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authorVineet Gupta <vgupta@synopsys.com>2017-01-24 10:23:42 -0800
committerVineet Gupta <vgupta@synopsys.com>2017-01-24 10:54:24 -0800
commit36425cd67052e3becf325fd4d3ba5691791ef7e4 (patch)
treef2772767efd2f9cd9f466d2e48c2b321d9753410 /arch/arc
parent92fdb527eecff7e5eb945a3fbf4743110f5c1171 (diff)
downloadlinux-36425cd67052e3becf325fd4d3ba5691791ef7e4.tar.bz2
ARC: udelay: fix inline assembler by adding LP_COUNT to clobber list
commit 3c7c7a2fc8811bc ("ARC: Don't use "+l" inline asm constraint") modified the inline assembly to setup LP_COUNT register manually and NOT rely on gcc to do it (with the +l inline assembler contraint hint, now being retired in the compiler) However the fix was flawed as we didn't add LP_COUNT to asm clobber list, meaning gcc doesn't know that LP_COUNT or zero-delay-loops are in action in the inline asm. This resulted in some fun - as nested ZOL loops were being generared | mov lp_count,250000 ;16 # tmp235, | lp .L__GCC__LP14 # <======= OUTER LOOP (gcc generated) | .L14: | ld r2, [r5] # MEM[(volatile u32 *)prephitmp_43], w | dmb 1 | breq r2, -1, @.L21 #, w,, | bbit0 r2,1,@.L13 # w,, | ld r4,[r7] ;25 # loops_per_jiffy, loops_per_jiffy | mpymu r3,r4,r6 #, loops_per_jiffy, tmp234 | | mov lp_count, r3 # <====== INNER LOOP (from inline asm) | lp 1f | nop | 1: | nop_s | .L__GCC__LP14: ; loop end, start is @.L14 #, This caused issues with drivers relying on sane behaviour of udelay friends. With LP_COUNT added to clobber list, gcc doesn't generate the outer loop in say above case. Addresses STAR 9001146134 Reported-by: Joao Pinto <jpinto@synopsys.com> Fixes: 3c7c7a2fc8811bc ("ARC: Don't use "+l" inline asm constraint") Cc: stable@vger.kernel.org Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc')
-rw-r--r--arch/arc/include/asm/delay.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/arc/include/asm/delay.h b/arch/arc/include/asm/delay.h
index a36e8601114d..d5da2115d78a 100644
--- a/arch/arc/include/asm/delay.h
+++ b/arch/arc/include/asm/delay.h
@@ -26,7 +26,9 @@ static inline void __delay(unsigned long loops)
" lp 1f \n"
" nop \n"
"1: \n"
- : : "r"(loops));
+ :
+ : "r"(loops)
+ : "lp_count");
}
extern void __bad_udelay(void);