diff options
Diffstat (limited to 'include/linux/clocksource.h')
| -rw-r--r-- | include/linux/clocksource.h | 45 |
1 files changed, 19 insertions, 26 deletions
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 6013021a3..a307bf629 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -118,6 +118,23 @@ struct clocksource { /* simplify initialization of mask field */ #define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) +static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from) +{ + /* freq = cyc/from + * mult/2^shift = ns/cyc + * mult = ns/cyc * 2^shift + * mult = from/freq * 2^shift + * mult = from * 2^shift / freq + * mult = (from<<shift) / freq + */ + u64 tmp = ((u64)from) << shift_constant; + + tmp += freq/2; /* round for do_div */ + do_div(tmp, freq); + + return (u32)tmp; +} + /** * clocksource_khz2mult - calculates mult from khz and shift * @khz: Clocksource frequency in KHz @@ -128,19 +145,7 @@ struct clocksource { */ static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) { - /* khz = cyc/(Million ns) - * mult/2^shift = ns/cyc - * mult = ns/cyc * 2^shift - * mult = 1Million/khz * 2^shift - * mult = 1000000 * 2^shift / khz - * mult = (1000000<<shift) / khz - */ - u64 tmp = ((u64)1000000) << shift_constant; - - tmp += khz/2; /* round for do_div */ - do_div(tmp, khz); - - return (u32)tmp; + return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC); } /** @@ -154,19 +159,7 @@ static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant) */ static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant) { - /* hz = cyc/(Billion ns) - * mult/2^shift = ns/cyc - * mult = ns/cyc * 2^shift - * mult = 1Billion/hz * 2^shift - * mult = 1000000000 * 2^shift / hz - * mult = (1000000000<<shift) / hz - */ - u64 tmp = ((u64)1000000000) << shift_constant; - - tmp += hz/2; /* round for do_div */ - do_div(tmp, hz); - - return (u32)tmp; + return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC); } /** |