5 * Copyright (C) 1993 Linus Torvalds
7 * Delay routines, using a pre-computed "loops_per_jiffy" value.
9 * Please note that ndelay(), udelay() and mdelay() may return early for
11 * 1. computed loops_per_jiffy too low (due to the time taken to
12 * execute the timer interrupt.)
13 * 2. cache behaviour affecting the time it takes to execute the
15 * 3. CPU clock rate changes.
17 * Please see this thread:
18 * http://lists.openwall.net/linux-kernel/2011/01/09/56
21 #include <linux/kernel.h>
23 extern unsigned long loops_per_jiffy;
25 #include <asm/delay.h>
28 * Using udelay() for intervals greater than a few milliseconds can
29 * risk overflow for high loops_per_jiffy (high bogomips) machines. The
30 * mdelay() provides a wrapper to prevent this. For delays greater
31 * than MAX_UDELAY_MS milliseconds, the wrapper is used. Architecture
32 * specific values can be defined in asm-???/delay.h as an override.
33 * The 2nd mdelay() definition ensures GCC will optimize away the
34 * while loop for the common cases where n <= MAX_UDELAY_MS -- Paul G.
38 #define MAX_UDELAY_MS 5
43 (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
44 ({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
48 static inline void ndelay(unsigned long x)
50 udelay(DIV_ROUND_UP(x, 1000));
52 #define ndelay(x) ndelay(x)
55 extern unsigned long lpj_fine;
56 void calibrate_delay(void);
57 void msleep(unsigned int msecs);
58 unsigned long msleep_interruptible(unsigned int msecs);
59 void usleep_range(unsigned long min, unsigned long max);
61 static inline void ssleep(unsigned int seconds)
63 msleep(seconds * 1000);
66 #endif /* defined(_LINUX_DELAY_H) */