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sam0_common: rtc: use GCLK4 on SAMD21

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The RTC expects to be clocked from a 1kHz source.
Previously it would re-configure GCLK2 from 32kHz to 1kHz when used.

Since GCLK2 is also used by EIC, this would break external interrupts
in strange and unexpected ways.

Dedicate a 1kHz clock to it to avoid the damage.
This commit is contained in:
Benjamin Valentin 2019-10-30 19:04:03 +01:00 committed by Benjamin Valentin
parent 5fa234e435
commit db2fa33660
1 changed files with 2 additions and 4 deletions
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6
cpu/sam0_common/periph/rtc.c
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@ -65,10 +65,8 @@ static inline void _rtc_set_enabled(bool on)
#ifdef CPU_SAMD21
static void _rtc_clock_setup(void)
{
/* Setup clock GCLK2 with OSC32K divided by 32 */
GCLK->GENDIV.reg = GCLK_GENDIV_ID(2) | GCLK_GENDIV_DIV(4);
GCLK->GENCTRL.bit.DIVSEL = 1;
GCLK->CLKCTRL.reg = GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN(2) | GCLK_CLKCTRL_ID_RTC;
/* Use 1024 Hz GCLK4 */
GCLK->CLKCTRL.reg = GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN(4) | GCLK_CLKCTRL_ID_RTC;
while (GCLK->STATUS.bit.SYNCBUSY) {}
}
#else