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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);
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);