA originally specified on the
     command line. For example:

     .set	mips32r2
     <some_insn>
     .set	mips0

Unfortunately method 2 does not work with nanoMIPS toolchains, where the
assembler rejects the .set mips0 directive like so:

     Error: cannot change ISA from nanoMIPS to mips0

In preparation for supporting nanoMIPS builds, switch all instances of
method 2 in generic non-platform-specific code to use push & pop as in
method 1 instead. The .set push & .set pop is arguably cleaner anyway,
and if nothing else it's good to consistently use one method.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/21037/
Cc: linux-mips@linux-mips.org

1 files changed, 20 insertions, 10 deletions

diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index 341a02c92985..402b80af91aa 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -1345,9 +1345,10 @@ do {								\
 			: "=r" (__res));				\
 	else								\
 		__asm__ vol(						\
+			".set\tpush\n\t"				\
 			".set\tmips32\n\t"				\
 			"mfc0\t%0, " #source ", " #sel "\n\t"		\
-			".set\tmips0\n\t"				\
+			".set\tpop\n\t"					\
 			: "=r" (__res));				\
 	__res;								\
 })
@@ -1358,15 +1359,17 @@ do {								\
 		__res = __read_64bit_c0_split(source, sel, vol);	\
 	else if (sel == 0)						\
 		__asm__ vol(						\
+			".set\tpush\n\t"				\
 			".set\tmips3\n\t"				\
 			"dmfc0\t%0, " #source "\n\t"			\
-			".set\tmips0"					\
+			".set\tpop"					\
 			: "=r" (__res));				\
 	else								\
 		__asm__ vol(						\
+			".set\tpush\n\t"				\
 			".set\tmips64\n\t"				\
 			"dmfc0\t%0, " #source ", " #sel "\n\t"		\
-			".set\tmips0"					\
+			".set\tpop"					\
 			: "=r" (__res));				\
 	__res;								\
 })
@@ -1391,9 +1394,10 @@ do {									\
 			: : "Jr" ((unsigned int)(value)));		\
 	else								\
 		__asm__ __volatile__(					\
+			".set\tpush\n\t"				\
 			".set\tmips32\n\t"				\
 			"mtc0\t%z0, " #register ", " #sel "\n\t"	\
-			".set\tmips0"					\
+			".set\tpop"					\
 			: : "Jr" ((unsigned int)(value)));		\
 } while (0)
 
@@ -1403,15 +1407,17 @@ do {									\
 		__write_64bit_c0_split(register, sel, value);		\
 	else if (sel == 0)						\
 		__asm__ __volatile__(					\
+			".set\tpush\n\t"				\
 			".set\tmips3\n\t"				\
 			"dmtc0\t%z0, " #register "\n\t"			\
-			".set\tmips0"					\
+			".set\tpop"					\
 			: : "Jr" (value));				\
 	else								\
 		__asm__ __volatile__(					\
+			".set\tpush\n\t"				\
 			".set\tmips64\n\t"				\
 			"dmtc0\t%z0, " #register ", " #sel "\n\t"	\
-			".set\tmips0"					\
+			".set\tpop"					\
 			: : "Jr" (value));				\
 } while (0)
 
@@ -1463,19 +1469,21 @@ do {									\
 	local_irq_save(__flags);					\
 	if (sel == 0)							\
 		__asm__ vol(						\
+			".set\tpush\n\t"				\
 			".set\tmips64\n\t"				\
 			"dmfc0\t%L0, " #source "\n\t"			\
 			"dsra\t%M0, %L0, 32\n\t"			\
 			"sll\t%L0, %L0, 0\n\t"				\
-			".set\tmips0"					\
+			".set\tpop"					\
 			: "=r" (__val));				\
 	else								\
 		__asm__ vol(						\
+			".set\tpush\n\t"				\
 			".set\tmips64\n\t"				\
 			"dmfc0\t%L0, " #source ", " #sel "\n\t"		\
 			"dsra\t%M0, %L0, 32\n\t"			\
 			"sll\t%L0, %L0, 0\n\t"				\
-			".set\tmips0"					\
+			".set\tpop"					\
 			: "=r" (__val));				\
 	local_irq_restore(__flags);					\
 									\
@@ -1498,23 +1506,25 @@ do {									\
 			: "+r" (__tmp));				\
 	else if (sel == 0)						\
 		__asm__ __volatile__(					\
+			".set\tpush\n\t"				\
 			".set\tmips64\n\t"				\
 			"dsll\t%L0, %L0, 32\n\t"			\
 			"dsrl\t%L0, %L0, 32\n\t"			\
 			"dsll\t%M0, %M0, 32\n\t"			\
 			"or\t%L0, %L0, %M0\n\t"				\
 			"dmtc0\t%L0, " #source "\n\t"			\
-			".set\tmips0"					\
+			".set\tpop"					\
 			: "+r" (__tmp));				\
 	else								\
 		__asm__ __volatile__(					\
+			".set\tpush\n\t"				\
 			".set\tmips64\n\t"				\
 			"dsll\t%L0, %L0, 32\n\t"			\
 			"dsrl\t%L0, %L0, 32\n\t"			\
 			"dsll\t%M0, %M0, 32\n\t"			\
 			"or\t%L0, %L0, %M0\n\t"				\
 			"dmtc0\t%L0, " #source ", " #sel "\n\t"		\
-			".set\tmips0"					\
+			".set\tpop"					\
 			: "+r" (__tmp));				\
 	local_irq_restore(__flags);					\
 } while (0)