xref: /openbmc/linux/arch/alpha/kernel/time.c (revision 3e26a691) 
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 clocksource time handling.
7  * 1997-09-10	Updated NTP code according to technical memorandum Jan '96
8  *		"A Kernel Model for Precision Timekeeping" by Dave Mills
9  * 1997-01-09    Adrian Sun
10  *      use interval timer if CONFIG_RTC=y
11  * 1997-10-29    John Bowman (bowman@math.ualberta.ca)
12  *      fixed tick loss calculation in timer_interrupt
13  *      (round system clock to nearest tick instead of truncating)
14  *      fixed algorithm in time_init for getting time from CMOS clock
15  * 1999-04-16	Thorsten Kranzkowski (dl8bcu@gmx.net)
16  *	fixed algorithm in do_gettimeofday() for calculating the precise time
17  *	from processor cycle counter (now taking lost_ticks into account)
18  * 2003-06-03	R. Scott Bailey <scott.bailey@eds.com>
19  *	Tighten sanity in time_init from 1% (10,000 PPM) to 250 PPM
20  */
21 #include <linux/errno.h>
22 #include <linux/module.h>
23 #include <linux/sched.h>
24 #include <linux/kernel.h>
25 #include <linux/param.h>
26 #include <linux/string.h>
27 #include <linux/mm.h>
28 #include <linux/delay.h>
29 #include <linux/ioport.h>
30 #include <linux/irq.h>
31 #include <linux/interrupt.h>
32 #include <linux/init.h>
33 #include <linux/bcd.h>
34 #include <linux/profile.h>
35 #include <linux/irq_work.h>
36 
37 #include <asm/uaccess.h>
38 #include <asm/io.h>
39 #include <asm/hwrpb.h>
40 
41 #include <linux/mc146818rtc.h>
42 #include <linux/time.h>
43 #include <linux/timex.h>
44 #include <linux/clocksource.h>
45 #include <linux/clockchips.h>
46 
47 #include "proto.h"
48 #include "irq_impl.h"
49 
50 DEFINE_SPINLOCK(rtc_lock);
51 EXPORT_SYMBOL(rtc_lock);
52 
53 unsigned long est_cycle_freq;
54 
55 #ifdef CONFIG_IRQ_WORK
56 
57 DEFINE_PER_CPU(u8, irq_work_pending);
58 
59 #define set_irq_work_pending_flag()  __this_cpu_write(irq_work_pending, 1)
60 #define test_irq_work_pending()      __this_cpu_read(irq_work_pending)
61 #define clear_irq_work_pending()     __this_cpu_write(irq_work_pending, 0)
62 
63 void arch_irq_work_raise(void)
64 {
65 	set_irq_work_pending_flag();
66 }
67 
68 #else  /* CONFIG_IRQ_WORK */
69 
70 #define test_irq_work_pending()      0
71 #define clear_irq_work_pending()
72 
73 #endif /* CONFIG_IRQ_WORK */
74 
75 
76 static inline __u32 rpcc(void)
77 {
78 	return __builtin_alpha_rpcc();
79 }
80 
81 
82 
83 /*
84  * The RTC as a clock_event_device primitive.
85  */
86 
87 static DEFINE_PER_CPU(struct clock_event_device, cpu_ce);
88 
89 irqreturn_t
90 rtc_timer_interrupt(int irq, void *dev)
91 {
92 	int cpu = smp_processor_id();
93 	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);
94 
95 	/* Don't run the hook for UNUSED or SHUTDOWN.  */
96 	if (likely(clockevent_state_periodic(ce)))
97 		ce->event_handler(ce);
98 
99 	if (test_irq_work_pending()) {
100 		clear_irq_work_pending();
101 		irq_work_run();
102 	}
103 
104 	return IRQ_HANDLED;
105 }
106 
107 static int
108 rtc_ce_set_next_event(unsigned long evt, struct clock_event_device *ce)
109 {
110 	/* This hook is for oneshot mode, which we don't support.  */
111 	return -EINVAL;
112 }
113 
114 static void __init
115 init_rtc_clockevent(void)
116 {
117 	int cpu = smp_processor_id();
118 	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);
119 
120 	*ce = (struct clock_event_device){
121 		.name = "rtc",
122 		.features = CLOCK_EVT_FEAT_PERIODIC,
123 		.rating = 100,
124 		.cpumask = cpumask_of(cpu),
125 		.set_next_event = rtc_ce_set_next_event,
126 	};
127 
128 	clockevents_config_and_register(ce, CONFIG_HZ, 0, 0);
129 }
130 
131 
132 /*
133  * The QEMU clock as a clocksource primitive.
134  */
135 
136 static cycle_t
137 qemu_cs_read(struct clocksource *cs)
138 {
139 	return qemu_get_vmtime();
140 }
141 
142 static struct clocksource qemu_cs = {
143 	.name                   = "qemu",
144 	.rating                 = 400,
145 	.read                   = qemu_cs_read,
146 	.mask                   = CLOCKSOURCE_MASK(64),
147 	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS,
148 	.max_idle_ns		= LONG_MAX
149 };
150 
151 
152 /*
153  * The QEMU alarm as a clock_event_device primitive.
154  */
155 
156 static int qemu_ce_shutdown(struct clock_event_device *ce)
157 {
158 	/* The mode member of CE is updated for us in generic code.
159 	   Just make sure that the event is disabled.  */
160 	qemu_set_alarm_abs(0);
161 	return 0;
162 }
163 
164 static int
165 qemu_ce_set_next_event(unsigned long evt, struct clock_event_device *ce)
166 {
167 	qemu_set_alarm_rel(evt);
168 	return 0;
169 }
170 
171 static irqreturn_t
172 qemu_timer_interrupt(int irq, void *dev)
173 {
174 	int cpu = smp_processor_id();
175 	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);
176 
177 	ce->event_handler(ce);
178 	return IRQ_HANDLED;
179 }
180 
181 static void __init
182 init_qemu_clockevent(void)
183 {
184 	int cpu = smp_processor_id();
185 	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);
186 
187 	*ce = (struct clock_event_device){
188 		.name = "qemu",
189 		.features = CLOCK_EVT_FEAT_ONESHOT,
190 		.rating = 400,
191 		.cpumask = cpumask_of(cpu),
192 		.set_state_shutdown = qemu_ce_shutdown,
193 		.set_state_oneshot = qemu_ce_shutdown,
194 		.tick_resume = qemu_ce_shutdown,
195 		.set_next_event = qemu_ce_set_next_event,
196 	};
197 
198 	clockevents_config_and_register(ce, NSEC_PER_SEC, 1000, LONG_MAX);
199 }
200 
201 
202 void __init
203 common_init_rtc(void)
204 {
205 	unsigned char x, sel = 0;
206 
207 	/* Reset periodic interrupt frequency.  */
208 #if CONFIG_HZ == 1024 || CONFIG_HZ == 1200
209  	x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
210 	/* Test includes known working values on various platforms
211 	   where 0x26 is wrong; we refuse to change those. */
212  	if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
213 		sel = RTC_REF_CLCK_32KHZ + 6;
214 	}
215 #elif CONFIG_HZ == 256 || CONFIG_HZ == 128 || CONFIG_HZ == 64 || CONFIG_HZ == 32
216 	sel = RTC_REF_CLCK_32KHZ + __builtin_ffs(32768 / CONFIG_HZ);
217 #else
218 # error "Unknown HZ from arch/alpha/Kconfig"
219 #endif
220 	if (sel) {
221 		printk(KERN_INFO "Setting RTC_FREQ to %d Hz (%x)\n",
222 		       CONFIG_HZ, sel);
223 		CMOS_WRITE(sel, RTC_FREQ_SELECT);
224  	}
225 
226 	/* Turn on periodic interrupts.  */
227 	x = CMOS_READ(RTC_CONTROL);
228 	if (!(x & RTC_PIE)) {
229 		printk("Turning on RTC interrupts.\n");
230 		x |= RTC_PIE;
231 		x &= ~(RTC_AIE | RTC_UIE);
232 		CMOS_WRITE(x, RTC_CONTROL);
233 	}
234 	(void) CMOS_READ(RTC_INTR_FLAGS);
235 
236 	outb(0x36, 0x43);	/* pit counter 0: system timer */
237 	outb(0x00, 0x40);
238 	outb(0x00, 0x40);
239 
240 	outb(0xb6, 0x43);	/* pit counter 2: speaker */
241 	outb(0x31, 0x42);
242 	outb(0x13, 0x42);
243 
244 	init_rtc_irq();
245 }
246 
247 
248 #ifndef CONFIG_ALPHA_WTINT
249 /*
250  * The RPCC as a clocksource primitive.
251  *
252  * While we have free-running timecounters running on all CPUs, and we make
253  * a half-hearted attempt in init_rtc_rpcc_info to sync the timecounter
254  * with the wall clock, that initialization isn't kept up-to-date across
255  * different time counters in SMP mode.  Therefore we can only use this
256  * method when there's only one CPU enabled.
257  *
258  * When using the WTINT PALcall, the RPCC may shift to a lower frequency,
259  * or stop altogether, while waiting for the interrupt.  Therefore we cannot
260  * use this method when WTINT is in use.
261  */
262 
263 static cycle_t read_rpcc(struct clocksource *cs)
264 {
265 	return rpcc();
266 }
267 
268 static struct clocksource clocksource_rpcc = {
269 	.name                   = "rpcc",
270 	.rating                 = 300,
271 	.read                   = read_rpcc,
272 	.mask                   = CLOCKSOURCE_MASK(32),
273 	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS
274 };
275 #endif /* ALPHA_WTINT */
276 
277 
278 /* Validate a computed cycle counter result against the known bounds for
279    the given processor core.  There's too much brokenness in the way of
280    timing hardware for any one method to work everywhere.  :-(
281 
282    Return 0 if the result cannot be trusted, otherwise return the argument.  */
283 
284 static unsigned long __init
285 validate_cc_value(unsigned long cc)
286 {
287 	static struct bounds {
288 		unsigned int min, max;
289 	} cpu_hz[] __initdata = {
290 		[EV3_CPU]    = {   50000000,  200000000 },	/* guess */
291 		[EV4_CPU]    = {  100000000,  300000000 },
292 		[LCA4_CPU]   = {  100000000,  300000000 },	/* guess */
293 		[EV45_CPU]   = {  200000000,  300000000 },
294 		[EV5_CPU]    = {  250000000,  433000000 },
295 		[EV56_CPU]   = {  333000000,  667000000 },
296 		[PCA56_CPU]  = {  400000000,  600000000 },	/* guess */
297 		[PCA57_CPU]  = {  500000000,  600000000 },	/* guess */
298 		[EV6_CPU]    = {  466000000,  600000000 },
299 		[EV67_CPU]   = {  600000000,  750000000 },
300 		[EV68AL_CPU] = {  750000000,  940000000 },
301 		[EV68CB_CPU] = { 1000000000, 1333333333 },
302 		/* None of the following are shipping as of 2001-11-01.  */
303 		[EV68CX_CPU] = { 1000000000, 1700000000 },	/* guess */
304 		[EV69_CPU]   = { 1000000000, 1700000000 },	/* guess */
305 		[EV7_CPU]    = {  800000000, 1400000000 },	/* guess */
306 		[EV79_CPU]   = { 1000000000, 2000000000 },	/* guess */
307 	};
308 
309 	/* Allow for some drift in the crystal.  10MHz is more than enough.  */
310 	const unsigned int deviation = 10000000;
311 
312 	struct percpu_struct *cpu;
313 	unsigned int index;
314 
315 	cpu = (struct percpu_struct *)((char*)hwrpb + hwrpb->processor_offset);
316 	index = cpu->type & 0xffffffff;
317 
318 	/* If index out of bounds, no way to validate.  */
319 	if (index >= ARRAY_SIZE(cpu_hz))
320 		return cc;
321 
322 	/* If index contains no data, no way to validate.  */
323 	if (cpu_hz[index].max == 0)
324 		return cc;
325 
326 	if (cc < cpu_hz[index].min - deviation
327 	    || cc > cpu_hz[index].max + deviation)
328 		return 0;
329 
330 	return cc;
331 }
332 
333 
334 /*
335  * Calibrate CPU clock using legacy 8254 timer/counter. Stolen from
336  * arch/i386/time.c.
337  */
338 
339 #define CALIBRATE_LATCH	0xffff
340 #define TIMEOUT_COUNT	0x100000
341 
342 static unsigned long __init
343 calibrate_cc_with_pit(void)
344 {
345 	int cc, count = 0;
346 
347 	/* Set the Gate high, disable speaker */
348 	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
349 
350 	/*
351 	 * Now let's take care of CTC channel 2
352 	 *
353 	 * Set the Gate high, program CTC channel 2 for mode 0,
354 	 * (interrupt on terminal count mode), binary count,
355 	 * load 5 * LATCH count, (LSB and MSB) to begin countdown.
356 	 */
357 	outb(0xb0, 0x43);		/* binary, mode 0, LSB/MSB, Ch 2 */
358 	outb(CALIBRATE_LATCH & 0xff, 0x42);	/* LSB of count */
359 	outb(CALIBRATE_LATCH >> 8, 0x42);	/* MSB of count */
360 
361 	cc = rpcc();
362 	do {
363 		count++;
364 	} while ((inb(0x61) & 0x20) == 0 && count < TIMEOUT_COUNT);
365 	cc = rpcc() - cc;
366 
367 	/* Error: ECTCNEVERSET or ECPUTOOFAST.  */
368 	if (count <= 1 || count == TIMEOUT_COUNT)
369 		return 0;
370 
371 	return ((long)cc * PIT_TICK_RATE) / (CALIBRATE_LATCH + 1);
372 }
373 
374 /* The Linux interpretation of the CMOS clock register contents:
375    When the Update-In-Progress (UIP) flag goes from 1 to 0, the
376    RTC registers show the second which has precisely just started.
377    Let's hope other operating systems interpret the RTC the same way.  */
378 
379 static unsigned long __init
380 rpcc_after_update_in_progress(void)
381 {
382 	do { } while (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP));
383 	do { } while (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
384 
385 	return rpcc();
386 }
387 
388 void __init
389 time_init(void)
390 {
391 	unsigned int cc1, cc2;
392 	unsigned long cycle_freq, tolerance;
393 	long diff;
394 
395 	if (alpha_using_qemu) {
396 		clocksource_register_hz(&qemu_cs, NSEC_PER_SEC);
397 		init_qemu_clockevent();
398 
399 		timer_irqaction.handler = qemu_timer_interrupt;
400 		init_rtc_irq();
401 		return;
402 	}
403 
404 	/* Calibrate CPU clock -- attempt #1.  */
405 	if (!est_cycle_freq)
406 		est_cycle_freq = validate_cc_value(calibrate_cc_with_pit());
407 
408 	cc1 = rpcc();
409 
410 	/* Calibrate CPU clock -- attempt #2.  */
411 	if (!est_cycle_freq) {
412 		cc1 = rpcc_after_update_in_progress();
413 		cc2 = rpcc_after_update_in_progress();
414 		est_cycle_freq = validate_cc_value(cc2 - cc1);
415 		cc1 = cc2;
416 	}
417 
418 	cycle_freq = hwrpb->cycle_freq;
419 	if (est_cycle_freq) {
420 		/* If the given value is within 250 PPM of what we calculated,
421 		   accept it.  Otherwise, use what we found.  */
422 		tolerance = cycle_freq / 4000;
423 		diff = cycle_freq - est_cycle_freq;
424 		if (diff < 0)
425 			diff = -diff;
426 		if ((unsigned long)diff > tolerance) {
427 			cycle_freq = est_cycle_freq;
428 			printk("HWRPB cycle frequency bogus.  "
429 			       "Estimated %lu Hz\n", cycle_freq);
430 		} else {
431 			est_cycle_freq = 0;
432 		}
433 	} else if (! validate_cc_value (cycle_freq)) {
434 		printk("HWRPB cycle frequency bogus, "
435 		       "and unable to estimate a proper value!\n");
436 	}
437 
438 	/* See above for restrictions on using clocksource_rpcc.  */
439 #ifndef CONFIG_ALPHA_WTINT
440 	if (hwrpb->nr_processors == 1)
441 		clocksource_register_hz(&clocksource_rpcc, cycle_freq);
442 #endif
443 
444 	/* Startup the timer source. */
445 	alpha_mv.init_rtc();
446 	init_rtc_clockevent();
447 }
448 
449 /* Initialize the clock_event_device for secondary cpus.  */
450 #ifdef CONFIG_SMP
451 void __init
452 init_clockevent(void)
453 {
454 	if (alpha_using_qemu)
455 		init_qemu_clockevent();
456 	else
457 		init_rtc_clockevent();
458 }
459 #endif
460