Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/sparc-2.6
[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/timex.h>
22
23 #include <asm/machvec.h>
24 #include <asm/delay.h>
25 #include <asm/hw_irq.h>
26 #include <asm/ptrace.h>
27 #include <asm/sal.h>
28 #include <asm/sections.h>
29 #include <asm/system.h>
30
31 volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
32
33 #ifdef CONFIG_IA64_DEBUG_IRQ
34
35 unsigned long last_cli_ip;
36 EXPORT_SYMBOL(last_cli_ip);
37
38 #endif
39
40 static struct time_interpolator itc_interpolator = {
41         .shift = 16,
42         .mask = 0xffffffffffffffffLL,
43         .source = TIME_SOURCE_CPU
44 };
45
46 static irqreturn_t
47 timer_interrupt (int irq, void *dev_id)
48 {
49         unsigned long new_itm;
50
51         if (unlikely(cpu_is_offline(smp_processor_id()))) {
52                 return IRQ_HANDLED;
53         }
54
55         platform_timer_interrupt(irq, dev_id);
56
57         new_itm = local_cpu_data->itm_next;
58
59         if (!time_after(ia64_get_itc(), new_itm))
60                 printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
61                        ia64_get_itc(), new_itm);
62
63         profile_tick(CPU_PROFILING);
64
65         while (1) {
66                 update_process_times(user_mode(get_irq_regs()));
67
68                 new_itm += local_cpu_data->itm_delta;
69
70                 if (smp_processor_id() == time_keeper_id) {
71                         /*
72                          * Here we are in the timer irq handler. We have irqs locally
73                          * disabled, but we don't know if the timer_bh is running on
74                          * another CPU. We need to avoid to SMP race by acquiring the
75                          * xtime_lock.
76                          */
77                         write_seqlock(&xtime_lock);
78                         do_timer(1);
79                         local_cpu_data->itm_next = new_itm;
80                         write_sequnlock(&xtime_lock);
81                 } else
82                         local_cpu_data->itm_next = new_itm;
83
84                 if (time_after(new_itm, ia64_get_itc()))
85                         break;
86
87                 /*
88                  * Allow IPIs to interrupt the timer loop.
89                  */
90                 local_irq_enable();
91                 local_irq_disable();
92         }
93
94         do {
95                 /*
96                  * If we're too close to the next clock tick for
97                  * comfort, we increase the safety margin by
98                  * intentionally dropping the next tick(s).  We do NOT
99                  * update itm.next because that would force us to call
100                  * do_timer() which in turn would let our clock run
101                  * too fast (with the potentially devastating effect
102                  * of losing monotony of time).
103                  */
104                 while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
105                         new_itm += local_cpu_data->itm_delta;
106                 ia64_set_itm(new_itm);
107                 /* double check, in case we got hit by a (slow) PMI: */
108         } while (time_after_eq(ia64_get_itc(), new_itm));
109         return IRQ_HANDLED;
110 }
111
112 /*
113  * Encapsulate access to the itm structure for SMP.
114  */
115 void
116 ia64_cpu_local_tick (void)
117 {
118         int cpu = smp_processor_id();
119         unsigned long shift = 0, delta;
120
121         /* arrange for the cycle counter to generate a timer interrupt: */
122         ia64_set_itv(IA64_TIMER_VECTOR);
123
124         delta = local_cpu_data->itm_delta;
125         /*
126          * Stagger the timer tick for each CPU so they don't occur all at (almost) the
127          * same time:
128          */
129         if (cpu) {
130                 unsigned long hi = 1UL << ia64_fls(cpu);
131                 shift = (2*(cpu - hi) + 1) * delta/hi/2;
132         }
133         local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
134         ia64_set_itm(local_cpu_data->itm_next);
135 }
136
137 static int nojitter;
138
139 static int __init nojitter_setup(char *str)
140 {
141         nojitter = 1;
142         printk("Jitter checking for ITC timers disabled\n");
143         return 1;
144 }
145
146 __setup("nojitter", nojitter_setup);
147
148
149 void __devinit
150 ia64_init_itm (void)
151 {
152         unsigned long platform_base_freq, itc_freq;
153         struct pal_freq_ratio itc_ratio, proc_ratio;
154         long status, platform_base_drift, itc_drift;
155
156         /*
157          * According to SAL v2.6, we need to use a SAL call to determine the platform base
158          * frequency and then a PAL call to determine the frequency ratio between the ITC
159          * and the base frequency.
160          */
161         status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
162                                     &platform_base_freq, &platform_base_drift);
163         if (status != 0) {
164                 printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
165         } else {
166                 status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
167                 if (status != 0)
168                         printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
169         }
170         if (status != 0) {
171                 /* invent "random" values */
172                 printk(KERN_ERR
173                        "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
174                 platform_base_freq = 100000000;
175                 platform_base_drift = -1;       /* no drift info */
176                 itc_ratio.num = 3;
177                 itc_ratio.den = 1;
178         }
179         if (platform_base_freq < 40000000) {
180                 printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
181                        platform_base_freq);
182                 platform_base_freq = 75000000;
183                 platform_base_drift = -1;
184         }
185         if (!proc_ratio.den)
186                 proc_ratio.den = 1;     /* avoid division by zero */
187         if (!itc_ratio.den)
188                 itc_ratio.den = 1;      /* avoid division by zero */
189
190         itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
191
192         local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
193         printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
194                "ITC freq=%lu.%03luMHz", smp_processor_id(),
195                platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
196                itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
197
198         if (platform_base_drift != -1) {
199                 itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
200                 printk("+/-%ldppm\n", itc_drift);
201         } else {
202                 itc_drift = -1;
203                 printk("\n");
204         }
205
206         local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
207         local_cpu_data->itc_freq = itc_freq;
208         local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
209         local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
210                                         + itc_freq/2)/itc_freq;
211
212         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
213                 itc_interpolator.frequency = local_cpu_data->itc_freq;
214                 itc_interpolator.drift = itc_drift;
215 #ifdef CONFIG_SMP
216                 /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
217                  * Jitter compensation requires a cmpxchg which may limit
218                  * the scalability of the syscalls for retrieving time.
219                  * The ITC synchronization is usually successful to within a few
220                  * ITC ticks but this is not a sure thing. If you need to improve
221                  * timer performance in SMP situations then boot the kernel with the
222                  * "nojitter" option. However, doing so may result in time fluctuating (maybe
223                  * even going backward) if the ITC offsets between the individual CPUs
224                  * are too large.
225                  */
226                 if (!nojitter) itc_interpolator.jitter = 1;
227 #endif
228                 register_time_interpolator(&itc_interpolator);
229         }
230
231         /* Setup the CPU local timer tick */
232         ia64_cpu_local_tick();
233 }
234
235 static struct irqaction timer_irqaction = {
236         .handler =      timer_interrupt,
237         .flags =        IRQF_DISABLED | IRQF_IRQPOLL,
238         .name =         "timer"
239 };
240
241 void __devinit ia64_disable_timer(void)
242 {
243         ia64_set_itv(1 << 16);
244 }
245
246 void __init
247 time_init (void)
248 {
249         register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
250         efi_gettimeofday(&xtime);
251         ia64_init_itm();
252
253         /*
254          * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
255          * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
256          */
257         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
258 }
259
260 /*
261  * Generic udelay assumes that if preemption is allowed and the thread
262  * migrates to another CPU, that the ITC values are synchronized across
263  * all CPUs.
264  */
265 static void
266 ia64_itc_udelay (unsigned long usecs)
267 {
268         unsigned long start = ia64_get_itc();
269         unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
270
271         while (time_before(ia64_get_itc(), end))
272                 cpu_relax();
273 }
274
275 void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
276
277 void
278 udelay (unsigned long usecs)
279 {
280         (*ia64_udelay)(usecs);
281 }
282 EXPORT_SYMBOL(udelay);
283
284 static unsigned long long ia64_itc_printk_clock(void)
285 {
286         if (ia64_get_kr(IA64_KR_PER_CPU_DATA))
287                 return sched_clock();
288         return 0;
289 }
290
291 static unsigned long long ia64_default_printk_clock(void)
292 {
293         return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES) *
294                 (1000000000/HZ);
295 }
296
297 unsigned long long (*ia64_printk_clock)(void) = &ia64_default_printk_clock;
298
299 unsigned long long printk_clock(void)
300 {
301         return ia64_printk_clock();
302 }
303
304 void __init
305 ia64_setup_printk_clock(void)
306 {
307         if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT))
308                 ia64_printk_clock = ia64_itc_printk_clock;
309 }