hrtimer hardware portability issue - linux

Question

I need a function be called exactly 256 timer every second in my driver (kernel module). I was using RTC, and it was working perfectly. But because of the need to have hwclock command and interrupt sharing issue, I had to use another way to have a timer.
So I tried to use hrtimer. I works almost almost good in a hardware configuration.
But whenever I install the driver on another machine with a different hardware, the hrtimer doesn't work good anymore, ie the timer function is called 230 times per second instead of 256 times per second. Both machines run same Linux version. Actually second machine runs a Linux compiled on the first one. And the also note that the second one is a pentium Intel celeron 333MHz machine.
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
And the code is:
#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");
}