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Diffstat (limited to 'include/linux/delay.h')
-rw-r--r-- | include/linux/delay.h | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/include/linux/delay.h b/include/linux/delay.h new file mode 100644 index 000000000..ff9cda975 --- /dev/null +++ b/include/linux/delay.h @@ -0,0 +1,92 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_DELAY_H +#define _LINUX_DELAY_H + +/* + * Copyright (C) 1993 Linus Torvalds + * + * Delay routines, using a pre-computed "loops_per_jiffy" value. + * + * Please note that ndelay(), udelay() and mdelay() may return early for + * several reasons: + * 1. computed loops_per_jiffy too low (due to the time taken to + * execute the timer interrupt.) + * 2. cache behaviour affecting the time it takes to execute the + * loop function. + * 3. CPU clock rate changes. + * + * Please see this thread: + * https://lists.openwall.net/linux-kernel/2011/01/09/56 + */ + +#include <linux/math.h> +#include <linux/sched.h> + +extern unsigned long loops_per_jiffy; + +#include <asm/delay.h> + +/* + * Using udelay() for intervals greater than a few milliseconds can + * risk overflow for high loops_per_jiffy (high bogomips) machines. The + * mdelay() provides a wrapper to prevent this. For delays greater + * than MAX_UDELAY_MS milliseconds, the wrapper is used. Architecture + * specific values can be defined in asm-???/delay.h as an override. + * The 2nd mdelay() definition ensures GCC will optimize away the + * while loop for the common cases where n <= MAX_UDELAY_MS -- Paul G. + */ + +#ifndef MAX_UDELAY_MS +#define MAX_UDELAY_MS 5 +#endif + +#ifndef mdelay +#define mdelay(n) (\ + (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \ + ({unsigned long __ms=(n); while (__ms--) udelay(1000);})) +#endif + +#ifndef ndelay +static inline void ndelay(unsigned long x) +{ + udelay(DIV_ROUND_UP(x, 1000)); +} +#define ndelay(x) ndelay(x) +#endif + +extern unsigned long lpj_fine; +void calibrate_delay(void); +unsigned long calibrate_delay_is_known(void); +void __attribute__((weak)) calibration_delay_done(void); +void msleep(unsigned int msecs); +unsigned long msleep_interruptible(unsigned int msecs); +void usleep_range_state(unsigned long min, unsigned long max, + unsigned int state); + +static inline void usleep_range(unsigned long min, unsigned long max) +{ + usleep_range_state(min, max, TASK_UNINTERRUPTIBLE); +} + +static inline void usleep_idle_range(unsigned long min, unsigned long max) +{ + usleep_range_state(min, max, TASK_IDLE); +} + +static inline void ssleep(unsigned int seconds) +{ + msleep(seconds * 1000); +} + +/* see Documentation/timers/timers-howto.rst for the thresholds */ +static inline void fsleep(unsigned long usecs) +{ + if (usecs <= 10) + udelay(usecs); + else if (usecs <= 20000) + usleep_range(usecs, 2 * usecs); + else + msleep(DIV_ROUND_UP(usecs, 1000)); +} + +#endif /* defined(_LINUX_DELAY_H) */ |