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
mc146818_get_time(struct rtc_time * time)11 unsigned 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
22 again:
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 }
121 EXPORT_SYMBOL_GPL(mc146818_get_time);
122
123 /* Set the current date and time in the real time clock. */
mc146818_set_time(struct rtc_time * time)124 int 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 }
218 EXPORT_SYMBOL_GPL(mc146818_set_time);
219