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-rw-r--r--drivers/char/hpet.c21
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);