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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#define UIP_RECHECK_DELAY 100 /* usec */
12#define UIP_RECHECK_DELAY_MS (USEC_PER_MSEC / UIP_RECHECK_DELAY)
13#define UIP_RECHECK_LOOPS_MS(x) (x / UIP_RECHECK_DELAY_MS)
14
15/*
16 * Execute a function while the UIP (Update-in-progress) bit of the RTC is
17 * unset. The timeout is configurable by the caller in ms.
18 *
19 * Warning: callback may be executed more then once.
20 */
21bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
22 int timeout,
23 void *param)
24{
25 int i;
26 unsigned long flags;
27 unsigned char seconds;
28
29 for (i = 0; UIP_RECHECK_LOOPS_MS(i) < timeout; i++) {
30 spin_lock_irqsave(&rtc_lock, flags);
31
32 /*
33 * Check whether there is an update in progress during which the
34 * readout is unspecified. The maximum update time is ~2ms. Poll
35 * for completion.
36 *
37 * Store the second value before checking UIP so a long lasting
38 * NMI which happens to hit after the UIP check cannot make
39 * an update cycle invisible.
40 */
41 seconds = CMOS_READ(RTC_SECONDS);
42
43 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
44 spin_unlock_irqrestore(&rtc_lock, flags);
45 udelay(UIP_RECHECK_DELAY);
46 continue;
47 }
48
49 /* Revalidate the above readout */
50 if (seconds != CMOS_READ(RTC_SECONDS)) {
51 spin_unlock_irqrestore(&rtc_lock, flags);
52 continue;
53 }
54
55 if (callback)
56 callback(seconds, param);
57
58 /*
59 * Check for the UIP bit again. If it is set now then
60 * the above values may contain garbage.
61 */
62 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
63 spin_unlock_irqrestore(&rtc_lock, flags);
64 udelay(UIP_RECHECK_DELAY);
65 continue;
66 }
67
68 /*
69 * A NMI might have interrupted the above sequence so check
70 * whether the seconds value has changed which indicates that
71 * the NMI took longer than the UIP bit was set. Unlikely, but
72 * possible and there is also virt...
73 */
74 if (seconds != CMOS_READ(RTC_SECONDS)) {
75 spin_unlock_irqrestore(&rtc_lock, flags);
76 continue;
77 }
78 spin_unlock_irqrestore(&rtc_lock, flags);
79
80 if (UIP_RECHECK_LOOPS_MS(i) >= 100)
81 pr_warn("Reading current time from RTC took around %li ms\n",
82 UIP_RECHECK_LOOPS_MS(i));
83
84 return true;
85 }
86 return false;
87}
88EXPORT_SYMBOL_GPL(mc146818_avoid_UIP);
89
90/*
91 * If the UIP (Update-in-progress) bit of the RTC is set for more then
92 * 10ms, the RTC is apparently broken or not present.
93 */
94bool mc146818_does_rtc_work(void)
95{
96 return mc146818_avoid_UIP(NULL, 1000, NULL);
97}
98EXPORT_SYMBOL_GPL(mc146818_does_rtc_work);
99
100struct mc146818_get_time_callback_param {
101 struct rtc_time *time;
102 unsigned char ctrl;
103#ifdef CONFIG_ACPI
104 unsigned char century;
105#endif
106#ifdef CONFIG_MACH_DECSTATION
107 unsigned int real_year;
108#endif
109};
110
111static void mc146818_get_time_callback(unsigned char seconds, void *param_in)
112{
113 struct mc146818_get_time_callback_param *p = param_in;
114
115 /*
116 * Only the values that we read from the RTC are set. We leave
117 * tm_wday, tm_yday and tm_isdst untouched. Even though the
118 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
119 * by the RTC when initially set to a non-zero value.
120 */
121 p->time->tm_sec = seconds;
122 p->time->tm_min = CMOS_READ(RTC_MINUTES);
123 p->time->tm_hour = CMOS_READ(RTC_HOURS);
124 p->time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
125 p->time->tm_mon = CMOS_READ(RTC_MONTH);
126 p->time->tm_year = CMOS_READ(RTC_YEAR);
127#ifdef CONFIG_MACH_DECSTATION
128 p->real_year = CMOS_READ(RTC_DEC_YEAR);
129#endif
130#ifdef CONFIG_ACPI
131 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
132 acpi_gbl_FADT.century) {
133 p->century = CMOS_READ(acpi_gbl_FADT.century);
134 } else {
135 p->century = 0;
136 }
137#endif
138
139 p->ctrl = CMOS_READ(RTC_CONTROL);
140}
141
142/**
143 * mc146818_get_time - Get the current time from the RTC
144 * @time: pointer to struct rtc_time to store the current time
145 * @timeout: timeout value in ms
146 *
147 * This function reads the current time from the RTC and stores it in the
148 * provided struct rtc_time. The timeout parameter specifies the maximum
149 * time to wait for the RTC to become ready.
150 *
151 * Return: 0 on success, -ETIMEDOUT if the RTC did not become ready within
152 * the specified timeout, or another error code if an error occurred.
153 */
154int mc146818_get_time(struct rtc_time *time, int timeout)
155{
156 struct mc146818_get_time_callback_param p = {
157 .time = time
158 };
159
160 if (!mc146818_avoid_UIP(mc146818_get_time_callback, timeout, &p)) {
161 memset(time, 0, sizeof(*time));
162 return -ETIMEDOUT;
163 }
164
165 if (!(p.ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
166 {
167 time->tm_sec = bcd2bin(time->tm_sec);
168 time->tm_min = bcd2bin(time->tm_min);
169 time->tm_hour = bcd2bin(time->tm_hour);
170 time->tm_mday = bcd2bin(time->tm_mday);
171 time->tm_mon = bcd2bin(time->tm_mon);
172 time->tm_year = bcd2bin(time->tm_year);
173#ifdef CONFIG_ACPI
174 p.century = bcd2bin(p.century);
175#endif
176 }
177
178#ifdef CONFIG_MACH_DECSTATION
179 time->tm_year += p.real_year - 72;
180#endif
181
182#ifdef CONFIG_ACPI
183 if (p.century > 19)
184 time->tm_year += (p.century - 19) * 100;
185#endif
186
187 /*
188 * Account for differences between how the RTC uses the values
189 * and how they are defined in a struct rtc_time;
190 */
191 if (time->tm_year <= 69)
192 time->tm_year += 100;
193
194 time->tm_mon--;
195
196 return 0;
197}
198EXPORT_SYMBOL_GPL(mc146818_get_time);
199
200/* AMD systems don't allow access to AltCentury with DV1 */
201static bool apply_amd_register_a_behavior(void)
202{
203#ifdef CONFIG_X86
204 if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
205 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
206 return true;
207#endif
208 return false;
209}
210
211/* Set the current date and time in the real time clock. */
212int mc146818_set_time(struct rtc_time *time)
213{
214 unsigned long flags;
215 unsigned char mon, day, hrs, min, sec;
216 unsigned char save_control, save_freq_select;
217 unsigned int yrs;
218#ifdef CONFIG_MACH_DECSTATION
219 unsigned int real_yrs;
220#endif
221 unsigned char century = 0;
222
223 yrs = time->tm_year;
224 mon = time->tm_mon + 1; /* tm_mon starts at zero */
225 day = time->tm_mday;
226 hrs = time->tm_hour;
227 min = time->tm_min;
228 sec = time->tm_sec;
229
230 if (yrs > 255) /* They are unsigned */
231 return -EINVAL;
232
233#ifdef CONFIG_MACH_DECSTATION
234 real_yrs = yrs;
235 yrs = 72;
236
237 /*
238 * We want to keep the year set to 73 until March
239 * for non-leap years, so that Feb, 29th is handled
240 * correctly.
241 */
242 if (!is_leap_year(real_yrs + 1900) && mon < 3) {
243 real_yrs--;
244 yrs = 73;
245 }
246#endif
247
248#ifdef CONFIG_ACPI
249 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
250 acpi_gbl_FADT.century) {
251 century = (yrs + 1900) / 100;
252 yrs %= 100;
253 }
254#endif
255
256 /* These limits and adjustments are independent of
257 * whether the chip is in binary mode or not.
258 */
259 if (yrs > 169)
260 return -EINVAL;
261
262 if (yrs >= 100)
263 yrs -= 100;
264
265 spin_lock_irqsave(&rtc_lock, flags);
266 save_control = CMOS_READ(RTC_CONTROL);
267 spin_unlock_irqrestore(&rtc_lock, flags);
268 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
269 sec = bin2bcd(sec);
270 min = bin2bcd(min);
271 hrs = bin2bcd(hrs);
272 day = bin2bcd(day);
273 mon = bin2bcd(mon);
274 yrs = bin2bcd(yrs);
275 century = bin2bcd(century);
276 }
277
278 spin_lock_irqsave(&rtc_lock, flags);
279 save_control = CMOS_READ(RTC_CONTROL);
280 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
281 save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
282 if (apply_amd_register_a_behavior())
283 CMOS_WRITE((save_freq_select & ~RTC_AMD_BANK_SELECT), RTC_FREQ_SELECT);
284 else
285 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
286
287#ifdef CONFIG_MACH_DECSTATION
288 CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
289#endif
290 CMOS_WRITE(yrs, RTC_YEAR);
291 CMOS_WRITE(mon, RTC_MONTH);
292 CMOS_WRITE(day, RTC_DAY_OF_MONTH);
293 CMOS_WRITE(hrs, RTC_HOURS);
294 CMOS_WRITE(min, RTC_MINUTES);
295 CMOS_WRITE(sec, RTC_SECONDS);
296#ifdef CONFIG_ACPI
297 if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
298 acpi_gbl_FADT.century)
299 CMOS_WRITE(century, acpi_gbl_FADT.century);
300#endif
301
302 CMOS_WRITE(save_control, RTC_CONTROL);
303 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
304
305 spin_unlock_irqrestore(&rtc_lock, flags);
306
307 return 0;
308}
309EXPORT_SYMBOL_GPL(mc146818_set_time);