drivers/idle/intel_idle.c

   1 /*
   2  * intel_idle.c - native hardware idle loop for modern Intel processors
   3  *
   4  * Copyright (c) 2010, Intel Corporation.
   5  * Len Brown <len.brown@intel.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms and conditions of the GNU General Public License,
   9  * version 2, as published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14  * more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along with
  17  * this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20
  21 /*
  22  * intel_idle is a cpuidle driver that loads on specific Intel processors
  23  * in lieu of the legacy ACPI processor_idle driver.  The intent is to
  24  * make Linux more efficient on these processors, as intel_idle knows
  25  * more than ACPI, as well as make Linux more immune to ACPI BIOS bugs.
  26  */
  27
  28 /*
  29  * Design Assumptions
  30  *
  31  * All CPUs have same idle states as boot CPU
  32  *
  33  * Chipset BM_STS (bus master status) bit is a NOP
  34  *      for preventing entry into deep C-stats
  35  */
  36
  37 /*
  38  * Known limitations
  39  *
  40  * The driver currently initializes for_each_online_cpu() upon modprobe.
  41  * It it unaware of subsequent processors hot-added to the system.
  42  * This means that if you boot with maxcpus=n and later online
  43  * processors above n, those processors will use C1 only.
  44  *
  45  * ACPI has a .suspend hack to turn off deep c-statees during suspend
  46  * to avoid complications with the lapic timer workaround.
  47  * Have not seen issues with suspend, but may need same workaround here.
  48  *
  49  * There is currently no kernel-based automatic probing/loading mechanism
  50  * if the driver is built as a module.
  51  */
  52
  53 /* un-comment DEBUG to enable pr_debug() statements */
  54 #define DEBUG
  55
  56 #include <linux/kernel.h>
  57 #include <linux/cpuidle.h>
  58 #include <linux/clockchips.h>
  59 #include <linux/hrtimer.h>      /* ktime_get_real() */
  60 #include <trace/events/power.h>
  61 #include <linux/sched.h>
  62 #include <linux/notifier.h>
  63 #include <linux/cpu.h>
  64 #include <asm/mwait.h>
  65 #include <asm/msr.h>
  66
  67 #define INTEL_IDLE_VERSION "0.4"
  68 #define PREFIX "intel_idle: "
  69
  70 static struct cpuidle_driver intel_idle_driver = {
  71         .name = "intel_idle",
  72         .owner = THIS_MODULE,
  73 };
  74 /* intel_idle.max_cstate=0 disables driver */
  75 static int max_cstate = MWAIT_MAX_NUM_CSTATES - 1;
  76
  77 static unsigned int mwait_substates;
  78
  79 #define LAPIC_TIMER_ALWAYS_RELIABLE 0xFFFFFFFF
  80 /* Reliable LAPIC Timer States, bit 1 for C1 etc.  */
  81 static unsigned int lapic_timer_reliable_states = (1 << 1);      /* Default to only C1 */
  82
  83 static struct cpuidle_device __percpu *intel_idle_cpuidle_devices;
  84 static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state);
  85
  86 static struct cpuidle_state *cpuidle_state_table;
  87
  88 /*
  89  * Hardware C-state auto-demotion may not always be optimal.
  90  * Indicate which enable bits to clear here.
  91  */
  92 static unsigned long long auto_demotion_disable_flags;
  93
  94 /*
  95  * Set this flag for states where the HW flushes the TLB for us
  96  * and so we don't need cross-calls to keep it consistent.
  97  * If this flag is set, SW flushes the TLB, so even if the
  98  * HW doesn't do the flushing, this flag is safe to use.
  99  */
 100 #define CPUIDLE_FLAG_TLB_FLUSHED        0x10000
 101
 102 /*
 103  * States are indexed by the cstate number,
 104  * which is also the index into the MWAIT hint array.
 105  * Thus C0 is a dummy.
 106  */
 107 static struct cpuidle_state nehalem_cstates[MWAIT_MAX_NUM_CSTATES] = {
 108         { /* MWAIT C0 */ },
 109         { /* MWAIT C1 */
 110                 .name = "C1-NHM",
 111                 .desc = "MWAIT 0x00",
 112                 .driver_data = (void *) 0x00,
 113                 .flags = CPUIDLE_FLAG_TIME_VALID,
 114                 .exit_latency = 3,
 115                 .target_residency = 6,
 116                 .enter = &intel_idle },
 117         { /* MWAIT C2 */
 118                 .name = "C3-NHM",
 119                 .desc = "MWAIT 0x10",
 120                 .driver_data = (void *) 0x10,
 121                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 122                 .exit_latency = 20,
 123                 .target_residency = 80,
 124                 .enter = &intel_idle },
 125         { /* MWAIT C3 */
 126                 .name = "C6-NHM",
 127                 .desc = "MWAIT 0x20",
 128                 .driver_data = (void *) 0x20,
 129                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 130                 .exit_latency = 200,
 131                 .target_residency = 800,
 132                 .enter = &intel_idle },
 133 };
 134
 135 static struct cpuidle_state snb_cstates[MWAIT_MAX_NUM_CSTATES] = {
 136         { /* MWAIT C0 */ },
 137         { /* MWAIT C1 */
 138                 .name = "C1-SNB",
 139                 .desc = "MWAIT 0x00",
 140                 .driver_data = (void *) 0x00,
 141                 .flags = CPUIDLE_FLAG_TIME_VALID,
 142                 .exit_latency = 1,
 143                 .target_residency = 1,
 144                 .enter = &intel_idle },
 145         { /* MWAIT C2 */
 146                 .name = "C3-SNB",
 147                 .desc = "MWAIT 0x10",
 148                 .driver_data = (void *) 0x10,
 149                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 150                 .exit_latency = 80,
 151                 .target_residency = 211,
 152                 .enter = &intel_idle },
 153         { /* MWAIT C3 */
 154                 .name = "C6-SNB",
 155                 .desc = "MWAIT 0x20",
 156                 .driver_data = (void *) 0x20,
 157                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 158                 .exit_latency = 104,
 159                 .target_residency = 345,
 160                 .enter = &intel_idle },
 161         { /* MWAIT C4 */
 162                 .name = "C7-SNB",
 163                 .desc = "MWAIT 0x30",
 164                 .driver_data = (void *) 0x30,
 165                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 166                 .exit_latency = 109,
 167                 .target_residency = 345,
 168                 .enter = &intel_idle },
 169 };
 170
 171 static struct cpuidle_state atom_cstates[MWAIT_MAX_NUM_CSTATES] = {
 172         { /* MWAIT C0 */ },
 173         { /* MWAIT C1 */
 174                 .name = "C1-ATM",
 175                 .desc = "MWAIT 0x00",
 176                 .driver_data = (void *) 0x00,
 177                 .flags = CPUIDLE_FLAG_TIME_VALID,
 178                 .exit_latency = 1,
 179                 .target_residency = 4,
 180                 .enter = &intel_idle },
 181         { /* MWAIT C2 */
 182                 .name = "C2-ATM",
 183                 .desc = "MWAIT 0x10",
 184                 .driver_data = (void *) 0x10,
 185                 .flags = CPUIDLE_FLAG_TIME_VALID,
 186                 .exit_latency = 20,
 187                 .target_residency = 80,
 188                 .enter = &intel_idle },
 189         { /* MWAIT C3 */ },
 190         { /* MWAIT C4 */
 191                 .name = "C4-ATM",
 192                 .desc = "MWAIT 0x30",
 193                 .driver_data = (void *) 0x30,
 194                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 195                 .exit_latency = 100,
 196                 .target_residency = 400,
 197                 .enter = &intel_idle },
 198         { /* MWAIT C5 */ },
 199         { /* MWAIT C6 */
 200                 .name = "C6-ATM",
 201                 .desc = "MWAIT 0x52",
 202                 .driver_data = (void *) 0x52,
 203                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 204                 .exit_latency = 140,
 205                 .target_residency = 560,
 206                 .enter = &intel_idle },
 207 };
 208
 209 /**
 210  * intel_idle
 211  * @dev: cpuidle_device
 212  * @state: cpuidle state
 213  *
 214  */
 215 static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state)
 216 {
 217         unsigned long ecx = 1; /* break on interrupt flag */
 218         unsigned long eax = (unsigned long)cpuidle_get_statedata(state);
 219         unsigned int cstate;
 220         ktime_t kt_before, kt_after;
 221         s64 usec_delta;
 222         int cpu = smp_processor_id();
 223
 224         cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1;
 225
 226         local_irq_disable();
 227
 228         /*
 229          * leave_mm() to avoid costly and often unnecessary wakeups
 230          * for flushing the user TLB's associated with the active mm.
 231          */
 232         if (state->flags & CPUIDLE_FLAG_TLB_FLUSHED)
 233                 leave_mm(cpu);
 234
 235         if (!(lapic_timer_reliable_states & (1 << (cstate))))
 236                 clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
 237
 238         kt_before = ktime_get_real();
 239
 240         stop_critical_timings();
 241         if (!need_resched()) {
 242
 243                 __monitor((void *)&current_thread_info()->flags, 0, 0);
 244                 smp_mb();
 245                 if (!need_resched())
 246                         __mwait(eax, ecx);
 247         }
 248
 249         start_critical_timings();
 250
 251         kt_after = ktime_get_real();
 252         usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
 253
 254         local_irq_enable();
 255
 256         if (!(lapic_timer_reliable_states & (1 << (cstate))))
 257                 clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
 258
 259         return usec_delta;
 260 }
 261
 262 static void __setup_broadcast_timer(void *arg)
 263 {
 264         unsigned long reason = (unsigned long)arg;
 265         int cpu = smp_processor_id();
 266
 267         reason = reason ?
 268                 CLOCK_EVT_NOTIFY_BROADCAST_ON : CLOCK_EVT_NOTIFY_BROADCAST_OFF;
 269
 270         clockevents_notify(reason, &cpu);
 271 }
 272
 273 static int setup_broadcast_cpuhp_notify(struct notifier_block *n,
 274                 unsigned long action, void *hcpu)
 275 {
 276         int hotcpu = (unsigned long)hcpu;
 277
 278         switch (action & 0xf) {
 279         case CPU_ONLINE:
 280                 smp_call_function_single(hotcpu, __setup_broadcast_timer,
 281                         (void *)true, 1);
 282                 break;
 283         }
 284         return NOTIFY_OK;
 285 }
 286
 287 static struct notifier_block setup_broadcast_notifier = {
 288         .notifier_call = setup_broadcast_cpuhp_notify,
 289 };
 290
 291 static void auto_demotion_disable(void *dummy)
 292 {
 293         unsigned long long msr_bits;
 294
 295         rdmsrl(MSR_NHM_SNB_PKG_CST_CFG_CTL, msr_bits);
 296         msr_bits &= ~auto_demotion_disable_flags;
 297         wrmsrl(MSR_NHM_SNB_PKG_CST_CFG_CTL, msr_bits);
 298 }
 299
 300 /*
 301  * intel_idle_probe()
 302  */
 303 static int intel_idle_probe(void)
 304 {
 305         unsigned int eax, ebx, ecx;
 306
 307         if (max_cstate == 0) {
 308                 pr_debug(PREFIX "disabled\n");
 309                 return -EPERM;
 310         }
 311
 312         if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
 313                 return -ENODEV;
 314
 315         if (!boot_cpu_has(X86_FEATURE_MWAIT))
 316                 return -ENODEV;
 317
 318         if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
 319                 return -ENODEV;
 320
 321         cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates);
 322
 323         if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
 324                 !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
 325                         return -ENODEV;
 326
 327         pr_debug(PREFIX "MWAIT substates: 0x%x\n", mwait_substates);
 328
 329
 330         if (boot_cpu_data.x86 != 6)     /* family 6 */
 331                 return -ENODEV;
 332
 333         switch (boot_cpu_data.x86_model) {
 334
 335         case 0x1A:      /* Core i7, Xeon 5500 series */
 336         case 0x1E:      /* Core i7 and i5 Processor - Lynnfield Jasper Forest */
 337         case 0x1F:      /* Core i7 and i5 Processor - Nehalem */
 338         case 0x2E:      /* Nehalem-EX Xeon */
 339         case 0x2F:      /* Westmere-EX Xeon */
 340         case 0x25:      /* Westmere */
 341         case 0x2C:      /* Westmere */
 342                 cpuidle_state_table = nehalem_cstates;
 343                 auto_demotion_disable_flags =
 344                         (NHM_C1_AUTO_DEMOTE | NHM_C3_AUTO_DEMOTE);
 345                 break;
 346
 347         case 0x1C:      /* 28 - Atom Processor */
 348                 cpuidle_state_table = atom_cstates;
 349                 break;
 350
 351         case 0x26:      /* 38 - Lincroft Atom Processor */
 352                 cpuidle_state_table = atom_cstates;
 353                 auto_demotion_disable_flags = ATM_LNC_C6_AUTO_DEMOTE;
 354                 break;
 355
 356         case 0x2A:      /* SNB */
 357         case 0x2D:      /* SNB Xeon */
 358                 cpuidle_state_table = snb_cstates;
 359                 break;
 360
 361         default:
 362                 pr_debug(PREFIX "does not run on family %d model %d\n",
 363                         boot_cpu_data.x86, boot_cpu_data.x86_model);
 364                 return -ENODEV;
 365         }
 366
 367         if (boot_cpu_has(X86_FEATURE_ARAT))     /* Always Reliable APIC Timer */
 368                 lapic_timer_reliable_states = LAPIC_TIMER_ALWAYS_RELIABLE;
 369         else {
 370                 smp_call_function(__setup_broadcast_timer, (void *)true, 1);
 371                 register_cpu_notifier(&setup_broadcast_notifier);
 372         }
 373
 374         pr_debug(PREFIX "v" INTEL_IDLE_VERSION
 375                 " model 0x%X\n", boot_cpu_data.x86_model);
 376
 377         pr_debug(PREFIX "lapic_timer_reliable_states 0x%x\n",
 378                 lapic_timer_reliable_states);
 379         return 0;
 380 }
 381
 382 /*
 383  * intel_idle_cpuidle_devices_uninit()
 384  * unregister, free cpuidle_devices
 385  */
 386 static void intel_idle_cpuidle_devices_uninit(void)
 387 {
 388         int i;
 389         struct cpuidle_device *dev;
 390
 391         for_each_online_cpu(i) {
 392                 dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
 393                 cpuidle_unregister_device(dev);
 394         }
 395
 396         free_percpu(intel_idle_cpuidle_devices);
 397         return;
 398 }
 399 /*
 400  * intel_idle_cpuidle_devices_init()
 401  * allocate, initialize, register cpuidle_devices
 402  */
 403 static int intel_idle_cpuidle_devices_init(void)
 404 {
 405         int i, cstate;
 406         struct cpuidle_device *dev;
 407
 408         intel_idle_cpuidle_devices = alloc_percpu(struct cpuidle_device);
 409         if (intel_idle_cpuidle_devices == NULL)
 410                 return -ENOMEM;
 411
 412         for_each_online_cpu(i) {
 413                 dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
 414
 415                 dev->state_count = 1;
 416
 417                 for (cstate = 1; cstate < MWAIT_MAX_NUM_CSTATES; ++cstate) {
 418                         int num_substates;
 419
 420                         if (cstate > max_cstate) {
 421                                 printk(PREFIX "max_cstate %d reached\n",
 422                                         max_cstate);
 423                                 break;
 424                         }
 425
 426                         /* does the state exist in CPUID.MWAIT? */
 427                         num_substates = (mwait_substates >> ((cstate) * 4))
 428                                                 & MWAIT_SUBSTATE_MASK;
 429                         if (num_substates == 0)
 430                                 continue;
 431                         /* is the state not enabled? */
 432                         if (cpuidle_state_table[cstate].enter == NULL) {
 433                                 /* does the driver not know about the state? */
 434                                 if (*cpuidle_state_table[cstate].name == '\0')
 435                                         pr_debug(PREFIX "unaware of model 0x%x"
 436                                                 " MWAIT %d please"
 437                                                 " contact lenb@kernel.org",
 438                                         boot_cpu_data.x86_model, cstate);
 439                                 continue;
 440                         }
 441
 442                         if ((cstate > 2) &&
 443                                 !boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
 444                                 mark_tsc_unstable("TSC halts in idle"
 445                                         " states deeper than C2");
 446
 447                         dev->states[dev->state_count] = /* structure copy */
 448                                 cpuidle_state_table[cstate];
 449
 450                         dev->state_count += 1;
 451                 }
 452
 453                 dev->cpu = i;
 454                 if (cpuidle_register_device(dev)) {
 455                         pr_debug(PREFIX "cpuidle_register_device %d failed!\n",
 456                                  i);
 457                         intel_idle_cpuidle_devices_uninit();
 458                         return -EIO;
 459                 }
 460         }
 461         if (auto_demotion_disable_flags)
 462                 smp_call_function(auto_demotion_disable, NULL, 1);
 463
 464         return 0;
 465 }
 466
 467
 468 static int __init intel_idle_init(void)
 469 {
 470         int retval;
 471
 472         /* Do not load intel_idle at all for now if idle= is passed */
 473         if (boot_option_idle_override != IDLE_NO_OVERRIDE)
 474                 return -ENODEV;
 475
 476         retval = intel_idle_probe();
 477         if (retval)
 478                 return retval;
 479
 480         retval = cpuidle_register_driver(&intel_idle_driver);
 481         if (retval) {
 482                 printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
 483                         cpuidle_get_driver()->name);
 484                 return retval;
 485         }
 486
 487         retval = intel_idle_cpuidle_devices_init();
 488         if (retval) {
 489                 cpuidle_unregister_driver(&intel_idle_driver);
 490                 return retval;
 491         }
 492
 493         return 0;
 494 }
 495
 496 static void __exit intel_idle_exit(void)
 497 {
 498         intel_idle_cpuidle_devices_uninit();
 499         cpuidle_unregister_driver(&intel_idle_driver);
 500
 501         if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE) {
 502                 smp_call_function(__setup_broadcast_timer, (void *)false, 1);
 503                 unregister_cpu_notifier(&setup_broadcast_notifier);
 504         }
 505
 506         return;
 507 }
 508
 509 module_init(intel_idle_init);
 510 module_exit(intel_idle_exit);
 511
 512 module_param(max_cstate, int, 0444);
 513
 514 MODULE_AUTHOR("Len Brown <len.brown@intel.com>");
 515 MODULE_DESCRIPTION("Cpuidle driver for Intel Hardware v" INTEL_IDLE_VERSION);
 516 MODULE_LICENSE("GPL");