1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_DELAY_H 3 #define _LINUX_DELAY_H 4 5 /* 6 * Copyright (C) 1993 Linus Torvalds 7 * 8 * Delay routines, using a pre-computed "loops_per_jiffy" value. 9 * 10 * Please note that ndelay(), udelay() and mdelay() may return early for 11 * several reasons: 12 * 1. computed loops_per_jiffy too low (due to the time taken to 13 * execute the timer interrupt.) 14 * 2. cache behaviour affecting the time it takes to execute the 15 * loop function. 16 * 3. CPU clock rate changes. 17 * 18 * Please see this thread: 19 * https://lists.openwall.net/linux-kernel/2011/01/09/56 20 */ 21 22 #include <linux/math.h> 23 #include <linux/sched.h> 24 25 extern unsigned long loops_per_jiffy; 26 27 #include <asm/delay.h> 28 29 /* 30 * Using udelay() for intervals greater than a few milliseconds can 31 * risk overflow for high loops_per_jiffy (high bogomips) machines. The 32 * mdelay() provides a wrapper to prevent this. For delays greater 33 * than MAX_UDELAY_MS milliseconds, the wrapper is used. Architecture 34 * specific values can be defined in asm-???/delay.h as an override. 35 * The 2nd mdelay() definition ensures GCC will optimize away the 36 * while loop for the common cases where n <= MAX_UDELAY_MS -- Paul G. 37 */ 38 39 #ifndef MAX_UDELAY_MS 40 #define MAX_UDELAY_MS 5 41 #endif 42 43 #ifndef mdelay 44 #define mdelay(n) (\ 45 (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \ 46 ({unsigned long __ms=(n); while (__ms--) udelay(1000);})) 47 #endif 48 49 #ifndef ndelay 50 static inline void ndelay(unsigned long x) 51 { 52 udelay(DIV_ROUND_UP(x, 1000)); 53 } 54 #define ndelay(x) ndelay(x) 55 #endif 56 57 extern unsigned long lpj_fine; 58 void calibrate_delay(void); 59 void __attribute__((weak)) calibration_delay_done(void); 60 void msleep(unsigned int msecs); 61 unsigned long msleep_interruptible(unsigned int msecs); 62 void usleep_range_state(unsigned long min, unsigned long max, 63 unsigned int state); 64 65 static inline void usleep_range(unsigned long min, unsigned long max) 66 { 67 usleep_range_state(min, max, TASK_UNINTERRUPTIBLE); 68 } 69 70 static inline void usleep_idle_range(unsigned long min, unsigned long max) 71 { 72 usleep_range_state(min, max, TASK_IDLE); 73 } 74 75 static inline void ssleep(unsigned int seconds) 76 { 77 msleep(seconds * 1000); 78 } 79 80 /* see Documentation/timers/timers-howto.rst for the thresholds */ 81 static inline void fsleep(unsigned long usecs) 82 { 83 if (usecs <= 10) 84 udelay(usecs); 85 else if (usecs <= 20000) 86 usleep_range(usecs, 2 * usecs); 87 else 88 msleep(DIV_ROUND_UP(usecs, 1000)); 89 } 90 91 #endif /* defined(_LINUX_DELAY_H) */ 92