It is easier to compute the expiration times of an HPET timer by using its frequency (i.e., the number of times it ticks in a second) than its period, as given in the capabilities register.
In addition to the HPET char driver, the HPET-based hardlockup detector will also need to know the timer's frequency. Thus, create a common function that both can use. Cc: "H. Peter Anvin" <[email protected]> Cc: Ashok Raj <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Tony Luck <[email protected]> Cc: Clemens Ladisch <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Philippe Ombredanne <[email protected]> Cc: Kate Stewart <[email protected]> Cc: "Rafael J. Wysocki" <[email protected]> Cc: "Ravi V. Shankar" <[email protected]> Cc: [email protected] Signed-off-by: Ricardo Neri <[email protected]> --- drivers/char/hpet.c | 31 +++++++++++++++++++++++++------ include/linux/hpet.h | 1 + 2 files changed, 26 insertions(+), 6 deletions(-) diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c index 4a22b4b41aef..b73b68c0e127 100644 --- a/drivers/char/hpet.c +++ b/drivers/char/hpet.c @@ -836,6 +836,29 @@ static unsigned long hpet_calibrate(struct hpets *hpetp) return ret; } +u64 hpet_get_ticks_per_sec(u64 hpet_caps) +{ + u64 ticks_per_sec, period; + + period = (hpet_caps & HPET_COUNTER_CLK_PERIOD_MASK) >> + HPET_COUNTER_CLK_PERIOD_SHIFT; /* fs, 10^-15 */ + + /* + * The frequency is the reciprocal of the period. The period is given + * femtoseconds per second. Thus, prepare a dividend to obtain the + * frequency in ticks per second. + */ + + /* 10^15 femtoseconds per second */ + ticks_per_sec = 1000000000000000uLL; + ticks_per_sec += period >> 1; /* round */ + + /* The quotient is put in the dividend. We drop the remainder. */ + do_div(ticks_per_sec, period); + + return ticks_per_sec; +} + int hpet_alloc(struct hpet_data *hdp) { u64 cap, mcfg; @@ -845,7 +868,6 @@ int hpet_alloc(struct hpet_data *hdp) size_t siz; struct hpet __iomem *hpet; static struct hpets *last; - unsigned long period; unsigned long long temp; u32 remainder; @@ -881,6 +903,8 @@ int hpet_alloc(struct hpet_data *hdp) cap = readq(&hpet->hpet_cap); + temp = hpet_get_ticks_per_sec(cap); + ntimer = ((cap & HPET_NUM_TIM_CAP_MASK) >> HPET_NUM_TIM_CAP_SHIFT) + 1; if (hpetp->hp_ntimer != ntimer) { @@ -897,11 +921,6 @@ int hpet_alloc(struct hpet_data *hdp) last = hpetp; - 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", diff --git a/include/linux/hpet.h b/include/linux/hpet.h index 8604564b985d..e7b36bcf4699 100644 --- a/include/linux/hpet.h +++ b/include/linux/hpet.h @@ -107,5 +107,6 @@ static inline void hpet_reserve_timer(struct hpet_data *hd, int timer) } int hpet_alloc(struct hpet_data *); +u64 hpet_get_ticks_per_sec(u64 hpet_caps); #endif /* !__HPET__ */ -- 2.17.1
