Merge branch 'upstream-linus' of master.kernel.org:/pub/scm/linux/kernel/git/jgarzik...
[linux-2.6] / arch / ia64 / kernel / time.c
1 /*
2  * linux/arch/ia64/kernel/time.c
3  *
4  * Copyright (C) 1998-2003 Hewlett-Packard Co
5  *      Stephane Eranian <eranian@hpl.hp.com>
6  *      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
12 #include <linux/cpu.h>
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/profile.h>
17 #include <linux/sched.h>
18 #include <linux/time.h>
19 #include <linux/interrupt.h>
20 #include <linux/efi.h>
21 #include <linux/profile.h>
22 #include <linux/timex.h>
23
24 #include <asm/machvec.h>
25 #include <asm/delay.h>
26 #include <asm/hw_irq.h>
27 #include <asm/ptrace.h>
28 #include <asm/sal.h>
29 #include <asm/sections.h>
30 #include <asm/system.h>
31
32 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
33
34 #ifdef CONFIG_IA64_DEBUG_IRQ
35
36 unsigned long last_cli_ip;
37 EXPORT_SYMBOL(last_cli_ip);
38
39 #endif
40
41 static struct time_interpolator itc_interpolator = {
42         .shift = 16,
43         .mask = 0xffffffffffffffffLL,
44         .source = TIME_SOURCE_CPU
45 };
46
47 static irqreturn_t
48 timer_interrupt (int irq, void *dev_id, struct pt_regs *regs)
49 {
50         unsigned long new_itm;
51
52         if (unlikely(cpu_is_offline(smp_processor_id()))) {
53                 return IRQ_HANDLED;
54         }
55
56         platform_timer_interrupt(irq, dev_id, regs);
57
58         new_itm = local_cpu_data->itm_next;
59
60         if (!time_after(ia64_get_itc(), new_itm))
61                 printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
62                        ia64_get_itc(), new_itm);
63
64         profile_tick(CPU_PROFILING, regs);
65
66         while (1) {
67                 update_process_times(user_mode(regs));
68
69                 new_itm += local_cpu_data->itm_delta;
70
71                 if (smp_processor_id() == time_keeper_id) {
72                         /*
73                          * Here we are in the timer irq handler. We have irqs locally
74                          * disabled, but we don't know if the timer_bh is running on
75                          * another CPU. We need to avoid to SMP race by acquiring the
76                          * xtime_lock.
77                          */
78                         write_seqlock(&xtime_lock);
79                         do_timer(1);
80                         local_cpu_data->itm_next = new_itm;
81                         write_sequnlock(&xtime_lock);
82                 } else
83                         local_cpu_data->itm_next = new_itm;
84
85                 if (time_after(new_itm, ia64_get_itc()))
86                         break;
87         }
88
89         do {
90                 /*
91                  * If we're too close to the next clock tick for
92                  * comfort, we increase the safety margin by
93                  * intentionally dropping the next tick(s).  We do NOT
94                  * update itm.next because that would force us to call
95                  * do_timer() which in turn would let our clock run
96                  * too fast (with the potentially devastating effect
97                  * of losing monotony of time).
98                  */
99                 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
100                         new_itm += local_cpu_data->itm_delta;
101                 ia64_set_itm(new_itm);
102                 /* double check, in case we got hit by a (slow) PMI: */
103         } while (time_after_eq(ia64_get_itc(), new_itm));
104         return IRQ_HANDLED;
105 }
106
107 /*
108  * Encapsulate access to the itm structure for SMP.
109  */
110 void
111 ia64_cpu_local_tick (void)
112 {
113         int cpu = smp_processor_id();
114         unsigned long shift = 0, delta;
115
116         /* arrange for the cycle counter to generate a timer interrupt: */
117         ia64_set_itv(IA64_TIMER_VECTOR);
118
119         delta = local_cpu_data->itm_delta;
120         /*
121          * Stagger the timer tick for each CPU so they don't occur all at (almost) the
122          * same time:
123          */
124         if (cpu) {
125                 unsigned long hi = 1UL << ia64_fls(cpu);
126                 shift = (2*(cpu - hi) + 1) * delta/hi/2;
127         }
128         local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
129         ia64_set_itm(local_cpu_data->itm_next);
130 }
131
132 static int nojitter;
133
134 static int __init nojitter_setup(char *str)
135 {
136         nojitter = 1;
137         printk("Jitter checking for ITC timers disabled\n");
138         return 1;
139 }
140
141 __setup("nojitter", nojitter_setup);
142
143
144 void __devinit
145 ia64_init_itm (void)
146 {
147         unsigned long platform_base_freq, itc_freq;
148         struct pal_freq_ratio itc_ratio, proc_ratio;
149         long status, platform_base_drift, itc_drift;
150
151         /*
152          * According to SAL v2.6, we need to use a SAL call to determine the platform base
153          * frequency and then a PAL call to determine the frequency ratio between the ITC
154          * and the base frequency.
155          */
156         status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
157                                     &platform_base_freq, &platform_base_drift);
158         if (status != 0) {
159                 printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
160         } else {
161                 status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
162                 if (status != 0)
163                         printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
164         }
165         if (status != 0) {
166                 /* invent "random" values */
167                 printk(KERN_ERR
168                        "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
169                 platform_base_freq = 100000000;
170                 platform_base_drift = -1;       /* no drift info */
171                 itc_ratio.num = 3;
172                 itc_ratio.den = 1;
173         }
174         if (platform_base_freq < 40000000) {
175                 printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
176                        platform_base_freq);
177                 platform_base_freq = 75000000;
178                 platform_base_drift = -1;
179         }
180         if (!proc_ratio.den)
181                 proc_ratio.den = 1;     /* avoid division by zero */
182         if (!itc_ratio.den)
183                 itc_ratio.den = 1;      /* avoid division by zero */
184
185         itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
186
187         local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
188         printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
189                "ITC freq=%lu.%03luMHz", smp_processor_id(),
190                platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
191                itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
192
193         if (platform_base_drift != -1) {
194                 itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
195                 printk("+/-%ldppm\n", itc_drift);
196         } else {
197                 itc_drift = -1;
198                 printk("\n");
199         }
200
201         local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
202         local_cpu_data->itc_freq = itc_freq;
203         local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
204         local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
205                                         + itc_freq/2)/itc_freq;
206
207         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
208                 itc_interpolator.frequency = local_cpu_data->itc_freq;
209                 itc_interpolator.drift = itc_drift;
210 #ifdef CONFIG_SMP
211                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
212                  * Jitter compensation requires a cmpxchg which may limit
213                  * the scalability of the syscalls for retrieving time.
214                  * The ITC synchronization is usually successful to within a few
215                  * ITC ticks but this is not a sure thing. If you need to improve
216                  * timer performance in SMP situations then boot the kernel with the
217                  * "nojitter" option. However, doing so may result in time fluctuating (maybe
218                  * even going backward) if the ITC offsets between the individual CPUs
219                  * are too large.
220                  */
221                 if (!nojitter) itc_interpolator.jitter = 1;
222 #endif
223                 register_time_interpolator(&itc_interpolator);
224         }
225
226         /* Setup the CPU local timer tick */
227         ia64_cpu_local_tick();
228 }
229
230 static struct irqaction timer_irqaction = {
231         .handler =      timer_interrupt,
232         .flags =        IRQF_DISABLED,
233         .name =         "timer"
234 };
235
236 void __devinit ia64_disable_timer(void)
237 {
238         ia64_set_itv(1 << 16);
239 }
240
241 void __init
242 time_init (void)
243 {
244         register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
245         efi_gettimeofday(&xtime);
246         ia64_init_itm();
247
248         /*
249          * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
250          * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
251          */
252         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
253 }
254
255 /*
256  * Generic udelay assumes that if preemption is allowed and the thread
257  * migrates to another CPU, that the ITC values are synchronized across
258  * all CPUs.
259  */
260 static void
261 ia64_itc_udelay (unsigned long usecs)
262 {
263         unsigned long start = ia64_get_itc();
264         unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
265
266         while (time_before(ia64_get_itc(), end))
267                 cpu_relax();
268 }
269
270 void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
271
272 void
273 udelay (unsigned long usecs)
274 {
275         (*ia64_udelay)(usecs);
276 }
277 EXPORT_SYMBOL(udelay);
278
279 static unsigned long long ia64_itc_printk_clock(void)
280 {
281         if (ia64_get_kr(IA64_KR_PER_CPU_DATA))
282                 return sched_clock();
283         return 0;
284 }
285
286 static unsigned long long ia64_default_printk_clock(void)
287 {
288         return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES) *
289                 (1000000000/HZ);
290 }
291
292 unsigned long long (*ia64_printk_clock)(void) = &ia64_default_printk_clock;
293
294 unsigned long long printk_clock(void)
295 {
296         return ia64_printk_clock();
297 }
298
299 void __init
300 ia64_setup_printk_clock(void)
301 {
302         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT))
303                 ia64_printk_clock = ia64_itc_printk_clock;
304 }