// SPDX-License-Identifier: GPL-2.0-only
#include <linux/bcd.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <linux/mc146818rtc.h>

#ifdef CONFIG_ACPI
#include <linux/acpi.h>
#endif

#define UIP_RECHECK_DELAY               100     /* usec */
#define UIP_RECHECK_DELAY_MS            (USEC_PER_MSEC / UIP_RECHECK_DELAY)
#define UIP_RECHECK_LOOPS_MS(x)         (x / UIP_RECHECK_DELAY_MS)

/*
 * Execute a function while the UIP (Update-in-progress) bit of the RTC is
 * unset. The timeout is configurable by the caller in ms.
 *
 * Warning: callback may be executed more then once.
 */
bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
                        int timeout,
                        void *param)
{
        int i;
        unsigned long flags;
        unsigned char seconds;

        for (i = 0; UIP_RECHECK_LOOPS_MS(i) < timeout; i++) {
                spin_lock_irqsave(&rtc_lock, flags);

                /*
                 * Check whether there is an update in progress during which the
                 * readout is unspecified. The maximum update time is ~2ms. Poll
                 * for completion.
                 *
                 * Store the second value before checking UIP so a long lasting
                 * NMI which happens to hit after the UIP check cannot make
                 * an update cycle invisible.
                 */
                seconds = CMOS_READ(RTC_SECONDS);

                if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
                        spin_unlock_irqrestore(&rtc_lock, flags);
                        udelay(UIP_RECHECK_DELAY);
                        continue;
                }

                /* Revalidate the above readout */
                if (seconds != CMOS_READ(RTC_SECONDS)) {
                        spin_unlock_irqrestore(&rtc_lock, flags);
                        continue;
                }

                if (callback)
                        callback(seconds, param);

                /*
                 * Check for the UIP bit again. If it is set now then
                 * the above values may contain garbage.
                 */
                if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
                        spin_unlock_irqrestore(&rtc_lock, flags);
                        udelay(UIP_RECHECK_DELAY);
                        continue;
                }

                /*
                 * A NMI might have interrupted the above sequence so check
                 * whether the seconds value has changed which indicates that
                 * the NMI took longer than the UIP bit was set. Unlikely, but
                 * possible and there is also virt...
                 */
                if (seconds != CMOS_READ(RTC_SECONDS)) {
                        spin_unlock_irqrestore(&rtc_lock, flags);
                        continue;
                }
                spin_unlock_irqrestore(&rtc_lock, flags);

                if (UIP_RECHECK_LOOPS_MS(i) >= 100)
                        pr_warn("Reading current time from RTC took around %li ms\n",
                                UIP_RECHECK_LOOPS_MS(i));

                return true;
        }
        return false;
}
EXPORT_SYMBOL_GPL(mc146818_avoid_UIP);

/*
 * If the UIP (Update-in-progress) bit of the RTC is set for more then
 * 10ms, the RTC is apparently broken or not present.
 */
bool mc146818_does_rtc_work(void)
{
        return mc146818_avoid_UIP(NULL, 1000, NULL);
}
EXPORT_SYMBOL_GPL(mc146818_does_rtc_work);

struct mc146818_get_time_callback_param {
        struct rtc_time *time;
        unsigned char ctrl;
#ifdef CONFIG_ACPI
        unsigned char century;
#endif
#ifdef CONFIG_MACH_DECSTATION
        unsigned int real_year;
#endif
};

static void mc146818_get_time_callback(unsigned char seconds, void *param_in)
{
        struct mc146818_get_time_callback_param *p = param_in;

        /*
         * Only the values that we read from the RTC are set. We leave
         * tm_wday, tm_yday and tm_isdst untouched. Even though the
         * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
         * by the RTC when initially set to a non-zero value.
         */
        p->time->tm_sec = seconds;
        p->time->tm_min = CMOS_READ(RTC_MINUTES);
        p->time->tm_hour = CMOS_READ(RTC_HOURS);
        p->time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
        p->time->tm_mon = CMOS_READ(RTC_MONTH);
        p->time->tm_year = CMOS_READ(RTC_YEAR);
#ifdef CONFIG_MACH_DECSTATION
        p->real_year = CMOS_READ(RTC_DEC_YEAR);
#endif
#ifdef CONFIG_ACPI
        if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
            acpi_gbl_FADT.century) {
                p->century = CMOS_READ(acpi_gbl_FADT.century);
        } else {
                p->century = 0;
        }
#endif

        p->ctrl = CMOS_READ(RTC_CONTROL);
}

/**
 * mc146818_get_time - Get the current time from the RTC
 * @time: pointer to struct rtc_time to store the current time
 * @timeout: timeout value in ms
 *
 * This function reads the current time from the RTC and stores it in the
 * provided struct rtc_time. The timeout parameter specifies the maximum
 * time to wait for the RTC to become ready.
 *
 * Return: 0 on success, -ETIMEDOUT if the RTC did not become ready within
 * the specified timeout, or another error code if an error occurred.
 */
int mc146818_get_time(struct rtc_time *time, int timeout)
{
        struct mc146818_get_time_callback_param p = {
                .time = time
        };

        if (!mc146818_avoid_UIP(mc146818_get_time_callback, timeout, &p)) {
                memset(time, 0, sizeof(*time));
                return -ETIMEDOUT;
        }

        if (!(p.ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
        {
                time->tm_sec = bcd2bin(time->tm_sec);
                time->tm_min = bcd2bin(time->tm_min);
                time->tm_hour = bcd2bin(time->tm_hour);
                time->tm_mday = bcd2bin(time->tm_mday);
                time->tm_mon = bcd2bin(time->tm_mon);
                time->tm_year = bcd2bin(time->tm_year);
#ifdef CONFIG_ACPI
                p.century = bcd2bin(p.century);
#endif
        }

#ifdef CONFIG_MACH_DECSTATION
        time->tm_year += p.real_year - 72;
#endif

#ifdef CONFIG_ACPI
        if (p.century > 19)
                time->tm_year += (p.century - 19) * 100;
#endif

        /*
         * Account for differences between how the RTC uses the values
         * and how they are defined in a struct rtc_time;
         */
        if (time->tm_year <= 69)
                time->tm_year += 100;

        time->tm_mon--;

        return 0;
}
EXPORT_SYMBOL_GPL(mc146818_get_time);

/* AMD systems don't allow access to AltCentury with DV1 */
static bool apply_amd_register_a_behavior(void)
{
#ifdef CONFIG_X86
        if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
            boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
                return true;
#endif
        return false;
}

/* Set the current date and time in the real time clock. */
int mc146818_set_time(struct rtc_time *time)
{
        unsigned long flags;
        unsigned char mon, day, hrs, min, sec;
        unsigned char save_control, save_freq_select;
        unsigned int yrs;
#ifdef CONFIG_MACH_DECSTATION
        unsigned int real_yrs;
#endif
        unsigned char century = 0;

        yrs = time->tm_year;
        mon = time->tm_mon + 1;   /* tm_mon starts at zero */
        day = time->tm_mday;
        hrs = time->tm_hour;
        min = time->tm_min;
        sec = time->tm_sec;

        if (yrs > 255)  /* They are unsigned */
                return -EINVAL;

#ifdef CONFIG_MACH_DECSTATION
        real_yrs = yrs;
        yrs = 72;

        /*
         * We want to keep the year set to 73 until March
         * for non-leap years, so that Feb, 29th is handled
         * correctly.
         */
        if (!is_leap_year(real_yrs + 1900) && mon < 3) {
                real_yrs--;
                yrs = 73;
        }
#endif

#ifdef CONFIG_ACPI
        if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
            acpi_gbl_FADT.century) {
                century = (yrs + 1900) / 100;
                yrs %= 100;
        }
#endif

        /* These limits and adjustments are independent of
         * whether the chip is in binary mode or not.
         */
        if (yrs > 169)
                return -EINVAL;

        if (yrs >= 100)
                yrs -= 100;

        spin_lock_irqsave(&rtc_lock, flags);
        save_control = CMOS_READ(RTC_CONTROL);
        spin_unlock_irqrestore(&rtc_lock, flags);
        if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                sec = bin2bcd(sec);
                min = bin2bcd(min);
                hrs = bin2bcd(hrs);
                day = bin2bcd(day);
                mon = bin2bcd(mon);
                yrs = bin2bcd(yrs);
                century = bin2bcd(century);
        }

        spin_lock_irqsave(&rtc_lock, flags);
        save_control = CMOS_READ(RTC_CONTROL);
        CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
        save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
        if (apply_amd_register_a_behavior())
                CMOS_WRITE((save_freq_select & ~RTC_AMD_BANK_SELECT), RTC_FREQ_SELECT);
        else
                CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);

#ifdef CONFIG_MACH_DECSTATION
        CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
#endif
        CMOS_WRITE(yrs, RTC_YEAR);
        CMOS_WRITE(mon, RTC_MONTH);
        CMOS_WRITE(day, RTC_DAY_OF_MONTH);
        CMOS_WRITE(hrs, RTC_HOURS);
        CMOS_WRITE(min, RTC_MINUTES);
        CMOS_WRITE(sec, RTC_SECONDS);
#ifdef CONFIG_ACPI
        if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
            acpi_gbl_FADT.century)
                CMOS_WRITE(century, acpi_gbl_FADT.century);
#endif

        CMOS_WRITE(save_control, RTC_CONTROL);
        CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);

        spin_unlock_irqrestore(&rtc_lock, flags);

        return 0;
}
EXPORT_SYMBOL_GPL(mc146818_set_time);