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drivers: timer: it8xxx2: enhances the accuracy of hw cycle calculation

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This commit enhances the accuracy of hardware cycle calculation before
setting the IT8xxx2 event timer. The next target cycle is calculated by
the last, elapsed, and expected timeout ticks. And then, the difference
in hardware cycles between the target cycle and the current cycle is set
into the event timer. This increased accuracy effectively resolves the
clock drift issue.

Tested with:
west build -p always -b it8xxx2_evb tests/kernel/timer/timer_api
     -T kernel.timer.tickless
west build -p always -b it8xxx2_evb tests/kernel/timer/timer_behavior
     -T kernel.timer.timer

Fixes #67474 #67833

Signed-off-by: Ruibin Chang <Ruibin.Chang@ite.com.tw>
Signed-off-by: Ren Chen <Ren.Chen@ite.com.tw>
This commit is contained in:
Ren Chen 2024-02-07 09:52:17 +08:00 committed by Anas Nashif
parent 417747886c
commit 765a4eb0b8
1 changed files with 24 additions and 12 deletions
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36
drivers/timer/ite_it8xxx2_timer.c
View file

@ -76,6 +76,9 @@ const int32_t z_sys_timer_irq_for_test = DT_IRQ_BY_IDX(DT_NODELABEL(timer), 5, i
static struct k_spinlock lock;
/* Last HW count that we called sys_clock_announce() */
static volatile uint32_t last_announced_hw_cnt;
/* Last system (kernel) elapse and ticks */
static volatile uint32_t last_elapsed;
static volatile uint32_t last_ticks;
enum ext_timer_raw_cnt {
EXT_NOT_RAW_CNT = 0,
@ -194,6 +197,8 @@ static void evt_timer_isr(const void *unused)
uint32_t dticks = (~(IT8XXX2_EXT_CNTOX(FREE_RUN_TIMER)) -
last_announced_hw_cnt) / HW_CNT_PER_SYS_TICK;
last_announced_hw_cnt += (dticks * HW_CNT_PER_SYS_TICK);
last_ticks += dticks;
last_elapsed = 0;
sys_clock_announce(dticks);
} else {
@ -246,21 +251,26 @@ void sys_clock_set_timeout(int32_t ticks, bool idle)
*/
k_spin_unlock(&lock, key);
return;
} else if (ticks <= 1) {
/*
* Ticks <= 1 means the kernel wants the tick announced
* as soon as possible, ideally no more than one system tick
* in the future. So set event timer count to 1 system tick or
* at least 1 hw count.
*/
hw_cnt = MAX((1 * HW_CNT_PER_SYS_TICK), 1);
} else {
uint32_t next_cycs;
uint32_t now;
uint32_t dcycles;
/*
* Set event timer count to EVENT_TIMER_MAX_CNT, after
* interrupt fired the remaining time will be set again
* by sys_clock_announce().
* If ticks <= 1 means the kernel wants the tick announced
* as soon as possible, ideally no more than one system tick
* in the future. So set event timer count to 1 HW tick.
*/
hw_cnt = MIN((ticks * HW_CNT_PER_SYS_TICK), EVENT_TIMER_MAX_CNT);
ticks = CLAMP(ticks, 1, (int32_t)EVEN_TIMER_MAX_CNT_SYS_TICK);
next_cycs = (last_ticks + last_elapsed + ticks) * HW_CNT_PER_SYS_TICK;
now = ~(IT8XXX2_EXT_CNTOX(FREE_RUN_TIMER));
if (unlikely(next_cycs <= now)) {
hw_cnt = 1;
} else {
dcycles = next_cycs - now;
hw_cnt = MIN(dcycles, EVENT_TIMER_MAX_CNT);
}
}
/* Set event timer 24-bit count */
@ -292,6 +302,8 @@ uint32_t sys_clock_elapsed(void)
*/
uint32_t dticks = (~(IT8XXX2_EXT_CNTOX(FREE_RUN_TIMER)) -
last_announced_hw_cnt) / HW_CNT_PER_SYS_TICK;
last_elapsed = dticks;
k_spin_unlock(&lock, key);
return dticks;