Messages in this thread Patch in this message | | | From | Christophe Leroy <> | Subject | [PATCH] powerpc/32: Use r2 in wrtspr() instead of r0 | Date | Fri, 22 Jan 2021 07:15:03 +0000 (UTC) |
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wrtspr() is a function to write an arbitrary value in a special register. It is used on 8xx to write to SPRN_NRI, SPRN_EID and SPRN_EIE. Writing any value to one of those will play with MSR EE and MSR RI regardless of that value.
r0 is used many places in the generated code and using r0 for that creates an unnecessary dependency of this instruction with preceding ones using r0 in a few places in vmlinux.
r2 is most likely the most stable register as it contains the pointer to 'current'.
Using r2 instead of r0 avoids that unnecessary dependency.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- arch/powerpc/include/asm/reg.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h index e40a921d78f9..32a9020e93ab 100644 --- a/arch/powerpc/include/asm/reg.h +++ b/arch/powerpc/include/asm/reg.h @@ -1392,8 +1392,7 @@ static inline void mtmsr_isync(unsigned long val) : "r" ((unsigned long)(v)) \ : "memory") #endif -#define wrtspr(rn) asm volatile("mtspr " __stringify(rn) ",0" : \ - : : "memory") +#define wrtspr(rn) asm volatile("mtspr " __stringify(rn) ",2" : : : "memory") static inline void wrtee(unsigned long val) { -- 2.25.0
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