err.no Git - linux-2.6/blob - arch/x86/kernel/tsc_32.c

   1 #include <linux/sched.h>
   2 #include <linux/clocksource.h>
   3 #include <linux/workqueue.h>
   4 #include <linux/cpufreq.h>
   5 #include <linux/jiffies.h>
   6 #include <linux/init.h>
   7 #include <linux/dmi.h>
   8
   9 #include <asm/delay.h>
  10 #include <asm/tsc.h>
  11 #include <asm/io.h>
  12 #include <asm/timer.h>
  13
  14 #include "mach_timer.h"
  15
  16 static int tsc_enabled;
  17
  18 /*
  19  * On some systems the TSC frequency does not
  20  * change with the cpu frequency. So we need
  21  * an extra value to store the TSC freq
  22  */
  23 unsigned int tsc_khz;
  24 EXPORT_SYMBOL_GPL(tsc_khz);
  25
  26 int tsc_disable;
  27
  28 #ifdef CONFIG_X86_TSC
  29 static int __init tsc_setup(char *str)
  30 {
  31         printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
  32                                 "cannot disable TSC.\n");
  33         return 1;
  34 }
  35 #else
  36 /*
  37  * disable flag for tsc. Takes effect by clearing the TSC cpu flag
  38  * in cpu/common.c
  39  */
  40 static int __init tsc_setup(char *str)
  41 {
  42         tsc_disable = 1;
  43
  44         return 1;
  45 }
  46 #endif
  47
  48 __setup("notsc", tsc_setup);
  49
  50 /*
  51  * code to mark and check if the TSC is unstable
  52  * due to cpufreq or due to unsynced TSCs
  53  */
  54 static int tsc_unstable;
  55
  56 int check_tsc_unstable(void)
  57 {
  58         return tsc_unstable;
  59 }
  60 EXPORT_SYMBOL_GPL(check_tsc_unstable);
  61
  62 /* Accelerators for sched_clock()
  63  * convert from cycles(64bits) => nanoseconds (64bits)
  64  *  basic equation:
  65  *              ns = cycles / (freq / ns_per_sec)
  66  *              ns = cycles * (ns_per_sec / freq)
  67  *              ns = cycles * (10^9 / (cpu_khz * 10^3))
  68  *              ns = cycles * (10^6 / cpu_khz)
  69  *
  70  *      Then we use scaling math (suggested by george@mvista.com) to get:
  71  *              ns = cycles * (10^6 * SC / cpu_khz) / SC
  72  *              ns = cycles * cyc2ns_scale / SC
  73  *
  74  *      And since SC is a constant power of two, we can convert the div
  75  *  into a shift.
  76  *
  77  *  We can use khz divisor instead of mhz to keep a better precision, since
  78  *  cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
  79  *  (mathieu.desnoyers@polymtl.ca)
  80  *
  81  *                      -johnstul@us.ibm.com "math is hard, lets go shopping!"
  82  */
  83 unsigned long cyc2ns_scale __read_mostly;
  84
  85 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
  86
  87 static inline void set_cyc2ns_scale(unsigned long cpu_khz)
  88 {
  89         cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
  90 }
  91
  92 /*
  93  * Scheduler clock - returns current time in nanosec units.
  94  */
  95 unsigned long long native_sched_clock(void)
  96 {
  97         unsigned long long this_offset;
  98
  99         /*
 100          * Fall back to jiffies if there's no TSC available:
 101          * ( But note that we still use it if the TSC is marked
 102          *   unstable. We do this because unlike Time Of Day,
 103          *   the scheduler clock tolerates small errors and it's
 104          *   very important for it to be as fast as the platform
 105          *   can achive it. )
 106          */
 107         if (unlikely(!tsc_enabled && !tsc_unstable))
 108                 /* No locking but a rare wrong value is not a big deal: */
 109                 return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
 110
 111         /* read the Time Stamp Counter: */
 112         rdtscll(this_offset);
 113
 114         /* return the value in ns */
 115         return cycles_2_ns(this_offset);
 116 }
 117
 118 /* We need to define a real function for sched_clock, to override the
 119    weak default version */
 120 #ifdef CONFIG_PARAVIRT
 121 unsigned long long sched_clock(void)
 122 {
 123         return paravirt_sched_clock();
 124 }
 125 #else
 126 unsigned long long sched_clock(void)
 127         __attribute__((alias("native_sched_clock")));
 128 #endif
 129
 130 unsigned long native_calculate_cpu_khz(void)
 131 {
 132         unsigned long long start, end;
 133         unsigned long count;
 134         u64 delta64 = (u64)ULLONG_MAX;
 135         int i;
 136         unsigned long flags;
 137
 138         local_irq_save(flags);
 139
 140         /* run 3 times to ensure the cache is warm */
 141         for (i = 0; i < 3; i++) {
 142                 mach_prepare_counter();
 143                 rdtscll(start);
 144                 mach_countup(&count);
 145                 rdtscll(end);
 146                 delta64 = min(delta64, (end - start));
 147         }
 148         /*
 149          * Error: ECTCNEVERSET
 150          * The CTC wasn't reliable: we got a hit on the very first read,
 151          * or the CPU was so fast/slow that the quotient wouldn't fit in
 152          * 32 bits..
 153          */
 154         if (count <= 1)
 155                 goto err;
 156
 157         /* cpu freq too fast: */
 158         if (delta64 > (1ULL<<32))
 159                 goto err;
 160
 161         /* cpu freq too slow: */
 162         if (delta64 <= CALIBRATE_TIME_MSEC)
 163                 goto err;
 164
 165         delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
 166         do_div(delta64,CALIBRATE_TIME_MSEC);
 167
 168         local_irq_restore(flags);
 169         return (unsigned long)delta64;
 170 err:
 171         local_irq_restore(flags);
 172         return 0;
 173 }
 174
 175 int recalibrate_cpu_khz(void)
 176 {
 177 #ifndef CONFIG_SMP
 178         unsigned long cpu_khz_old = cpu_khz;
 179
 180         if (cpu_has_tsc) {
 181                 cpu_khz = calculate_cpu_khz();
 182                 tsc_khz = cpu_khz;
 183                 cpu_data(0).loops_per_jiffy =
 184                         cpufreq_scale(cpu_data(0).loops_per_jiffy,
 185                                         cpu_khz_old, cpu_khz);
 186                 return 0;
 187         } else
 188                 return -ENODEV;
 189 #else
 190         return -ENODEV;
 191 #endif
 192 }
 193
 194 EXPORT_SYMBOL(recalibrate_cpu_khz);
 195
 196 #ifdef CONFIG_CPU_FREQ
 197
 198 /*
 199  * if the CPU frequency is scaled, TSC-based delays will need a different
 200  * loops_per_jiffy value to function properly.
 201  */
 202 static unsigned int ref_freq = 0;
 203 static unsigned long loops_per_jiffy_ref = 0;
 204 static unsigned long cpu_khz_ref = 0;
 205
 206 static int
 207 time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
 208 {
 209         struct cpufreq_freqs *freq = data;
 210
 211         if (!ref_freq) {
 212                 if (!freq->old){
 213                         ref_freq = freq->new;
 214                         return 0;
 215                 }
 216                 ref_freq = freq->old;
 217                 loops_per_jiffy_ref = cpu_data(freq->cpu).loops_per_jiffy;
 218                 cpu_khz_ref = cpu_khz;
 219         }
 220
 221         if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
 222             (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
 223             (val == CPUFREQ_RESUMECHANGE)) {
 224                 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
 225                         cpu_data(freq->cpu).loops_per_jiffy =
 226                                 cpufreq_scale(loops_per_jiffy_ref,
 227                                                 ref_freq, freq->new);
 228
 229                 if (cpu_khz) {
 230
 231                         if (num_online_cpus() == 1)
 232                                 cpu_khz = cpufreq_scale(cpu_khz_ref,
 233                                                 ref_freq, freq->new);
 234                         if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
 235                                 tsc_khz = cpu_khz;
 236                                 set_cyc2ns_scale(cpu_khz);
 237                                 /*
 238                                  * TSC based sched_clock turns
 239                                  * to junk w/ cpufreq
 240                                  */
 241                                 mark_tsc_unstable("cpufreq changes");
 242                         }
 243                 }
 244         }
 245
 246         return 0;
 247 }
 248
 249 static struct notifier_block time_cpufreq_notifier_block = {
 250         .notifier_call  = time_cpufreq_notifier
 251 };
 252
 253 static int __init cpufreq_tsc(void)
 254 {
 255         return cpufreq_register_notifier(&time_cpufreq_notifier_block,
 256                                          CPUFREQ_TRANSITION_NOTIFIER);
 257 }
 258 core_initcall(cpufreq_tsc);
 259
 260 #endif
 261
 262 /* clock source code */
 263
 264 static unsigned long current_tsc_khz = 0;
 265
 266 static cycle_t read_tsc(void)
 267 {
 268         cycle_t ret;
 269
 270         rdtscll(ret);
 271
 272         return ret;
 273 }
 274
 275 static struct clocksource clocksource_tsc = {
 276         .name                   = "tsc",
 277         .rating                 = 300,
 278         .read                   = read_tsc,
 279         .mask                   = CLOCKSOURCE_MASK(64),
 280         .mult                   = 0, /* to be set */
 281         .shift                  = 22,
 282         .flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
 283                                   CLOCK_SOURCE_MUST_VERIFY,
 284 };
 285
 286 void mark_tsc_unstable(char *reason)
 287 {
 288         if (!tsc_unstable) {
 289                 tsc_unstable = 1;
 290                 tsc_enabled = 0;
 291                 printk("Marking TSC unstable due to: %s.\n", reason);
 292                 /* Can be called before registration */
 293                 if (clocksource_tsc.mult)
 294                         clocksource_change_rating(&clocksource_tsc, 0);
 295                 else
 296                         clocksource_tsc.rating = 0;
 297         }
 298 }
 299 EXPORT_SYMBOL_GPL(mark_tsc_unstable);
 300
 301 static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d)
 302 {
 303         printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
 304                        d->ident);
 305         tsc_unstable = 1;
 306         return 0;
 307 }
 308
 309 /* List of systems that have known TSC problems */
 310 static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
 311         {
 312          .callback = dmi_mark_tsc_unstable,
 313          .ident = "IBM Thinkpad 380XD",
 314          .matches = {
 315                      DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
 316                      DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
 317                      },
 318          },
 319          {}
 320 };
 321
 322 /*
 323  * Make an educated guess if the TSC is trustworthy and synchronized
 324  * over all CPUs.
 325  */
 326 __cpuinit int unsynchronized_tsc(void)
 327 {
 328         if (!cpu_has_tsc || tsc_unstable)
 329                 return 1;
 330         /*
 331          * Intel systems are normally all synchronized.
 332          * Exceptions must mark TSC as unstable:
 333          */
 334         if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
 335                 /* assume multi socket systems are not synchronized: */
 336                 if (num_possible_cpus() > 1)
 337                         tsc_unstable = 1;
 338         }
 339         return tsc_unstable;
 340 }
 341
 342 /*
 343  * Geode_LX - the OLPC CPU has a possibly a very reliable TSC
 344  */
 345 #ifdef CONFIG_MGEODE_LX
 346 /* RTSC counts during suspend */
 347 #define RTSC_SUSP 0x100
 348
 349 static void __init check_geode_tsc_reliable(void)
 350 {
 351         unsigned long res_low, res_high;
 352
 353         rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
 354         if (res_low & RTSC_SUSP)
 355                 clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
 356 }
 357 #else
 358 static inline void check_geode_tsc_reliable(void) { }
 359 #endif
 360
 361
 362 void __init tsc_init(void)
 363 {
 364         if (!cpu_has_tsc || tsc_disable)
 365                 goto out_no_tsc;
 366
 367         cpu_khz = calculate_cpu_khz();
 368         tsc_khz = cpu_khz;
 369
 370         if (!cpu_khz)
 371                 goto out_no_tsc;
 372
 373         printk("Detected %lu.%03lu MHz processor.\n",
 374                                 (unsigned long)cpu_khz / 1000,
 375                                 (unsigned long)cpu_khz % 1000);
 376
 377         set_cyc2ns_scale(cpu_khz);
 378         use_tsc_delay();
 379
 380         /* Check and install the TSC clocksource */
 381         dmi_check_system(bad_tsc_dmi_table);
 382
 383         unsynchronized_tsc();
 384         check_geode_tsc_reliable();
 385         current_tsc_khz = tsc_khz;
 386         clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
 387                                                         clocksource_tsc.shift);
 388         /* lower the rating if we already know its unstable: */
 389         if (check_tsc_unstable()) {
 390                 clocksource_tsc.rating = 0;
 391                 clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
 392         } else
 393                 tsc_enabled = 1;
 394
 395         clocksource_register(&clocksource_tsc);
 396
 397         return;
 398
 399 out_no_tsc:
 400         /*
 401          * Set the tsc_disable flag if there's no TSC support, this
 402          * makes it a fast flag for the kernel to see whether it
 403          * should be using the TSC.
 404          */
 405         tsc_disable = 1;
 406 }