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git.ipfire.org Git - thirdparty/linux.git/blob - include/linux/delay.h
1 /* SPDX-License-Identifier: GPL-2.0 */
6 * Copyright (C) 1993 Linus Torvalds
8 * Delay routines, using a pre-computed "loops_per_jiffy" value.
10 * Please note that ndelay(), udelay() and mdelay() may return early for
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
16 * 3. CPU clock rate changes.
18 * Please see this thread:
19 * https://lists.openwall.net/linux-kernel/2011/01/09/56
22 #include <linux/math.h>
23 #include <linux/sched.h>
25 extern unsigned long loops_per_jiffy
;
27 #include <asm/delay.h>
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.
40 #define MAX_UDELAY_MS 5
45 (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
46 ({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
50 static inline void ndelay(unsigned long x
)
52 udelay(DIV_ROUND_UP(x
, 1000));
54 #define ndelay(x) ndelay(x)
57 extern unsigned long lpj_fine
;
58 void calibrate_delay(void);
59 unsigned long calibrate_delay_is_known(void);
60 void __attribute__((weak
)) calibration_delay_done(void);
61 void msleep(unsigned int msecs
);
62 unsigned long msleep_interruptible(unsigned int msecs
);
63 void usleep_range_state(unsigned long min
, unsigned long max
,
66 static inline void usleep_range(unsigned long min
, unsigned long max
)
68 usleep_range_state(min
, max
, TASK_UNINTERRUPTIBLE
);
71 static inline void usleep_idle_range(unsigned long min
, unsigned long max
)
73 usleep_range_state(min
, max
, TASK_IDLE
);
76 static inline void ssleep(unsigned int seconds
)
78 msleep(seconds
* 1000);
81 /* see Documentation/timers/timers-howto.rst for the thresholds */
82 static inline void fsleep(unsigned long usecs
)
86 else if (usecs
<= 20000)
87 usleep_range(usecs
, 2 * usecs
);
89 msleep(DIV_ROUND_UP(usecs
, 1000));
92 #endif /* defined(_LINUX_DELAY_H) */