1 /* 2 * Copyright (C) 1995-2004 Russell King 3 * 4 * Delay routines, using a pre-computed "loops_per_second" value. 5 */ 6 #ifndef __ASM_ARM_DELAY_H 7 #define __ASM_ARM_DELAY_H 8 9 #include <asm/param.h> /* HZ */ 10 11 extern void __delay(int loops); 12 13 /* 14 * This function intentionally does not exist; if you see references to 15 * it, it means that you're calling udelay() with an out of range value. 16 * 17 * With currently imposed limits, this means that we support a max delay 18 * of 2000us. Further limits: HZ<=1000 and bogomips<=3355 19 */ 20 extern void __bad_udelay(void); 21 22 /* 23 * division by multiplication: you don't have to worry about 24 * loss of precision. 25 * 26 * Use only for very small delays ( < 1 msec). Should probably use a 27 * lookup table, really, as the multiplications take much too long with 28 * short delays. This is a "reasonable" implementation, though (and the 29 * first constant multiplications gets optimized away if the delay is 30 * a constant) 31 */ 32 extern void __udelay(unsigned long usecs); 33 extern void __const_udelay(unsigned long); 34 35 #define MAX_UDELAY_MS 2 36 37 #define udelay(n) \ 38 (__builtin_constant_p(n) ? \ 39 ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \ 40 __const_udelay((n) * ((2199023U*HZ)>>11))) : \ 41 __udelay(n)) 42 43 #endif /* defined(_ARM_DELAY_H) */ 44 45