1 /*
2 * linux/arch/parisc/kernel/time.c
3 *
4 * Copyright (C) 1991, 1992, 1995 Linus Torvalds
5 * Modifications for ARM (C) 1994, 1995, 1996,1997 Russell King
6 * Copyright (C) 1999 SuSE GmbH, (Philipp Rumpf, prumpf@tux.org)
7 *
8 * 1994-07-02 Alan Modra
9 * fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
10 * 1998-12-20 Updated NTP code according to technical memorandum Jan '96
11 * "A Kernel Model for Precision Timekeeping" by Dave Mills
12 */
13 #include <linux/errno.h>
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/kernel.h>
17 #include <linux/param.h>
18 #include <linux/string.h>
19 #include <linux/mm.h>
20 #include <linux/interrupt.h>
21 #include <linux/time.h>
22 #include <linux/init.h>
23 #include <linux/smp.h>
24 #include <linux/profile.h>
25 #include <linux/clocksource.h>
26 #include <linux/platform_device.h>
27 #include <linux/ftrace.h>
28
29 #include <asm/uaccess.h>
30 #include <asm/io.h>
31 #include <asm/irq.h>
32 #include <asm/page.h>
33 #include <asm/param.h>
34 #include <asm/pdc.h>
35 #include <asm/led.h>
36
37 #include <linux/timex.h>
38
39 static unsigned long clocktick __read_mostly; /* timer cycles per tick */
40
41 /*
42 * We keep time on PA-RISC Linux by using the Interval Timer which is
43 * a pair of registers; one is read-only and one is write-only; both
44 * accessed through CR16. The read-only register is 32 or 64 bits wide,
45 * and increments by 1 every CPU clock tick. The architecture only
46 * guarantees us a rate between 0.5 and 2, but all implementations use a
47 * rate of 1. The write-only register is 32-bits wide. When the lowest
48 * 32 bits of the read-only register compare equal to the write-only
49 * register, it raises a maskable external interrupt. Each processor has
50 * an Interval Timer of its own and they are not synchronised.
51 *
52 * We want to generate an interrupt every 1/HZ seconds. So we program
53 * CR16 to interrupt every @clocktick cycles. The it_value in cpu_data
54 * is programmed with the intended time of the next tick. We can be
55 * held off for an arbitrarily long period of time by interrupts being
56 * disabled, so we may miss one or more ticks.
57 */
timer_interrupt(int irq,void * dev_id)58 irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
59 {
60 unsigned long now, now2;
61 unsigned long next_tick;
62 unsigned long cycles_elapsed, ticks_elapsed = 1;
63 unsigned long cycles_remainder;
64 unsigned int cpu = smp_processor_id();
65 struct cpuinfo_parisc *cpuinfo = &per_cpu(cpu_data, cpu);
66
67 /* gcc can optimize for "read-only" case with a local clocktick */
68 unsigned long cpt = clocktick;
69
70 profile_tick(CPU_PROFILING);
71
72 /* Initialize next_tick to the expected tick time. */
73 next_tick = cpuinfo->it_value;
74
75 /* Get current cycle counter (Control Register 16). */
76 now = mfctl(16);
77
78 cycles_elapsed = now - next_tick;
79
80 if ((cycles_elapsed >> 6) < cpt) {
81 /* use "cheap" math (add/subtract) instead
82 * of the more expensive div/mul method
83 */
84 cycles_remainder = cycles_elapsed;
85 while (cycles_remainder > cpt) {
86 cycles_remainder -= cpt;
87 ticks_elapsed++;
88 }
89 } else {
90 /* TODO: Reduce this to one fdiv op */
91 cycles_remainder = cycles_elapsed % cpt;
92 ticks_elapsed += cycles_elapsed / cpt;
93 }
94
95 /* convert from "division remainder" to "remainder of clock tick" */
96 cycles_remainder = cpt - cycles_remainder;
97
98 /* Determine when (in CR16 cycles) next IT interrupt will fire.
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 + cycles_remainder;
103
104 cpuinfo->it_value = next_tick;
105
106 /* Program the IT when to deliver the next interrupt.
107 * Only bottom 32-bits of next_tick are writable in CR16!
108 */
109 mtctl(next_tick, 16);
110
111 /* Skip one clocktick on purpose if we missed next_tick.
112 * The new CR16 must be "later" than current CR16 otherwise
113 * itimer would not fire until CR16 wrapped - e.g 4 seconds
114 * later on a 1Ghz processor. We'll account for the missed
115 * tick on the next timer interrupt.
116 *
117 * "next_tick - now" will always give the difference regardless
118 * if one or the other wrapped. If "now" is "bigger" we'll end up
119 * with a very large unsigned number.
120 */
121 now2 = mfctl(16);
122 if (next_tick - now2 > cpt)
123 mtctl(next_tick+cpt, 16);
124
125 #if 1
126 /*
127 * GGG: DEBUG code for how many cycles programming CR16 used.
128 */
129 if (unlikely(now2 - now > 0x3000)) /* 12K cycles */
130 printk (KERN_CRIT "timer_interrupt(CPU %d): SLOW! 0x%lx cycles!"
131 " cyc %lX rem %lX "
132 " next/now %lX/%lX\n",
133 cpu, now2 - now, cycles_elapsed, cycles_remainder,
134 next_tick, now );
135 #endif
136
137 /* Can we differentiate between "early CR16" (aka Scenario 1) and
138 * "long delay" (aka Scenario 3)? I don't think so.
139 *
140 * Timer_interrupt will be delivered at least a few hundred cycles
141 * after the IT fires. But it's arbitrary how much time passes
142 * before we call it "late". I've picked one second.
143 *
144 * It's important NO printk's are between reading CR16 and
145 * setting up the next value. May introduce huge variance.
146 */
147 if (unlikely(ticks_elapsed > HZ)) {
148 /* Scenario 3: very long delay? bad in any case */
149 printk (KERN_CRIT "timer_interrupt(CPU %d): delayed!"
150 " cycles %lX rem %lX "
151 " next/now %lX/%lX\n",
152 cpu,
153 cycles_elapsed, cycles_remainder,
154 next_tick, now );
155 }
156
157 /* Done mucking with unreliable delivery of interrupts.
158 * Go do system house keeping.
159 */
160
161 if (!--cpuinfo->prof_counter) {
162 cpuinfo->prof_counter = cpuinfo->prof_multiplier;
163 update_process_times(user_mode(get_irq_regs()));
164 }
165
166 if (cpu == 0)
167 xtime_update(ticks_elapsed);
168
169 return IRQ_HANDLED;
170 }
171
172
profile_pc(struct pt_regs * regs)173 unsigned long profile_pc(struct pt_regs *regs)
174 {
175 unsigned long pc = instruction_pointer(regs);
176
177 if (regs->gr[0] & PSW_N)
178 pc -= 4;
179
180 #ifdef CONFIG_SMP
181 if (in_lock_functions(pc))
182 pc = regs->gr[2];
183 #endif
184
185 return pc;
186 }
187 EXPORT_SYMBOL(profile_pc);
188
189
190 /* clock source code */
191
read_cr16(struct clocksource * cs)192 static cycle_t read_cr16(struct clocksource *cs)
193 {
194 return get_cycles();
195 }
196
197 static struct clocksource clocksource_cr16 = {
198 .name = "cr16",
199 .rating = 300,
200 .read = read_cr16,
201 .mask = CLOCKSOURCE_MASK(BITS_PER_LONG),
202 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
203 };
204
update_cr16_clocksource(void)205 int update_cr16_clocksource(void)
206 {
207 /* since the cr16 cycle counters are not synchronized across CPUs,
208 we'll check if we should switch to a safe clocksource: */
209 if (clocksource_cr16.rating != 0 && num_online_cpus() > 1) {
210 clocksource_change_rating(&clocksource_cr16, 0);
211 return 1;
212 }
213
214 return 0;
215 }
216
start_cpu_itimer(void)217 void __init start_cpu_itimer(void)
218 {
219 unsigned int cpu = smp_processor_id();
220 unsigned long next_tick = mfctl(16) + clocktick;
221
222 mtctl(next_tick, 16); /* kick off Interval Timer (CR16) */
223
224 per_cpu(cpu_data, cpu).it_value = next_tick;
225 }
226
rtc_init(void)227 static int __init rtc_init(void)
228 {
229 struct platform_device *pdev;
230
231 pdev = platform_device_register_simple("rtc-generic", -1, NULL, 0);
232 return PTR_ERR_OR_ZERO(pdev);
233 }
234 device_initcall(rtc_init);
235
read_persistent_clock(struct timespec * ts)236 void read_persistent_clock(struct timespec *ts)
237 {
238 static struct pdc_tod tod_data;
239 if (pdc_tod_read(&tod_data) == 0) {
240 ts->tv_sec = tod_data.tod_sec;
241 ts->tv_nsec = tod_data.tod_usec * 1000;
242 } else {
243 printk(KERN_ERR "Error reading tod clock\n");
244 ts->tv_sec = 0;
245 ts->tv_nsec = 0;
246 }
247 }
248
time_init(void)249 void __init time_init(void)
250 {
251 unsigned long current_cr16_khz;
252
253 clocktick = (100 * PAGE0->mem_10msec) / HZ;
254
255 start_cpu_itimer(); /* get CPU 0 started */
256
257 /* register at clocksource framework */
258 current_cr16_khz = PAGE0->mem_10msec/10; /* kHz */
259 clocksource_register_khz(&clocksource_cr16, current_cr16_khz);
260 }
261