xref: /openbmc/linux/arch/alpha/kernel/time.c (revision 91531b05) 
1 /*
2  *  linux/arch/alpha/kernel/time.c
3  *
4  *  Copyright (C) 1991, 1992, 1995, 1999, 2000  Linus Torvalds
5  *
6  * This file contains the PC-specific time handling details:
7  * reading the RTC at bootup, etc..
8  * 1994-07-02    Alan Modra
9  *	fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
10  * 1995-03-26    Markus Kuhn
11  *      fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887
12  *      precision CMOS clock update
13  * 1997-09-10	Updated NTP code according to technical memorandum Jan '96
14  *		"A Kernel Model for Precision Timekeeping" by Dave Mills
15  * 1997-01-09    Adrian Sun
16  *      use interval timer if CONFIG_RTC=y
17  * 1997-10-29    John Bowman (bowman@math.ualberta.ca)
18  *      fixed tick loss calculation in timer_interrupt
19  *      (round system clock to nearest tick instead of truncating)
20  *      fixed algorithm in time_init for getting time from CMOS clock
21  * 1999-04-16	Thorsten Kranzkowski (dl8bcu@gmx.net)
22  *	fixed algorithm in do_gettimeofday() for calculating the precise time
23  *	from processor cycle counter (now taking lost_ticks into account)
24  * 2000-08-13	Jan-Benedict Glaw <jbglaw@lug-owl.de>
25  * 	Fixed time_init to be aware of epoches != 1900. This prevents
26  * 	booting up in 2048 for me;) Code is stolen from rtc.c.
27  * 2003-06-03	R. Scott Bailey <scott.bailey@eds.com>
28  *	Tighten sanity in time_init from 1% (10,000 PPM) to 250 PPM
29  */
30 #include <linux/errno.h>
31 #include <linux/module.h>
32 #include <linux/sched.h>
33 #include <linux/kernel.h>
34 #include <linux/param.h>
35 #include <linux/string.h>
36 #include <linux/mm.h>
37 #include <linux/delay.h>
38 #include <linux/ioport.h>
39 #include <linux/irq.h>
40 #include <linux/interrupt.h>
41 #include <linux/init.h>
42 #include <linux/bcd.h>
43 #include <linux/profile.h>
44 #include <linux/irq_work.h>
45 
46 #include <asm/uaccess.h>
47 #include <asm/io.h>
48 #include <asm/hwrpb.h>
49 #include <asm/rtc.h>
50 
51 #include <linux/mc146818rtc.h>
52 #include <linux/time.h>
53 #include <linux/timex.h>
54 #include <linux/clocksource.h>
55 
56 #include "proto.h"
57 #include "irq_impl.h"
58 
59 static int set_rtc_mmss(unsigned long);
60 
61 DEFINE_SPINLOCK(rtc_lock);
62 EXPORT_SYMBOL(rtc_lock);
63 
64 #define TICK_SIZE (tick_nsec / 1000)
65 
66 /*
67  * Shift amount by which scaled_ticks_per_cycle is scaled.  Shifting
68  * by 48 gives us 16 bits for HZ while keeping the accuracy good even
69  * for large CPU clock rates.
70  */
71 #define FIX_SHIFT	48
72 
73 /* lump static variables together for more efficient access: */
74 static struct {
75 	/* cycle counter last time it got invoked */
76 	__u32 last_time;
77 	/* ticks/cycle * 2^48 */
78 	unsigned long scaled_ticks_per_cycle;
79 	/* partial unused tick */
80 	unsigned long partial_tick;
81 } state;
82 
83 unsigned long est_cycle_freq;
84 
85 #ifdef CONFIG_IRQ_WORK
86 
87 DEFINE_PER_CPU(u8, irq_work_pending);
88 
89 #define set_irq_work_pending_flag()  __get_cpu_var(irq_work_pending) = 1
90 #define test_irq_work_pending()      __get_cpu_var(irq_work_pending)
91 #define clear_irq_work_pending()     __get_cpu_var(irq_work_pending) = 0
92 
93 void arch_irq_work_raise(void)
94 {
95 	set_irq_work_pending_flag();
96 }
97 
98 #else  /* CONFIG_IRQ_WORK */
99 
100 #define test_irq_work_pending()      0
101 #define clear_irq_work_pending()
102 
103 #endif /* CONFIG_IRQ_WORK */
104 
105 
106 static inline __u32 rpcc(void)
107 {
108 	return __builtin_alpha_rpcc();
109 }
110 
111 int update_persistent_clock(struct timespec now)
112 {
113 	return set_rtc_mmss(now.tv_sec);
114 }
115 
116 void read_persistent_clock(struct timespec *ts)
117 {
118 	unsigned int year, mon, day, hour, min, sec, epoch;
119 
120 	sec = CMOS_READ(RTC_SECONDS);
121 	min = CMOS_READ(RTC_MINUTES);
122 	hour = CMOS_READ(RTC_HOURS);
123 	day = CMOS_READ(RTC_DAY_OF_MONTH);
124 	mon = CMOS_READ(RTC_MONTH);
125 	year = CMOS_READ(RTC_YEAR);
126 
127 	if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
128 		sec = bcd2bin(sec);
129 		min = bcd2bin(min);
130 		hour = bcd2bin(hour);
131 		day = bcd2bin(day);
132 		mon = bcd2bin(mon);
133 		year = bcd2bin(year);
134 	}
135 
136 	/* PC-like is standard; used for year >= 70 */
137 	epoch = 1900;
138 	if (year < 20)
139 		epoch = 2000;
140 	else if (year >= 20 && year < 48)
141 		/* NT epoch */
142 		epoch = 1980;
143 	else if (year >= 48 && year < 70)
144 		/* Digital UNIX epoch */
145 		epoch = 1952;
146 
147 	printk(KERN_INFO "Using epoch = %d\n", epoch);
148 
149 	if ((year += epoch) < 1970)
150 		year += 100;
151 
152 	ts->tv_sec = mktime(year, mon, day, hour, min, sec);
153 	ts->tv_nsec = 0;
154 }
155 
156 
157 
158 /*
159  * timer_interrupt() needs to keep up the real-time clock,
160  * as well as call the "xtime_update()" routine every clocktick
161  */
162 irqreturn_t timer_interrupt(int irq, void *dev)
163 {
164 	unsigned long delta;
165 	__u32 now;
166 	long nticks;
167 
168 #ifndef CONFIG_SMP
169 	/* Not SMP, do kernel PC profiling here.  */
170 	profile_tick(CPU_PROFILING);
171 #endif
172 
173 	/*
174 	 * Calculate how many ticks have passed since the last update,
175 	 * including any previous partial leftover.  Save any resulting
176 	 * fraction for the next pass.
177 	 */
178 	now = rpcc();
179 	delta = now - state.last_time;
180 	state.last_time = now;
181 	delta = delta * state.scaled_ticks_per_cycle + state.partial_tick;
182 	state.partial_tick = delta & ((1UL << FIX_SHIFT) - 1);
183 	nticks = delta >> FIX_SHIFT;
184 
185 	if (nticks)
186 		xtime_update(nticks);
187 
188 	if (test_irq_work_pending()) {
189 		clear_irq_work_pending();
190 		irq_work_run();
191 	}
192 
193 #ifndef CONFIG_SMP
194 	while (nticks--)
195 		update_process_times(user_mode(get_irq_regs()));
196 #endif
197 
198 	return IRQ_HANDLED;
199 }
200 
201 void __init
202 common_init_rtc(void)
203 {
204 	unsigned char x;
205 
206 	/* Reset periodic interrupt frequency.  */
207 	x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
208         /* Test includes known working values on various platforms
209            where 0x26 is wrong; we refuse to change those. */
210 	if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
211 		printk("Setting RTC_FREQ to 1024 Hz (%x)\n", x);
212 		CMOS_WRITE(0x26, RTC_FREQ_SELECT);
213 	}
214 
215 	/* Turn on periodic interrupts.  */
216 	x = CMOS_READ(RTC_CONTROL);
217 	if (!(x & RTC_PIE)) {
218 		printk("Turning on RTC interrupts.\n");
219 		x |= RTC_PIE;
220 		x &= ~(RTC_AIE | RTC_UIE);
221 		CMOS_WRITE(x, RTC_CONTROL);
222 	}
223 	(void) CMOS_READ(RTC_INTR_FLAGS);
224 
225 	outb(0x36, 0x43);	/* pit counter 0: system timer */
226 	outb(0x00, 0x40);
227 	outb(0x00, 0x40);
228 
229 	outb(0xb6, 0x43);	/* pit counter 2: speaker */
230 	outb(0x31, 0x42);
231 	outb(0x13, 0x42);
232 
233 	init_rtc_irq();
234 }
235 
236 unsigned int common_get_rtc_time(struct rtc_time *time)
237 {
238 	return __get_rtc_time(time);
239 }
240 
241 int common_set_rtc_time(struct rtc_time *time)
242 {
243 	return __set_rtc_time(time);
244 }
245 
246 /* Validate a computed cycle counter result against the known bounds for
247    the given processor core.  There's too much brokenness in the way of
248    timing hardware for any one method to work everywhere.  :-(
249 
250    Return 0 if the result cannot be trusted, otherwise return the argument.  */
251 
252 static unsigned long __init
253 validate_cc_value(unsigned long cc)
254 {
255 	static struct bounds {
256 		unsigned int min, max;
257 	} cpu_hz[] __initdata = {
258 		[EV3_CPU]    = {   50000000,  200000000 },	/* guess */
259 		[EV4_CPU]    = {  100000000,  300000000 },
260 		[LCA4_CPU]   = {  100000000,  300000000 },	/* guess */
261 		[EV45_CPU]   = {  200000000,  300000000 },
262 		[EV5_CPU]    = {  250000000,  433000000 },
263 		[EV56_CPU]   = {  333000000,  667000000 },
264 		[PCA56_CPU]  = {  400000000,  600000000 },	/* guess */
265 		[PCA57_CPU]  = {  500000000,  600000000 },	/* guess */
266 		[EV6_CPU]    = {  466000000,  600000000 },
267 		[EV67_CPU]   = {  600000000,  750000000 },
268 		[EV68AL_CPU] = {  750000000,  940000000 },
269 		[EV68CB_CPU] = { 1000000000, 1333333333 },
270 		/* None of the following are shipping as of 2001-11-01.  */
271 		[EV68CX_CPU] = { 1000000000, 1700000000 },	/* guess */
272 		[EV69_CPU]   = { 1000000000, 1700000000 },	/* guess */
273 		[EV7_CPU]    = {  800000000, 1400000000 },	/* guess */
274 		[EV79_CPU]   = { 1000000000, 2000000000 },	/* guess */
275 	};
276 
277 	/* Allow for some drift in the crystal.  10MHz is more than enough.  */
278 	const unsigned int deviation = 10000000;
279 
280 	struct percpu_struct *cpu;
281 	unsigned int index;
282 
283 	cpu = (struct percpu_struct *)((char*)hwrpb + hwrpb->processor_offset);
284 	index = cpu->type & 0xffffffff;
285 
286 	/* If index out of bounds, no way to validate.  */
287 	if (index >= ARRAY_SIZE(cpu_hz))
288 		return cc;
289 
290 	/* If index contains no data, no way to validate.  */
291 	if (cpu_hz[index].max == 0)
292 		return cc;
293 
294 	if (cc < cpu_hz[index].min - deviation
295 	    || cc > cpu_hz[index].max + deviation)
296 		return 0;
297 
298 	return cc;
299 }
300 
301 
302 /*
303  * Calibrate CPU clock using legacy 8254 timer/counter. Stolen from
304  * arch/i386/time.c.
305  */
306 
307 #define CALIBRATE_LATCH	0xffff
308 #define TIMEOUT_COUNT	0x100000
309 
310 static unsigned long __init
311 calibrate_cc_with_pit(void)
312 {
313 	int cc, count = 0;
314 
315 	/* Set the Gate high, disable speaker */
316 	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
317 
318 	/*
319 	 * Now let's take care of CTC channel 2
320 	 *
321 	 * Set the Gate high, program CTC channel 2 for mode 0,
322 	 * (interrupt on terminal count mode), binary count,
323 	 * load 5 * LATCH count, (LSB and MSB) to begin countdown.
324 	 */
325 	outb(0xb0, 0x43);		/* binary, mode 0, LSB/MSB, Ch 2 */
326 	outb(CALIBRATE_LATCH & 0xff, 0x42);	/* LSB of count */
327 	outb(CALIBRATE_LATCH >> 8, 0x42);	/* MSB of count */
328 
329 	cc = rpcc();
330 	do {
331 		count++;
332 	} while ((inb(0x61) & 0x20) == 0 && count < TIMEOUT_COUNT);
333 	cc = rpcc() - cc;
334 
335 	/* Error: ECTCNEVERSET or ECPUTOOFAST.  */
336 	if (count <= 1 || count == TIMEOUT_COUNT)
337 		return 0;
338 
339 	return ((long)cc * PIT_TICK_RATE) / (CALIBRATE_LATCH + 1);
340 }
341 
342 /* The Linux interpretation of the CMOS clock register contents:
343    When the Update-In-Progress (UIP) flag goes from 1 to 0, the
344    RTC registers show the second which has precisely just started.
345    Let's hope other operating systems interpret the RTC the same way.  */
346 
347 static unsigned long __init
348 rpcc_after_update_in_progress(void)
349 {
350 	do { } while (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP));
351 	do { } while (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
352 
353 	return rpcc();
354 }
355 
356 #ifndef CONFIG_SMP
357 /* Until and unless we figure out how to get cpu cycle counters
358    in sync and keep them there, we can't use the rpcc.  */
359 static cycle_t read_rpcc(struct clocksource *cs)
360 {
361 	cycle_t ret = (cycle_t)rpcc();
362 	return ret;
363 }
364 
365 static struct clocksource clocksource_rpcc = {
366 	.name                   = "rpcc",
367 	.rating                 = 300,
368 	.read                   = read_rpcc,
369 	.mask                   = CLOCKSOURCE_MASK(32),
370 	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS
371 };
372 
373 static inline void register_rpcc_clocksource(long cycle_freq)
374 {
375 	clocksource_register_hz(&clocksource_rpcc, cycle_freq);
376 }
377 #else /* !CONFIG_SMP */
378 static inline void register_rpcc_clocksource(long cycle_freq)
379 {
380 }
381 #endif /* !CONFIG_SMP */
382 
383 void __init
384 time_init(void)
385 {
386 	unsigned int cc1, cc2;
387 	unsigned long cycle_freq, tolerance;
388 	long diff;
389 
390 	/* Calibrate CPU clock -- attempt #1.  */
391 	if (!est_cycle_freq)
392 		est_cycle_freq = validate_cc_value(calibrate_cc_with_pit());
393 
394 	cc1 = rpcc();
395 
396 	/* Calibrate CPU clock -- attempt #2.  */
397 	if (!est_cycle_freq) {
398 		cc1 = rpcc_after_update_in_progress();
399 		cc2 = rpcc_after_update_in_progress();
400 		est_cycle_freq = validate_cc_value(cc2 - cc1);
401 		cc1 = cc2;
402 	}
403 
404 	cycle_freq = hwrpb->cycle_freq;
405 	if (est_cycle_freq) {
406 		/* If the given value is within 250 PPM of what we calculated,
407 		   accept it.  Otherwise, use what we found.  */
408 		tolerance = cycle_freq / 4000;
409 		diff = cycle_freq - est_cycle_freq;
410 		if (diff < 0)
411 			diff = -diff;
412 		if ((unsigned long)diff > tolerance) {
413 			cycle_freq = est_cycle_freq;
414 			printk("HWRPB cycle frequency bogus.  "
415 			       "Estimated %lu Hz\n", cycle_freq);
416 		} else {
417 			est_cycle_freq = 0;
418 		}
419 	} else if (! validate_cc_value (cycle_freq)) {
420 		printk("HWRPB cycle frequency bogus, "
421 		       "and unable to estimate a proper value!\n");
422 	}
423 
424 	/* From John Bowman <bowman@math.ualberta.ca>: allow the values
425 	   to settle, as the Update-In-Progress bit going low isn't good
426 	   enough on some hardware.  2ms is our guess; we haven't found
427 	   bogomips yet, but this is close on a 500Mhz box.  */
428 	__delay(1000000);
429 
430 
431 	if (HZ > (1<<16)) {
432 		extern void __you_loose (void);
433 		__you_loose();
434 	}
435 
436 	register_rpcc_clocksource(cycle_freq);
437 
438 	state.last_time = cc1;
439 	state.scaled_ticks_per_cycle
440 		= ((unsigned long) HZ << FIX_SHIFT) / cycle_freq;
441 	state.partial_tick = 0L;
442 
443 	/* Startup the timer source. */
444 	alpha_mv.init_rtc();
445 }
446 
447 /*
448  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
449  * called 500 ms after the second nowtime has started, because when
450  * nowtime is written into the registers of the CMOS clock, it will
451  * jump to the next second precisely 500 ms later. Check the Motorola
452  * MC146818A or Dallas DS12887 data sheet for details.
453  *
454  * BUG: This routine does not handle hour overflow properly; it just
455  *      sets the minutes. Usually you won't notice until after reboot!
456  */
457 
458 
459 static int
460 set_rtc_mmss(unsigned long nowtime)
461 {
462 	int retval = 0;
463 	int real_seconds, real_minutes, cmos_minutes;
464 	unsigned char save_control, save_freq_select;
465 
466 	/* irq are locally disabled here */
467 	spin_lock(&rtc_lock);
468 	/* Tell the clock it's being set */
469 	save_control = CMOS_READ(RTC_CONTROL);
470 	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
471 
472 	/* Stop and reset prescaler */
473 	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
474 	CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
475 
476 	cmos_minutes = CMOS_READ(RTC_MINUTES);
477 	if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
478 		cmos_minutes = bcd2bin(cmos_minutes);
479 
480 	/*
481 	 * since we're only adjusting minutes and seconds,
482 	 * don't interfere with hour overflow. This avoids
483 	 * messing with unknown time zones but requires your
484 	 * RTC not to be off by more than 15 minutes
485 	 */
486 	real_seconds = nowtime % 60;
487 	real_minutes = nowtime / 60;
488 	if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1) {
489 		/* correct for half hour time zone */
490 		real_minutes += 30;
491 	}
492 	real_minutes %= 60;
493 
494 	if (abs(real_minutes - cmos_minutes) < 30) {
495 		if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
496 			real_seconds = bin2bcd(real_seconds);
497 			real_minutes = bin2bcd(real_minutes);
498 		}
499 		CMOS_WRITE(real_seconds,RTC_SECONDS);
500 		CMOS_WRITE(real_minutes,RTC_MINUTES);
501 	} else {
502 		printk_once(KERN_NOTICE
503 		       "set_rtc_mmss: can't update from %d to %d\n",
504 		       cmos_minutes, real_minutes);
505  		retval = -1;
506 	}
507 
508 	/* The following flags have to be released exactly in this order,
509 	 * otherwise the DS12887 (popular MC146818A clone with integrated
510 	 * battery and quartz) will not reset the oscillator and will not
511 	 * update precisely 500 ms later. You won't find this mentioned in
512 	 * the Dallas Semiconductor data sheets, but who believes data
513 	 * sheets anyway ...                           -- Markus Kuhn
514 	 */
515 	CMOS_WRITE(save_control, RTC_CONTROL);
516 	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
517 	spin_unlock(&rtc_lock);
518 
519 	return retval;
520 }
521