Question

我需要一个函数在我的驱动程序（内核模块）中每秒调用256个计时器。我正在使用RTC，它运行得很好。但由于需要有hwclock命令和中断共享问题，我不得不用另一种方式来获得一个计时器。所以我试着用hrtimer。我的硬件配置几乎都很好。

但每当我在另一台具有不同硬件的机器上安装驱动程序时，hrtimer就不再有效了，即定时器功能每秒调用230次而不是每秒256次。两台机器都运行相同的Linux版本。实际上第二台机器运行在第一台机器上编译的Linux。并且还注意到第二个是奔腾Intel celeron 333MHz机器。

My linux is:
uname -a: Linux debian-32-pc 3.2.0-4-686-pae #1 SMP Debian 3.2.63-2+deb7u2 i686 GNU/Linux

代码是：

#include <linux/module.h>
#include <linux/version.h>
#include <linux/kernel.h>
#include <linux/hrtimer.h>

void handle_timer();

size_t timestamp = 0;
static struct hrtimer hr_timer;
#define MS_TO_NS(x) (x * 1E6L)
#define HRTIMER_FREQUENCY 256
int HRTIMER_PERIOD = 1E9L / HRTIMER_FREQUENCY; // some time is actually wasted to rerun the timer


enum hrtimer_restart my_hrtimer_callback(struct hrtimer *timer){
  handle_timer();
  int overrun;
  ktime_t now;
  ktime_t period = (ktime_t){ .tv64 = HRTIMER_PERIOD }; // in nano seconds
    for (;;) {
        now = hrtimer_cb_get_time(timer);
        overrun = hrtimer_forward(timer, now, period);

        if (!overrun)
            break;
    }

  return HRTIMER_RESTART;
}
void start_timer(){
  ktime_t ktime;
  ktime = ktime_set(0, HRTIMER_PERIOD);
  hrtimer_init(&hr_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  hr_timer.function = &my_hrtimer_callback;
  hrtimer_start(&hr_timer, ktime, HRTIMER_MODE_REL);
}

void stop_timer(){
  hrtimer_cancel(&hr_timer);
}


long cc = 0;
long ccc = 0;

void handle_timer(){
    int i;

    cc++;
    if (cc==256){
        cc=0;
        ccc++;
        printk("<1>Timer count %d   %d (%d)\n", ccc, HRTIMER_PERIOD, HRTIMER_FREQUENCY);
    }
}

static int __init _init(void)
{
    printk(KERN_INFO "registered");
    start_timer();
    return 0;
}

static void __exit _exit(void)
{
    stop_timer();
    printk(KERN_INFO "unregistered");
}

hrtimer硬件可移植性问题

0 个答案: