xtensa: fix __delay for small loop count

Avoid __delay counter underflow for loop counts < 2.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

diff --git a/arch/xtensa/include/asm/delay.h b/arch/xtensa/include/asm/delay.h
index 3899610..742b89f 100644 (file)
--- a/arch/xtensa/include/asm/delay.h
+++ b/arch/xtensa/include/asm/delay.h
@@ -19,9 +19,12 @@ extern unsigned long loops_per_jiffy;
 
 static inline void __delay(unsigned long loops)
 {
-       /* 2 cycles per loop. */
-       __asm__ __volatile__ ("1: addi %0, %0, -2; bgeui %0, 2, 1b"
-                             : "=r" (loops) : "0" (loops));
+       if (__builtin_constant_p(loops) && loops < 2)
+               __asm__ __volatile__ ("nop");
+       else if (loops >= 2)
+               /* 2 cycles per loop. */
+               __asm__ __volatile__ ("1: addi %0, %0, -2; bgeui %0, 2, 1b"
+                               : "+r" (loops));
 }
 
 /* For SMP/NUMA systems, change boot_cpu_data to something like