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kernel: Do not use sys_clock_ticks_per_sec in _ms_to_ticks()

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The value of sys_clock_ticks_per_sec is obtained using
simple integer division with rounding toward zero. As result
using this variable in _ms_to_ticks() introduces some error.

This commit eliminates sys_clock_ticks_per_sec from equation
used in _ms_to_ticks() removing introduced error.

Also, this commit fixes #8895.

Signed-off-by: Piotr Zięcik <piotr.ziecik@nordicsemi.no>
This commit is contained in:
Piotr Zięcik 2018-07-23 14:09:10 +02:00 • committed by Anas Nashif
commit 3c7f990367
1 changed files with 3 additions and 3 deletions
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6
include/kernel.h
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@ -1357,9 +1357,9 @@ static ALWAYS_INLINE s32_t _ms_to_ticks(s32_t ms)
#ifdef _NEED_PRECISE_TICK_MS_CONVERSION
/* use 64-bit math to keep precision */
s64_t ms_ticks_per_sec = (s64_t)ms * sys_clock_ticks_per_sec;
return (s32_t)ceiling_fraction(ms_ticks_per_sec, MSEC_PER_SEC);
return (s32_t)ceiling_fraction(
(s64_t)ms * sys_clock_hw_cycles_per_sec,
(s64_t)MSEC_PER_SEC * sys_clock_hw_cycles_per_tick);
#else
/* simple division keeps precision */
s32_t ms_per_tick = MSEC_PER_SEC / sys_clock_ticks_per_sec;