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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 * http://lists.openwall.net/linux-kernel/2011/01/09/56
22 #include <linux/kernel.h>
24 extern unsigned long loops_per_jiffy
;
26 #include <asm/delay.h>
29 * Using udelay() for intervals greater than a few milliseconds can
30 * risk overflow for high loops_per_jiffy (high bogomips) machines. The
31 * mdelay() provides a wrapper to prevent this. For delays greater
32 * than MAX_UDELAY_MS milliseconds, the wrapper is used. Architecture
33 * specific values can be defined in asm-???/delay.h as an override.
34 * The 2nd mdelay() definition ensures GCC will optimize away the
35 * while loop for the common cases where n <= MAX_UDELAY_MS -- Paul G.
39 #define MAX_UDELAY_MS 5
44 (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
45 ({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
49 static inline void ndelay(unsigned long x
)
51 udelay(DIV_ROUND_UP(x
, 1000));
53 #define ndelay(x) ndelay(x)
56 extern unsigned long lpj_fine
;
57 void calibrate_delay(void);
58 void msleep(unsigned int msecs
);
59 unsigned long msleep_interruptible(unsigned int msecs
);
60 void usleep_range(unsigned long min
, unsigned long max
);
62 static inline void ssleep(unsigned int seconds
)
64 msleep(seconds
* 1000);
67 #endif /* defined(_LINUX_DELAY_H) */