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path: root/drivers/char/hpet.c
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Diffstat (limited to 'drivers/char/hpet.c')
-rw-r--r--drivers/char/hpet.c32
1 files changed, 19 insertions, 13 deletions
diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
index b619ca5eaf8c..a1eb14e6d9f7 100644
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -78,7 +78,7 @@ struct hpets {
struct hpet __iomem *hp_hpet;
unsigned long hp_hpet_phys;
struct time_interpolator *hp_interpolator;
- unsigned long hp_period;
+ unsigned long long hp_tick_freq;
unsigned long hp_delta;
unsigned int hp_ntimer;
unsigned int hp_which;
@@ -427,12 +427,14 @@ static int hpet_ioctl_ieon(struct hpet_dev *devp)
return 0;
}
-static inline unsigned long hpet_time_div(unsigned long dis)
+/* converts Hz to number of timer ticks */
+static inline unsigned long hpet_time_div(struct hpets *hpets,
+ unsigned long dis)
{
- unsigned long long m = 1000000000000000ULL;
+ unsigned long long m;
+ m = hpets->hp_tick_freq + (dis >> 1);
do_div(m, dis);
-
return (unsigned long)m;
}
@@ -480,7 +482,7 @@ hpet_ioctl_common(struct hpet_dev *devp, int cmd, unsigned long arg, int kernel)
{
struct hpet_info info;
- info.hi_ireqfreq = hpet_time_div(hpetp->hp_period *
+ info.hi_ireqfreq = hpet_time_div(hpetp,
devp->hd_ireqfreq);
info.hi_flags =
readq(&timer->hpet_config) & Tn_PER_INT_CAP_MASK;
@@ -524,7 +526,7 @@ hpet_ioctl_common(struct hpet_dev *devp, int cmd, unsigned long arg, int kernel)
break;
}
- devp->hd_ireqfreq = hpet_time_div(hpetp->hp_period * arg);
+ devp->hd_ireqfreq = hpet_time_div(hpetp, arg);
}
return err;
@@ -713,7 +715,7 @@ static void hpet_register_interpolator(struct hpets *hpetp)
ti->source = TIME_SOURCE_MMIO64;
ti->shift = 10;
ti->addr = &hpetp->hp_hpet->hpet_mc;
- ti->frequency = hpet_time_div(hpets->hp_period);
+ ti->frequency = hpetp->hp_tick_freq;
ti->drift = HPET_DRIFT;
ti->mask = -1;
@@ -750,7 +752,7 @@ static unsigned long hpet_calibrate(struct hpets *hpetp)
t = read_counter(&timer->hpet_compare);
i = 0;
- count = hpet_time_div(hpetp->hp_period * TICK_CALIBRATE);
+ count = hpet_time_div(hpetp, TICK_CALIBRATE);
local_irq_save(flags);
@@ -775,7 +777,8 @@ int hpet_alloc(struct hpet_data *hdp)
size_t siz;
struct hpet __iomem *hpet;
static struct hpets *last = (struct hpets *)0;
- unsigned long ns;
+ unsigned long ns, period;
+ unsigned long long temp;
/*
* hpet_alloc can be called by platform dependent code.
@@ -825,8 +828,12 @@ int hpet_alloc(struct hpet_data *hdp)
last = hpetp;
- hpetp->hp_period = (cap & HPET_COUNTER_CLK_PERIOD_MASK) >>
- HPET_COUNTER_CLK_PERIOD_SHIFT;
+ period = (cap & HPET_COUNTER_CLK_PERIOD_MASK) >>
+ HPET_COUNTER_CLK_PERIOD_SHIFT; /* fs, 10^-15 */
+ temp = 1000000000000000uLL; /* 10^15 femtoseconds per second */
+ temp += period >> 1; /* round */
+ do_div(temp, period);
+ hpetp->hp_tick_freq = temp; /* ticks per second */
printk(KERN_INFO "hpet%d: at MMIO 0x%lx, IRQ%s",
hpetp->hp_which, hdp->hd_phys_address,
@@ -835,8 +842,7 @@ int hpet_alloc(struct hpet_data *hdp)
printk("%s %d", i > 0 ? "," : "", hdp->hd_irq[i]);
printk("\n");
- ns = hpetp->hp_period; /* femptoseconds, 10^-15 */
- ns /= 1000000; /* convert to nanoseconds, 10^-9 */
+ ns = period / 1000000; /* convert to nanoseconds, 10^-9 */
printk(KERN_INFO "hpet%d: %ldns tick, %d %d-bit timers\n",
hpetp->hp_which, ns, hpetp->hp_ntimer,
cap & HPET_COUNTER_SIZE_MASK ? 64 : 32);