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drivers: rtc: stm32: add calibration feature

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This adds the set_calibration and get_calibration API functions to the
STM32 RTC driver

Signed-off-by: Johan Lafon <johan.lafon@syslinbit.com>
This commit is contained in:
Johan Lafon 2023-09-05 17:23:31 +02:00 • committed by Fabio Baltieri
commit 8aa6531aed
1 changed files with 94 additions and 0 deletions
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94
drivers/rtc/rtc_ll_stm32.c
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@ -1,5 +1,6 @@
/*
* Copyright (c) 2023 Prevas A/S
* Copyright (c) 2023 Syslinbit
*
* SPDX-License-Identifier: Apache-2.0
*
@ -15,6 +16,7 @@
#include <zephyr/drivers/rtc.h>
#include <zephyr/drivers/clock_control/stm32_clock_control.h>
#include <zephyr/drivers/clock_control.h>
#include <zephyr/sys/util.h>
#include <soc.h>
#include <stm32_ll_pwr.h>
#include <stm32_ll_rcc.h>
@ -30,6 +32,29 @@ LOG_MODULE_REGISTER(rtc_stm32, CONFIG_RTC_LOG_LEVEL);
/* struct tm start: 1st, Jan, 1900 */
#define TM_TO_RTC_OFFSET 100
/* Convert part per billion calibration value to a number of clock pulses added or removed each
* 2^20 clock cycles so it is suitable for the CALR register fields
*
* nb_pulses = ppb * 2^20 / 10^9 = ppb * 2^11 / 5^9 = ppb * 2048 / 1953125
*/
#define PPB_TO_NB_PULSES(ppb) DIV_ROUND_CLOSEST((ppb) * 2048, 1953125)
/* Convert CALR register value (number of clock pulses added or removed each 2^20 clock cycles)
* to part ber billion calibration value
*
* ppb = nb_pulses * 10^9 / 2^20 = nb_pulses * 5^9 / 2^11 = nb_pulses * 1953125 / 2048
*/
#define NB_PULSES_TO_PPB(pulses) DIV_ROUND_CLOSEST((pulses) * 1953125, 2048)
/* CALP field can only be 512 or 0 as in reality CALP is a single bit field representing 512 pulses
* added every 2^20 clock cycles
*/
#define MAX_CALP (512)
#define MAX_CALM (511)
#define MAX_PPB NB_PULSES_TO_PPB(MAX_CALP)
#define MIN_PPB -NB_PULSES_TO_PPB(MAX_CALM)
struct rtc_stm32_config {
LL_RTC_InitTypeDef ll_rtc_config;
const struct stm32_pclken *pclken;
@ -154,11 +179,80 @@ static int rtc_stm32_get_time(const struct device *dev, struct rtc_time *timeptr
return 0;
}
#ifdef CONFIG_RTC_CALIBRATION
static int rtc_stm32_set_calibration(const struct device *dev, int32_t calibration)
{
ARG_UNUSED(dev);
/* Note : calibration is considered here to be ppb value to apply
* on clock period (not frequency) but with an opposite sign
*/
if ((calibration > MAX_PPB) || (calibration < MIN_PPB)) {
/* out of supported range */
return -EINVAL;
}
int32_t nb_pulses = PPB_TO_NB_PULSES(calibration);
/* we tested calibration against supported range
* so theoretically nb_pulses is also within range
*/
__ASSERT_NO_MSG(nb_pulses <= MAX_CALP);
__ASSERT_NO_MSG(nb_pulses >= -MAX_CALM);
uint32_t calp, calm;
if (nb_pulses > 0) {
calp = LL_RTC_CALIB_INSERTPULSE_SET;
calm = MAX_CALP - nb_pulses;
} else {
calp = LL_RTC_CALIB_INSERTPULSE_NONE;
calm = -nb_pulses;
}
/* wait for recalibration to be ok if a previous recalibration occurred */
if (!WAIT_FOR(LL_RTC_IsActiveFlag_RECALP(RTC) == 0, 100000, k_msleep(1))) {
return -EIO;
}
LL_RTC_DisableWriteProtection(RTC);
MODIFY_REG(RTC->CALR, RTC_CALR_CALP | RTC_CALR_CALM, calp | calm);
LL_RTC_EnableWriteProtection(RTC);
return 0;
}
static int rtc_stm32_get_calibration(const struct device *dev, int32_t *calibration)
{
ARG_UNUSED(dev);
uint32_t calp_enabled = LL_RTC_CAL_IsPulseInserted(RTC);
uint32_t calm = LL_RTC_CAL_GetMinus(RTC);
int32_t nb_pulses = -((int32_t) calm);
if (calp_enabled) {
nb_pulses += MAX_CALP;
}
*calibration = NB_PULSES_TO_PPB(nb_pulses);
return 0;
}
#endif /* CONFIG_RTC_CALIBRATION */
struct rtc_driver_api rtc_stm32_driver_api = {
.set_time = rtc_stm32_set_time,
.get_time = rtc_stm32_get_time,
/* RTC_ALARM not supported */
/* RTC_UPDATE not supported */
#ifdef CONFIG_RTC_CALIBRATION
.set_calibration = rtc_stm32_set_calibration,
.get_calibration = rtc_stm32_get_calibration,
#endif /* CONFIG_RTC_CALIBRATION */
};
#define RTC_STM32_DEV_CFG(n) \