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 */
mc146818_is_updating(void)14 static 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
mc146818_get_time(struct rtc_time * time)25 unsigned 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 }
100 EXPORT_SYMBOL_GPL(mc146818_get_time);
101
102 /* Set the current date and time in the real time clock. */
mc146818_set_time(struct rtc_time * time)103 int 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 }
199 EXPORT_SYMBOL_GPL(mc146818_set_time);
200