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driver: timer: stm32_lptim: fix excess ticks

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Some ticks are counted additionally when the autoreload
interrupts were too close together.
This patch improve the counts of the clock cycle.
lptim_fired worked badly in particular because the flag ARRM
was not raised when the interrupt was forced.

Signed-off-by: Julien D'Ascenzio <julien.dascenzio@paratronic.fr>
This commit is contained in:
Julien D'Ascenzio 2020-06-03 14:07:26 +02:00 • committed by Carles Cufí
commit 37e50a6775
1 changed files with 19 additions and 17 deletions
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36
drivers/timer/stm32_lptim_timer.c
View file

@ -30,13 +30,15 @@
/* nb of LPTIM counter unit per kernel tick */
#define COUNT_PER_TICK (LPTIM_CLOCK / CONFIG_SYS_CLOCK_TICKS_PER_SEC)
/* minimum nb of clock cycles to have to set autoreload register correctly */
#define LPTIM_GUARD_VALUE 2
/* A 32bit value cannot exceed 0xFFFFFFFF/LPTIM_TIMEBASE counting cycles.
* This is for example about of 65000 x 2000ms when clocked by LSI
*/
static u32_t accumulated_lptim_cnt;
static struct k_spinlock lock;
volatile u8_t lptim_fired;
static void lptim_irq_handler(struct device *unused)
{
@ -51,13 +53,6 @@ static void lptim_irq_handler(struct device *unused)
/* do not change ARR yet, z_clock_announce will do */
LL_LPTIM_ClearFLAG_ARRM(LPTIM1);
if (lptim_fired) {
lptim_fired = 0;
#if defined(LPTIM_CR_COUNTRST)
LL_LPTIM_ResetCounter(LPTIM1);
#endif
}
/* increase the total nb of autoreload count
* used in the z_timer_cycle_get_32() function.
* Reading the CNT register gives a reliable value
@ -147,7 +142,6 @@ int z_clock_driver_init(struct device *device)
LL_LPTIM_ClearFlag_ARROK(LPTIM1);
accumulated_lptim_cnt = 0;
lptim_fired = 0;
/* Enable the LPTIM1 counter */
LL_LPTIM_Enable(LPTIM1);
@ -212,6 +206,17 @@ void z_clock_set_timeout(s32_t ticks, bool idle)
lp_time = LL_LPTIM_GetCounter(LPTIM1);
}
u32_t autoreload = LL_LPTIM_GetAutoReload(LPTIM1);
if (LL_LPTIM_IsActiveFlag_ARRM(LPTIM1)
|| ((autoreload - lp_time) < LPTIM_GUARD_VALUE)) {
/* interrupt happens or happens soon.
* It's impossible to set autoreload value.
*/
k_spin_unlock(&lock, key);
return;
}
/* calculate the next arr value (cannot exceed 16bit)
* adjust the next ARR match value to align on Ticks
* from the current counter value to first next Tick
@ -227,15 +232,12 @@ void z_clock_set_timeout(s32_t ticks, bool idle)
if (next_arr > LPTIM_TIMEBASE) {
next_arr = LPTIM_TIMEBASE;
}
/* If we are close to the roll over of the ticker counter
* change current tick so it can be compared with buffer.
* If this event got outdated fire interrupt right now,
* else schedule it normally.
/* The new autoreload value must be LPTIM_GUARD_VALUE clock cycles
* after current lptim to make sure we don't miss
* an autoreload interrupt
*/
if (next_arr <= ((lp_time + 1) & LPTIM_TIMEBASE)) {
NVIC_SetPendingIRQ(LPTIM1_IRQn);
lptim_fired = 1;
else if (next_arr < (lp_time + LPTIM_GUARD_VALUE)) {
next_arr = lp_time + LPTIM_GUARD_VALUE;
}
/* ARROK bit validates previous write operation to ARR register */