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 percision, 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;
 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         }
 147         /*
 148          * Error: ECTCNEVERSET
 149          * The CTC wasn't reliable: we got a hit on the very first read,
 150          * or the CPU was so fast/slow that the quotient wouldn't fit in
 151          * 32 bits..
 152          */
 153         if (count <= 1)
 154                 goto err;
 155
 156         delta64 = end - start;
 157
 158         /* cpu freq too fast: */
 159         if (delta64 > (1ULL<<32))
 160                 goto err;
 161
 162         /* cpu freq too slow: */
 163         if (delta64 <= CALIBRATE_TIME_MSEC)
 164                 goto err;
 165
 166         delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
 167         do_div(delta64,CALIBRATE_TIME_MSEC);
 168
 169         local_irq_restore(flags);
 170         return (unsigned long)delta64;
 171 err:
 172         local_irq_restore(flags);
 173         return 0;
 174 }
 175
 176 int recalibrate_cpu_khz(void)
 177 {
 178 #ifndef CONFIG_SMP
 179         unsigned long cpu_khz_old = cpu_khz;
 180
 181         if (cpu_has_tsc) {
 182                 cpu_khz = calculate_cpu_khz();
 183                 tsc_khz = cpu_khz;
 184                 cpu_data[0].loops_per_jiffy =
 185                         cpufreq_scale(cpu_data[0].loops_per_jiffy,
 186                                         cpu_khz_old, cpu_khz);
 187                 return 0;
 188         } else
 189                 return -ENODEV;
 190 #else
 191         return -ENODEV;
 192 #endif
 193 }
 194
 195 EXPORT_SYMBOL(recalibrate_cpu_khz);
 196
 197 #ifdef CONFIG_CPU_FREQ
 198
 199 /*
 200  * if the CPU frequency is scaled, TSC-based delays will need a different
 201  * loops_per_jiffy value to function properly.
 202  */
 203 static unsigned int ref_freq = 0;
 204 static unsigned long loops_per_jiffy_ref = 0;
 205 static unsigned long cpu_khz_ref = 0;
 206
 207 static int
 208 time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
 209 {
 210         struct cpufreq_freqs *freq = data;
 211
 212         if (!ref_freq) {
 213                 if (!freq->old){
 214                         ref_freq = freq->new;
 215                         return 0;
 216                 }
 217                 ref_freq = freq->old;
 218                 loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy;
 219                 cpu_khz_ref = cpu_khz;
 220         }
 221
 222         if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
 223             (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
 224             (val == CPUFREQ_RESUMECHANGE)) {
 225                 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
 226                         cpu_data[freq->cpu].loops_per_jiffy =
 227                                 cpufreq_scale(loops_per_jiffy_ref,
 228                                                 ref_freq, freq->new);
 229
 230                 if (cpu_khz) {
 231
 232                         if (num_online_cpus() == 1)
 233                                 cpu_khz = cpufreq_scale(cpu_khz_ref,
 234                                                 ref_freq, freq->new);
 235                         if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
 236                                 tsc_khz = cpu_khz;
 237                                 set_cyc2ns_scale(cpu_khz);
 238                                 /*
 239                                  * TSC based sched_clock turns
 240                                  * to junk w/ cpufreq
 241                                  */
 242                                 mark_tsc_unstable("cpufreq changes");
 243                         }
 244                 }
 245         }
 246
 247         return 0;
 248 }
 249
 250 static struct notifier_block time_cpufreq_notifier_block = {
 251         .notifier_call  = time_cpufreq_notifier
 252 };
 253
 254 static int __init cpufreq_tsc(void)
 255 {
 256         return cpufreq_register_notifier(&time_cpufreq_notifier_block,
 257                                          CPUFREQ_TRANSITION_NOTIFIER);
 258 }
 259 core_initcall(cpufreq_tsc);
 260
 261 #endif
 262
 263 /* clock source code */
 264
 265 static unsigned long current_tsc_khz = 0;
 266
 267 static cycle_t read_tsc(void)
 268 {
 269         cycle_t ret;
 270
 271         rdtscll(ret);
 272
 273         return ret;
 274 }
 275
 276 static struct clocksource clocksource_tsc = {
 277         .name                   = "tsc",
 278         .rating                 = 300,
 279         .read                   = read_tsc,
 280         .mask                   = CLOCKSOURCE_MASK(64),
 281         .mult                   = 0, /* to be set */
 282         .shift                  = 22,
 283         .flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
 284                                   CLOCK_SOURCE_MUST_VERIFY,
 285 };
 286
 287 void mark_tsc_unstable(char *reason)
 288 {
 289         if (!tsc_unstable) {
 290                 tsc_unstable = 1;
 291                 tsc_enabled = 0;
 292                 printk("Marking TSC unstable due to: %s.\n", reason);
 293                 /* Can be called before registration */
 294                 if (clocksource_tsc.mult)
 295                         clocksource_change_rating(&clocksource_tsc, 0);
 296                 else
 297                         clocksource_tsc.rating = 0;
 298         }
 299 }
 300 EXPORT_SYMBOL_GPL(mark_tsc_unstable);
 301
 302 static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d)
 303 {
 304         printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
 305                        d->ident);
 306         tsc_unstable = 1;
 307         return 0;
 308 }
 309
 310 /* List of systems that have known TSC problems */
 311 static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
 312         {
 313          .callback = dmi_mark_tsc_unstable,
 314          .ident = "IBM Thinkpad 380XD",
 315          .matches = {
 316                      DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
 317                      DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
 318                      },
 319          },
 320          {}
 321 };
 322
 323 /*
 324  * Make an educated guess if the TSC is trustworthy and synchronized
 325  * over all CPUs.
 326  */
 327 __cpuinit int unsynchronized_tsc(void)
 328 {
 329         if (!cpu_has_tsc || tsc_unstable)
 330                 return 1;
 331         /*
 332          * Intel systems are normally all synchronized.
 333          * Exceptions must mark TSC as unstable:
 334          */
 335         if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
 336                 /* assume multi socket systems are not synchronized: */
 337                 if (num_possible_cpus() > 1)
 338                         tsc_unstable = 1;
 339         }
 340         return tsc_unstable;
 341 }
 342
 343 /*
 344  * Geode_LX - the OLPC CPU has a possibly a very reliable TSC
 345  */
 346 #ifdef CONFIG_MGEODE_LX
 347 /* RTSC counts during suspend */
 348 #define RTSC_SUSP 0x100
 349
 350 static void __init check_geode_tsc_reliable(void)
 351 {
 352         unsigned long res_low, res_high;
 353
 354         rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
 355         if (res_low & RTSC_SUSP)
 356                 clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
 357 }
 358 #else
 359 static inline void check_geode_tsc_reliable(void) { }
 360 #endif
 361
 362
 363 void __init tsc_init(void)
 364 {
 365         if (!cpu_has_tsc || tsc_disable)
 366                 goto out_no_tsc;
 367
 368         cpu_khz = calculate_cpu_khz();
 369         tsc_khz = cpu_khz;
 370
 371         if (!cpu_khz)
 372                 goto out_no_tsc;
 373
 374         printk("Detected %lu.%03lu MHz processor.\n",
 375                                 (unsigned long)cpu_khz / 1000,
 376                                 (unsigned long)cpu_khz % 1000);
 377
 378         set_cyc2ns_scale(cpu_khz);
 379         use_tsc_delay();
 380
 381         /* Check and install the TSC clocksource */
 382         dmi_check_system(bad_tsc_dmi_table);
 383
 384         unsynchronized_tsc();
 385         check_geode_tsc_reliable();
 386         current_tsc_khz = tsc_khz;
 387         clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
 388                                                         clocksource_tsc.shift);
 389         /* lower the rating if we already know its unstable: */
 390         if (check_tsc_unstable()) {
 391                 clocksource_tsc.rating = 0;
 392                 clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
 393         } else
 394                 tsc_enabled = 1;
 395
 396         clocksource_register(&clocksource_tsc);
 397
 398         return;
 399
 400 out_no_tsc:
 401         /*
 402          * Set the tsc_disable flag if there's no TSC support, this
 403          * makes it a fast flag for the kernel to see whether it
 404          * should be using the TSC.
 405          */
 406         tsc_disable = 1;
 407 }