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kernel: Improve tick <-> ms conversion.

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The kernel incorrectly assumed, that system timer frequency is always
divisible without remainder by couple "natural" tick rates (like 100).
As result on some SoCs, time calculations was not correct, producing
strange effects (invalid sleep times, incorrect k_uptime_get() etc.).

This commit enables accurate, but costly (using 64-bit math) tick <-> ms
conversion if the selected tick interval is not exact due to hardware
limitations.

Also, this commit fixes tests in which removed _ms_per_tick were used.

Signed-off-by: Piotr Zięcik <piotr.ziecik@nordicsemi.no>
This commit is contained in:
Piotr Zięcik 2018-06-11 14:24:41 +02:00 • committed by Anas Nashif
commit 91fe22ec7d
2 changed files with 34 additions and 12 deletions
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41
include/kernel.h
View file

@ -1319,21 +1319,37 @@ __syscall void *k_thread_custom_data_get(void);
/* kernel clocks */
#if (MSEC_PER_SEC % sys_clock_ticks_per_sec) == 0
#define _ms_per_tick (MSEC_PER_SEC / sys_clock_ticks_per_sec)
#else
/* yields horrible 64-bit math on many architectures: try to avoid */
#ifdef CONFIG_SYS_CLOCK_EXISTS
#if (CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC % sys_clock_ticks_per_sec) != 0
#define _NEED_PRECISE_TICK_MS_CONVERSION
#elif (MSEC_PER_SEC % sys_clock_ticks_per_sec) != 0
#define _NON_OPTIMIZED_TICKS_PER_SEC
#endif
#ifdef _NON_OPTIMIZED_TICKS_PER_SEC
#define _NEED_PRECISE_TICK_MS_CONVERSION
#endif
#endif
static ALWAYS_INLINE s32_t _ms_to_ticks(s32_t ms)
{
#ifdef _NON_OPTIMIZED_TICKS_PER_SEC
#ifdef CONFIG_SYS_CLOCK_EXISTS
#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);
#else
return (s32_t)ceiling_fraction((u32_t)ms, _ms_per_tick);
/* simple division keeps precision */
s32_t ms_per_tick = MSEC_PER_SEC / sys_clock_ticks_per_sec;
return (s32_t)ceiling_fraction(ms, ms_per_tick);
#endif
#else
__ASSERT(ms == 0, "ms not zero");
return 0;
#endif
}
@ -1348,10 +1364,15 @@ static inline s64_t __ticks_to_ms(s64_t ticks)
{
#ifdef CONFIG_SYS_CLOCK_EXISTS
#ifdef _NON_OPTIMIZED_TICKS_PER_SEC
return (MSEC_PER_SEC * (u64_t)ticks) / sys_clock_ticks_per_sec;
#ifdef _NEED_PRECISE_TICK_MS_CONVERSION
/* use 64-bit math to keep precision */
return (u64_t)ticks * sys_clock_hw_cycles_per_tick * MSEC_PER_SEC /
CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC;
#else
return (u64_t)ticks * _ms_per_tick;
/* simple multiplication keeps precision */
u32_t ms_per_tick = MSEC_PER_SEC / sys_clock_ticks_per_sec;
return (u64_t)ticks * ms_per_tick;
#endif
#else

5
tests/kernel/early_sleep/src/main.c
View file

@ -94,8 +94,9 @@ static void test_early_sleep(void)
*/
k_thread_priority_set(k_current_get(), 0);
TC_PRINT("msec per tick: %d, ticks to sleep: %d\n",
_ms_per_tick, TEST_TICKS_TO_SLEEP);
TC_PRINT("msec per tick: %lld.%03lld, ticks to sleep: %d\n",
__ticks_to_ms(1000) / 1000, __ticks_to_ms(1000) % 1000,
TEST_TICKS_TO_SLEEP);
/* Create a lower priority thread */
helper_ttid = k_thread_create(&helper_tdata,