1// SPDX-License-Identifier: GPL-2.0-only
  2#include <linux/bcd.h>
  3#include <linux/delay.h>
  4#include <linux/export.h>
  5#include <linux/mc146818rtc.h>
  6
  7#ifdef CONFIG_ACPI
  8#include <linux/acpi.h>
  9#endif
 10
 11/*
 12 * Returns true if a clock update is in progress
 13 */
 14static inline unsigned char mc146818_is_updating(void)
 15{
 16	unsigned char uip;
 17	unsigned long flags;
 18
 19	spin_lock_irqsave(&rtc_lock, flags);
 20	uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
 21	spin_unlock_irqrestore(&rtc_lock, flags);
 22	return uip;
 23}
 24
 25unsigned int mc146818_get_time(struct rtc_time *time)
 26{
 27	unsigned char ctrl;
 28	unsigned long flags;
 29	unsigned char century = 0;
 30
 31#ifdef CONFIG_MACH_DECSTATION
 32	unsigned int real_year;
 33#endif
 34
 35	/*
 36	 * read RTC once any update in progress is done. The update
 37	 * can take just over 2ms. We wait 20ms. There is no need to
 38	 * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP.
 39	 * If you need to know *exactly* when a second has started, enable
 40	 * periodic update complete interrupts, (via ioctl) and then
 41	 * immediately read /dev/rtc which will block until you get the IRQ.
 42	 * Once the read clears, read the RTC time (again via ioctl). Easy.
 43	 */
 44	if (mc146818_is_updating())
 45		mdelay(20);
 46
 47	/*
 48	 * Only the values that we read from the RTC are set. We leave
 49	 * tm_wday, tm_yday and tm_isdst untouched. Even though the
 50	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
 51	 * by the RTC when initially set to a non-zero value.
 52	 */
 53	spin_lock_irqsave(&rtc_lock, flags);
 54	time->tm_sec = CMOS_READ(RTC_SECONDS);
 55	time->tm_min = CMOS_READ(RTC_MINUTES);
 56	time->tm_hour = CMOS_READ(RTC_HOURS);
 57	time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
 58	time->tm_mon = CMOS_READ(RTC_MONTH);
 59	time->tm_year = CMOS_READ(RTC_YEAR);
 60#ifdef CONFIG_MACH_DECSTATION
 61	real_year = CMOS_READ(RTC_DEC_YEAR);
 62#endif
 63#ifdef CONFIG_ACPI
 64	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 65	    acpi_gbl_FADT.century)
 66		century = CMOS_READ(acpi_gbl_FADT.century);
 67#endif
 68	ctrl = CMOS_READ(RTC_CONTROL);
 69	spin_unlock_irqrestore(&rtc_lock, flags);
 70
 71	if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
 72	{
 73		time->tm_sec = bcd2bin(time->tm_sec);
 74		time->tm_min = bcd2bin(time->tm_min);
 75		time->tm_hour = bcd2bin(time->tm_hour);
 76		time->tm_mday = bcd2bin(time->tm_mday);
 77		time->tm_mon = bcd2bin(time->tm_mon);
 78		time->tm_year = bcd2bin(time->tm_year);
 79		century = bcd2bin(century);
 80	}
 81
 82#ifdef CONFIG_MACH_DECSTATION
 83	time->tm_year += real_year - 72;
 84#endif
 85
 86	if (century > 20)
 87		time->tm_year += (century - 19) * 100;
 88
 89	/*
 90	 * Account for differences between how the RTC uses the values
 91	 * and how they are defined in a struct rtc_time;
 92	 */
 93	if (time->tm_year <= 69)
 94		time->tm_year += 100;
 95
 96	time->tm_mon--;
 97
 98	return RTC_24H;
 99}
100EXPORT_SYMBOL_GPL(mc146818_get_time);
101
102/* Set the current date and time in the real time clock. */
103int mc146818_set_time(struct rtc_time *time)
104{
105	unsigned long flags;
106	unsigned char mon, day, hrs, min, sec;
107	unsigned char save_control, save_freq_select;
108	unsigned int yrs;
109#ifdef CONFIG_MACH_DECSTATION
110	unsigned int real_yrs, leap_yr;
111#endif
112	unsigned char century = 0;
113
114	yrs = time->tm_year;
115	mon = time->tm_mon + 1;   /* tm_mon starts at zero */
116	day = time->tm_mday;
117	hrs = time->tm_hour;
118	min = time->tm_min;
119	sec = time->tm_sec;
120
121	if (yrs > 255)	/* They are unsigned */
122		return -EINVAL;
123
124	spin_lock_irqsave(&rtc_lock, flags);
125#ifdef CONFIG_MACH_DECSTATION
126	real_yrs = yrs;
127	leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) ||
128			!((yrs + 1900) % 400));
129	yrs = 72;
130
131	/*
132	 * We want to keep the year set to 73 until March
133	 * for non-leap years, so that Feb, 29th is handled
134	 * correctly.
135	 */
136	if (!leap_yr && mon < 3) {
137		real_yrs--;
138		yrs = 73;
139	}
140#endif
141
142#ifdef CONFIG_ACPI
143	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
144	    acpi_gbl_FADT.century) {
145		century = (yrs + 1900) / 100;
146		yrs %= 100;
147	}
148#endif
149
150	/* These limits and adjustments are independent of
151	 * whether the chip is in binary mode or not.
152	 */
153	if (yrs > 169) {
154		spin_unlock_irqrestore(&rtc_lock, flags);
155		return -EINVAL;
156	}
157
158	if (yrs >= 100)
159		yrs -= 100;
160
161	if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
162	    || RTC_ALWAYS_BCD) {
163		sec = bin2bcd(sec);
164		min = bin2bcd(min);
165		hrs = bin2bcd(hrs);
166		day = bin2bcd(day);
167		mon = bin2bcd(mon);
168		yrs = bin2bcd(yrs);
169		century = bin2bcd(century);
170	}
171
172	save_control = CMOS_READ(RTC_CONTROL);
173	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
174	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
175	CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
176
177#ifdef CONFIG_MACH_DECSTATION
178	CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
179#endif
180	CMOS_WRITE(yrs, RTC_YEAR);
181	CMOS_WRITE(mon, RTC_MONTH);
182	CMOS_WRITE(day, RTC_DAY_OF_MONTH);
183	CMOS_WRITE(hrs, RTC_HOURS);
184	CMOS_WRITE(min, RTC_MINUTES);
185	CMOS_WRITE(sec, RTC_SECONDS);
186#ifdef CONFIG_ACPI
187	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
188	    acpi_gbl_FADT.century)
189		CMOS_WRITE(century, acpi_gbl_FADT.century);
190#endif
191
192	CMOS_WRITE(save_control, RTC_CONTROL);
193	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
194
195	spin_unlock_irqrestore(&rtc_lock, flags);
196
197	return 0;
198}
199EXPORT_SYMBOL_GPL(mc146818_set_time);