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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/arch/alpha/kernel/time.c
4 *
5 * Copyright (C) 1991, 1992, 1995, 1999, 2000 Linus Torvalds
6 *
7 * This file contains the clocksource time handling.
8 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
9 * "A Kernel Model for Precision Timekeeping" by Dave Mills
10 * 1997-01-09 Adrian Sun
11 * use interval timer if CONFIG_RTC=y
12 * 1997-10-29 John Bowman (bowman@math.ualberta.ca)
13 * fixed tick loss calculation in timer_interrupt
14 * (round system clock to nearest tick instead of truncating)
15 * fixed algorithm in time_init for getting time from CMOS clock
16 * 1999-04-16 Thorsten Kranzkowski (dl8bcu@gmx.net)
17 * fixed algorithm in do_gettimeofday() for calculating the precise time
18 * from processor cycle counter (now taking lost_ticks into account)
19 * 2003-06-03 R. Scott Bailey <scott.bailey@eds.com>
20 * Tighten sanity in time_init from 1% (10,000 PPM) to 250 PPM
21 */
22#include <linux/errno.h>
23#include <linux/module.h>
24#include <linux/sched.h>
25#include <linux/kernel.h>
26#include <linux/param.h>
27#include <linux/string.h>
28#include <linux/mm.h>
29#include <linux/delay.h>
30#include <linux/ioport.h>
31#include <linux/irq.h>
32#include <linux/interrupt.h>
33#include <linux/init.h>
34#include <linux/bcd.h>
35#include <linux/profile.h>
36#include <linux/irq_work.h>
37
38#include <linux/uaccess.h>
39#include <asm/io.h>
40#include <asm/hwrpb.h>
41
42#include <linux/mc146818rtc.h>
43#include <linux/time.h>
44#include <linux/timex.h>
45#include <linux/clocksource.h>
46#include <linux/clockchips.h>
47
48#include "proto.h"
49#include "irq_impl.h"
50
51DEFINE_SPINLOCK(rtc_lock);
52EXPORT_SYMBOL(rtc_lock);
53
54unsigned long est_cycle_freq;
55
56#ifdef CONFIG_IRQ_WORK
57
58DEFINE_PER_CPU(u8, irq_work_pending);
59
60#define set_irq_work_pending_flag() __this_cpu_write(irq_work_pending, 1)
61#define test_irq_work_pending() __this_cpu_read(irq_work_pending)
62#define clear_irq_work_pending() __this_cpu_write(irq_work_pending, 0)
63
64void arch_irq_work_raise(void)
65{
66 set_irq_work_pending_flag();
67}
68
69#else /* CONFIG_IRQ_WORK */
70
71#define test_irq_work_pending() 0
72#define clear_irq_work_pending()
73
74#endif /* CONFIG_IRQ_WORK */
75
76
77static inline __u32 rpcc(void)
78{
79 return __builtin_alpha_rpcc();
80}
81
82
83
84/*
85 * The RTC as a clock_event_device primitive.
86 */
87
88static DEFINE_PER_CPU(struct clock_event_device, cpu_ce);
89
90irqreturn_t
91rtc_timer_interrupt(int irq, void *dev)
92{
93 int cpu = smp_processor_id();
94 struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);
95
96 /* Don't run the hook for UNUSED or SHUTDOWN. */
97 if (likely(clockevent_state_periodic(ce)))
98 ce->event_handler(ce);
99
100 if (test_irq_work_pending()) {
101 clear_irq_work_pending();
102 irq_work_run();
103 }
104
105 return IRQ_HANDLED;
106}
107
108static int
109rtc_ce_set_next_event(unsigned long evt, struct clock_event_device *ce)
110{
111 /* This hook is for oneshot mode, which we don't support. */
112 return -EINVAL;
113}
114
115static void __init
116init_rtc_clockevent(void)
117{
118 int cpu = smp_processor_id();
119 struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);
120
121 *ce = (struct clock_event_device){
122 .name = "rtc",
123 .features = CLOCK_EVT_FEAT_PERIODIC,
124 .rating = 100,
125 .cpumask = cpumask_of(cpu),
126 .set_next_event = rtc_ce_set_next_event,
127 };
128
129 clockevents_config_and_register(dev: ce, CONFIG_HZ, min_delta: 0, max_delta: 0);
130}
131
132
133/*
134 * The QEMU clock as a clocksource primitive.
135 */
136
137static u64
138qemu_cs_read(struct clocksource *cs)
139{
140 return qemu_get_vmtime();
141}
142
143static struct clocksource qemu_cs = {
144 .name = "qemu",
145 .rating = 400,
146 .read = qemu_cs_read,
147 .mask = CLOCKSOURCE_MASK(64),
148 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
149 .max_idle_ns = LONG_MAX
150};
151
152
153/*
154 * The QEMU alarm as a clock_event_device primitive.
155 */
156
157static int qemu_ce_shutdown(struct clock_event_device *ce)
158{
159 /* The mode member of CE is updated for us in generic code.
160 Just make sure that the event is disabled. */
161 qemu_set_alarm_abs(0);
162 return 0;
163}
164
165static int
166qemu_ce_set_next_event(unsigned long evt, struct clock_event_device *ce)
167{
168 qemu_set_alarm_rel(evt);
169 return 0;
170}
171
172static irqreturn_t
173qemu_timer_interrupt(int irq, void *dev)
174{
175 int cpu = smp_processor_id();
176 struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);
177
178 ce->event_handler(ce);
179 return IRQ_HANDLED;
180}
181
182static void __init
183init_qemu_clockevent(void)
184{
185 int cpu = smp_processor_id();
186 struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);
187
188 *ce = (struct clock_event_device){
189 .name = "qemu",
190 .features = CLOCK_EVT_FEAT_ONESHOT,
191 .rating = 400,
192 .cpumask = cpumask_of(cpu),
193 .set_state_shutdown = qemu_ce_shutdown,
194 .set_state_oneshot = qemu_ce_shutdown,
195 .tick_resume = qemu_ce_shutdown,
196 .set_next_event = qemu_ce_set_next_event,
197 };
198
199 clockevents_config_and_register(dev: ce, NSEC_PER_SEC, min_delta: 1000, LONG_MAX);
200}
201
202
203void __init
204common_init_rtc(void)
205{
206 unsigned char x, sel = 0;
207
208 /* Reset periodic interrupt frequency. */
209#if CONFIG_HZ == 1024 || CONFIG_HZ == 1200
210 x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
211 /* Test includes known working values on various platforms
212 where 0x26 is wrong; we refuse to change those. */
213 if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
214 sel = RTC_REF_CLCK_32KHZ + 6;
215 }
216#elif CONFIG_HZ == 256 || CONFIG_HZ == 128 || CONFIG_HZ == 64 || CONFIG_HZ == 32
217 sel = RTC_REF_CLCK_32KHZ + __builtin_ffs(32768 / CONFIG_HZ);
218#else
219# error "Unknown HZ from arch/alpha/Kconfig"
220#endif
221 if (sel) {
222 printk(KERN_INFO "Setting RTC_FREQ to %d Hz (%x)\n",
223 CONFIG_HZ, sel);
224 CMOS_WRITE(sel, RTC_FREQ_SELECT);
225 }
226
227 /* Turn on periodic interrupts. */
228 x = CMOS_READ(RTC_CONTROL);
229 if (!(x & RTC_PIE)) {
230 printk("Turning on RTC interrupts.\n");
231 x |= RTC_PIE;
232 x &= ~(RTC_AIE | RTC_UIE);
233 CMOS_WRITE(x, RTC_CONTROL);
234 }
235 (void) CMOS_READ(RTC_INTR_FLAGS);
236
237 outb(value: 0x36, port: 0x43); /* pit counter 0: system timer */
238 outb(value: 0x00, port: 0x40);
239 outb(value: 0x00, port: 0x40);
240
241 outb(value: 0xb6, port: 0x43); /* pit counter 2: speaker */
242 outb(value: 0x31, port: 0x42);
243 outb(value: 0x13, port: 0x42);
244
245 init_rtc_irq(NULL);
246}
247
248
249#ifndef CONFIG_ALPHA_WTINT
250/*
251 * The RPCC as a clocksource primitive.
252 *
253 * While we have free-running timecounters running on all CPUs, and we make
254 * a half-hearted attempt in init_rtc_rpcc_info to sync the timecounter
255 * with the wall clock, that initialization isn't kept up-to-date across
256 * different time counters in SMP mode. Therefore we can only use this
257 * method when there's only one CPU enabled.
258 *
259 * When using the WTINT PALcall, the RPCC may shift to a lower frequency,
260 * or stop altogether, while waiting for the interrupt. Therefore we cannot
261 * use this method when WTINT is in use.
262 */
263
264static u64 read_rpcc(struct clocksource *cs)
265{
266 return rpcc();
267}
268
269static struct clocksource clocksource_rpcc = {
270 .name = "rpcc",
271 .rating = 300,
272 .read = read_rpcc,
273 .mask = CLOCKSOURCE_MASK(32),
274 .flags = CLOCK_SOURCE_IS_CONTINUOUS
275};
276#endif /* ALPHA_WTINT */
277
278
279/* Validate a computed cycle counter result against the known bounds for
280 the given processor core. There's too much brokenness in the way of
281 timing hardware for any one method to work everywhere. :-(
282
283 Return 0 if the result cannot be trusted, otherwise return the argument. */
284
285static unsigned long __init
286validate_cc_value(unsigned long cc)
287{
288 static struct bounds {
289 unsigned int min, max;
290 } cpu_hz[] __initdata = {
291 [EV3_CPU] = { 50000000, 200000000 }, /* guess */
292 [EV4_CPU] = { 100000000, 300000000 },
293 [LCA4_CPU] = { 100000000, 300000000 }, /* guess */
294 [EV45_CPU] = { 200000000, 300000000 },
295 [EV5_CPU] = { 250000000, 433000000 },
296 [EV56_CPU] = { 333000000, 667000000 },
297 [PCA56_CPU] = { 400000000, 600000000 }, /* guess */
298 [PCA57_CPU] = { 500000000, 600000000 }, /* guess */
299 [EV6_CPU] = { 466000000, 600000000 },
300 [EV67_CPU] = { 600000000, 750000000 },
301 [EV68AL_CPU] = { 750000000, 940000000 },
302 [EV68CB_CPU] = { 1000000000, 1333333333 },
303 /* None of the following are shipping as of 2001-11-01. */
304 [EV68CX_CPU] = { 1000000000, 1700000000 }, /* guess */
305 [EV69_CPU] = { 1000000000, 1700000000 }, /* guess */
306 [EV7_CPU] = { 800000000, 1400000000 }, /* guess */
307 [EV79_CPU] = { 1000000000, 2000000000 }, /* guess */
308 };
309
310 /* Allow for some drift in the crystal. 10MHz is more than enough. */
311 const unsigned int deviation = 10000000;
312
313 struct percpu_struct *cpu;
314 unsigned int index;
315
316 cpu = (struct percpu_struct *)((char*)hwrpb + hwrpb->processor_offset);
317 index = cpu->type & 0xffffffff;
318
319 /* If index out of bounds, no way to validate. */
320 if (index >= ARRAY_SIZE(cpu_hz))
321 return cc;
322
323 /* If index contains no data, no way to validate. */
324 if (cpu_hz[index].max == 0)
325 return cc;
326
327 if (cc < cpu_hz[index].min - deviation
328 || cc > cpu_hz[index].max + deviation)
329 return 0;
330
331 return cc;
332}
333
334
335/*
336 * Calibrate CPU clock using legacy 8254 timer/counter. Stolen from
337 * arch/i386/time.c.
338 */
339
340#define CALIBRATE_LATCH 0xffff
341#define TIMEOUT_COUNT 0x100000
342
343static unsigned long __init
344calibrate_cc_with_pit(void)
345{
346 int cc, count = 0;
347
348 /* Set the Gate high, disable speaker */
349 outb(value: (inb(port: 0x61) & ~0x02) | 0x01, port: 0x61);
350
351 /*
352 * Now let's take care of CTC channel 2
353 *
354 * Set the Gate high, program CTC channel 2 for mode 0,
355 * (interrupt on terminal count mode), binary count,
356 * load 5 * LATCH count, (LSB and MSB) to begin countdown.
357 */
358 outb(value: 0xb0, port: 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */
359 outb(CALIBRATE_LATCH & 0xff, port: 0x42); /* LSB of count */
360 outb(CALIBRATE_LATCH >> 8, port: 0x42); /* MSB of count */
361
362 cc = rpcc();
363 do {
364 count++;
365 } while ((inb(port: 0x61) & 0x20) == 0 && count < TIMEOUT_COUNT);
366 cc = rpcc() - cc;
367
368 /* Error: ECTCNEVERSET or ECPUTOOFAST. */
369 if (count <= 1 || count == TIMEOUT_COUNT)
370 return 0;
371
372 return ((long)cc * PIT_TICK_RATE) / (CALIBRATE_LATCH + 1);
373}
374
375/* The Linux interpretation of the CMOS clock register contents:
376 When the Update-In-Progress (UIP) flag goes from 1 to 0, the
377 RTC registers show the second which has precisely just started.
378 Let's hope other operating systems interpret the RTC the same way. */
379
380static unsigned long __init
381rpcc_after_update_in_progress(void)
382{
383 do { } while (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP));
384 do { } while (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
385
386 return rpcc();
387}
388
389void __init
390time_init(void)
391{
392 unsigned int cc1, cc2;
393 unsigned long cycle_freq, tolerance;
394 long diff;
395
396 if (alpha_using_qemu) {
397 clocksource_register_hz(cs: &qemu_cs, NSEC_PER_SEC);
398 init_qemu_clockevent();
399 init_rtc_irq(handler: qemu_timer_interrupt);
400 return;
401 }
402
403 /* Calibrate CPU clock -- attempt #1. */
404 if (!est_cycle_freq)
405 est_cycle_freq = validate_cc_value(cc: calibrate_cc_with_pit());
406
407 cc1 = rpcc();
408
409 /* Calibrate CPU clock -- attempt #2. */
410 if (!est_cycle_freq) {
411 cc1 = rpcc_after_update_in_progress();
412 cc2 = rpcc_after_update_in_progress();
413 est_cycle_freq = validate_cc_value(cc: cc2 - cc1);
414 cc1 = cc2;
415 }
416
417 cycle_freq = hwrpb->cycle_freq;
418 if (est_cycle_freq) {
419 /* If the given value is within 250 PPM of what we calculated,
420 accept it. Otherwise, use what we found. */
421 tolerance = cycle_freq / 4000;
422 diff = cycle_freq - est_cycle_freq;
423 if (diff < 0)
424 diff = -diff;
425 if ((unsigned long)diff > tolerance) {
426 cycle_freq = est_cycle_freq;
427 printk("HWRPB cycle frequency bogus. "
428 "Estimated %lu Hz\n", cycle_freq);
429 } else {
430 est_cycle_freq = 0;
431 }
432 } else if (! validate_cc_value (cc: cycle_freq)) {
433 printk("HWRPB cycle frequency bogus, "
434 "and unable to estimate a proper value!\n");
435 }
436
437 /* See above for restrictions on using clocksource_rpcc. */
438#ifndef CONFIG_ALPHA_WTINT
439 if (hwrpb->nr_processors == 1)
440 clocksource_register_hz(cs: &clocksource_rpcc, hz: cycle_freq);
441#endif
442
443 /* Startup the timer source. */
444 alpha_mv.init_rtc();
445 init_rtc_clockevent();
446}
447
448/* Initialize the clock_event_device for secondary cpus. */
449#ifdef CONFIG_SMP
450void __init
451init_clockevent(void)
452{
453 if (alpha_using_qemu)
454 init_qemu_clockevent();
455 else
456 init_rtc_clockevent();
457}
458#endif
459

source code of linux/arch/alpha/kernel/time.c