Quelle delay.h Sprache: C

/* 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.
* Sleep routines using timer list timers or hrtimers.
*/

#include <linux/math.h>
#include <linux/sched.h>
#include <linux/jiffies.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
/**
* mdelay - Inserting a delay based on milliseconds with busy waiting
* @n: requested delay in milliseconds
*
* See udelay() for basic information about mdelay() and it's variants.
*
* Please double check, whether mdelay() is the right way to go or whether a
* refactoring of the code is the better variant to be able to use msleep()
* instead.
*/
#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);

/**
* usleep_range - Sleep for an approximate time
* @min: Minimum time in microseconds to sleep
* @max: Maximum time in microseconds to sleep
*
* For basic information please refere to usleep_range_state().
*
* The task will be in the state TASK_UNINTERRUPTIBLE during the sleep.
*/
static inline void usleep_range(unsigned long min, unsigned long max)
{
usleep_range_state(min, max, TASK_UNINTERRUPTIBLE);
}

/**
* usleep_range_idle - Sleep for an approximate time with idle time accounting
* @min: Minimum time in microseconds to sleep
* @max: Maximum time in microseconds to sleep
*
* For basic information please refere to usleep_range_state().
*
* The sleeping task has the state TASK_IDLE during the sleep to prevent
* contribution to the load avarage.
*/
static inline void usleep_range_idle(unsigned long min, unsigned long max)
{
usleep_range_state(min, max, TASK_IDLE);
}

/**
* ssleep - wrapper for seconds around msleep
* @seconds: Requested sleep duration in seconds
*
* Please refere to msleep() for detailed information.
*/
static inline void ssleep(unsigned int seconds)
{
msleep(seconds * 1000);
}

static const unsigned int max_slack_shift = 2;
#define USLEEP_RANGE_UPPER_BOUND ((TICK_NSEC << max_slack_shift) / NSEC_PER_USEC)

/**
* fsleep - flexible sleep which autoselects the best mechanism
* @usecs: requested sleep duration in microseconds
*
* flseep() selects the best mechanism that will provide maximum 25% slack
* to the requested sleep duration. Therefore it uses:
*
* * udelay() loop for sleep durations <= 10 microseconds to avoid hrtimer
*   overhead for really short sleep durations.
* * usleep_range() for sleep durations which would lead with the usage of
*   msleep() to a slack larger than 25%. This depends on the granularity of
*   jiffies.
* * msleep() for all other sleep durations.
*
* Note: When %CONFIG_HIGH_RES_TIMERS is not set, all sleeps are processed with
* the granularity of jiffies and the slack might exceed 25% especially for
* short sleep durations.
*/
static inline void fsleep(unsigned long usecs)
{
if (usecs <= 10)
  udelay(usecs);
else if (usecs < USLEEP_RANGE_UPPER_BOUND)
  usleep_range(usecs, usecs + (usecs >> max_slack_shift));
else
  msleep(DIV_ROUND_UP(usecs, USEC_PER_MSEC));
}

#endif /* defined(_LINUX_DELAY_H) */

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