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drivers: rtc: stm32: avoid reset induced time drift

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Calling LL_RTC_Init causes the RTC to stop while being configured thus
inducing time drift. This commit avoids doing it at each reset if the RTC
is already properly configured.

Signed-off-by: Johan Lafon <johan.lafon@syslinbit.com>
This commit is contained in:
Johan Lafon 2023-09-11 13:45:24 +02:00 • committed by Fabio Baltieri
commit cdab80eece
1 changed files with 28 additions and 3 deletions
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31
drivers/rtc/rtc_ll_stm32.c
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@ -66,11 +66,35 @@ struct rtc_stm32_data {
/* Currently empty */
};
static int rtc_stm32_configure(const struct device *dev)
{
const struct rtc_stm32_config *cfg = dev->config;
uint32_t hour_format = LL_RTC_GetHourFormat(RTC);
uint32_t sync_prescaler = LL_RTC_GetSynchPrescaler(RTC);
uint32_t async_prescaler = LL_RTC_GetAsynchPrescaler(RTC);
/* configuration process requires to stop the RTC counter so do it
* only if needed to avoid inducing time drift at each reset
*/
if ((hour_format != cfg->ll_rtc_config.HourFormat) ||
(sync_prescaler != cfg->ll_rtc_config.SynchPrescaler) ||
(async_prescaler != cfg->ll_rtc_config.AsynchPrescaler)) {
if (LL_RTC_Init(RTC, ((LL_RTC_InitTypeDef *)&cfg->ll_rtc_config)) != SUCCESS) {
return -EIO;
}
}
return 0;
}
static int rtc_stm32_init(const struct device *dev)
{
const struct device *const clk = DEVICE_DT_GET(STM32_CLOCK_CONTROL_NODE);
const struct rtc_stm32_config *cfg = dev->config;
int err = 0;
if (!device_is_ready(clk)) {
LOG_ERR("clock control device not ready");
return -ENODEV;
@ -98,8 +122,9 @@ static int rtc_stm32_init(const struct device *dev)
z_stm32_hsem_unlock(CFG_HW_RCC_SEMID);
if (LL_RTC_Init(RTC, ((LL_RTC_InitTypeDef *)&cfg->ll_rtc_config)) != SUCCESS) {
return -EIO;
err = rtc_stm32_configure(dev);
if (err) {
return err;
}
#ifdef RTC_CR_BYPSHAD
@ -108,7 +133,7 @@ static int rtc_stm32_init(const struct device *dev)
LL_RTC_EnableWriteProtection(RTC);
#endif /* RTC_CR_BYPSHAD */
return 0;
return err;
}
static const struct stm32_pclken rtc_clk[] = STM32_DT_INST_CLOCKS(0);