File: /usr/src/linux/arch/ia64/kernel/time.c
1 /*
2 * linux/arch/ia64/kernel/time.c
3 *
4 * Copyright (C) 1998-2001 Hewlett-Packard Co
5 * Copyright (C) 1998-2000 Stephane Eranian <eranian@hpl.hp.com>
6 * Copyright (C) 1999-2001 David Mosberger <davidm@hpl.hp.com>
7 * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
8 * Copyright (C) 1999-2000 VA Linux Systems
9 * Copyright (C) 1999-2000 Walt Drummond <drummond@valinux.com>
10 */
11 #include <linux/config.h>
12
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/sched.h>
16 #include <linux/time.h>
17 #include <linux/interrupt.h>
18
19 #include <asm/delay.h>
20 #include <asm/efi.h>
21 #include <asm/hw_irq.h>
22 #include <asm/ptrace.h>
23 #include <asm/sal.h>
24 #include <asm/system.h>
25
26 extern rwlock_t xtime_lock;
27 extern unsigned long wall_jiffies;
28 extern unsigned long last_time_offset;
29
30 #ifdef CONFIG_IA64_DEBUG_IRQ
31
32 unsigned long last_cli_ip;
33
34 #endif
35
36 static void
37 do_profile (unsigned long ip)
38 {
39 extern unsigned long prof_cpu_mask;
40 extern char _stext;
41
42 if (!((1UL << smp_processor_id()) & prof_cpu_mask))
43 return;
44
45 if (prof_buffer && current->pid) {
46 ip -= (unsigned long) &_stext;
47 ip >>= prof_shift;
48 /*
49 * Don't ignore out-of-bounds IP values silently, put them into the last
50 * histogram slot, so if present, they will show up as a sharp peak.
51 */
52 if (ip > prof_len - 1)
53 ip = prof_len - 1;
54
55 atomic_inc((atomic_t *) &prof_buffer[ip]);
56 }
57 }
58
59 /*
60 * Return the number of micro-seconds that elapsed since the last update to jiffy. The
61 * xtime_lock must be at least read-locked when calling this routine.
62 */
63 static inline unsigned long
64 gettimeoffset (void)
65 {
66 unsigned long elapsed_cycles, lost = jiffies - wall_jiffies;
67 unsigned long now, last_tick;
68 # define time_keeper_id 0 /* smp_processor_id() of time-keeper */
69
70 last_tick = (cpu_data(time_keeper_id)->itm_next
71 - (lost + 1)*cpu_data(time_keeper_id)->itm_delta);
72
73 now = ia64_get_itc();
74 if ((long) (now - last_tick) < 0) {
75 # if 1
76 printk("CPU %d: now < last_tick (now=0x%lx,last_tick=0x%lx)!\n",
77 smp_processor_id(), now, last_tick);
78 # endif
79 return last_time_offset;
80 }
81 elapsed_cycles = now - last_tick;
82 return (elapsed_cycles*local_cpu_data->usec_per_cyc) >> IA64_USEC_PER_CYC_SHIFT;
83 }
84
85 void
86 do_settimeofday (struct timeval *tv)
87 {
88 write_lock_irq(&xtime_lock);
89 {
90 /*
91 * This is revolting. We need to set "xtime" correctly. However, the value
92 * in this location is the value at the most recent update of wall time.
93 * Discover what correction gettimeofday would have done, and then undo
94 * it!
95 */
96 tv->tv_usec -= gettimeoffset();
97 tv->tv_usec -= (jiffies - wall_jiffies) * (1000000 / HZ);
98
99 while (tv->tv_usec < 0) {
100 tv->tv_usec += 1000000;
101 tv->tv_sec--;
102 }
103
104 xtime = *tv;
105 time_adjust = 0; /* stop active adjtime() */
106 time_status |= STA_UNSYNC;
107 time_maxerror = NTP_PHASE_LIMIT;
108 time_esterror = NTP_PHASE_LIMIT;
109 }
110 write_unlock_irq(&xtime_lock);
111 }
112
113 void
114 do_gettimeofday (struct timeval *tv)
115 {
116 unsigned long flags, usec, sec, old;
117
118 read_lock_irqsave(&xtime_lock, flags);
119 {
120 usec = gettimeoffset();
121
122 /*
123 * Ensure time never goes backwards, even when ITC on different CPUs are
124 * not perfectly synchronized.
125 */
126 do {
127 old = last_time_offset;
128 if (usec <= old) {
129 usec = old;
130 break;
131 }
132 } while (cmpxchg(&last_time_offset, old, usec) != old);
133
134 sec = xtime.tv_sec;
135 usec += xtime.tv_usec;
136 }
137 read_unlock_irqrestore(&xtime_lock, flags);
138
139 while (usec >= 1000000) {
140 usec -= 1000000;
141 ++sec;
142 }
143
144 tv->tv_sec = sec;
145 tv->tv_usec = usec;
146 }
147
148 static void
149 timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
150 {
151 unsigned long new_itm;
152
153 new_itm = local_cpu_data->itm_next;
154
155 if (!time_after(ia64_get_itc(), new_itm))
156 printk("Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
157 ia64_get_itc(), new_itm);
158
159 while (1) {
160 /*
161 * Do kernel PC profiling here. We multiply the instruction number by
162 * four so that we can use a prof_shift of 2 to get instruction-level
163 * instead of just bundle-level accuracy.
164 */
165 if (!user_mode(regs))
166 do_profile(regs->cr_iip + 4*ia64_psr(regs)->ri);
167
168 #ifdef CONFIG_SMP
169 smp_do_timer(regs);
170 #endif
171 new_itm += local_cpu_data->itm_delta;
172
173 if (smp_processor_id() == 0) {
174 /*
175 * Here we are in the timer irq handler. We have irqs locally
176 * disabled, but we don't know if the timer_bh is running on
177 * another CPU. We need to avoid to SMP race by acquiring the
178 * xtime_lock.
179 */
180 write_lock(&xtime_lock);
181 do_timer(regs);
182 local_cpu_data->itm_next = new_itm;
183 write_unlock(&xtime_lock);
184 } else
185 local_cpu_data->itm_next = new_itm;
186
187 if (time_after(new_itm, ia64_get_itc()))
188 break;
189 }
190
191 do {
192 /*
193 * If we're too close to the next clock tick for comfort, we increase the
194 * saftey margin by intentionally dropping the next tick(s). We do NOT update
195 * itm.next because that would force us to call do_timer() which in turn would
196 * let our clock run too fast (with the potentially devastating effect of
197 * losing monotony of time).
198 */
199 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
200 new_itm += local_cpu_data->itm_delta;
201 ia64_set_itm(new_itm);
202 /* double check, in case we got hit by a (slow) PMI: */
203 } while (time_after_eq(ia64_get_itc(), new_itm));
204 }
205
206 /*
207 * Encapsulate access to the itm structure for SMP.
208 */
209 void __init
210 ia64_cpu_local_tick (void)
211 {
212 int cpu = smp_processor_id();
213 unsigned long shift = 0, delta;
214
215 /* arrange for the cycle counter to generate a timer interrupt: */
216 ia64_set_itv(IA64_TIMER_VECTOR);
217
218 delta = local_cpu_data->itm_delta;
219 /*
220 * Stagger the timer tick for each CPU so they don't occur all at (almost) the
221 * same time:
222 */
223 if (cpu) {
224 unsigned long hi = 1UL << ia64_fls(cpu);
225 shift = (2*(cpu - hi) + 1) * delta/hi/2;
226 }
227 local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
228 ia64_set_itm(local_cpu_data->itm_next);
229 }
230
231 void __init
232 ia64_init_itm (void)
233 {
234 unsigned long platform_base_freq, itc_freq, drift;
235 struct pal_freq_ratio itc_ratio, proc_ratio;
236 long status;
237
238 /*
239 * According to SAL v2.6, we need to use a SAL call to determine the platform base
240 * frequency and then a PAL call to determine the frequency ratio between the ITC
241 * and the base frequency.
242 */
243 status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM, &platform_base_freq, &drift);
244 if (status != 0) {
245 printk("SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
246 } else {
247 status = ia64_pal_freq_ratios(&proc_ratio, 0, &itc_ratio);
248 if (status != 0)
249 printk("PAL_FREQ_RATIOS failed with status=%ld\n", status);
250 }
251 if (status != 0) {
252 /* invent "random" values */
253 printk("SAL/PAL failed to obtain frequency info---inventing reasonably values\n");
254 platform_base_freq = 100000000;
255 itc_ratio.num = 3;
256 itc_ratio.den = 1;
257 }
258 if (platform_base_freq < 40000000) {
259 printk("Platform base frequency %lu bogus---resetting to 75MHz!\n",
260 platform_base_freq);
261 platform_base_freq = 75000000;
262 }
263 if (!proc_ratio.den)
264 proc_ratio.den = 1; /* avoid division by zero */
265 if (!itc_ratio.den)
266 itc_ratio.den = 1; /* avoid division by zero */
267
268 itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
269 local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
270 printk("CPU %d: base freq=%lu.%03luMHz, ITC ratio=%lu/%lu, ITC freq=%lu.%03luMHz\n",
271 smp_processor_id(),
272 platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
273 itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
274
275 local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
276 local_cpu_data->itc_freq = itc_freq;
277 local_cpu_data->cyc_per_usec = (itc_freq + 500000) / 1000000;
278 local_cpu_data->usec_per_cyc = ((1000000UL<<IA64_USEC_PER_CYC_SHIFT)
279 + itc_freq/2)/itc_freq;
280
281 /* Setup the CPU local timer tick */
282 ia64_cpu_local_tick();
283 }
284
285 static struct irqaction timer_irqaction = {
286 handler: timer_interrupt,
287 flags: SA_INTERRUPT,
288 name: "timer"
289 };
290
291 void __init
292 time_init (void)
293 {
294 register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
295 efi_gettimeofday((struct timeval *) &xtime);
296 ia64_init_itm();
297 }
298