1 /* 2 * acpi_pad.c ACPI Processor Aggregator Driver 3 * 4 * Copyright (c) 2009, Intel Corporation. 5 * 6 * This program is free software; you can redistribute it and/or modify it 7 * under the terms and conditions of the GNU General Public License, 8 * version 2, as published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for 13 * more details. 14 * 15 */ 16 17 #include <linux/kernel.h> 18 #include <linux/cpumask.h> 19 #include <linux/module.h> 20 #include <linux/init.h> 21 #include <linux/types.h> 22 #include <linux/kthread.h> 23 #include <linux/freezer.h> 24 #include <linux/cpu.h> 25 #include <linux/tick.h> 26 #include <linux/slab.h> 27 #include <linux/acpi.h> 28 #include <asm/mwait.h> 29 30 #define ACPI_PROCESSOR_AGGREGATOR_CLASS "acpi_pad" 31 #define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator" 32 #define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80 33 static DEFINE_MUTEX(isolated_cpus_lock); 34 static DEFINE_MUTEX(round_robin_lock); 35 36 static unsigned long power_saving_mwait_eax; 37 38 static unsigned char tsc_detected_unstable; 39 static unsigned char tsc_marked_unstable; 40 41 static void power_saving_mwait_init(void) 42 { 43 unsigned int eax, ebx, ecx, edx; 44 unsigned int highest_cstate = 0; 45 unsigned int highest_subcstate = 0; 46 int i; 47 48 if (!boot_cpu_has(X86_FEATURE_MWAIT)) 49 return; 50 if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) 51 return; 52 53 cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); 54 55 if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) || 56 !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) 57 return; 58 59 edx >>= MWAIT_SUBSTATE_SIZE; 60 for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { 61 if (edx & MWAIT_SUBSTATE_MASK) { 62 highest_cstate = i; 63 highest_subcstate = edx & MWAIT_SUBSTATE_MASK; 64 } 65 } 66 power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | 67 (highest_subcstate - 1); 68 69 #if defined(CONFIG_X86) 70 switch (boot_cpu_data.x86_vendor) { 71 case X86_VENDOR_AMD: 72 case X86_VENDOR_INTEL: 73 /* 74 * AMD Fam10h TSC will tick in all 75 * C/P/S0/S1 states when this bit is set. 76 */ 77 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) 78 tsc_detected_unstable = 1; 79 break; 80 default: 81 /* TSC could halt in idle */ 82 tsc_detected_unstable = 1; 83 } 84 #endif 85 } 86 87 static unsigned long cpu_weight[NR_CPUS]; 88 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1}; 89 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS); 90 static void round_robin_cpu(unsigned int tsk_index) 91 { 92 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); 93 cpumask_var_t tmp; 94 int cpu; 95 unsigned long min_weight = -1; 96 unsigned long uninitialized_var(preferred_cpu); 97 98 if (!alloc_cpumask_var(&tmp, GFP_KERNEL)) 99 return; 100 101 mutex_lock(&round_robin_lock); 102 cpumask_clear(tmp); 103 for_each_cpu(cpu, pad_busy_cpus) 104 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu)); 105 cpumask_andnot(tmp, cpu_online_mask, tmp); 106 /* avoid HT sibilings if possible */ 107 if (cpumask_empty(tmp)) 108 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus); 109 if (cpumask_empty(tmp)) { 110 mutex_unlock(&round_robin_lock); 111 return; 112 } 113 for_each_cpu(cpu, tmp) { 114 if (cpu_weight[cpu] < min_weight) { 115 min_weight = cpu_weight[cpu]; 116 preferred_cpu = cpu; 117 } 118 } 119 120 if (tsk_in_cpu[tsk_index] != -1) 121 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 122 tsk_in_cpu[tsk_index] = preferred_cpu; 123 cpumask_set_cpu(preferred_cpu, pad_busy_cpus); 124 cpu_weight[preferred_cpu]++; 125 mutex_unlock(&round_robin_lock); 126 127 set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu)); 128 } 129 130 static void exit_round_robin(unsigned int tsk_index) 131 { 132 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); 133 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 134 tsk_in_cpu[tsk_index] = -1; 135 } 136 137 static unsigned int idle_pct = 5; /* percentage */ 138 static unsigned int round_robin_time = 1; /* second */ 139 static int power_saving_thread(void *data) 140 { 141 struct sched_param param = {.sched_priority = 1}; 142 int do_sleep; 143 unsigned int tsk_index = (unsigned long)data; 144 u64 last_jiffies = 0; 145 146 sched_setscheduler(current, SCHED_RR, ¶m); 147 148 while (!kthread_should_stop()) { 149 unsigned long expire_time; 150 151 try_to_freeze(); 152 153 /* round robin to cpus */ 154 expire_time = last_jiffies + round_robin_time * HZ; 155 if (time_before(expire_time, jiffies)) { 156 last_jiffies = jiffies; 157 round_robin_cpu(tsk_index); 158 } 159 160 do_sleep = 0; 161 162 expire_time = jiffies + HZ * (100 - idle_pct) / 100; 163 164 while (!need_resched()) { 165 if (tsc_detected_unstable && !tsc_marked_unstable) { 166 /* TSC could halt in idle, so notify users */ 167 mark_tsc_unstable("TSC halts in idle"); 168 tsc_marked_unstable = 1; 169 } 170 local_irq_disable(); 171 tick_broadcast_enable(); 172 tick_broadcast_enter(); 173 stop_critical_timings(); 174 175 mwait_idle_with_hints(power_saving_mwait_eax, 1); 176 177 start_critical_timings(); 178 tick_broadcast_exit(); 179 local_irq_enable(); 180 181 if (time_before(expire_time, jiffies)) { 182 do_sleep = 1; 183 break; 184 } 185 } 186 187 /* 188 * current sched_rt has threshold for rt task running time. 189 * When a rt task uses 95% CPU time, the rt thread will be 190 * scheduled out for 5% CPU time to not starve other tasks. But 191 * the mechanism only works when all CPUs have RT task running, 192 * as if one CPU hasn't RT task, RT task from other CPUs will 193 * borrow CPU time from this CPU and cause RT task use > 95% 194 * CPU time. To make 'avoid starvation' work, takes a nap here. 195 */ 196 if (unlikely(do_sleep)) 197 schedule_timeout_killable(HZ * idle_pct / 100); 198 199 /* If an external event has set the need_resched flag, then 200 * we need to deal with it, or this loop will continue to 201 * spin without calling __mwait(). 202 */ 203 if (unlikely(need_resched())) 204 schedule(); 205 } 206 207 exit_round_robin(tsk_index); 208 return 0; 209 } 210 211 static struct task_struct *ps_tsks[NR_CPUS]; 212 static unsigned int ps_tsk_num; 213 static int create_power_saving_task(void) 214 { 215 int rc; 216 217 ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread, 218 (void *)(unsigned long)ps_tsk_num, 219 "acpi_pad/%d", ps_tsk_num); 220 221 if (IS_ERR(ps_tsks[ps_tsk_num])) { 222 rc = PTR_ERR(ps_tsks[ps_tsk_num]); 223 ps_tsks[ps_tsk_num] = NULL; 224 } else { 225 rc = 0; 226 ps_tsk_num++; 227 } 228 229 return rc; 230 } 231 232 static void destroy_power_saving_task(void) 233 { 234 if (ps_tsk_num > 0) { 235 ps_tsk_num--; 236 kthread_stop(ps_tsks[ps_tsk_num]); 237 ps_tsks[ps_tsk_num] = NULL; 238 } 239 } 240 241 static void set_power_saving_task_num(unsigned int num) 242 { 243 if (num > ps_tsk_num) { 244 while (ps_tsk_num < num) { 245 if (create_power_saving_task()) 246 return; 247 } 248 } else if (num < ps_tsk_num) { 249 while (ps_tsk_num > num) 250 destroy_power_saving_task(); 251 } 252 } 253 254 static void acpi_pad_idle_cpus(unsigned int num_cpus) 255 { 256 get_online_cpus(); 257 258 num_cpus = min_t(unsigned int, num_cpus, num_online_cpus()); 259 set_power_saving_task_num(num_cpus); 260 261 put_online_cpus(); 262 } 263 264 static uint32_t acpi_pad_idle_cpus_num(void) 265 { 266 return ps_tsk_num; 267 } 268 269 static ssize_t acpi_pad_rrtime_store(struct device *dev, 270 struct device_attribute *attr, const char *buf, size_t count) 271 { 272 unsigned long num; 273 if (kstrtoul(buf, 0, &num)) 274 return -EINVAL; 275 if (num < 1 || num >= 100) 276 return -EINVAL; 277 mutex_lock(&isolated_cpus_lock); 278 round_robin_time = num; 279 mutex_unlock(&isolated_cpus_lock); 280 return count; 281 } 282 283 static ssize_t acpi_pad_rrtime_show(struct device *dev, 284 struct device_attribute *attr, char *buf) 285 { 286 return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time); 287 } 288 static DEVICE_ATTR(rrtime, S_IRUGO|S_IWUSR, 289 acpi_pad_rrtime_show, 290 acpi_pad_rrtime_store); 291 292 static ssize_t acpi_pad_idlepct_store(struct device *dev, 293 struct device_attribute *attr, const char *buf, size_t count) 294 { 295 unsigned long num; 296 if (kstrtoul(buf, 0, &num)) 297 return -EINVAL; 298 if (num < 1 || num >= 100) 299 return -EINVAL; 300 mutex_lock(&isolated_cpus_lock); 301 idle_pct = num; 302 mutex_unlock(&isolated_cpus_lock); 303 return count; 304 } 305 306 static ssize_t acpi_pad_idlepct_show(struct device *dev, 307 struct device_attribute *attr, char *buf) 308 { 309 return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct); 310 } 311 static DEVICE_ATTR(idlepct, S_IRUGO|S_IWUSR, 312 acpi_pad_idlepct_show, 313 acpi_pad_idlepct_store); 314 315 static ssize_t acpi_pad_idlecpus_store(struct device *dev, 316 struct device_attribute *attr, const char *buf, size_t count) 317 { 318 unsigned long num; 319 if (kstrtoul(buf, 0, &num)) 320 return -EINVAL; 321 mutex_lock(&isolated_cpus_lock); 322 acpi_pad_idle_cpus(num); 323 mutex_unlock(&isolated_cpus_lock); 324 return count; 325 } 326 327 static ssize_t acpi_pad_idlecpus_show(struct device *dev, 328 struct device_attribute *attr, char *buf) 329 { 330 return cpumap_print_to_pagebuf(false, buf, 331 to_cpumask(pad_busy_cpus_bits)); 332 } 333 334 static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR, 335 acpi_pad_idlecpus_show, 336 acpi_pad_idlecpus_store); 337 338 static int acpi_pad_add_sysfs(struct acpi_device *device) 339 { 340 int result; 341 342 result = device_create_file(&device->dev, &dev_attr_idlecpus); 343 if (result) 344 return -ENODEV; 345 result = device_create_file(&device->dev, &dev_attr_idlepct); 346 if (result) { 347 device_remove_file(&device->dev, &dev_attr_idlecpus); 348 return -ENODEV; 349 } 350 result = device_create_file(&device->dev, &dev_attr_rrtime); 351 if (result) { 352 device_remove_file(&device->dev, &dev_attr_idlecpus); 353 device_remove_file(&device->dev, &dev_attr_idlepct); 354 return -ENODEV; 355 } 356 return 0; 357 } 358 359 static void acpi_pad_remove_sysfs(struct acpi_device *device) 360 { 361 device_remove_file(&device->dev, &dev_attr_idlecpus); 362 device_remove_file(&device->dev, &dev_attr_idlepct); 363 device_remove_file(&device->dev, &dev_attr_rrtime); 364 } 365 366 /* 367 * Query firmware how many CPUs should be idle 368 * return -1 on failure 369 */ 370 static int acpi_pad_pur(acpi_handle handle) 371 { 372 struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL}; 373 union acpi_object *package; 374 int num = -1; 375 376 if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer))) 377 return num; 378 379 if (!buffer.length || !buffer.pointer) 380 return num; 381 382 package = buffer.pointer; 383 384 if (package->type == ACPI_TYPE_PACKAGE && 385 package->package.count == 2 && 386 package->package.elements[0].integer.value == 1) /* rev 1 */ 387 388 num = package->package.elements[1].integer.value; 389 390 kfree(buffer.pointer); 391 return num; 392 } 393 394 static void acpi_pad_handle_notify(acpi_handle handle) 395 { 396 int num_cpus; 397 uint32_t idle_cpus; 398 struct acpi_buffer param = { 399 .length = 4, 400 .pointer = (void *)&idle_cpus, 401 }; 402 403 mutex_lock(&isolated_cpus_lock); 404 num_cpus = acpi_pad_pur(handle); 405 if (num_cpus < 0) { 406 mutex_unlock(&isolated_cpus_lock); 407 return; 408 } 409 acpi_pad_idle_cpus(num_cpus); 410 idle_cpus = acpi_pad_idle_cpus_num(); 411 acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, ¶m); 412 mutex_unlock(&isolated_cpus_lock); 413 } 414 415 static void acpi_pad_notify(acpi_handle handle, u32 event, 416 void *data) 417 { 418 struct acpi_device *device = data; 419 420 switch (event) { 421 case ACPI_PROCESSOR_AGGREGATOR_NOTIFY: 422 acpi_pad_handle_notify(handle); 423 acpi_bus_generate_netlink_event(device->pnp.device_class, 424 dev_name(&device->dev), event, 0); 425 break; 426 default: 427 pr_warn("Unsupported event [0x%x]\n", event); 428 break; 429 } 430 } 431 432 static int acpi_pad_add(struct acpi_device *device) 433 { 434 acpi_status status; 435 436 strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME); 437 strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS); 438 439 if (acpi_pad_add_sysfs(device)) 440 return -ENODEV; 441 442 status = acpi_install_notify_handler(device->handle, 443 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device); 444 if (ACPI_FAILURE(status)) { 445 acpi_pad_remove_sysfs(device); 446 return -ENODEV; 447 } 448 449 return 0; 450 } 451 452 static int acpi_pad_remove(struct acpi_device *device) 453 { 454 mutex_lock(&isolated_cpus_lock); 455 acpi_pad_idle_cpus(0); 456 mutex_unlock(&isolated_cpus_lock); 457 458 acpi_remove_notify_handler(device->handle, 459 ACPI_DEVICE_NOTIFY, acpi_pad_notify); 460 acpi_pad_remove_sysfs(device); 461 return 0; 462 } 463 464 static const struct acpi_device_id pad_device_ids[] = { 465 {"ACPI000C", 0}, 466 {"", 0}, 467 }; 468 MODULE_DEVICE_TABLE(acpi, pad_device_ids); 469 470 static struct acpi_driver acpi_pad_driver = { 471 .name = "processor_aggregator", 472 .class = ACPI_PROCESSOR_AGGREGATOR_CLASS, 473 .ids = pad_device_ids, 474 .ops = { 475 .add = acpi_pad_add, 476 .remove = acpi_pad_remove, 477 }, 478 }; 479 480 static int __init acpi_pad_init(void) 481 { 482 power_saving_mwait_init(); 483 if (power_saving_mwait_eax == 0) 484 return -EINVAL; 485 486 return acpi_bus_register_driver(&acpi_pad_driver); 487 } 488 489 static void __exit acpi_pad_exit(void) 490 { 491 acpi_bus_unregister_driver(&acpi_pad_driver); 492 } 493 494 module_init(acpi_pad_init); 495 module_exit(acpi_pad_exit); 496 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>"); 497 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver"); 498 MODULE_LICENSE("GPL"); 499