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/memory.h> 10 #include <asm/param.h> /* HZ */ 11 12 #define MAX_UDELAY_MS 2 13 #define UDELAY_MULT ((UL(2199023) * HZ) >> 11) 14 #define UDELAY_SHIFT 30 15 16 #ifndef __ASSEMBLY__ 17 18 extern struct arm_delay_ops { 19 void (*delay)(unsigned long); 20 void (*const_udelay)(unsigned long); 21 void (*udelay)(unsigned long); 22 } arm_delay_ops; 23 24 #define __delay(n) arm_delay_ops.delay(n) 25 26 /* 27 * This function intentionally does not exist; if you see references to 28 * it, it means that you're calling udelay() with an out of range value. 29 * 30 * With currently imposed limits, this means that we support a max delay 31 * of 2000us. Further limits: HZ<=1000 and bogomips<=3355 32 */ 33 extern void __bad_udelay(void); 34 35 /* 36 * division by multiplication: you don't have to worry about 37 * loss of precision. 38 * 39 * Use only for very small delays ( < 2 msec). Should probably use a 40 * lookup table, really, as the multiplications take much too long with 41 * short delays. This is a "reasonable" implementation, though (and the 42 * first constant multiplications gets optimized away if the delay is 43 * a constant) 44 */ 45 #define __udelay(n) arm_delay_ops.udelay(n) 46 #define __const_udelay(n) arm_delay_ops.const_udelay(n) 47 48 #define udelay(n) \ 49 (__builtin_constant_p(n) ? \ 50 ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \ 51 __const_udelay((n) * UDELAY_MULT)) : \ 52 __udelay(n)) 53 54 /* Loop-based definitions for assembly code. */ 55 extern void __loop_delay(unsigned long loops); 56 extern void __loop_udelay(unsigned long usecs); 57 extern void __loop_const_udelay(unsigned long); 58 59 #endif /* __ASSEMBLY__ */ 60 61 #endif /* defined(_ARM_DELAY_H) */ 62 63