On Fri, 14 Jun 2019, Thomas Gleixner wrote: > On Thu, 23 May 2019, Ricardo Neri wrote: > > int hpet_alloc(struct hpet_data *hdp) > > { > > u64 cap, mcfg; > > @@ -844,7 +867,6 @@ int hpet_alloc(struct hpet_data *hdp) > > struct hpets *hpetp; > > struct hpet __iomem *hpet; > > static struct hpets *last; > > - unsigned long period; > > unsigned long long temp; > > u32 remainder; > > > > @@ -894,12 +916,7 @@ 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 */ > > + hpetp->hp_tick_freq = hpet_get_ticks_per_sec(cap); > > Why are we actually computing this over and over? > > In hpet_enable() which is the first function invoked we have: > > /* > * The period is a femto seconds value. Convert it to a > * frequency. > */ > freq = FSEC_PER_SEC; > do_div(freq, hpet_period); > hpet_freq = freq; > > So we already have ticks per second, aka frequency, right? So why do we > need yet another function instead of using the value which is computed > once? The frequency of the HPET channels has to be identical no matter > what. If it's not HPET is broken beyond repair.
Aside of that this change breaks the IA64 support for /dev/hpet. Thanks, tglx