rtc_osc_init.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <soc/rtc.h>
#include <soc/rtc_common.h>
 
/* 32k clock calibration */
static int rtc_eosc_cali(void)
{
        u16 diff_left, diff_right, cksel;
        u16 val = 0;
        u16 middle;
        u16 left = RTC_XOSCCALI_START;
        u16 right = RTC_XOSCCALI_END;
 
        rtc_read(PMIC_RG_FQMTR_CKSEL, &cksel);
        cksel &= ~PMIC_FQMTR_CKSEL_MASK;
        /* select EOSC_32 as fixed clock */
        rtc_write(PMIC_RG_FQMTR_CKSEL, cksel | PMIC_FQMTR_FIX_CLK_EOSC_32K);
        rtc_read(PMIC_RG_FQMTR_CKSEL, &cksel);
        rtc_info("PMIC_RG_FQMTR_CKSEL=%#x\n", cksel);
 
        while (left <= right) {
                middle = (right + left) / 2;
                if (middle == left)
                        break;
 
                /* select 26M as target clock */
                val = rtc_get_frequency_meter(middle, PMIC_FQMTR_CON0_FQM26M_CK, 0);
                if (val >= RTC_FQMTR_LOW_BASE && val <= RTC_FQMTR_HIGH_BASE)
                        break;
 
                if (val > RTC_FQMTR_HIGH_BASE)
                        right = middle;
                else
                        left = middle;
        }
 
        if (val >= RTC_FQMTR_LOW_BASE && val <= RTC_FQMTR_HIGH_BASE)
                return middle;
 
        val = rtc_get_frequency_meter(left, PMIC_FQMTR_CON0_FQM26M_CK, 0);
        diff_left = ABS(val - RTC_FQMTR_LOW_BASE);
 
        val = rtc_get_frequency_meter(right, PMIC_FQMTR_CON0_FQM26M_CK, 0);
        diff_right = ABS(val - RTC_FQMTR_LOW_BASE);
 
        rtc_info("left: %d, middle: %d, right: %d\n", left, middle, right);
        if (diff_left < diff_right)
                return left;
        else
                return right;
}
 
void rtc_osc_init(void)
{
        u16 osc32con;
 
        /* enable 32K export */
        rtc_gpio_init();
        /* calibrate eosc32 for powerdown clock */
        rtc_read(RTC_OSC32CON, &osc32con);
        rtc_info("osc32con val = %#x\n", osc32con);
        osc32con &= ~RTC_XOSCCALI_MASK;
        osc32con |= rtc_eosc_cali() & RTC_XOSCCALI_MASK;
        rtc_xosc_write(osc32con);
        rtc_info("EOSC32 cali val = %#x\n", osc32con);
}