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 <asm/mwait.h>
  63
  64 #define INTEL_IDLE_VERSION "0.4"
  65 #define PREFIX "intel_idle: "
  66
  67 static struct cpuidle_driver intel_idle_driver = {
  68         .name = "intel_idle",
  69         .owner = THIS_MODULE,
  70 };
  71 /* intel_idle.max_cstate=0 disables driver */
  72 static int max_cstate = MWAIT_MAX_NUM_CSTATES - 1;
  73
  74 static unsigned int mwait_substates;
  75
  76 /* Reliable LAPIC Timer States, bit 1 for C1 etc.  */
  77 static unsigned int lapic_timer_reliable_states = (1 << 1);      /* Default to only C1 */
  78
  79 static struct cpuidle_device __percpu *intel_idle_cpuidle_devices;
  80 static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state);
  81
  82 static struct cpuidle_state *cpuidle_state_table;
  83
  84 /*
  85  * States are indexed by the cstate number,
  86  * which is also the index into the MWAIT hint array.
  87  * Thus C0 is a dummy.
  88  */
  89 static struct cpuidle_state nehalem_cstates[MWAIT_MAX_NUM_CSTATES] = {
  90         { /* MWAIT C0 */ },
  91         { /* MWAIT C1 */
  92                 .name = "NHM-C1",
  93                 .desc = "MWAIT 0x00",
  94                 .driver_data = (void *) 0x00,
  95                 .flags = CPUIDLE_FLAG_TIME_VALID,
  96                 .exit_latency = 3,
  97                 .target_residency = 6,
  98                 .enter = &intel_idle },
  99         { /* MWAIT C2 */
 100                 .name = "NHM-C3",
 101                 .desc = "MWAIT 0x10",
 102                 .driver_data = (void *) 0x10,
 103                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 104                 .exit_latency = 20,
 105                 .target_residency = 80,
 106                 .enter = &intel_idle },
 107         { /* MWAIT C3 */
 108                 .name = "NHM-C6",
 109                 .desc = "MWAIT 0x20",
 110                 .driver_data = (void *) 0x20,
 111                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 112                 .exit_latency = 200,
 113                 .target_residency = 800,
 114                 .enter = &intel_idle },
 115 };
 116
 117 static struct cpuidle_state snb_cstates[MWAIT_MAX_NUM_CSTATES] = {
 118         { /* MWAIT C0 */ },
 119         { /* MWAIT C1 */
 120                 .name = "SNB-C1",
 121                 .desc = "MWAIT 0x00",
 122                 .driver_data = (void *) 0x00,
 123                 .flags = CPUIDLE_FLAG_TIME_VALID,
 124                 .exit_latency = 1,
 125                 .target_residency = 4,
 126                 .enter = &intel_idle },
 127         { /* MWAIT C2 */
 128                 .name = "SNB-C3",
 129                 .desc = "MWAIT 0x10",
 130                 .driver_data = (void *) 0x10,
 131                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 132                 .exit_latency = 80,
 133                 .target_residency = 160,
 134                 .enter = &intel_idle },
 135         { /* MWAIT C3 */
 136                 .name = "SNB-C6",
 137                 .desc = "MWAIT 0x20",
 138                 .driver_data = (void *) 0x20,
 139                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 140                 .exit_latency = 104,
 141                 .target_residency = 208,
 142                 .enter = &intel_idle },
 143         { /* MWAIT C4 */
 144                 .name = "SNB-C7",
 145                 .desc = "MWAIT 0x30",
 146                 .driver_data = (void *) 0x30,
 147                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 148                 .exit_latency = 109,
 149                 .target_residency = 300,
 150                 .enter = &intel_idle },
 151 };
 152
 153 static struct cpuidle_state atom_cstates[MWAIT_MAX_NUM_CSTATES] = {
 154         { /* MWAIT C0 */ },
 155         { /* MWAIT C1 */
 156                 .name = "ATM-C1",
 157                 .desc = "MWAIT 0x00",
 158                 .driver_data = (void *) 0x00,
 159                 .flags = CPUIDLE_FLAG_TIME_VALID,
 160                 .exit_latency = 1,
 161                 .target_residency = 4,
 162                 .enter = &intel_idle },
 163         { /* MWAIT C2 */
 164                 .name = "ATM-C2",
 165                 .desc = "MWAIT 0x10",
 166                 .driver_data = (void *) 0x10,
 167                 .flags = CPUIDLE_FLAG_TIME_VALID,
 168                 .exit_latency = 20,
 169                 .target_residency = 80,
 170                 .enter = &intel_idle },
 171         { /* MWAIT C3 */ },
 172         { /* MWAIT C4 */
 173                 .name = "ATM-C4",
 174                 .desc = "MWAIT 0x30",
 175                 .driver_data = (void *) 0x30,
 176                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 177                 .exit_latency = 100,
 178                 .target_residency = 400,
 179                 .enter = &intel_idle },
 180         { /* MWAIT C5 */ },
 181         { /* MWAIT C6 */
 182                 .name = "ATM-C6",
 183                 .desc = "MWAIT 0x52",
 184                 .driver_data = (void *) 0x52,
 185                 .flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_TLB_FLUSHED,
 186                 .exit_latency = 140,
 187                 .target_residency = 560,
 188                 .enter = &intel_idle },
 189 };
 190
 191 /**
 192  * intel_idle
 193  * @dev: cpuidle_device
 194  * @state: cpuidle state
 195  *
 196  */
 197 static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state)
 198 {
 199         unsigned long ecx = 1; /* break on interrupt flag */
 200         unsigned long eax = (unsigned long)cpuidle_get_statedata(state);
 201         unsigned int cstate;
 202         ktime_t kt_before, kt_after;
 203         s64 usec_delta;
 204         int cpu = smp_processor_id();
 205
 206         cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1;
 207
 208         local_irq_disable();
 209
 210         /*
 211          * leave_mm() to avoid costly and often unnecessary wakeups
 212          * for flushing the user TLB's associated with the active mm.
 213          */
 214         if (state->flags & CPUIDLE_FLAG_TLB_FLUSHED)
 215                 leave_mm(cpu);
 216
 217         if (!(lapic_timer_reliable_states & (1 << (cstate))))
 218                 clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
 219
 220         kt_before = ktime_get_real();
 221
 222         stop_critical_timings();
 223 #ifndef MODULE
 224         trace_power_start(POWER_CSTATE, (eax >> 4) + 1, cpu);
 225 #endif
 226         if (!need_resched()) {
 227
 228                 __monitor((void *)&current_thread_info()->flags, 0, 0);
 229                 smp_mb();
 230                 if (!need_resched())
 231                         __mwait(eax, ecx);
 232         }
 233
 234         start_critical_timings();
 235
 236         kt_after = ktime_get_real();
 237         usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
 238
 239         local_irq_enable();
 240
 241         if (!(lapic_timer_reliable_states & (1 << (cstate))))
 242                 clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
 243
 244         return usec_delta;
 245 }
 246
 247 /*
 248  * intel_idle_probe()
 249  */
 250 static int intel_idle_probe(void)
 251 {
 252         unsigned int eax, ebx, ecx;
 253
 254         if (max_cstate == 0) {
 255                 pr_debug(PREFIX "disabled\n");
 256                 return -EPERM;
 257         }
 258
 259         if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
 260                 return -ENODEV;
 261
 262         if (!boot_cpu_has(X86_FEATURE_MWAIT))
 263                 return -ENODEV;
 264
 265         if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
 266                 return -ENODEV;
 267
 268         cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates);
 269
 270         if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
 271                 !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
 272                         return -ENODEV;
 273
 274         pr_debug(PREFIX "MWAIT substates: 0x%x\n", mwait_substates);
 275
 276
 277         if (boot_cpu_data.x86 != 6)     /* family 6 */
 278                 return -ENODEV;
 279
 280         switch (boot_cpu_data.x86_model) {
 281
 282         case 0x1A:      /* Core i7, Xeon 5500 series */
 283         case 0x1E:      /* Core i7 and i5 Processor - Lynnfield Jasper Forest */
 284         case 0x1F:      /* Core i7 and i5 Processor - Nehalem */
 285         case 0x2E:      /* Nehalem-EX Xeon */
 286         case 0x2F:      /* Westmere-EX Xeon */
 287         case 0x25:      /* Westmere */
 288         case 0x2C:      /* Westmere */
 289                 cpuidle_state_table = nehalem_cstates;
 290                 break;
 291
 292         case 0x1C:      /* 28 - Atom Processor */
 293         case 0x26:      /* 38 - Lincroft Atom Processor */
 294                 cpuidle_state_table = atom_cstates;
 295                 break;
 296
 297         case 0x2A:      /* SNB */
 298         case 0x2D:      /* SNB Xeon */
 299                 cpuidle_state_table = snb_cstates;
 300                 break;
 301
 302         default:
 303                 pr_debug(PREFIX "does not run on family %d model %d\n",
 304                         boot_cpu_data.x86, boot_cpu_data.x86_model);
 305                 return -ENODEV;
 306         }
 307
 308         if (boot_cpu_has(X86_FEATURE_ARAT))     /* Always Reliable APIC Timer */
 309                 lapic_timer_reliable_states = 0xFFFFFFFF;
 310
 311         pr_debug(PREFIX "v" INTEL_IDLE_VERSION
 312                 " model 0x%X\n", boot_cpu_data.x86_model);
 313
 314         pr_debug(PREFIX "lapic_timer_reliable_states 0x%x\n",
 315                 lapic_timer_reliable_states);
 316         return 0;
 317 }
 318
 319 /*
 320  * intel_idle_cpuidle_devices_uninit()
 321  * unregister, free cpuidle_devices
 322  */
 323 static void intel_idle_cpuidle_devices_uninit(void)
 324 {
 325         int i;
 326         struct cpuidle_device *dev;
 327
 328         for_each_online_cpu(i) {
 329                 dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
 330                 cpuidle_unregister_device(dev);
 331         }
 332
 333         free_percpu(intel_idle_cpuidle_devices);
 334         return;
 335 }
 336 /*
 337  * intel_idle_cpuidle_devices_init()
 338  * allocate, initialize, register cpuidle_devices
 339  */
 340 static int intel_idle_cpuidle_devices_init(void)
 341 {
 342         int i, cstate;
 343         struct cpuidle_device *dev;
 344
 345         intel_idle_cpuidle_devices = alloc_percpu(struct cpuidle_device);
 346         if (intel_idle_cpuidle_devices == NULL)
 347                 return -ENOMEM;
 348
 349         for_each_online_cpu(i) {
 350                 dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
 351
 352                 dev->state_count = 1;
 353
 354                 for (cstate = 1; cstate < MWAIT_MAX_NUM_CSTATES; ++cstate) {
 355                         int num_substates;
 356
 357                         if (cstate > max_cstate) {
 358                                 printk(PREFIX "max_cstate %d reached\n",
 359                                         max_cstate);
 360                                 break;
 361                         }
 362
 363                         /* does the state exist in CPUID.MWAIT? */
 364                         num_substates = (mwait_substates >> ((cstate) * 4))
 365                                                 & MWAIT_SUBSTATE_MASK;
 366                         if (num_substates == 0)
 367                                 continue;
 368                         /* is the state not enabled? */
 369                         if (cpuidle_state_table[cstate].enter == NULL) {
 370                                 /* does the driver not know about the state? */
 371                                 if (*cpuidle_state_table[cstate].name == '\0')
 372                                         pr_debug(PREFIX "unaware of model 0x%x"
 373                                                 " MWAIT %d please"
 374                                                 " contact lenb@kernel.org",
 375                                         boot_cpu_data.x86_model, cstate);
 376                                 continue;
 377                         }
 378
 379                         if ((cstate > 2) &&
 380                                 !boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
 381                                 mark_tsc_unstable("TSC halts in idle"
 382                                         " states deeper than C2");
 383
 384                         dev->states[dev->state_count] = /* structure copy */
 385                                 cpuidle_state_table[cstate];
 386
 387                         dev->state_count += 1;
 388                 }
 389
 390                 dev->cpu = i;
 391                 if (cpuidle_register_device(dev)) {
 392                         pr_debug(PREFIX "cpuidle_register_device %d failed!\n",
 393                                  i);
 394                         intel_idle_cpuidle_devices_uninit();
 395                         return -EIO;
 396                 }
 397         }
 398
 399         return 0;
 400 }
 401
 402
 403 static int __init intel_idle_init(void)
 404 {
 405         int retval;
 406
 407         retval = intel_idle_probe();
 408         if (retval)
 409                 return retval;
 410
 411         retval = cpuidle_register_driver(&intel_idle_driver);
 412         if (retval) {
 413                 printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
 414                         cpuidle_get_driver()->name);
 415                 return retval;
 416         }
 417
 418         retval = intel_idle_cpuidle_devices_init();
 419         if (retval) {
 420                 cpuidle_unregister_driver(&intel_idle_driver);
 421                 return retval;
 422         }
 423
 424         return 0;
 425 }
 426
 427 static void __exit intel_idle_exit(void)
 428 {
 429         intel_idle_cpuidle_devices_uninit();
 430         cpuidle_unregister_driver(&intel_idle_driver);
 431
 432         return;
 433 }
 434
 435 module_init(intel_idle_init);
 436 module_exit(intel_idle_exit);
 437
 438 module_param(max_cstate, int, 0444);
 439
 440 MODULE_AUTHOR("Len Brown <len.brown@intel.com>");
 441 MODULE_DESCRIPTION("Cpuidle driver for Intel Hardware v" INTEL_IDLE_VERSION);
 442 MODULE_LICENSE("GPL");