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 profile_tick(CPU_PROFILING);
74
75 /* Initialize next_tick to the old expected tick time. */
76 next_tick = cpuinfo->it_value;
77
78 /* Calculate how many ticks have elapsed. */
79 now = mfctl(16);
80 do {
81 ++ticks_elapsed;
82 next_tick += cpt;
83 } while (next_tick - now > cpt);
84
85 /* Store (in CR16 cycles) up to when we are accounting right now. */
86 cpuinfo->it_value = next_tick;
87
88 /* Go do system house keeping. */
89 if (cpu == 0)
90 xtime_update(ticks_elapsed);
91
92 update_process_times(user_mode(get_irq_regs()));
93
94 /* Skip clockticks on purpose if we know we would miss those.
95 * The new CR16 must be "later" than current CR16 otherwise
96 * itimer would not fire until CR16 wrapped - e.g 4 seconds
97 * later on a 1Ghz processor. We'll account for the missed
98 * ticks on the next timer interrupt.
99 * We want IT to fire modulo clocktick even if we miss/skip some.
100 * But those interrupts don't in fact get delivered that regularly.
101 *
102 * "next_tick - now" will always give the difference regardless
103 * if one or the other wrapped. If "now" is "bigger" we'll end up
104 * with a very large unsigned number.
105 */
106 now = mfctl(16);
107 while (next_tick - now > cpt)
108 next_tick += cpt;
109
110 /* Program the IT when to deliver the next interrupt.
111 * Only bottom 32-bits of next_tick are writable in CR16!
112 * Timer interrupt will be delivered at least a few hundred cycles
113 * after the IT fires, so if we are too close (<= 8000 cycles) to the
114 * next cycle, simply skip it.
115 */
116 if (next_tick - now <= 8000)
117 next_tick += cpt;
118 mtctl(next_tick, 16);
119
120 return IRQ_HANDLED;
121 }
122
123
profile_pc(struct pt_regs * regs)124 unsigned long profile_pc(struct pt_regs *regs)
125 {
126 unsigned long pc = instruction_pointer(regs);
127
128 if (regs->gr[0] & PSW_N)
129 pc -= 4;
130
131 #ifdef CONFIG_SMP
132 if (in_lock_functions(pc))
133 pc = regs->gr[2];
134 #endif
135
136 return pc;
137 }
138 EXPORT_SYMBOL(profile_pc);
139
140
141 /* clock source code */
142
read_cr16(struct clocksource * cs)143 static u64 notrace read_cr16(struct clocksource *cs)
144 {
145 return get_cycles();
146 }
147
148 static struct clocksource clocksource_cr16 = {
149 .name = "cr16",
150 .rating = 300,
151 .read = read_cr16,
152 .mask = CLOCKSOURCE_MASK(BITS_PER_LONG),
153 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
154 };
155
start_cpu_itimer(void)156 void __init start_cpu_itimer(void)
157 {
158 unsigned int cpu = smp_processor_id();
159 unsigned long next_tick = mfctl(16) + clocktick;
160
161 mtctl(next_tick, 16); /* kick off Interval Timer (CR16) */
162
163 per_cpu(cpu_data, cpu).it_value = next_tick;
164 }
165
166 #if IS_ENABLED(CONFIG_RTC_DRV_GENERIC)
rtc_generic_get_time(struct device * dev,struct rtc_time * tm)167 static int rtc_generic_get_time(struct device *dev, struct rtc_time *tm)
168 {
169 struct pdc_tod tod_data;
170
171 memset(tm, 0, sizeof(*tm));
172 if (pdc_tod_read(&tod_data) < 0)
173 return -EOPNOTSUPP;
174
175 /* we treat tod_sec as unsigned, so this can work until year 2106 */
176 rtc_time64_to_tm(tod_data.tod_sec, tm);
177 return 0;
178 }
179
rtc_generic_set_time(struct device * dev,struct rtc_time * tm)180 static int rtc_generic_set_time(struct device *dev, struct rtc_time *tm)
181 {
182 time64_t secs = rtc_tm_to_time64(tm);
183
184 if (pdc_tod_set(secs, 0) < 0)
185 return -EOPNOTSUPP;
186
187 return 0;
188 }
189
190 static const struct rtc_class_ops rtc_generic_ops = {
191 .read_time = rtc_generic_get_time,
192 .set_time = rtc_generic_set_time,
193 };
194
rtc_init(void)195 static int __init rtc_init(void)
196 {
197 struct platform_device *pdev;
198
199 pdev = platform_device_register_data(NULL, "rtc-generic", -1,
200 &rtc_generic_ops,
201 sizeof(rtc_generic_ops));
202
203 return PTR_ERR_OR_ZERO(pdev);
204 }
205 device_initcall(rtc_init);
206 #endif
207
read_persistent_clock64(struct timespec64 * ts)208 void read_persistent_clock64(struct timespec64 *ts)
209 {
210 static struct pdc_tod tod_data;
211 if (pdc_tod_read(&tod_data) == 0) {
212 ts->tv_sec = tod_data.tod_sec;
213 ts->tv_nsec = tod_data.tod_usec * 1000;
214 } else {
215 printk(KERN_ERR "Error reading tod clock\n");
216 ts->tv_sec = 0;
217 ts->tv_nsec = 0;
218 }
219 }
220
221
read_cr16_sched_clock(void)222 static u64 notrace read_cr16_sched_clock(void)
223 {
224 return get_cycles();
225 }
226
227
228 /*
229 * timer interrupt and sched_clock() initialization
230 */
231
time_init(void)232 void __init time_init(void)
233 {
234 unsigned long cr16_hz;
235
236 clocktick = (100 * PAGE0->mem_10msec) / HZ;
237 start_cpu_itimer(); /* get CPU 0 started */
238
239 cr16_hz = 100 * PAGE0->mem_10msec; /* Hz */
240
241 /* register as sched_clock source */
242 sched_clock_register(read_cr16_sched_clock, BITS_PER_LONG, cr16_hz);
243 }
244
init_cr16_clocksource(void)245 static int __init init_cr16_clocksource(void)
246 {
247 /*
248 * The cr16 interval timers are not syncronized across CPUs, even if
249 * they share the same socket.
250 */
251 if (num_online_cpus() > 1 && !running_on_qemu) {
252 clocksource_cr16.name = "cr16_unstable";
253 clocksource_cr16.flags = CLOCK_SOURCE_UNSTABLE;
254 clocksource_cr16.rating = 0;
255 }
256
257 /* XXX: We may want to mark sched_clock stable here if cr16 clocks are
258 * in sync:
259 * (clocksource_cr16.flags == CLOCK_SOURCE_IS_CONTINUOUS) */
260
261 /* register at clocksource framework */
262 clocksource_register_hz(&clocksource_cr16,
263 100 * PAGE0->mem_10msec);
264
265 return 0;
266 }
267
268 device_initcall(init_cr16_clocksource);
269