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(2147 * HZ + 483648 * HZ / 1000000) 14 #define UDELAY_SHIFT 31 15 16 #ifndef __ASSEMBLY__ 17 18 struct delay_timer { 19 unsigned long (*read_current_timer)(void); 20 unsigned long freq; 21 }; 22 23 extern struct arm_delay_ops { 24 void (*delay)(unsigned long); 25 void (*const_udelay)(unsigned long); 26 void (*udelay)(unsigned long); 27 unsigned long ticks_per_jiffy; 28 } arm_delay_ops; 29 30 #define __delay(n) arm_delay_ops.delay(n) 31 32 /* 33 * This function intentionally does not exist; if you see references to 34 * it, it means that you're calling udelay() with an out of range value. 35 * 36 * With currently imposed limits, this means that we support a max delay 37 * of 2000us. Further limits: HZ<=1000 38 */ 39 extern void __bad_udelay(void); 40 41 /* 42 * division by multiplication: you don't have to worry about 43 * loss of precision. 44 * 45 * Use only for very small delays ( < 2 msec). Should probably use a 46 * lookup table, really, as the multiplications take much too long with 47 * short delays. This is a "reasonable" implementation, though (and the 48 * first constant multiplications gets optimized away if the delay is 49 * a constant) 50 */ 51 #define __udelay(n) arm_delay_ops.udelay(n) 52 #define __const_udelay(n) arm_delay_ops.const_udelay(n) 53 54 #define udelay(n) \ 55 (__builtin_constant_p(n) ? \ 56 ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \ 57 __const_udelay((n) * UDELAY_MULT)) : \ 58 __udelay(n)) 59 60 /* Loop-based definitions for assembly code. */ 61 extern void __loop_delay(unsigned long loops); 62 extern void __loop_udelay(unsigned long usecs); 63 extern void __loop_const_udelay(unsigned long); 64 65 /* Delay-loop timer registration. */ 66 #define ARCH_HAS_READ_CURRENT_TIMER 67 extern void register_current_timer_delay(const struct delay_timer *timer); 68 69 #endif /* __ASSEMBLY__ */ 70 71 #endif /* defined(_ARM_DELAY_H) */ 72 73