// 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, leap_yr;
#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;
leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) ||
!((yrs + 1900) % 400));
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 (!leap_yr && 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);
