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 | */ |
17 | bool 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(lock: &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(lock: &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(lock: &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(lock: &rtc_lock, flags); |
71 | continue; |
72 | } |
73 | spin_unlock_irqrestore(lock: &rtc_lock, flags); |
74 | |
75 | return true; |
76 | } |
77 | return false; |
78 | } |
79 | EXPORT_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 | */ |
85 | bool mc146818_does_rtc_work(void) |
86 | { |
87 | return mc146818_avoid_UIP(NULL, NULL); |
88 | } |
89 | EXPORT_SYMBOL_GPL(mc146818_does_rtc_work); |
90 | |
91 | struct 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 | |
102 | static 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 | |
133 | int 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 | } |
177 | EXPORT_SYMBOL_GPL(mc146818_get_time); |
178 | |
179 | /* AMD systems don't allow access to AltCentury with DV1 */ |
180 | static 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. */ |
191 | int 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(lock: &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(lock: &rtc_lock, flags); |
287 | |
288 | return 0; |
289 | } |
290 | EXPORT_SYMBOL_GPL(mc146818_set_time); |
291 | |