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 31volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */ 32 33#ifdef CONFIG_IA64_DEBUG_IRQ 34 35unsigned long last_cli_ip; 36EXPORT_SYMBOL(last_cli_ip); 37 38#endif 39 40static struct time_interpolator itc_interpolator = { 41 .shift = 16, 42 .mask = 0xffffffffffffffffLL, 43 .source = TIME_SOURCE_CPU 44}; 45 46static irqreturn_t 47timer_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 */ 115void 116ia64_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 137static int nojitter; 138 139static 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 149void __devinit 150ia64_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 235static struct irqaction timer_irqaction = { 236 .handler = timer_interrupt, 237 .flags = IRQF_DISABLED | IRQF_IRQPOLL, 238 .name = "timer" 239}; 240 241void __devinit ia64_disable_timer(void) 242{ 243 ia64_set_itv(1 << 16); 244} 245 246void __init 247time_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 */ 265static void 266ia64_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 275void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay; 276 277void 278udelay (unsigned long usecs) 279{ 280 (*ia64_udelay)(usecs); 281} 282EXPORT_SYMBOL(udelay); 283 284static 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 291static unsigned long long ia64_default_printk_clock(void) 292{ 293 return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES) * 294 (1000000000/HZ); 295} 296 297unsigned long long (*ia64_printk_clock)(void) = &ia64_default_printk_clock; 298 299unsigned long long printk_clock(void) 300{ 301 return ia64_printk_clock(); 302} 303 304void __init 305ia64_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} 310