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
 11unsigned int mc146818_get_time(struct rtc_time *time)
 12{
 13	unsigned char ctrl;
 14	unsigned long flags;
 15	unsigned char century = 0;
 16	bool retry;
 17
 18#ifdef CONFIG_MACH_DECSTATION
 19	unsigned int real_year;
 20#endif
 21
 22again:
 23	spin_lock_irqsave(&rtc_lock, flags);
 24	/* Ensure that the RTC is accessible. Bit 6 must be 0! */
 25	if (WARN_ON_ONCE((CMOS_READ(RTC_VALID) & 0x40) != 0)) {
 26		spin_unlock_irqrestore(&rtc_lock, flags);
 27		memset(time, 0xff, sizeof(*time));
 28		return 0;
 29	}
 30
 31	/*
 32	 * Check whether there is an update in progress during which the
 33	 * readout is unspecified. The maximum update time is ~2ms. Poll
 34	 * every msec for completion.
 35	 *
 36	 * Store the second value before checking UIP so a long lasting NMI
 37	 * which happens to hit after the UIP check cannot make an update
 38	 * cycle invisible.
 39	 */
 40	time->tm_sec = CMOS_READ(RTC_SECONDS);
 41
 42	if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
 43		spin_unlock_irqrestore(&rtc_lock, flags);
 44		mdelay(1);
 45		goto again;
 46	}
 47
 48	/* Revalidate the above readout */
 49	if (time->tm_sec != CMOS_READ(RTC_SECONDS)) {
 50		spin_unlock_irqrestore(&rtc_lock, flags);
 51		goto again;
 52	}
 53
 54	/*
 55	 * Only the values that we read from the RTC are set. We leave
 56	 * tm_wday, tm_yday and tm_isdst untouched. Even though the
 57	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
 58	 * by the RTC when initially set to a non-zero value.
 59	 */
 60	time->tm_min = CMOS_READ(RTC_MINUTES);
 61	time->tm_hour = CMOS_READ(RTC_HOURS);
 62	time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
 63	time->tm_mon = CMOS_READ(RTC_MONTH);
 64	time->tm_year = CMOS_READ(RTC_YEAR);
 65#ifdef CONFIG_MACH_DECSTATION
 66	real_year = CMOS_READ(RTC_DEC_YEAR);
 67#endif
 68#ifdef CONFIG_ACPI
 69	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 70	    acpi_gbl_FADT.century)
 71		century = CMOS_READ(acpi_gbl_FADT.century);
 72#endif
 73	ctrl = CMOS_READ(RTC_CONTROL);
 74	/*
 75	 * Check for the UIP bit again. If it is set now then
 76	 * the above values may contain garbage.
 77	 */
 78	retry = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP;
 79	/*
 80	 * A NMI might have interrupted the above sequence so check whether
 81	 * the seconds value has changed which indicates that the NMI took
 82	 * longer than the UIP bit was set. Unlikely, but possible and
 83	 * there is also virt...
 84	 */
 85	retry |= time->tm_sec != CMOS_READ(RTC_SECONDS);
 86
 87	spin_unlock_irqrestore(&rtc_lock, flags);
 88
 89	if (retry)
 90		goto again;
 91
 92	if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
 93	{
 94		time->tm_sec = bcd2bin(time->tm_sec);
 95		time->tm_min = bcd2bin(time->tm_min);
 96		time->tm_hour = bcd2bin(time->tm_hour);
 97		time->tm_mday = bcd2bin(time->tm_mday);
 98		time->tm_mon = bcd2bin(time->tm_mon);
 99		time->tm_year = bcd2bin(time->tm_year);
100		century = bcd2bin(century);
101	}
102
103#ifdef CONFIG_MACH_DECSTATION
104	time->tm_year += real_year - 72;
105#endif
106
107	if (century > 20)
108		time->tm_year += (century - 19) * 100;
109
110	/*
111	 * Account for differences between how the RTC uses the values
112	 * and how they are defined in a struct rtc_time;
113	 */
114	if (time->tm_year <= 69)
115		time->tm_year += 100;
116
117	time->tm_mon--;
118
119	return RTC_24H;
120}
121EXPORT_SYMBOL_GPL(mc146818_get_time);
122
123/* Set the current date and time in the real time clock. */
124int mc146818_set_time(struct rtc_time *time)
125{
126	unsigned long flags;
127	unsigned char mon, day, hrs, min, sec;
128	unsigned char save_control, save_freq_select;
129	unsigned int yrs;
130#ifdef CONFIG_MACH_DECSTATION
131	unsigned int real_yrs, leap_yr;
132#endif
133	unsigned char century = 0;
134
135	yrs = time->tm_year;
136	mon = time->tm_mon + 1;   /* tm_mon starts at zero */
137	day = time->tm_mday;
138	hrs = time->tm_hour;
139	min = time->tm_min;
140	sec = time->tm_sec;
141
142	if (yrs > 255)	/* They are unsigned */
143		return -EINVAL;
144
145#ifdef CONFIG_MACH_DECSTATION
146	real_yrs = yrs;
147	leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) ||
148			!((yrs + 1900) % 400));
149	yrs = 72;
150
151	/*
152	 * We want to keep the year set to 73 until March
153	 * for non-leap years, so that Feb, 29th is handled
154	 * correctly.
155	 */
156	if (!leap_yr && mon < 3) {
157		real_yrs--;
158		yrs = 73;
159	}
160#endif
161
162#ifdef CONFIG_ACPI
163	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
164	    acpi_gbl_FADT.century) {
165		century = (yrs + 1900) / 100;
166		yrs %= 100;
167	}
168#endif
169
170	/* These limits and adjustments are independent of
171	 * whether the chip is in binary mode or not.
172	 */
173	if (yrs > 169)
174		return -EINVAL;
175
176	if (yrs >= 100)
177		yrs -= 100;
178
179	if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
180	    || RTC_ALWAYS_BCD) {
181		sec = bin2bcd(sec);
182		min = bin2bcd(min);
183		hrs = bin2bcd(hrs);
184		day = bin2bcd(day);
185		mon = bin2bcd(mon);
186		yrs = bin2bcd(yrs);
187		century = bin2bcd(century);
188	}
189
190	spin_lock_irqsave(&rtc_lock, flags);
191	save_control = CMOS_READ(RTC_CONTROL);
192	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
193	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
194	CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
195
196#ifdef CONFIG_MACH_DECSTATION
197	CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
198#endif
199	CMOS_WRITE(yrs, RTC_YEAR);
200	CMOS_WRITE(mon, RTC_MONTH);
201	CMOS_WRITE(day, RTC_DAY_OF_MONTH);
202	CMOS_WRITE(hrs, RTC_HOURS);
203	CMOS_WRITE(min, RTC_MINUTES);
204	CMOS_WRITE(sec, RTC_SECONDS);
205#ifdef CONFIG_ACPI
206	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
207	    acpi_gbl_FADT.century)
208		CMOS_WRITE(century, acpi_gbl_FADT.century);
209#endif
210
211	CMOS_WRITE(save_control, RTC_CONTROL);
212	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
213
214	spin_unlock_irqrestore(&rtc_lock, flags);
215
216	return 0;
217}
218EXPORT_SYMBOL_GPL(mc146818_set_time);