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cpu/sam0_common: timer: don't ignore frequency in timer_init()

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Now that we can query the GCLK frequency at run-time, there is no need
to implicitely hard-code the timer frequency in the config struct anymore.
This commit is contained in:
Benjamin Valentin 2020-04-19 00:32:50 +02:00
parent 91200aa6ea
commit c05984b341
1 changed files with 26 additions and 2 deletions
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28
cpu/sam0_common/periph/timer.c
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@ -71,19 +71,43 @@ static inline void _irq_enable(tim_t tim)
NVIC_EnableIRQ(timer_config[tim].irq);
}
static uint8_t _get_prescaler(unsigned long freq_out, unsigned long freq_in)
{
uint8_t scale = 0;
while (freq_in > freq_out) {
freq_in >>= 1;
/* after DIV16 the prescaler gets more coarse */
if (++scale > TC_CTRLA_PRESCALER_DIV16_Val) {
freq_in >>= 1;
}
}
/* fail if output frequency can't be derived from input frequency */
assert(freq_in == freq_out);
return scale;
}
/**
* @brief Setup the given timer
*/
int timer_init(tim_t tim, unsigned long freq, timer_cb_t cb, void *arg)
{
(void) freq;
const tc32_conf_t *cfg = &timer_config[tim];
uint8_t scale = _get_prescaler(freq, sam0_gclk_freq(cfg->gclk_src));
/* make sure given device is valid */
if (tim >= TIMER_NUMOF) {
return -1;
}
/* make sure the prescaler is withing range */
if (scale > TC_CTRLA_PRESCALER_DIV1024_Val) {
DEBUG("[timer %d] scale %d is out of range\n", tim, scale);
return -1;
}
/* make sure the timer is not running */
timer_stop(tim);
@ -104,7 +128,7 @@ int timer_init(tim_t tim, unsigned long freq, timer_cb_t cb, void *arg)
#ifdef TC_CTRLA_WAVEGEN_NFRQ
| TC_CTRLA_WAVEGEN_NFRQ
#endif
| cfg->prescaler
| TC_CTRLA_PRESCALER(scale)
| TC_CTRLA_PRESCSYNC_RESYNC;
#ifdef TC_WAVE_WAVEGEN_NFRQ