static void select_rtc_slow_clk(rtc_slow_freq_t slow_clk)
{
if (slow_clk == RTC_SLOW_FREQ_32K_XTAL) {
/* 32k XTAL oscillator needs to be enabled and running before it can
* be used. Hardware doesn't have a direct way of checking if the
* oscillator is running. Here we use rtc_clk_cal function to count
* the number of main XTAL cycles in the given number of 32k XTAL
* oscillator cycles. If the 32k XTAL has not started up, calibration
* will time out, returning 0.
*/
rtc_clk_32k_enable(true);
uint32_t cal_val = 0;
uint32_t wait = 0;
// increment of 'wait' counter equivalent to 3 seconds
const uint32_t warning_timeout = 3 /* sec */ * 32768 /* Hz */ / (2 * XTAL_32K_DETECT_CYCLES);
ESP_EARLY_LOGD(TAG, "waiting for 32k oscillator to start up")
do {
++wait;
cal_val = rtc_clk_cal(RTC_CAL_32K_XTAL, XTAL_32K_DETECT_CYCLES);
if (wait % warning_timeout == 0) {
ESP_EARLY_LOGW(TAG, "still waiting for 32k oscillator to start up");
}
} while (cal_val == 0);
ESP_EARLY_LOGD(TAG, "32k oscillator ready, wait=%d", wait);
}
void rtc_clk_init(rtc_clk_config_t cfg)
{
rtc_cpu_freq_config_t old_config, new_config;
/* If we get a TG WDT system reset while running at 240MHz,
* DPORT_CPUPERIOD_SEL register will be reset to 0 resulting in 120MHz
* APB and CPU frequencies after reset. This will cause issues with XTAL
* frequency estimation, so we switch to XTAL frequency first.
*
* Ideally we would only do this if RTC_CNTL_SOC_CLK_SEL == PLL and
* PLL is configured for 480M, but it takes less time to switch to 40M and
* run the following code than querying the PLL does.
*/
if (REG_GET_FIELD(RTC_CNTL_CLK_CONF_REG, RTC_CNTL_SOC_CLK_SEL) == RTC_CNTL_SOC_CLK_SEL_PLL) {
/* We don't know actual XTAL frequency yet, assume 40MHz.
* REF_TICK divider will be corrected below, once XTAL frequency is
* determined.
*/
rtc_clk_cpu_freq_to_xtal(40, 1);
}
/* Set tuning parameters for 8M and 150k clocks.
* Note: this doesn't attempt to set the clocks to precise frequencies.
* Instead, we calibrate these clocks against XTAL frequency later, when necessary.
* - SCK_DCAP value controls tuning of 150k clock.
* The higher the value of DCAP is, the lower is the frequency.
* - CK8M_DFREQ value controls tuning of 8M clock.
* CLK_8M_DFREQ constant gives the best temperature characteristics.
*/
REG_SET_FIELD(RTC_CNTL_REG, RTC_CNTL_SCK_DCAP, cfg.slow_clk_dcap);
REG_SET_FIELD(RTC_CNTL_CLK_CONF_REG, RTC_CNTL_CK8M_DFREQ, cfg.clk_8m_dfreq);
/* Configure 8M clock division */
REG_SET_FIELD(RTC_CNTL_CLK_CONF_REG, RTC_CNTL_CK8M_DIV_SEL, cfg.clk_8m_div);
/* Enable the internal bus used to configure PLLs */
SET_PERI_REG_BITS(ANA_CONFIG_REG, ANA_CONFIG_M, ANA_CONFIG_M, ANA_CONFIG_S);
CLEAR_PERI_REG_MASK(ANA_CONFIG_REG, I2C_APLL_M | I2C_BBPLL_M);
/* Estimate XTAL frequency */
rtc_xtal_freq_t xtal_freq = cfg.xtal_freq;
if (xtal_freq == RTC_XTAL_FREQ_AUTO) {
if (clk_val_is_valid(READ_PERI_REG(RTC_XTAL_FREQ_REG))) {
/* XTAL frequency has already been set, use existing value */
xtal_freq = rtc_clk_xtal_freq_get();
} else {
/* Not set yet, estimate XTAL frequency based on RTC_FAST_CLK */
xtal_freq = rtc_clk_xtal_freq_estimate();
if (xtal_freq == RTC_XTAL_FREQ_AUTO) {
SOC_LOGW(TAG, "Can't estimate XTAL frequency, assuming 26MHz");
xtal_freq = RTC_XTAL_FREQ_26M;
}
}
} else if (!clk_val_is_valid(READ_PERI_REG(RTC_XTAL_FREQ_REG))) {
/* Exact frequency was set in sdkconfig, but still warn if autodetected
* frequency is different. If autodetection failed, worst case we get a
* bit of garbage output.
*/
rtc_xtal_freq_t est_xtal_freq = rtc_clk_xtal_freq_estimate();
if (est_xtal_freq != xtal_freq) {
SOC_LOGW(TAG, "Possibly invalid CONFIG_ESP32_XTAL_FREQ setting (%dMHz). Detected %d MHz.",
xtal_freq, est_xtal_freq);
}
}
uart_tx_wait_idle(0);
rtc_clk_xtal_freq_update(xtal_freq);
rtc_clk_apb_freq_update(xtal_freq * MHZ);
/* Set CPU frequency */
rtc_clk_cpu_freq_get_config(&old_config);
uint32_t freq_before = old_config.freq_mhz;
bool res = rtc_clk_cpu_freq_mhz_to_config(cfg.cpu_freq_mhz, &new_config);
if (!res) {
SOC_LOGE(TAG, "invalid CPU frequency value");
abort();
}
rtc_clk_cpu_freq_set_config(&new_config);
/* Configure REF_TICK */
REG_WRITE(APB_CTRL_XTAL_TICK_CONF_REG, xtal_freq - 1);
REG_WRITE(APB_CTRL_PLL_TICK_CONF_REG, APB_CLK_FREQ / MHZ - 1); /* Under PLL, APB frequency is always 80MHz */
/* Re-calculate the ccount to make time calculation correct. */
XTHAL_SET_CCOUNT( XTHAL_GET_CCOUNT() * cfg.cpu_freq_mhz / freq_before );
/* Slow & fast clocks setup */
if (cfg.slow_freq == RTC_SLOW_FREQ_32K_XTAL) {
rtc_clk_32k_enable(true);
}
if (cfg.fast_freq == RTC_FAST_FREQ_8M) {
bool need_8md256 = cfg.slow_freq == RTC_SLOW_FREQ_8MD256;
rtc_clk_8m_enable(true, need_8md256);
}
rtc_clk_fast_freq_set(cfg.fast_freq);
rtc_clk_slow_freq_set(cfg.slow_freq);
}
