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, 4 insertions, 3 deletions

diff --git a/arch/mips/include/asm/mipsmtregs.h b/arch/mips/include/asm/mipsmtregs.h
index 212336b7c0f4..be4cf9d477be 100644
--- a/arch/mips/include/asm/mipsmtregs.h
+++ b/arch/mips/include/asm/mipsmtregs.h
@@ -255,12 +255,12 @@ static inline unsigned int dmt(void)
 static inline void __raw_emt(void)
 {
 	__asm__ __volatile__(
+	"	.set	push						\n"
 	"	.set	noreorder					\n"
 	"	.set	mips32r2					\n"
 	"	.word	0x41600be1			# emt		\n"
 	"	ehb							\n"
-	"	.set	mips0						\n"
-	"	.set	reorder");
+	"	.set	pop");
 }
 
 /* enable multi-threaded execution if previous suggested it should be.
@@ -277,9 +277,10 @@ static inline void emt(int previous)
 static inline void ehb(void)
 {
 	__asm__ __volatile__(
+	"	.set	push					\n"
 	"	.set	mips32r2				\n"
 	"	ehb						\n"
-	"	.set	mips0					\n");
+	"	.set	pop					\n");
 }
 
 #define mftc0(rt,sel)							\