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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 * Execute a function while the UIP (Update-in-progress) bit of the RTC is
13 * unset.
14 *
15 * Warning: callback may be executed more then once.
16 */
17bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
18 void *param)
19{
20 int i;
21 unsigned long flags;
22 unsigned char seconds;
23
24 for (i = 0; i < 100; i++) {
25 spin_lock_irqsave(&rtc_lock, flags);
26
27 /*
28 * Check whether there is an update in progress during which the
29 * readout is unspecified. The maximum update time is ~2ms. Poll
30 * every 100 usec for completion.
31 *
32 * Store the second value before checking UIP so a long lasting
33 * NMI which happens to hit after the UIP check cannot make
34 * an update cycle invisible.
35 */
36 seconds = CMOS_READ(RTC_SECONDS);
37
38 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
39 spin_unlock_irqrestore(&rtc_lock, flags);
40 udelay(100);
41 continue;
42 }
43
44 /* Revalidate the above readout */
45 if (seconds != CMOS_READ(RTC_SECONDS)) {
46 spin_unlock_irqrestore(&rtc_lock, flags);
47 continue;
48 }
49
50 if (callback)
51 callback(seconds, param);
52
53 /*
54 * Check for the UIP bit again. If it is set now then
55 * the above values may contain garbage.
56 */
57 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
58 spin_unlock_irqrestore(&rtc_lock, flags);
59 udelay(100);
60 continue;
61 }
62
63 /*
64 * A NMI might have interrupted the above sequence so check
65 * whether the seconds value has changed which indicates that
66 * the NMI took longer than the UIP bit was set. Unlikely, but
67 * possible and there is also virt...
68 */
69 if (seconds != CMOS_READ(RTC_SECONDS)) {
70 spin_unlock_irqrestore(&rtc_lock, flags);
71 continue;
72 }
73 spin_unlock_irqrestore(&rtc_lock, flags);
74
75 return true;
76 }
77 return false;
78}
79EXPORT_SYMBOL_GPL(mc146818_avoid_UIP);
80
81/*
82 * If the UIP (Update-in-progress) bit of the RTC is set for more then
83 * 10ms, the RTC is apparently broken or not present.
84 */
85bool mc146818_does_rtc_work(void)
86{
87 return mc146818_avoid_UIP(NULL, NULL);
88}
89EXPORT_SYMBOL_GPL(mc146818_does_rtc_work);
90
91struct mc146818_get_time_callback_param {
92 struct rtc_time *time;
93 unsigned char ctrl;
94#ifdef CONFIG_ACPI
95 unsigned char century;
96#endif
97#ifdef CONFIG_MACH_DECSTATION
98 unsigned int real_year;
99#endif
100};
101
102static void mc146818_get_time_callback(unsigned char seconds, void *param_in)
103{
104 struct mc146818_get_time_callback_param *p = param_in;
105
106 /*
107 * Only the values that we read from the RTC are set. We leave
108 * tm_wday, tm_yday and tm_isdst untouched. Even though the
109 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
110 * by the RTC when initially set to a non-zero value.
111 */
112 p->time->tm_sec = seconds;
113 p->time->tm_min = CMOS_READ(RTC_MINUTES);
114 p->time->tm_hour = CMOS_READ(RTC_HOURS);
115 p->time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
116 p->time->tm_mon = CMOS_READ(RTC_MONTH);
117 p->time->tm_year = CMOS_READ(RTC_YEAR);
118#ifdef CONFIG_MACH_DECSTATION
119 p->real_year = CMOS_READ(RTC_DEC_YEAR);
120#endif
121#ifdef CONFIG_ACPI
122 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
123 acpi_gbl_FADT.century) {
124 p->century = CMOS_READ(acpi_gbl_FADT.century);
125 } else {
126 p->century = 0;
127 }
128#endif
129
130 p->ctrl = CMOS_READ(RTC_CONTROL);
131}
132
133int mc146818_get_time(struct rtc_time *time)
134{
135 struct mc146818_get_time_callback_param p = {
136 .time = time
137 };
138
139 if (!mc146818_avoid_UIP(mc146818_get_time_callback, &p)) {
140 memset(time, 0, sizeof(*time));
141 return -EIO;
142 }
143
144 if (!(p.ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
145 {
146 time->tm_sec = bcd2bin(time->tm_sec);
147 time->tm_min = bcd2bin(time->tm_min);
148 time->tm_hour = bcd2bin(time->tm_hour);
149 time->tm_mday = bcd2bin(time->tm_mday);
150 time->tm_mon = bcd2bin(time->tm_mon);
151 time->tm_year = bcd2bin(time->tm_year);
152#ifdef CONFIG_ACPI
153 p.century = bcd2bin(p.century);
154#endif
155 }
156
157#ifdef CONFIG_MACH_DECSTATION
158 time->tm_year += p.real_year - 72;
159#endif
160
161#ifdef CONFIG_ACPI
162 if (p.century > 19)
163 time->tm_year += (p.century - 19) * 100;
164#endif
165
166 /*
167 * Account for differences between how the RTC uses the values
168 * and how they are defined in a struct rtc_time;
169 */
170 if (time->tm_year <= 69)
171 time->tm_year += 100;
172
173 time->tm_mon--;
174
175 return 0;
176}
177EXPORT_SYMBOL_GPL(mc146818_get_time);
178
179/* AMD systems don't allow access to AltCentury with DV1 */
180static bool apply_amd_register_a_behavior(void)
181{
182#ifdef CONFIG_X86
183 if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
184 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
185 return true;
186#endif
187 return false;
188}
189
190/* Set the current date and time in the real time clock. */
191int mc146818_set_time(struct rtc_time *time)
192{
193 unsigned long flags;
194 unsigned char mon, day, hrs, min, sec;
195 unsigned char save_control, save_freq_select;
196 unsigned int yrs;
197#ifdef CONFIG_MACH_DECSTATION
198 unsigned int real_yrs, leap_yr;
199#endif
200 unsigned char century = 0;
201
202 yrs = time->tm_year;
203 mon = time->tm_mon + 1; /* tm_mon starts at zero */
204 day = time->tm_mday;
205 hrs = time->tm_hour;
206 min = time->tm_min;
207 sec = time->tm_sec;
208
209 if (yrs > 255) /* They are unsigned */
210 return -EINVAL;
211
212#ifdef CONFIG_MACH_DECSTATION
213 real_yrs = yrs;
214 leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) ||
215 !((yrs + 1900) % 400));
216 yrs = 72;
217
218 /*
219 * We want to keep the year set to 73 until March
220 * for non-leap years, so that Feb, 29th is handled
221 * correctly.
222 */
223 if (!leap_yr && mon < 3) {
224 real_yrs--;
225 yrs = 73;
226 }
227#endif
228
229#ifdef CONFIG_ACPI
230 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
231 acpi_gbl_FADT.century) {
232 century = (yrs + 1900) / 100;
233 yrs %= 100;
234 }
235#endif
236
237 /* These limits and adjustments are independent of
238 * whether the chip is in binary mode or not.
239 */
240 if (yrs > 169)
241 return -EINVAL;
242
243 if (yrs >= 100)
244 yrs -= 100;
245
246 spin_lock_irqsave(&rtc_lock, flags);
247 save_control = CMOS_READ(RTC_CONTROL);
248 spin_unlock_irqrestore(&rtc_lock, flags);
249 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
250 sec = bin2bcd(sec);
251 min = bin2bcd(min);
252 hrs = bin2bcd(hrs);
253 day = bin2bcd(day);
254 mon = bin2bcd(mon);
255 yrs = bin2bcd(yrs);
256 century = bin2bcd(century);
257 }
258
259 spin_lock_irqsave(&rtc_lock, flags);
260 save_control = CMOS_READ(RTC_CONTROL);
261 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
262 save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
263 if (apply_amd_register_a_behavior())
264 CMOS_WRITE((save_freq_select & ~RTC_AMD_BANK_SELECT), RTC_FREQ_SELECT);
265 else
266 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
267
268#ifdef CONFIG_MACH_DECSTATION
269 CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
270#endif
271 CMOS_WRITE(yrs, RTC_YEAR);
272 CMOS_WRITE(mon, RTC_MONTH);
273 CMOS_WRITE(day, RTC_DAY_OF_MONTH);
274 CMOS_WRITE(hrs, RTC_HOURS);
275 CMOS_WRITE(min, RTC_MINUTES);
276 CMOS_WRITE(sec, RTC_SECONDS);
277#ifdef CONFIG_ACPI
278 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
279 acpi_gbl_FADT.century)
280 CMOS_WRITE(century, acpi_gbl_FADT.century);
281#endif
282
283 CMOS_WRITE(save_control, RTC_CONTROL);
284 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
285
286 spin_unlock_irqrestore(&rtc_lock, flags);
287
288 return 0;
289}
290EXPORT_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
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);