diff options
Diffstat (limited to 'drivers/char/hpet.c')
| -rw-r--r-- | drivers/char/hpet.c | 31 |
1 files changed, 24 insertions, 7 deletions
diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c index 7066e801b9d..34d6a1cab8d 100644 --- a/drivers/char/hpet.c +++ b/drivers/char/hpet.c @@ -84,8 +84,6 @@ static struct clocksource clocksource_hpet = { .rating = 250, .read = read_hpet, .mask = CLOCKSOURCE_MASK(64), - .mult = 0, /* to be calculated */ - .shift = 10, .flags = CLOCK_SOURCE_IS_CONTINUOUS, }; static struct clocksource *hpet_clocksource; @@ -165,11 +163,32 @@ static irqreturn_t hpet_interrupt(int irq, void *data) * This has the effect of treating non-periodic like periodic. */ if ((devp->hd_flags & (HPET_IE | HPET_PERIODIC)) == HPET_IE) { - unsigned long m, t; + unsigned long m, t, mc, base, k; + struct hpet __iomem *hpet = devp->hd_hpet; + struct hpets *hpetp = devp->hd_hpets; t = devp->hd_ireqfreq; m = read_counter(&devp->hd_timer->hpet_compare); - write_counter(t + m, &devp->hd_timer->hpet_compare); + mc = read_counter(&hpet->hpet_mc); + /* The time for the next interrupt would logically be t + m, + * however, if we are very unlucky and the interrupt is delayed + * for longer than t then we will completely miss the next + * interrupt if we set t + m and an application will hang. + * Therefore we need to make a more complex computation assuming + * that there exists a k for which the following is true: + * k * t + base < mc + delta + * (k + 1) * t + base > mc + delta + * where t is the interval in hpet ticks for the given freq, + * base is the theoretical start value 0 < base < t, + * mc is the main counter value at the time of the interrupt, + * delta is the time it takes to write the a value to the + * comparator. + * k may then be computed as (mc - base + delta) / t . + */ + base = mc % t; + k = (mc - base + hpetp->hp_delta) / t; + write_counter(t * (k + 1) + base, + &devp->hd_timer->hpet_compare); } if (devp->hd_flags & HPET_SHARED_IRQ) @@ -934,9 +953,7 @@ int hpet_alloc(struct hpet_data *hdp) if (!hpet_clocksource) { hpet_mctr = (void __iomem *)&hpetp->hp_hpet->hpet_mc; CLKSRC_FSYS_MMIO_SET(clocksource_hpet.fsys_mmio, hpet_mctr); - clocksource_hpet.mult = clocksource_hz2mult(hpetp->hp_tick_freq, - clocksource_hpet.shift); - clocksource_register(&clocksource_hpet); + clocksource_register_hz(&clocksource_hpet, hpetp->hp_tick_freq); hpetp->hp_clocksource = &clocksource_hpet; hpet_clocksource = &clocksource_hpet; } |