diff options
| -rw-r--r-- | drivers/char/hpet.c | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c index 4a9f3492b92..70a770ac013 100644 --- a/drivers/char/hpet.c +++ b/drivers/char/hpet.c @@ -166,9 +166,8 @@ static irqreturn_t hpet_interrupt(int irq, void *data) unsigned long m, t; t = devp->hd_ireqfreq; - m = read_counter(&devp->hd_hpet->hpet_mc); - write_counter(t + m + devp->hd_hpets->hp_delta, - &devp->hd_timer->hpet_compare); + m = read_counter(&devp->hd_timer->hpet_compare); + write_counter(t + m, &devp->hd_timer->hpet_compare); } if (devp->hd_flags & HPET_SHARED_IRQ) @@ -504,21 +503,25 @@ static int hpet_ioctl_ieon(struct hpet_dev *devp) g = v | Tn_32MODE_CNF_MASK | Tn_INT_ENB_CNF_MASK; if (devp->hd_flags & HPET_PERIODIC) { - write_counter(t, &timer->hpet_compare); g |= Tn_TYPE_CNF_MASK; - v |= Tn_TYPE_CNF_MASK; - writeq(v, &timer->hpet_config); - v |= Tn_VAL_SET_CNF_MASK; + v |= Tn_TYPE_CNF_MASK | Tn_VAL_SET_CNF_MASK; writeq(v, &timer->hpet_config); local_irq_save(flags); - /* NOTE: what we modify here is a hidden accumulator + /* + * NOTE: First we modify the hidden accumulator * register supported by periodic-capable comparators. * We never want to modify the (single) counter; that - * would affect all the comparators. + * would affect all the comparators. The value written + * is the counter value when the first interrupt is due. */ m = read_counter(&hpet->hpet_mc); write_counter(t + m + hpetp->hp_delta, &timer->hpet_compare); + /* + * Then we modify the comparator, indicating the period + * for subsequent interrupt. + */ + write_counter(t, &timer->hpet_compare); } else { local_irq_save(flags); m = read_counter(&hpet->hpet_mc); |