linux-kernel - [PATCH v2] MIPS: Stop using dla in 32 bit kernels

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Date:	Thu, 4 Feb 2016 16:40:37 +0000
From:	Paul Burton <paul.burton@...tec.com>
To:	<linux-mips@...ux-mips.org>
CC:	Paul Burton <paul.burton@...tec.com>,
	<linux-kernel@...r.kernel.org>,
	James Hogan <james.hogan@...tec.com>,
	Markos Chandras <markos.chandras@...tec.com>,
	Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH v2] MIPS: Stop using dla in 32 bit kernels

The instruction_hazard macro made use of the dla pseudo-instruction even
for 32 bit kernels. Although it surrounded that use with ".set mips64rX"
that isn't sufficient to avoid warnings for MIPSr6 CONFIG_32BIT=y
kernels. For example this can be reproduced using maltasmvp_defconfig &
changing only the CPU type to 64r6 (CONFIG_CPU_MIPS64_R6):

      CC      arch/mips/mm/c-r4k.o
    {standard input}: Assembler messages:
    {standard input}:4105: Warning: dla used to load 32-bit register;
        recommend using la instead
    {standard input}:4129: Warning: dla used to load 32-bit register;
        recommend using la instead

Avoid this by instead making use of the PTR_LA macro which defines the
appropriate variant of the "la" instruction to use. The .set <isa>
directive is then no longer needed for the la pseudo-instruction, but
needs to remain around the jr.hb for pre-MIPSr2 kernels.

Tested with Codescape GNU Tools 2015.06-05 for MIPS IMG Linux, which
includes binutils 2.24.90 & gcc 4.9.2.

Signed-off-by: Paul Burton <paul.burton@...tec.com>

---

Changes in v2:
- Leave .set <isa> around jr.hb.
- Describe how to reproduce in the commit message.

 arch/mips/include/asm/hazards.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/mips/include/asm/hazards.h b/arch/mips/include/asm/hazards.h
index 7b99efd..835c770 100644
--- a/arch/mips/include/asm/hazards.h
+++ b/arch/mips/include/asm/hazards.h
@@ -11,6 +11,7 @@
 #define _ASM_HAZARDS_H

 #include <linux/stringify.h>
+#include <asm/asm.h>
 #include <asm/compiler.h>

 #define ___ssnop							\
@@ -65,8 +66,8 @@ do {									\
 	unsigned long tmp;						\
 									\
 	__asm__ __volatile__(						\
+	"	" __stringify(PTR_LA) "	%0, 1f			\n"	\
 	"	.set "MIPS_ISA_LEVEL"				\n"	\
-	"	dla	%0, 1f					\n"	\
 	"	jr.hb	%0					\n"	\
 	"	.set	mips0					\n"	\
 	"1:							\n"	\
-- 
2.7.0