Linux jiffies Timers and Hrtimer high-precision timers "turn"

This article was reproduced from: http://blog.csdn.net/dosculler/article/details/7932315

First, jiffies timer, hz=100, precision can only reach 10ms.

Note: Use Jiffies+msecs_to_jiffies (xx ms), can achieve MS level, but not enough precision

#include <linux/jiffies.h>//do-->jiffies Call header file
#include <linux/timer.h>//do-->timer_list Structural bodies

static struct timer_list ms_timer;//do--> define timer_list struct body

static void Ms_timer_handler (void)//do--> defines the timer handler function

{
PRINTK ("Do_debug----------->%s\n", __func__);
Ms_timer.expires=jiffies+hz;

Ms_timer.expires=jiffies+msecs_to_jiffies (10);
ms_timer.function=&ms_timer_handler;
Add_timer (&ms_timer);

}

Static int32_t xxx_init (void)
{
Hrtimer_init_module ();
Init_timer (&ms_timer); Do--> Initialization Timer
Ms_timer.expires=jiffies+msecs_to_jiffies (10); Do--> define Interrupt Time: 10ms Enter interrupt

Ms_timer.expires=jiffies+hz;
Ms_timer.data= (unsigned long) ms_timer;//distinguish between different timers, not verified
ms_timer.function=&ms_timer_handler; Do--> Defining timer Interrupt handling functions

Add_timer (&ms_timer); do--> increase the registration timer to make the timer effective

｝

Second, Hrtimer high-precision timer, can be achieved NS level, here to do milliseconds as follows:

Note: The actual is the nanosecond level, where Ktime_set (const long secs, const unsigned long nsecs) is determined, parameters can be achieved in the nanosecond level.

#include <linux/dma-mapping.h>//do-->hrtimer contains the following three header files/* DMA APIs */
#include <linux/hrtimer.h>

#include <linux/time.h>/* struct TIMESPEC */

#define KER_PRINT (FMT, ...) printk ("<ker-driver>" FMT, # #__VA_ARGS__);
static struct Hrtimer Vibe_timer;

static struct work_struct vibe_work;
static int value = 2000; /* Note: In milliseconds ms Time out setting,2 seconds */

static enum Hrtimer_restart vibrator_timer_func (struct Hrtimer *timer)//do--> callback function, called when interrupted
{

struct TIMESPEC uptime;

Do_posix_clock_monotonic_gettime (&uptime);
Ker_print ("time:%lu.%0 2lu\n ",

(unsigned long) uptime.tv_sec,
(Uptime.tv_nsec/(nsec_per_sec/1000)));

Ker_print ("vibrator_timer_func\n");
Schedule_work (&vibe_work);
return hrtimer_norestart;

}
static void Vibe_work_func (struct work_struct *work)//do--> Task Force column function
{

Ker_print ("' Vibe_work_func '-->work\n");
Msleep (50); /* CPU sleep */

Vibe_timer.function = Vibrator_timer_func;
Hrtimer_start (&vibe_timer,

Ktime_set (value/1000, (value%) * 1000000), Hrtimer_mode_rel);
}

static void Ker_driver_init (void)//do-->hrtimer high-precision timer initialization function
{

struct TIMESPEC uptime;

Ker_print ("ker_driver_init\n");
Hrtimer_init (&vibe_timer, Clock_monotonic, Hrtimer_mode_rel); Do-->hrtimer Timer Initialization

Vibe_timer.function = Vibrator_timer_func; Do-->hrtimer Timer callback function
Hrtimer_start (&vibe_timer,

Ktime_set (value/1000, (value%) * 1000000), Hrtimer_mode_rel); Do-->hrtimer timer time initialization, where Ktime_set (sec, nanosecond)

Do_posix_clock_monotonic_gettime (&uptime); Thread settling time, used to compare (timer) at this time
Ker_print ("time:%lu.%0 2lu\n ",

(unsigned long) uptime.tv_sec,
(Uptime.tv_nsec/(nsec_per_sec/1000)));

Init_work (&vibe_work, Vibe_work_func); /* Intialize the Work Queue * *//Initialize working queues

}

Static int32_t xxxx_init (void)

{

Ker_driver_init ();

....

}

Linux jiffies Timers and Hrtimer high-precision timers "turn"