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 and to get an accurate reading */
 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                         continue;
 155
 156                 /* cpu freq too slow: */
 157                 if ((end - start) <= CALIBRATE_TIME_MSEC)
 158                         continue;
 159
 160                 /*
 161                  * We want the minimum time of all runs in case one of them
 162                  * is inaccurate due to SMI or other delay
 163                  */
 164                 delta64 = min(delta64, (end - start));
 165         }
 166
 167         /* cpu freq too fast (or every run was bad): */
 168         if (delta64 > (1ULL<<32))
 169                 goto err;
 170
 171         delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
 172         do_div(delta64,CALIBRATE_TIME_MSEC);
 173
 174         local_irq_restore(flags);
 175         return (unsigned long)delta64;
 176 err:
 177         local_irq_restore(flags);
 178         return 0;
 179 }
 180
 181 int recalibrate_cpu_khz(void)
 182 {
 183 #ifndef CONFIG_SMP
 184         unsigned long cpu_khz_old = cpu_khz;
 185
 186         if (cpu_has_tsc) {
 187                 cpu_khz = calculate_cpu_khz();
 188                 tsc_khz = cpu_khz;
 189                 cpu_data(0).loops_per_jiffy =
 190                         cpufreq_scale(cpu_data(0).loops_per_jiffy,
 191                                         cpu_khz_old, cpu_khz);
 192                 return 0;
 193         } else
 194                 return -ENODEV;
 195 #else
 196         return -ENODEV;
 197 #endif
 198 }
 199
 200 EXPORT_SYMBOL(recalibrate_cpu_khz);
 201
 202 #ifdef CONFIG_CPU_FREQ
 203
 204 /*
 205  * if the CPU frequency is scaled, TSC-based delays will need a different
 206  * loops_per_jiffy value to function properly.
 207  */
 208 static unsigned int ref_freq = 0;
 209 static unsigned long loops_per_jiffy_ref = 0;
 210 static unsigned long cpu_khz_ref = 0;
 211
 212 static int
 213 time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
 214 {
 215         struct cpufreq_freqs *freq = data;
 216
 217         if (!ref_freq) {
 218                 if (!freq->old){
 219                         ref_freq = freq->new;
 220                         return 0;
 221                 }
 222                 ref_freq = freq->old;
 223                 loops_per_jiffy_ref = cpu_data(freq->cpu).loops_per_jiffy;
 224                 cpu_khz_ref = cpu_khz;
 225         }
 226
 227         if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
 228             (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
 229             (val == CPUFREQ_RESUMECHANGE)) {
 230                 if (!(freq->flags & CPUFREQ_CONST_LOOPS))
 231                         cpu_data(freq->cpu).loops_per_jiffy =
 232                                 cpufreq_scale(loops_per_jiffy_ref,
 233                                                 ref_freq, freq->new);
 234
 235                 if (cpu_khz) {
 236
 237                         if (num_online_cpus() == 1)
 238                                 cpu_khz = cpufreq_scale(cpu_khz_ref,
 239                                                 ref_freq, freq->new);
 240                         if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
 241                                 tsc_khz = cpu_khz;
 242                                 set_cyc2ns_scale(cpu_khz);
 243                                 /*
 244                                  * TSC based sched_clock turns
 245                                  * to junk w/ cpufreq
 246                                  */
 247                                 mark_tsc_unstable("cpufreq changes");
 248                         }
 249                 }
 250         }
 251
 252         return 0;
 253 }
 254
 255 static struct notifier_block time_cpufreq_notifier_block = {
 256         .notifier_call  = time_cpufreq_notifier
 257 };
 258
 259 static int __init cpufreq_tsc(void)
 260 {
 261         return cpufreq_register_notifier(&time_cpufreq_notifier_block,
 262                                          CPUFREQ_TRANSITION_NOTIFIER);
 263 }
 264 core_initcall(cpufreq_tsc);
 265
 266 #endif
 267
 268 /* clock source code */
 269
 270 static unsigned long current_tsc_khz = 0;
 271
 272 static cycle_t read_tsc(void)
 273 {
 274         cycle_t ret;
 275
 276         rdtscll(ret);
 277
 278         return ret;
 279 }
 280
 281 static struct clocksource clocksource_tsc = {
 282         .name                   = "tsc",
 283         .rating                 = 300,
 284         .read                   = read_tsc,
 285         .mask                   = CLOCKSOURCE_MASK(64),
 286         .mult                   = 0, /* to be set */
 287         .shift                  = 22,
 288         .flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
 289                                   CLOCK_SOURCE_MUST_VERIFY,
 290 };
 291
 292 void mark_tsc_unstable(char *reason)
 293 {
 294         if (!tsc_unstable) {
 295                 tsc_unstable = 1;
 296                 tsc_enabled = 0;
 297                 printk("Marking TSC unstable due to: %s.\n", reason);
 298                 /* Can be called before registration */
 299                 if (clocksource_tsc.mult)
 300                         clocksource_change_rating(&clocksource_tsc, 0);
 301                 else
 302                         clocksource_tsc.rating = 0;
 303         }
 304 }
 305 EXPORT_SYMBOL_GPL(mark_tsc_unstable);
 306
 307 static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d)
 308 {
 309         printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
 310                        d->ident);
 311         tsc_unstable = 1;
 312         return 0;
 313 }
 314
 315 /* List of systems that have known TSC problems */
 316 static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
 317         {
 318          .callback = dmi_mark_tsc_unstable,
 319          .ident = "IBM Thinkpad 380XD",
 320          .matches = {
 321                      DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
 322                      DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
 323                      },
 324          },
 325          {}
 326 };
 327
 328 /*
 329  * Make an educated guess if the TSC is trustworthy and synchronized
 330  * over all CPUs.
 331  */
 332 __cpuinit int unsynchronized_tsc(void)
 333 {
 334         if (!cpu_has_tsc || tsc_unstable)
 335                 return 1;
 336         /*
 337          * Intel systems are normally all synchronized.
 338          * Exceptions must mark TSC as unstable:
 339          */
 340         if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
 341                 /* assume multi socket systems are not synchronized: */
 342                 if (num_possible_cpus() > 1)
 343                         tsc_unstable = 1;
 344         }
 345         return tsc_unstable;
 346 }
 347
 348 /*
 349  * Geode_LX - the OLPC CPU has a possibly a very reliable TSC
 350  */
 351 #ifdef CONFIG_MGEODE_LX
 352 /* RTSC counts during suspend */
 353 #define RTSC_SUSP 0x100
 354
 355 static void __init check_geode_tsc_reliable(void)
 356 {
 357         unsigned long res_low, res_high;
 358
 359         rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
 360         if (res_low & RTSC_SUSP)
 361                 clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
 362 }
 363 #else
 364 static inline void check_geode_tsc_reliable(void) { }
 365 #endif
 366
 367
 368 void __init tsc_init(void)
 369 {
 370         if (!cpu_has_tsc || tsc_disable)
 371                 goto out_no_tsc;
 372
 373         cpu_khz = calculate_cpu_khz();
 374         tsc_khz = cpu_khz;
 375
 376         if (!cpu_khz)
 377                 goto out_no_tsc;
 378
 379         printk("Detected %lu.%03lu MHz processor.\n",
 380                                 (unsigned long)cpu_khz / 1000,
 381                                 (unsigned long)cpu_khz % 1000);
 382
 383         set_cyc2ns_scale(cpu_khz);
 384         use_tsc_delay();
 385
 386         /* Check and install the TSC clocksource */
 387         dmi_check_system(bad_tsc_dmi_table);
 388
 389         unsynchronized_tsc();
 390         check_geode_tsc_reliable();
 391         current_tsc_khz = tsc_khz;
 392         clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
 393                                                         clocksource_tsc.shift);
 394         /* lower the rating if we already know its unstable: */
 395         if (check_tsc_unstable()) {
 396                 clocksource_tsc.rating = 0;
 397                 clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
 398         } else
 399                 tsc_enabled = 1;
 400
 401         clocksource_register(&clocksource_tsc);
 402
 403         return;
 404
 405 out_no_tsc:
 406         /*
 407          * Set the tsc_disable flag if there's no TSC support, this
 408          * makes it a fast flag for the kernel to see whether it
 409          * should be using the TSC.
 410          */
 411         tsc_disable = 1;
 412 }