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 /* round robin to cpus */ 152 expire_time = last_jiffies + round_robin_time * HZ; 153 if (time_before(expire_time, jiffies)) { 154 last_jiffies = jiffies; 155 round_robin_cpu(tsk_index); 156 } 157 158 do_sleep = 0; 159 160 expire_time = jiffies + HZ * (100 - idle_pct) / 100; 161 162 while (!need_resched()) { 163 if (tsc_detected_unstable && !tsc_marked_unstable) { 164 /* TSC could halt in idle, so notify users */ 165 mark_tsc_unstable("TSC halts in idle"); 166 tsc_marked_unstable = 1; 167 } 168 local_irq_disable(); 169 tick_broadcast_enable(); 170 tick_broadcast_enter(); 171 stop_critical_timings(); 172 173 mwait_idle_with_hints(power_saving_mwait_eax, 1); 174 175 start_critical_timings(); 176 tick_broadcast_exit(); 177 local_irq_enable(); 178 179 if (time_before(expire_time, jiffies)) { 180 do_sleep = 1; 181 break; 182 } 183 } 184 185 /* 186 * current sched_rt has threshold for rt task running time. 187 * When a rt task uses 95% CPU time, the rt thread will be 188 * scheduled out for 5% CPU time to not starve other tasks. But 189 * the mechanism only works when all CPUs have RT task running, 190 * as if one CPU hasn't RT task, RT task from other CPUs will 191 * borrow CPU time from this CPU and cause RT task use > 95% 192 * CPU time. To make 'avoid starvation' work, takes a nap here. 193 */ 194 if (unlikely(do_sleep)) 195 schedule_timeout_killable(HZ * idle_pct / 100); 196 197 /* If an external event has set the need_resched flag, then 198 * we need to deal with it, or this loop will continue to 199 * spin without calling __mwait(). 200 */ 201 if (unlikely(need_resched())) 202 schedule(); 203 } 204 205 exit_round_robin(tsk_index); 206 return 0; 207 } 208 209 static struct task_struct *ps_tsks[NR_CPUS]; 210 static unsigned int ps_tsk_num; 211 static int create_power_saving_task(void) 212 { 213 int rc; 214 215 ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread, 216 (void *)(unsigned long)ps_tsk_num, 217 "acpi_pad/%d", ps_tsk_num); 218 219 if (IS_ERR(ps_tsks[ps_tsk_num])) { 220 rc = PTR_ERR(ps_tsks[ps_tsk_num]); 221 ps_tsks[ps_tsk_num] = NULL; 222 } else { 223 rc = 0; 224 ps_tsk_num++; 225 } 226 227 return rc; 228 } 229 230 static void destroy_power_saving_task(void) 231 { 232 if (ps_tsk_num > 0) { 233 ps_tsk_num--; 234 kthread_stop(ps_tsks[ps_tsk_num]); 235 ps_tsks[ps_tsk_num] = NULL; 236 } 237 } 238 239 static void set_power_saving_task_num(unsigned int num) 240 { 241 if (num > ps_tsk_num) { 242 while (ps_tsk_num < num) { 243 if (create_power_saving_task()) 244 return; 245 } 246 } else if (num < ps_tsk_num) { 247 while (ps_tsk_num > num) 248 destroy_power_saving_task(); 249 } 250 } 251 252 static void acpi_pad_idle_cpus(unsigned int num_cpus) 253 { 254 get_online_cpus(); 255 256 num_cpus = min_t(unsigned int, num_cpus, num_online_cpus()); 257 set_power_saving_task_num(num_cpus); 258 259 put_online_cpus(); 260 } 261 262 static uint32_t acpi_pad_idle_cpus_num(void) 263 { 264 return ps_tsk_num; 265 } 266 267 static ssize_t acpi_pad_rrtime_store(struct device *dev, 268 struct device_attribute *attr, const char *buf, size_t count) 269 { 270 unsigned long num; 271 if (kstrtoul(buf, 0, &num)) 272 return -EINVAL; 273 if (num < 1 || num >= 100) 274 return -EINVAL; 275 mutex_lock(&isolated_cpus_lock); 276 round_robin_time = num; 277 mutex_unlock(&isolated_cpus_lock); 278 return count; 279 } 280 281 static ssize_t acpi_pad_rrtime_show(struct device *dev, 282 struct device_attribute *attr, char *buf) 283 { 284 return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time); 285 } 286 static DEVICE_ATTR(rrtime, S_IRUGO|S_IWUSR, 287 acpi_pad_rrtime_show, 288 acpi_pad_rrtime_store); 289 290 static ssize_t acpi_pad_idlepct_store(struct device *dev, 291 struct device_attribute *attr, const char *buf, size_t count) 292 { 293 unsigned long num; 294 if (kstrtoul(buf, 0, &num)) 295 return -EINVAL; 296 if (num < 1 || num >= 100) 297 return -EINVAL; 298 mutex_lock(&isolated_cpus_lock); 299 idle_pct = num; 300 mutex_unlock(&isolated_cpus_lock); 301 return count; 302 } 303 304 static ssize_t acpi_pad_idlepct_show(struct device *dev, 305 struct device_attribute *attr, char *buf) 306 { 307 return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct); 308 } 309 static DEVICE_ATTR(idlepct, S_IRUGO|S_IWUSR, 310 acpi_pad_idlepct_show, 311 acpi_pad_idlepct_store); 312 313 static ssize_t acpi_pad_idlecpus_store(struct device *dev, 314 struct device_attribute *attr, const char *buf, size_t count) 315 { 316 unsigned long num; 317 if (kstrtoul(buf, 0, &num)) 318 return -EINVAL; 319 mutex_lock(&isolated_cpus_lock); 320 acpi_pad_idle_cpus(num); 321 mutex_unlock(&isolated_cpus_lock); 322 return count; 323 } 324 325 static ssize_t acpi_pad_idlecpus_show(struct device *dev, 326 struct device_attribute *attr, char *buf) 327 { 328 return cpumap_print_to_pagebuf(false, buf, 329 to_cpumask(pad_busy_cpus_bits)); 330 } 331 332 static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR, 333 acpi_pad_idlecpus_show, 334 acpi_pad_idlecpus_store); 335 336 static int acpi_pad_add_sysfs(struct acpi_device *device) 337 { 338 int result; 339 340 result = device_create_file(&device->dev, &dev_attr_idlecpus); 341 if (result) 342 return -ENODEV; 343 result = device_create_file(&device->dev, &dev_attr_idlepct); 344 if (result) { 345 device_remove_file(&device->dev, &dev_attr_idlecpus); 346 return -ENODEV; 347 } 348 result = device_create_file(&device->dev, &dev_attr_rrtime); 349 if (result) { 350 device_remove_file(&device->dev, &dev_attr_idlecpus); 351 device_remove_file(&device->dev, &dev_attr_idlepct); 352 return -ENODEV; 353 } 354 return 0; 355 } 356 357 static void acpi_pad_remove_sysfs(struct acpi_device *device) 358 { 359 device_remove_file(&device->dev, &dev_attr_idlecpus); 360 device_remove_file(&device->dev, &dev_attr_idlepct); 361 device_remove_file(&device->dev, &dev_attr_rrtime); 362 } 363 364 /* 365 * Query firmware how many CPUs should be idle 366 * return -1 on failure 367 */ 368 static int acpi_pad_pur(acpi_handle handle) 369 { 370 struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL}; 371 union acpi_object *package; 372 int num = -1; 373 374 if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer))) 375 return num; 376 377 if (!buffer.length || !buffer.pointer) 378 return num; 379 380 package = buffer.pointer; 381 382 if (package->type == ACPI_TYPE_PACKAGE && 383 package->package.count == 2 && 384 package->package.elements[0].integer.value == 1) /* rev 1 */ 385 386 num = package->package.elements[1].integer.value; 387 388 kfree(buffer.pointer); 389 return num; 390 } 391 392 static void acpi_pad_handle_notify(acpi_handle handle) 393 { 394 int num_cpus; 395 uint32_t idle_cpus; 396 struct acpi_buffer param = { 397 .length = 4, 398 .pointer = (void *)&idle_cpus, 399 }; 400 401 mutex_lock(&isolated_cpus_lock); 402 num_cpus = acpi_pad_pur(handle); 403 if (num_cpus < 0) { 404 mutex_unlock(&isolated_cpus_lock); 405 return; 406 } 407 acpi_pad_idle_cpus(num_cpus); 408 idle_cpus = acpi_pad_idle_cpus_num(); 409 acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, ¶m); 410 mutex_unlock(&isolated_cpus_lock); 411 } 412 413 static void acpi_pad_notify(acpi_handle handle, u32 event, 414 void *data) 415 { 416 struct acpi_device *device = data; 417 418 switch (event) { 419 case ACPI_PROCESSOR_AGGREGATOR_NOTIFY: 420 acpi_pad_handle_notify(handle); 421 acpi_bus_generate_netlink_event(device->pnp.device_class, 422 dev_name(&device->dev), event, 0); 423 break; 424 default: 425 pr_warn("Unsupported event [0x%x]\n", event); 426 break; 427 } 428 } 429 430 static int acpi_pad_add(struct acpi_device *device) 431 { 432 acpi_status status; 433 434 strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME); 435 strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS); 436 437 if (acpi_pad_add_sysfs(device)) 438 return -ENODEV; 439 440 status = acpi_install_notify_handler(device->handle, 441 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device); 442 if (ACPI_FAILURE(status)) { 443 acpi_pad_remove_sysfs(device); 444 return -ENODEV; 445 } 446 447 return 0; 448 } 449 450 static int acpi_pad_remove(struct acpi_device *device) 451 { 452 mutex_lock(&isolated_cpus_lock); 453 acpi_pad_idle_cpus(0); 454 mutex_unlock(&isolated_cpus_lock); 455 456 acpi_remove_notify_handler(device->handle, 457 ACPI_DEVICE_NOTIFY, acpi_pad_notify); 458 acpi_pad_remove_sysfs(device); 459 return 0; 460 } 461 462 static const struct acpi_device_id pad_device_ids[] = { 463 {"ACPI000C", 0}, 464 {"", 0}, 465 }; 466 MODULE_DEVICE_TABLE(acpi, pad_device_ids); 467 468 static struct acpi_driver acpi_pad_driver = { 469 .name = "processor_aggregator", 470 .class = ACPI_PROCESSOR_AGGREGATOR_CLASS, 471 .ids = pad_device_ids, 472 .ops = { 473 .add = acpi_pad_add, 474 .remove = acpi_pad_remove, 475 }, 476 }; 477 478 static int __init acpi_pad_init(void) 479 { 480 power_saving_mwait_init(); 481 if (power_saving_mwait_eax == 0) 482 return -EINVAL; 483 484 return acpi_bus_register_driver(&acpi_pad_driver); 485 } 486 487 static void __exit acpi_pad_exit(void) 488 { 489 acpi_bus_unregister_driver(&acpi_pad_driver); 490 } 491 492 module_init(acpi_pad_init); 493 module_exit(acpi_pad_exit); 494 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>"); 495 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver"); 496 MODULE_LICENSE("GPL"); 497