arch/arm/kernel/smp.c

   1 /*
   2  *  linux/arch/arm/kernel/smp.c
   3  *
   4  *  Copyright (C) 2002 ARM Limited, All Rights Reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/module.h>
  11 #include <linux/delay.h>
  12 #include <linux/init.h>
  13 #include <linux/spinlock.h>
  14 #include <linux/sched.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/cache.h>
  17 #include <linux/profile.h>
  18 #include <linux/errno.h>
  19 #include <linux/mm.h>
  20 #include <linux/err.h>
  21 #include <linux/cpu.h>
  22 #include <linux/seq_file.h>
  23 #include <linux/irq.h>
  24 #include <linux/percpu.h>
  25 #include <linux/clockchips.h>
  26 #include <linux/completion.h>
  27 #include <linux/cpufreq.h>
  28
  29 #include <linux/atomic.h>
  30 #include <asm/smp.h>
  31 #include <asm/cacheflush.h>
  32 #include <asm/cpu.h>
  33 #include <asm/cputype.h>
  34 #include <asm/exception.h>
  35 #include <asm/idmap.h>
  36 #include <asm/topology.h>
  37 #include <asm/mmu_context.h>
  38 #include <asm/pgtable.h>
  39 #include <asm/pgalloc.h>
  40 #include <asm/processor.h>
  41 #include <asm/sections.h>
  42 #include <asm/tlbflush.h>
  43 #include <asm/ptrace.h>
  44 #include <asm/localtimer.h>
  45 #include <asm/smp_plat.h>
  46 #include <asm/virt.h>
  47 #include <asm/mach/arch.h>
  48
  49 /*
  50  * as from 2.5, kernels no longer have an init_tasks structure
  51  * so we need some other way of telling a new secondary core
  52  * where to place its SVC stack
  53  */
  54 struct secondary_data secondary_data;
  55
  56 /*
  57  * control for which core is the next to come out of the secondary
  58  * boot "holding pen"
  59  */
  60 volatile int __cpuinitdata pen_release = -1;
  61
  62 enum ipi_msg_type {
  63         IPI_WAKEUP,
  64         IPI_TIMER,
  65         IPI_RESCHEDULE,
  66         IPI_CALL_FUNC,
  67         IPI_CALL_FUNC_SINGLE,
  68         IPI_CPU_STOP,
  69 };
  70
  71 static DECLARE_COMPLETION(cpu_running);
  72
  73 static struct smp_operations smp_ops;
  74
  75 void __init smp_set_ops(struct smp_operations *ops)
  76 {
  77         if (ops)
  78                 smp_ops = *ops;
  79 };
  80
  81 int __cpuinit __cpu_up(unsigned int cpu, struct task_struct *idle)
  82 {
  83         int ret;
  84
  85         /*
  86          * We need to tell the secondary core where to find
  87          * its stack and the page tables.
  88          */
  89         secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
  90         secondary_data.pgdir = virt_to_phys(idmap_pgd);
  91         secondary_data.swapper_pg_dir = virt_to_phys(swapper_pg_dir);
  92         __cpuc_flush_dcache_area(&secondary_data, sizeof(secondary_data));
  93         outer_clean_range(__pa(&secondary_data), __pa(&secondary_data + 1));
  94
  95         /*
  96          * Now bring the CPU into our world.
  97          */
  98         ret = boot_secondary(cpu, idle);
  99         if (ret == 0) {
 100                 /*
 101                  * CPU was successfully started, wait for it
 102                  * to come online or time out.
 103                  */
 104                 wait_for_completion_timeout(&cpu_running,
 105                                                  msecs_to_jiffies(1000));
 106
 107                 if (!cpu_online(cpu)) {
 108                         pr_crit("CPU%u: failed to come online\n", cpu);
 109                         ret = -EIO;
 110                 }
 111         } else {
 112                 pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
 113         }
 114
 115         secondary_data.stack = NULL;
 116         secondary_data.pgdir = 0;
 117
 118         return ret;
 119 }
 120
 121 /* platform specific SMP operations */
 122 void __init smp_init_cpus(void)
 123 {
 124         if (smp_ops.smp_init_cpus)
 125                 smp_ops.smp_init_cpus();
 126 }
 127
 128 static void __init platform_smp_prepare_cpus(unsigned int max_cpus)
 129 {
 130         if (smp_ops.smp_prepare_cpus)
 131                 smp_ops.smp_prepare_cpus(max_cpus);
 132 }
 133
 134 static void __cpuinit platform_secondary_init(unsigned int cpu)
 135 {
 136         if (smp_ops.smp_secondary_init)
 137                 smp_ops.smp_secondary_init(cpu);
 138 }
 139
 140 int __cpuinit boot_secondary(unsigned int cpu, struct task_struct *idle)
 141 {
 142         if (smp_ops.smp_boot_secondary)
 143                 return smp_ops.smp_boot_secondary(cpu, idle);
 144         return -ENOSYS;
 145 }
 146
 147 #ifdef CONFIG_HOTPLUG_CPU
 148 static void percpu_timer_stop(void);
 149
 150 static int platform_cpu_kill(unsigned int cpu)
 151 {
 152         if (smp_ops.cpu_kill)
 153                 return smp_ops.cpu_kill(cpu);
 154         return 1;
 155 }
 156
 157 static void platform_cpu_die(unsigned int cpu)
 158 {
 159         if (smp_ops.cpu_die)
 160                 smp_ops.cpu_die(cpu);
 161 }
 162
 163 static int platform_cpu_disable(unsigned int cpu)
 164 {
 165         if (smp_ops.cpu_disable)
 166                 return smp_ops.cpu_disable(cpu);
 167
 168         /*
 169          * By default, allow disabling all CPUs except the first one,
 170          * since this is special on a lot of platforms, e.g. because
 171          * of clock tick interrupts.
 172          */
 173         return cpu == 0 ? -EPERM : 0;
 174 }
 175 /*
 176  * __cpu_disable runs on the processor to be shutdown.
 177  */
 178 int __cpuinit __cpu_disable(void)
 179 {
 180         unsigned int cpu = smp_processor_id();
 181         int ret;
 182
 183         ret = platform_cpu_disable(cpu);
 184         if (ret)
 185                 return ret;
 186
 187         /*
 188          * Take this CPU offline.  Once we clear this, we can't return,
 189          * and we must not schedule until we're ready to give up the cpu.
 190          */
 191         set_cpu_online(cpu, false);
 192
 193         /*
 194          * OK - migrate IRQs away from this CPU
 195          */
 196         migrate_irqs();
 197
 198         /*
 199          * Stop the local timer for this CPU.
 200          */
 201         percpu_timer_stop();
 202
 203         /*
 204          * Flush user cache and TLB mappings, and then remove this CPU
 205          * from the vm mask set of all processes.
 206          *
 207          * Caches are flushed to the Level of Unification Inner Shareable
 208          * to write-back dirty lines to unified caches shared by all CPUs.
 209          */
 210         flush_cache_louis();
 211         local_flush_tlb_all();
 212
 213         clear_tasks_mm_cpumask(cpu);
 214
 215         return 0;
 216 }
 217
 218 static DECLARE_COMPLETION(cpu_died);
 219
 220 /*
 221  * called on the thread which is asking for a CPU to be shutdown -
 222  * waits until shutdown has completed, or it is timed out.
 223  */
 224 void __cpuinit __cpu_die(unsigned int cpu)
 225 {
 226         if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) {
 227                 pr_err("CPU%u: cpu didn't die\n", cpu);
 228                 return;
 229         }
 230         printk(KERN_NOTICE "CPU%u: shutdown\n", cpu);
 231
 232         if (!platform_cpu_kill(cpu))
 233                 printk("CPU%u: unable to kill\n", cpu);
 234 }
 235
 236 /*
 237  * Called from the idle thread for the CPU which has been shutdown.
 238  *
 239  * Note that we disable IRQs here, but do not re-enable them
 240  * before returning to the caller. This is also the behaviour
 241  * of the other hotplug-cpu capable cores, so presumably coming
 242  * out of idle fixes this.
 243  */
 244 void __ref cpu_die(void)
 245 {
 246         unsigned int cpu = smp_processor_id();
 247
 248         idle_task_exit();
 249
 250         local_irq_disable();
 251         mb();
 252
 253         /* Tell __cpu_die() that this CPU is now safe to dispose of */
 254         RCU_NONIDLE(complete(&cpu_died));
 255
 256         /*
 257          * actual CPU shutdown procedure is at least platform (if not
 258          * CPU) specific.
 259          */
 260         platform_cpu_die(cpu);
 261
 262         /*
 263          * Do not return to the idle loop - jump back to the secondary
 264          * cpu initialisation.  There's some initialisation which needs
 265          * to be repeated to undo the effects of taking the CPU offline.
 266          */
 267         __asm__("mov    sp, %0\n"
 268         "       mov     fp, #0\n"
 269         "       b       secondary_start_kernel"
 270                 :
 271                 : "r" (task_stack_page(current) + THREAD_SIZE - 8));
 272 }
 273 #endif /* CONFIG_HOTPLUG_CPU */
 274
 275 /*
 276  * Called by both boot and secondaries to move global data into
 277  * per-processor storage.
 278  */
 279 static void __cpuinit smp_store_cpu_info(unsigned int cpuid)
 280 {
 281         struct cpuinfo_arm *cpu_info = &per_cpu(cpu_data, cpuid);
 282
 283         cpu_info->loops_per_jiffy = loops_per_jiffy;
 284         cpu_info->cpuid = read_cpuid_id();
 285
 286         store_cpu_topology(cpuid);
 287 }
 288
 289 static void percpu_timer_setup(void);
 290
 291 /*
 292  * This is the secondary CPU boot entry.  We're using this CPUs
 293  * idle thread stack, but a set of temporary page tables.
 294  */
 295 asmlinkage void __cpuinit secondary_start_kernel(void)
 296 {
 297         struct mm_struct *mm = &init_mm;
 298         unsigned int cpu;
 299
 300         /*
 301          * The identity mapping is uncached (strongly ordered), so
 302          * switch away from it before attempting any exclusive accesses.
 303          */
 304         cpu_switch_mm(mm->pgd, mm);
 305         enter_lazy_tlb(mm, current);
 306         local_flush_tlb_all();
 307
 308         /*
 309          * All kernel threads share the same mm context; grab a
 310          * reference and switch to it.
 311          */
 312         cpu = smp_processor_id();
 313         atomic_inc(&mm->mm_count);
 314         current->active_mm = mm;
 315         cpumask_set_cpu(cpu, mm_cpumask(mm));
 316
 317         cpu_init();
 318
 319         printk("CPU%u: Booted secondary processor\n", cpu);
 320
 321         preempt_disable();
 322         trace_hardirqs_off();
 323
 324         /*
 325          * Give the platform a chance to do its own initialisation.
 326          */
 327         platform_secondary_init(cpu);
 328
 329         notify_cpu_starting(cpu);
 330
 331         calibrate_delay();
 332
 333         smp_store_cpu_info(cpu);
 334
 335         /*
 336          * OK, now it's safe to let the boot CPU continue.  Wait for
 337          * the CPU migration code to notice that the CPU is online
 338          * before we continue - which happens after __cpu_up returns.
 339          */
 340         set_cpu_online(cpu, true);
 341         complete(&cpu_running);
 342
 343         /*
 344          * Setup the percpu timer for this CPU.
 345          */
 346         percpu_timer_setup();
 347
 348         local_irq_enable();
 349         local_fiq_enable();
 350
 351         /*
 352          * OK, it's off to the idle thread for us
 353          */
 354         cpu_idle();
 355 }
 356
 357 void __init smp_cpus_done(unsigned int max_cpus)
 358 {
 359         int cpu;
 360         unsigned long bogosum = 0;
 361
 362         for_each_online_cpu(cpu)
 363                 bogosum += per_cpu(cpu_data, cpu).loops_per_jiffy;
 364
 365         printk(KERN_INFO "SMP: Total of %d processors activated "
 366                "(%lu.%02lu BogoMIPS).\n",
 367                num_online_cpus(),
 368                bogosum / (500000/HZ),
 369                (bogosum / (5000/HZ)) % 100);
 370
 371         hyp_mode_check();
 372 }
 373
 374 void __init smp_prepare_boot_cpu(void)
 375 {
 376         set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
 377 }
 378
 379 void __init smp_prepare_cpus(unsigned int max_cpus)
 380 {
 381         unsigned int ncores = num_possible_cpus();
 382
 383         init_cpu_topology();
 384
 385         smp_store_cpu_info(smp_processor_id());
 386
 387         /*
 388          * are we trying to boot more cores than exist?
 389          */
 390         if (max_cpus > ncores)
 391                 max_cpus = ncores;
 392         if (ncores > 1 && max_cpus) {
 393                 /*
 394                  * Enable the local timer or broadcast device for the
 395                  * boot CPU, but only if we have more than one CPU.
 396                  */
 397                 percpu_timer_setup();
 398
 399                 /*
 400                  * Initialise the present map, which describes the set of CPUs
 401                  * actually populated at the present time. A platform should
 402                  * re-initialize the map in platform_smp_prepare_cpus() if
 403                  * present != possible (e.g. physical hotplug).
 404                  */
 405                 init_cpu_present(cpu_possible_mask);
 406
 407                 /*
 408                  * Initialise the SCU if there are more than one CPU
 409                  * and let them know where to start.
 410                  */
 411                 platform_smp_prepare_cpus(max_cpus);
 412         }
 413 }
 414
 415 static void (*smp_cross_call)(const struct cpumask *, unsigned int);
 416
 417 void __init set_smp_cross_call(void (*fn)(const struct cpumask *, unsigned int))
 418 {
 419         if (!smp_cross_call)
 420                 smp_cross_call = fn;
 421 }
 422
 423 void arch_send_call_function_ipi_mask(const struct cpumask *mask)
 424 {
 425         smp_cross_call(mask, IPI_CALL_FUNC);
 426 }
 427
 428 void arch_send_wakeup_ipi_mask(const struct cpumask *mask)
 429 {
 430         smp_cross_call(mask, IPI_WAKEUP);
 431 }
 432
 433 void arch_send_call_function_single_ipi(int cpu)
 434 {
 435         smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);
 436 }
 437
 438 static const char *ipi_types[NR_IPI] = {
 439 #define S(x,s)  [x] = s
 440         S(IPI_WAKEUP, "CPU wakeup interrupts"),
 441         S(IPI_TIMER, "Timer broadcast interrupts"),
 442         S(IPI_RESCHEDULE, "Rescheduling interrupts"),
 443         S(IPI_CALL_FUNC, "Function call interrupts"),
 444         S(IPI_CALL_FUNC_SINGLE, "Single function call interrupts"),
 445         S(IPI_CPU_STOP, "CPU stop interrupts"),
 446 };
 447
 448 void show_ipi_list(struct seq_file *p, int prec)
 449 {
 450         unsigned int cpu, i;
 451
 452         for (i = 0; i < NR_IPI; i++) {
 453                 seq_printf(p, "%*s%u: ", prec - 1, "IPI", i);
 454
 455                 for_each_online_cpu(cpu)
 456                         seq_printf(p, "%10u ",
 457                                    __get_irq_stat(cpu, ipi_irqs[i]));
 458
 459                 seq_printf(p, " %s\n", ipi_types[i]);
 460         }
 461 }
 462
 463 u64 smp_irq_stat_cpu(unsigned int cpu)
 464 {
 465         u64 sum = 0;
 466         int i;
 467
 468         for (i = 0; i < NR_IPI; i++)
 469                 sum += __get_irq_stat(cpu, ipi_irqs[i]);
 470
 471         return sum;
 472 }
 473
 474 /*
 475  * Timer (local or broadcast) support
 476  */
 477 static DEFINE_PER_CPU(struct clock_event_device, percpu_clockevent);
 478
 479 static void ipi_timer(void)
 480 {
 481         struct clock_event_device *evt = &__get_cpu_var(percpu_clockevent);
 482         evt->event_handler(evt);
 483 }
 484
 485 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 486 static void smp_timer_broadcast(const struct cpumask *mask)
 487 {
 488         smp_cross_call(mask, IPI_TIMER);
 489 }
 490 #else
 491 #define smp_timer_broadcast     NULL
 492 #endif
 493
 494 static void broadcast_timer_set_mode(enum clock_event_mode mode,
 495         struct clock_event_device *evt)
 496 {
 497 }
 498
 499 static void __cpuinit broadcast_timer_setup(struct clock_event_device *evt)
 500 {
 501         evt->name       = "dummy_timer";
 502         evt->features   = CLOCK_EVT_FEAT_ONESHOT |
 503                           CLOCK_EVT_FEAT_PERIODIC |
 504                           CLOCK_EVT_FEAT_DUMMY;
 505         evt->rating     = 400;
 506         evt->mult       = 1;
 507         evt->set_mode   = broadcast_timer_set_mode;
 508
 509         clockevents_register_device(evt);
 510 }
 511
 512 static struct local_timer_ops *lt_ops;
 513
 514 #ifdef CONFIG_LOCAL_TIMERS
 515 int local_timer_register(struct local_timer_ops *ops)
 516 {
 517         if (!is_smp() || !setup_max_cpus)
 518                 return -ENXIO;
 519
 520         if (lt_ops)
 521                 return -EBUSY;
 522
 523         lt_ops = ops;
 524         return 0;
 525 }
 526 #endif
 527
 528 static void __cpuinit percpu_timer_setup(void)
 529 {
 530         unsigned int cpu = smp_processor_id();
 531         struct clock_event_device *evt = &per_cpu(percpu_clockevent, cpu);
 532
 533         evt->cpumask = cpumask_of(cpu);
 534         evt->broadcast = smp_timer_broadcast;
 535
 536         if (!lt_ops || lt_ops->setup(evt))
 537                 broadcast_timer_setup(evt);
 538 }
 539
 540 #ifdef CONFIG_HOTPLUG_CPU
 541 /*
 542  * The generic clock events code purposely does not stop the local timer
 543  * on CPU_DEAD/CPU_DEAD_FROZEN hotplug events, so we have to do it
 544  * manually here.
 545  */
 546 static void percpu_timer_stop(void)
 547 {
 548         unsigned int cpu = smp_processor_id();
 549         struct clock_event_device *evt = &per_cpu(percpu_clockevent, cpu);
 550
 551         if (lt_ops)
 552                 lt_ops->stop(evt);
 553 }
 554 #endif
 555
 556 static DEFINE_RAW_SPINLOCK(stop_lock);
 557
 558 /*
 559  * ipi_cpu_stop - handle IPI from smp_send_stop()
 560  */
 561 static void ipi_cpu_stop(unsigned int cpu)
 562 {
 563         if (system_state == SYSTEM_BOOTING ||
 564             system_state == SYSTEM_RUNNING) {
 565                 raw_spin_lock(&stop_lock);
 566                 printk(KERN_CRIT "CPU%u: stopping\n", cpu);
 567                 dump_stack();
 568                 raw_spin_unlock(&stop_lock);
 569         }
 570
 571         set_cpu_online(cpu, false);
 572
 573         local_fiq_disable();
 574         local_irq_disable();
 575
 576         while (1)
 577                 cpu_relax();
 578 }
 579
 580 /*
 581  * Main handler for inter-processor interrupts
 582  */
 583 asmlinkage void __exception_irq_entry do_IPI(int ipinr, struct pt_regs *regs)
 584 {
 585         handle_IPI(ipinr, regs);
 586 }
 587
 588 void handle_IPI(int ipinr, struct pt_regs *regs)
 589 {
 590         unsigned int cpu = smp_processor_id();
 591         struct pt_regs *old_regs = set_irq_regs(regs);
 592
 593         if (ipinr < NR_IPI)
 594                 __inc_irq_stat(cpu, ipi_irqs[ipinr]);
 595
 596         switch (ipinr) {
 597         case IPI_WAKEUP:
 598                 break;
 599
 600         case IPI_TIMER:
 601                 irq_enter();
 602                 ipi_timer();
 603                 irq_exit();
 604                 break;
 605
 606         case IPI_RESCHEDULE:
 607                 scheduler_ipi();
 608                 break;
 609
 610         case IPI_CALL_FUNC:
 611                 irq_enter();
 612                 generic_smp_call_function_interrupt();
 613                 irq_exit();
 614                 break;
 615
 616         case IPI_CALL_FUNC_SINGLE:
 617                 irq_enter();
 618                 generic_smp_call_function_single_interrupt();
 619                 irq_exit();
 620                 break;
 621
 622         case IPI_CPU_STOP:
 623                 irq_enter();
 624                 ipi_cpu_stop(cpu);
 625                 irq_exit();
 626                 break;
 627
 628         default:
 629                 printk(KERN_CRIT "CPU%u: Unknown IPI message 0x%x\n",
 630                        cpu, ipinr);
 631                 break;
 632         }
 633         set_irq_regs(old_regs);
 634 }
 635
 636 void smp_send_reschedule(int cpu)
 637 {
 638         smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
 639 }
 640
 641 #ifdef CONFIG_HOTPLUG_CPU
 642 static void smp_kill_cpus(cpumask_t *mask)
 643 {
 644         unsigned int cpu;
 645         for_each_cpu(cpu, mask)
 646                 platform_cpu_kill(cpu);
 647 }
 648 #else
 649 static void smp_kill_cpus(cpumask_t *mask) { }
 650 #endif
 651
 652 void smp_send_stop(void)
 653 {
 654         unsigned long timeout;
 655         struct cpumask mask;
 656
 657         cpumask_copy(&mask, cpu_online_mask);
 658         cpumask_clear_cpu(smp_processor_id(), &mask);
 659         if (!cpumask_empty(&mask))
 660                 smp_cross_call(&mask, IPI_CPU_STOP);
 661
 662         /* Wait up to one second for other CPUs to stop */
 663         timeout = USEC_PER_SEC;
 664         while (num_online_cpus() > 1 && timeout--)
 665                 udelay(1);
 666
 667         if (num_online_cpus() > 1)
 668                 pr_warning("SMP: failed to stop secondary CPUs\n");
 669
 670         smp_kill_cpus(&mask);
 671 }
 672
 673 /*
 674  * not supported here
 675  */
 676 int setup_profiling_timer(unsigned int multiplier)
 677 {
 678         return -EINVAL;
 679 }
 680
 681 #ifdef CONFIG_CPU_FREQ
 682
 683 static DEFINE_PER_CPU(unsigned long, l_p_j_ref);
 684 static DEFINE_PER_CPU(unsigned long, l_p_j_ref_freq);
 685 static unsigned long global_l_p_j_ref;
 686 static unsigned long global_l_p_j_ref_freq;
 687
 688 static int cpufreq_callback(struct notifier_block *nb,
 689                                         unsigned long val, void *data)
 690 {
 691         struct cpufreq_freqs *freq = data;
 692         int cpu = freq->cpu;
 693
 694         if (freq->flags & CPUFREQ_CONST_LOOPS)
 695                 return NOTIFY_OK;
 696
 697         if (!per_cpu(l_p_j_ref, cpu)) {
 698                 per_cpu(l_p_j_ref, cpu) =
 699                         per_cpu(cpu_data, cpu).loops_per_jiffy;
 700                 per_cpu(l_p_j_ref_freq, cpu) = freq->old;
 701                 if (!global_l_p_j_ref) {
 702                         global_l_p_j_ref = loops_per_jiffy;
 703                         global_l_p_j_ref_freq = freq->old;
 704                 }
 705         }
 706
 707         if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
 708             (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
 709             (val == CPUFREQ_RESUMECHANGE || val == CPUFREQ_SUSPENDCHANGE)) {
 710                 loops_per_jiffy = cpufreq_scale(global_l_p_j_ref,
 711                                                 global_l_p_j_ref_freq,
 712                                                 freq->new);
 713                 per_cpu(cpu_data, cpu).loops_per_jiffy =
 714                         cpufreq_scale(per_cpu(l_p_j_ref, cpu),
 715                                         per_cpu(l_p_j_ref_freq, cpu),
 716                                         freq->new);
 717         }
 718         return NOTIFY_OK;
 719 }
 720
 721 static struct notifier_block cpufreq_notifier = {
 722         .notifier_call  = cpufreq_callback,
 723 };
 724
 725 static int __init register_cpufreq_notifier(void)
 726 {
 727         return cpufreq_register_notifier(&cpufreq_notifier,
 728                                                 CPUFREQ_TRANSITION_NOTIFIER);
 729 }
 730 core_initcall(register_cpufreq_notifier);
 731
 732 #endif