1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/arch/parisc/kernel/time.c
4 *
5 * Copyright (C) 1991, 1992, 1995 Linus Torvalds
6 * Modifications for ARM (C) 1994, 1995, 1996,1997 Russell King
7 * Copyright (C) 1999 SuSE GmbH, (Philipp Rumpf, prumpf@tux.org)
8 *
9 * 1994-07-02 Alan Modra
10 * fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
11 * 1998-12-20 Updated NTP code according to technical memorandum Jan '96
12 * "A Kernel Model for Precision Timekeeping" by Dave Mills
13 */
14 #include <linux/errno.h>
15 #include <linux/module.h>
16 #include <linux/rtc.h>
17 #include <linux/sched.h>
18 #include <linux/sched/clock.h>
19 #include <linux/sched_clock.h>
20 #include <linux/kernel.h>
21 #include <linux/param.h>
22 #include <linux/string.h>
23 #include <linux/mm.h>
24 #include <linux/interrupt.h>
25 #include <linux/time.h>
26 #include <linux/init.h>
27 #include <linux/smp.h>
28 #include <linux/profile.h>
29 #include <linux/clocksource.h>
30 #include <linux/platform_device.h>
31 #include <linux/ftrace.h>
32
33 #include <linux/uaccess.h>
34 #include <asm/io.h>
35 #include <asm/irq.h>
36 #include <asm/page.h>
37 #include <asm/param.h>
38 #include <asm/pdc.h>
39 #include <asm/led.h>
40
41 #include <linux/timex.h>
42
43 static unsigned long clocktick __ro_after_init; /* timer cycles per tick */
44
45 /*
46 * We keep time on PA-RISC Linux by using the Interval Timer which is
47 * a pair of registers; one is read-only and one is write-only; both
48 * accessed through CR16. The read-only register is 32 or 64 bits wide,
49 * and increments by 1 every CPU clock tick. The architecture only
50 * guarantees us a rate between 0.5 and 2, but all implementations use a
51 * rate of 1. The write-only register is 32-bits wide. When the lowest
52 * 32 bits of the read-only register compare equal to the write-only
53 * register, it raises a maskable external interrupt. Each processor has
54 * an Interval Timer of its own and they are not synchronised.
55 *
56 * We want to generate an interrupt every 1/HZ seconds. So we program
57 * CR16 to interrupt every @clocktick cycles. The it_value in cpu_data
58 * is programmed with the intended time of the next tick. We can be
59 * held off for an arbitrarily long period of time by interrupts being
60 * disabled, so we may miss one or more ticks.
61 */
timer_interrupt(int irq,void * dev_id)62 irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
63 {
64 unsigned long now;
65 unsigned long next_tick;
66 unsigned long ticks_elapsed = 0;
67 unsigned int cpu = smp_processor_id();
68 struct cpuinfo_parisc *cpuinfo = &per_cpu(cpu_data, cpu);
69
70 /* gcc can optimize for "read-only" case with a local clocktick */
71 unsigned long cpt = clocktick;
72
73 /* Initialize next_tick to the old expected tick time. */
74 next_tick = cpuinfo->it_value;
75
76 /* Calculate how many ticks have elapsed. */
77 now = mfctl(16);
78 do {
79 ++ticks_elapsed;
80 next_tick += cpt;
81 } while (next_tick - now > cpt);
82
83 /* Store (in CR16 cycles) up to when we are accounting right now. */
84 cpuinfo->it_value = next_tick;
85
86 /* Go do system house keeping. */
87 if (cpu != 0)
88 ticks_elapsed = 0;
89 legacy_timer_tick(ticks_elapsed);
90
91 /* Skip clockticks on purpose if we know we would miss those.
92 * The new CR16 must be "later" than current CR16 otherwise
93 * itimer would not fire until CR16 wrapped - e.g 4 seconds
94 * later on a 1Ghz processor. We'll account for the missed
95 * ticks on the next timer interrupt.
96 * We want IT to fire modulo clocktick even if we miss/skip some.
97 * But those interrupts don't in fact get delivered that regularly.
98 *
99 * "next_tick - now" will always give the difference regardless
100 * if one or the other wrapped. If "now" is "bigger" we'll end up
101 * with a very large unsigned number.
102 */
103 now = mfctl(16);
104 while (next_tick - now > cpt)
105 next_tick += cpt;
106
107 /* Program the IT when to deliver the next interrupt.
108 * Only bottom 32-bits of next_tick are writable in CR16!
109 * Timer interrupt will be delivered at least a few hundred cycles
110 * after the IT fires, so if we are too close (<= 8000 cycles) to the
111 * next cycle, simply skip it.
112 */
113 if (next_tick - now <= 8000)
114 next_tick += cpt;
115 mtctl(next_tick, 16);
116
117 return IRQ_HANDLED;
118 }
119
120
profile_pc(struct pt_regs * regs)121 unsigned long profile_pc(struct pt_regs *regs)
122 {
123 unsigned long pc = instruction_pointer(regs);
124
125 if (regs->gr[0] & PSW_N)
126 pc -= 4;
127
128 #ifdef CONFIG_SMP
129 if (in_lock_functions(pc))
130 pc = regs->gr[2];
131 #endif
132
133 return pc;
134 }
135 EXPORT_SYMBOL(profile_pc);
136
137
138 /* clock source code */
139
read_cr16(struct clocksource * cs)140 static u64 notrace read_cr16(struct clocksource *cs)
141 {
142 return get_cycles();
143 }
144
145 static struct clocksource clocksource_cr16 = {
146 .name = "cr16",
147 .rating = 300,
148 .read = read_cr16,
149 .mask = CLOCKSOURCE_MASK(BITS_PER_LONG),
150 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
151 };
152
start_cpu_itimer(void)153 void __init start_cpu_itimer(void)
154 {
155 unsigned int cpu = smp_processor_id();
156 unsigned long next_tick = mfctl(16) + clocktick;
157
158 mtctl(next_tick, 16); /* kick off Interval Timer (CR16) */
159
160 per_cpu(cpu_data, cpu).it_value = next_tick;
161 }
162
163 #if IS_ENABLED(CONFIG_RTC_DRV_GENERIC)
rtc_generic_get_time(struct device * dev,struct rtc_time * tm)164 static int rtc_generic_get_time(struct device *dev, struct rtc_time *tm)
165 {
166 struct pdc_tod tod_data;
167
168 memset(tm, 0, sizeof(*tm));
169 if (pdc_tod_read(&tod_data) < 0)
170 return -EOPNOTSUPP;
171
172 /* we treat tod_sec as unsigned, so this can work until year 2106 */
173 rtc_time64_to_tm(tod_data.tod_sec, tm);
174 return 0;
175 }
176
rtc_generic_set_time(struct device * dev,struct rtc_time * tm)177 static int rtc_generic_set_time(struct device *dev, struct rtc_time *tm)
178 {
179 time64_t secs = rtc_tm_to_time64(tm);
180 int ret;
181
182 /* hppa has Y2K38 problem: pdc_tod_set() takes an u32 value! */
183 ret = pdc_tod_set(secs, 0);
184 if (ret != 0) {
185 pr_warn("pdc_tod_set(%lld) returned error %d\n", secs, ret);
186 if (ret == PDC_INVALID_ARG)
187 return -EINVAL;
188 return -EOPNOTSUPP;
189 }
190
191 return 0;
192 }
193
194 static const struct rtc_class_ops rtc_generic_ops = {
195 .read_time = rtc_generic_get_time,
196 .set_time = rtc_generic_set_time,
197 };
198
rtc_init(void)199 static int __init rtc_init(void)
200 {
201 struct platform_device *pdev;
202
203 pdev = platform_device_register_data(NULL, "rtc-generic", -1,
204 &rtc_generic_ops,
205 sizeof(rtc_generic_ops));
206
207 return PTR_ERR_OR_ZERO(pdev);
208 }
209 device_initcall(rtc_init);
210 #endif
211
read_persistent_clock64(struct timespec64 * ts)212 void read_persistent_clock64(struct timespec64 *ts)
213 {
214 static struct pdc_tod tod_data;
215 if (pdc_tod_read(&tod_data) == 0) {
216 ts->tv_sec = tod_data.tod_sec;
217 ts->tv_nsec = tod_data.tod_usec * 1000;
218 } else {
219 printk(KERN_ERR "Error reading tod clock\n");
220 ts->tv_sec = 0;
221 ts->tv_nsec = 0;
222 }
223 }
224
225
read_cr16_sched_clock(void)226 static u64 notrace read_cr16_sched_clock(void)
227 {
228 return get_cycles();
229 }
230
231
232 /*
233 * timer interrupt and sched_clock() initialization
234 */
235
time_init(void)236 void __init time_init(void)
237 {
238 unsigned long cr16_hz;
239
240 clocktick = (100 * PAGE0->mem_10msec) / HZ;
241 start_cpu_itimer(); /* get CPU 0 started */
242
243 cr16_hz = 100 * PAGE0->mem_10msec; /* Hz */
244
245 /* register as sched_clock source */
246 sched_clock_register(read_cr16_sched_clock, BITS_PER_LONG, cr16_hz);
247 }
248
init_cr16_clocksource(void)249 static int __init init_cr16_clocksource(void)
250 {
251 /*
252 * The cr16 interval timers are not syncronized across CPUs, even if
253 * they share the same socket.
254 */
255 if (num_online_cpus() > 1 && !running_on_qemu) {
256 /* mark sched_clock unstable */
257 clear_sched_clock_stable();
258
259 clocksource_cr16.name = "cr16_unstable";
260 clocksource_cr16.flags = CLOCK_SOURCE_UNSTABLE;
261 clocksource_cr16.rating = 0;
262 }
263
264 /* register at clocksource framework */
265 clocksource_register_hz(&clocksource_cr16,
266 100 * PAGE0->mem_10msec);
267
268 return 0;
269 }
270
271 device_initcall(init_cr16_clocksource);
272