summaryrefslogtreecommitdiff
path: root/drivers/rtc/rtc-mc146818-lib.c
blob: 651bf3c279c7462151096cf8565a56fffab9052d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/bcd.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <linux/mc146818rtc.h>

#ifdef CONFIG_ACPI
#include <linux/acpi.h>
#endif

#define UIP_RECHECK_DELAY		100	/* usec */
#define UIP_RECHECK_DELAY_MS		(USEC_PER_MSEC / UIP_RECHECK_DELAY)
#define UIP_RECHECK_LOOPS_MS(x)		(x / UIP_RECHECK_DELAY_MS)

/*
 * Execute a function while the UIP (Update-in-progress) bit of the RTC is
 * unset. The timeout is configurable by the caller in ms.
 *
 * Warning: callback may be executed more then once.
 */
bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
			int timeout,
			void *param)
{
	int i;
	unsigned long flags;
	unsigned char seconds;

	for (i = 0; UIP_RECHECK_LOOPS_MS(i) < timeout; i++) {
		spin_lock_irqsave(&rtc_lock, flags);

		/*
		 * Check whether there is an update in progress during which the
		 * readout is unspecified. The maximum update time is ~2ms. Poll
		 * for completion.
		 *
		 * Store the second value before checking UIP so a long lasting
		 * NMI which happens to hit after the UIP check cannot make
		 * an update cycle invisible.
		 */
		seconds = CMOS_READ(RTC_SECONDS);

		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
			spin_unlock_irqrestore(&rtc_lock, flags);
			udelay(UIP_RECHECK_DELAY);
			continue;
		}

		/* Revalidate the above readout */
		if (seconds != CMOS_READ(RTC_SECONDS)) {
			spin_unlock_irqrestore(&rtc_lock, flags);
			continue;
		}

		if (callback)
			callback(seconds, param);

		/*
		 * Check for the UIP bit again. If it is set now then
		 * the above values may contain garbage.
		 */
		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
			spin_unlock_irqrestore(&rtc_lock, flags);
			udelay(UIP_RECHECK_DELAY);
			continue;
		}

		/*
		 * A NMI might have interrupted the above sequence so check
		 * whether the seconds value has changed which indicates that
		 * the NMI took longer than the UIP bit was set. Unlikely, but
		 * possible and there is also virt...
		 */
		if (seconds != CMOS_READ(RTC_SECONDS)) {
			spin_unlock_irqrestore(&rtc_lock, flags);
			continue;
		}
		spin_unlock_irqrestore(&rtc_lock, flags);

		if (UIP_RECHECK_LOOPS_MS(i) >= 100)
			pr_warn("Reading current time from RTC took around %li ms\n",
				UIP_RECHECK_LOOPS_MS(i));

		return true;
	}
	return false;
}
EXPORT_SYMBOL_GPL(mc146818_avoid_UIP);

/*
 * If the UIP (Update-in-progress) bit of the RTC is set for more then
 * 10ms, the RTC is apparently broken or not present.
 */
bool mc146818_does_rtc_work(void)
{
	return mc146818_avoid_UIP(NULL, 1000, NULL);
}
EXPORT_SYMBOL_GPL(mc146818_does_rtc_work);

struct mc146818_get_time_callback_param {
	struct rtc_time *time;
	unsigned char ctrl;
#ifdef CONFIG_ACPI
	unsigned char century;
#endif
#ifdef CONFIG_MACH_DECSTATION
	unsigned int real_year;
#endif
};

static void mc146818_get_time_callback(unsigned char seconds, void *param_in)
{
	struct mc146818_get_time_callback_param *p = param_in;

	/*
	 * Only the values that we read from the RTC are set. We leave
	 * tm_wday, tm_yday and tm_isdst untouched. Even though the
	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
	 * by the RTC when initially set to a non-zero value.
	 */
	p->time->tm_sec = seconds;
	p->time->tm_min = CMOS_READ(RTC_MINUTES);
	p->time->tm_hour = CMOS_READ(RTC_HOURS);
	p->time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
	p->time->tm_mon = CMOS_READ(RTC_MONTH);
	p->time->tm_year = CMOS_READ(RTC_YEAR);
#ifdef CONFIG_MACH_DECSTATION
	p->real_year = CMOS_READ(RTC_DEC_YEAR);
#endif
#ifdef CONFIG_ACPI
	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
	    acpi_gbl_FADT.century) {
		p->century = CMOS_READ(acpi_gbl_FADT.century);
	} else {
		p->century = 0;
	}
#endif

	p->ctrl = CMOS_READ(RTC_CONTROL);
}

/**
 * mc146818_get_time - Get the current time from the RTC
 * @time: pointer to struct rtc_time to store the current time
 * @timeout: timeout value in ms
 *
 * This function reads the current time from the RTC and stores it in the
 * provided struct rtc_time. The timeout parameter specifies the maximum
 * time to wait for the RTC to become ready.
 *
 * Return: 0 on success, -ETIMEDOUT if the RTC did not become ready within
 * the specified timeout, or another error code if an error occurred.
 */
int mc146818_get_time(struct rtc_time *time, int timeout)
{
	struct mc146818_get_time_callback_param p = {
		.time = time
	};

	if (!mc146818_avoid_UIP(mc146818_get_time_callback, timeout, &p)) {
		memset(time, 0, sizeof(*time));
		return -ETIMEDOUT;
	}

	if (!(p.ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
	{
		time->tm_sec = bcd2bin(time->tm_sec);
		time->tm_min = bcd2bin(time->tm_min);
		time->tm_hour = bcd2bin(time->tm_hour);
		time->tm_mday = bcd2bin(time->tm_mday);
		time->tm_mon = bcd2bin(time->tm_mon);
		time->tm_year = bcd2bin(time->tm_year);
#ifdef CONFIG_ACPI
		p.century = bcd2bin(p.century);
#endif
	}

#ifdef CONFIG_MACH_DECSTATION
	time->tm_year += p.real_year - 72;
#endif

#ifdef CONFIG_ACPI
	if (p.century > 19)
		time->tm_year += (p.century - 19) * 100;
#endif

	/*
	 * Account for differences between how the RTC uses the values
	 * and how they are defined in a struct rtc_time;
	 */
	if (time->tm_year <= 69)
		time->tm_year += 100;

	time->tm_mon--;

	return 0;
}
EXPORT_SYMBOL_GPL(mc146818_get_time);

/* AMD systems don't allow access to AltCentury with DV1 */
static bool apply_amd_register_a_behavior(void)
{
#ifdef CONFIG_X86
	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
	    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
		return true;
#endif
	return false;
}

/* Set the current date and time in the real time clock. */
int mc146818_set_time(struct rtc_time *time)
{
	unsigned long flags;
	unsigned char mon, day, hrs, min, sec;
	unsigned char save_control, save_freq_select;
	unsigned int yrs;
#ifdef CONFIG_MACH_DECSTATION
	unsigned int real_yrs, leap_yr;
#endif
	unsigned char century = 0;

	yrs = time->tm_year;
	mon = time->tm_mon + 1;   /* tm_mon starts at zero */
	day = time->tm_mday;
	hrs = time->tm_hour;
	min = time->tm_min;
	sec = time->tm_sec;

	if (yrs > 255)	/* They are unsigned */
		return -EINVAL;

#ifdef CONFIG_MACH_DECSTATION
	real_yrs = yrs;
	leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) ||
			!((yrs + 1900) % 400));
	yrs = 72;

	/*
	 * We want to keep the year set to 73 until March
	 * for non-leap years, so that Feb, 29th is handled
	 * correctly.
	 */
	if (!leap_yr && mon < 3) {
		real_yrs--;
		yrs = 73;
	}
#endif

#ifdef CONFIG_ACPI
	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
	    acpi_gbl_FADT.century) {
		century = (yrs + 1900) / 100;
		yrs %= 100;
	}
#endif

	/* These limits and adjustments are independent of
	 * whether the chip is in binary mode or not.
	 */
	if (yrs > 169)
		return -EINVAL;

	if (yrs >= 100)
		yrs -= 100;

	spin_lock_irqsave(&rtc_lock, flags);
	save_control = CMOS_READ(RTC_CONTROL);
	spin_unlock_irqrestore(&rtc_lock, flags);
	if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
		sec = bin2bcd(sec);
		min = bin2bcd(min);
		hrs = bin2bcd(hrs);
		day = bin2bcd(day);
		mon = bin2bcd(mon);
		yrs = bin2bcd(yrs);
		century = bin2bcd(century);
	}

	spin_lock_irqsave(&rtc_lock, flags);
	save_control = CMOS_READ(RTC_CONTROL);
	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
	if (apply_amd_register_a_behavior())
		CMOS_WRITE((save_freq_select & ~RTC_AMD_BANK_SELECT), RTC_FREQ_SELECT);
	else
		CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);

#ifdef CONFIG_MACH_DECSTATION
	CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
#endif
	CMOS_WRITE(yrs, RTC_YEAR);
	CMOS_WRITE(mon, RTC_MONTH);
	CMOS_WRITE(day, RTC_DAY_OF_MONTH);
	CMOS_WRITE(hrs, RTC_HOURS);
	CMOS_WRITE(min, RTC_MINUTES);
	CMOS_WRITE(sec, RTC_SECONDS);
#ifdef CONFIG_ACPI
	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
	    acpi_gbl_FADT.century)
		CMOS_WRITE(century, acpi_gbl_FADT.century);
#endif

	CMOS_WRITE(save_control, RTC_CONTROL);
	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);

	spin_unlock_irqrestore(&rtc_lock, flags);

	return 0;
}
EXPORT_SYMBOL_GPL(mc146818_set_time);