rtc_stm32.c

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#include "clock_stm32.h"

#include <cfg/compiler.h>
#include <cfg/module.h>
#include <cfg/debug.h>

#include <io/stm32.h>
#include <io/stm32_pwr.h>

#include <cpu/power.h> // cpu_relax()

#include <drv/rtc.h>

/* PWR registers base */
static struct PWR *PWR = (struct PWR *)PWR_BASE;

/* RTC clock source: LSE */
#define RTC_CLKSRC  0x00000100
/* RTC clock: 32768 Hz */
#define RTC_CLOCK   32768
/* RTC clock period (in ms) */
#define RTC_PERIOD      1000

/* RTC control register */
#define RTC_CRH     (*(reg16_t *)(RTC_BASE + 0x00))
#define RTC_CRL     (*(reg16_t *)(RTC_BASE + 0x04))

#define RTC_CRL_SECIE         BV(0)
#define RTC_CRL_ALRIE         BV(1)
#define RTC_CRL_OWIE          BV(2)

#define RTC_CRL_SECF          BV(0)
#define RTC_CRL_ALRF          BV(1)
#define RTC_CRL_OWF           BV(2)
#define RTC_CRL_RSF           BV(3)
#define RTC_CRL_CNF           BV(4)
#define RTC_CRL_RTOFF         BV(5)

/* RTC prescaler load register */
#define RTC_PRLH    (*(reg16_t *)(RTC_BASE + 0x08))
#define RTC_PRLL    (*(reg16_t *)(RTC_BASE + 0x0c))

/* RTC prescaler divider register */
#define RTC_DIVH    (*(reg16_t *)(RTC_BASE + 0x10))
#define RTC_DIVL    (*(reg16_t *)(RTC_BASE + 0x14))

/* RTC counter register */
#define RTC_CNTH    (*(reg16_t *)(RTC_BASE + 0x18))
#define RTC_CNTL    (*(reg16_t *)(RTC_BASE + 0x1c))

/* RTC alarm register */
#define RTC_ALRH    (*(reg16_t *)(RTC_BASE + 0x20))
#define RTC_ALRL    (*(reg16_t *)(RTC_BASE + 0x24))

static void rtc_enterConfig(void)
{
    /* Enter configuration mode */
    RTC_CRL |= RTC_CRL_CNF;
}

static void rtc_exitConfig(void)
{
    /* Exit from configuration mode */
    RTC_CRL &= ~RTC_CRL_CNF;
    while (!(RTC_CRL & RTC_CRL_RTOFF))
        cpu_relax();
}

uint32_t rtc_time(void)
{
    return (RTC_CNTH << 16) | RTC_CNTL;
}

void rtc_setTime(uint32_t val)
{
    rtc_enterConfig();
    RTC_CNTH = (val >> 16) & 0xffff;
    RTC_CNTL = val & 0xffff;
    rtc_exitConfig();
}

/* Initialize the RTC clock */
int rtc_init(void)
{
#if CONFIG_KERN
    MOD_CHECK(proc);
#endif
    /* Enable clock for Power interface */
    RCC->APB1ENR |= RCC_APB1_PWR;

    /* Enable access to RTC registers */
    PWR->CR |= PWR_CR_DBP;

    /* Enable LSE */
    RCC->BDCR |= RCC_BDCR_LSEON;
    /* Wait for LSE ready */
    while (!(RCC->BDCR & RCC_BDCR_LSERDY))
        cpu_relax();

    /* Set clock source and enable RTC peripheral */
    RCC->BDCR |= RTC_CLKSRC | RCC_BDCR_RTCEN;

    rtc_enterConfig();

    /* Set prescaler */
    RTC_PRLH = ((RTC_PERIOD * RTC_CLOCK / 1000 - 1) >> 16) & 0xff;
    RTC_PRLL = ((RTC_PERIOD * RTC_CLOCK / 1000 - 1)) & 0xffff;

    rtc_exitConfig();

    /* Disable access to the RTC registers */
    PWR->CR &= ~PWR_CR_DBP;

    return 0;
}