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 #include <xen/xen.h> 30 31 #define ACPI_PROCESSOR_AGGREGATOR_CLASS "acpi_pad" 32 #define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator" 33 #define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80 34 static DEFINE_MUTEX(isolated_cpus_lock); 35 static DEFINE_MUTEX(round_robin_lock); 36 37 static unsigned long power_saving_mwait_eax; 38 39 static unsigned char tsc_detected_unstable; 40 static unsigned char tsc_marked_unstable; 41 42 static void power_saving_mwait_init(void) 43 { 44 unsigned int eax, ebx, ecx, edx; 45 unsigned int highest_cstate = 0; 46 unsigned int highest_subcstate = 0; 47 int i; 48 49 if (!boot_cpu_has(X86_FEATURE_MWAIT)) 50 return; 51 if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) 52 return; 53 54 cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); 55 56 if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) || 57 !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) 58 return; 59 60 edx >>= MWAIT_SUBSTATE_SIZE; 61 for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { 62 if (edx & MWAIT_SUBSTATE_MASK) { 63 highest_cstate = i; 64 highest_subcstate = edx & MWAIT_SUBSTATE_MASK; 65 } 66 } 67 power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | 68 (highest_subcstate - 1); 69 70 #if defined(CONFIG_X86) 71 switch (boot_cpu_data.x86_vendor) { 72 case X86_VENDOR_AMD: 73 case X86_VENDOR_INTEL: 74 /* 75 * AMD Fam10h TSC will tick in all 76 * C/P/S0/S1 states when this bit is set. 77 */ 78 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) 79 tsc_detected_unstable = 1; 80 break; 81 default: 82 /* TSC could halt in idle */ 83 tsc_detected_unstable = 1; 84 } 85 #endif 86 } 87 88 static unsigned long cpu_weight[NR_CPUS]; 89 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1}; 90 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS); 91 static void round_robin_cpu(unsigned int tsk_index) 92 { 93 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); 94 cpumask_var_t tmp; 95 int cpu; 96 unsigned long min_weight = -1; 97 unsigned long uninitialized_var(preferred_cpu); 98 99 if (!alloc_cpumask_var(&tmp, GFP_KERNEL)) 100 return; 101 102 mutex_lock(&round_robin_lock); 103 cpumask_clear(tmp); 104 for_each_cpu(cpu, pad_busy_cpus) 105 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu)); 106 cpumask_andnot(tmp, cpu_online_mask, tmp); 107 /* avoid HT sibilings if possible */ 108 if (cpumask_empty(tmp)) 109 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus); 110 if (cpumask_empty(tmp)) { 111 mutex_unlock(&round_robin_lock); 112 return; 113 } 114 for_each_cpu(cpu, tmp) { 115 if (cpu_weight[cpu] < min_weight) { 116 min_weight = cpu_weight[cpu]; 117 preferred_cpu = cpu; 118 } 119 } 120 121 if (tsk_in_cpu[tsk_index] != -1) 122 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 123 tsk_in_cpu[tsk_index] = preferred_cpu; 124 cpumask_set_cpu(preferred_cpu, pad_busy_cpus); 125 cpu_weight[preferred_cpu]++; 126 mutex_unlock(&round_robin_lock); 127 128 set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu)); 129 } 130 131 static void exit_round_robin(unsigned int tsk_index) 132 { 133 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); 134 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 135 tsk_in_cpu[tsk_index] = -1; 136 } 137 138 static unsigned int idle_pct = 5; /* percentage */ 139 static unsigned int round_robin_time = 1; /* second */ 140 static int power_saving_thread(void *data) 141 { 142 struct sched_param param = {.sched_priority = 1}; 143 int do_sleep; 144 unsigned int tsk_index = (unsigned long)data; 145 u64 last_jiffies = 0; 146 147 sched_setscheduler(current, SCHED_RR, ¶m); 148 149 while (!kthread_should_stop()) { 150 unsigned long expire_time; 151 152 /* round robin to cpus */ 153 expire_time = last_jiffies + round_robin_time * HZ; 154 if (time_before(expire_time, jiffies)) { 155 last_jiffies = jiffies; 156 round_robin_cpu(tsk_index); 157 } 158 159 do_sleep = 0; 160 161 expire_time = jiffies + HZ * (100 - idle_pct) / 100; 162 163 while (!need_resched()) { 164 if (tsc_detected_unstable && !tsc_marked_unstable) { 165 /* TSC could halt in idle, so notify users */ 166 mark_tsc_unstable("TSC halts in idle"); 167 tsc_marked_unstable = 1; 168 } 169 local_irq_disable(); 170 tick_broadcast_enable(); 171 tick_broadcast_enter(); 172 stop_critical_timings(); 173 174 mwait_idle_with_hints(power_saving_mwait_eax, 1); 175 176 start_critical_timings(); 177 tick_broadcast_exit(); 178 local_irq_enable(); 179 180 if (time_before(expire_time, jiffies)) { 181 do_sleep = 1; 182 break; 183 } 184 } 185 186 /* 187 * current sched_rt has threshold for rt task running time. 188 * When a rt task uses 95% CPU time, the rt thread will be 189 * scheduled out for 5% CPU time to not starve other tasks. But 190 * the mechanism only works when all CPUs have RT task running, 191 * as if one CPU hasn't RT task, RT task from other CPUs will 192 * borrow CPU time from this CPU and cause RT task use > 95% 193 * CPU time. To make 'avoid starvation' work, takes a nap here. 194 */ 195 if (unlikely(do_sleep)) 196 schedule_timeout_killable(HZ * idle_pct / 100); 197 198 /* If an external event has set the need_resched flag, then 199 * we need to deal with it, or this loop will continue to 200 * spin without calling __mwait(). 201 */ 202 if (unlikely(need_resched())) 203 schedule(); 204 } 205 206 exit_round_robin(tsk_index); 207 return 0; 208 } 209 210 static struct task_struct *ps_tsks[NR_CPUS]; 211 static unsigned int ps_tsk_num; 212 static int create_power_saving_task(void) 213 { 214 int rc; 215 216 ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread, 217 (void *)(unsigned long)ps_tsk_num, 218 "acpi_pad/%d", ps_tsk_num); 219 220 if (IS_ERR(ps_tsks[ps_tsk_num])) { 221 rc = PTR_ERR(ps_tsks[ps_tsk_num]); 222 ps_tsks[ps_tsk_num] = NULL; 223 } else { 224 rc = 0; 225 ps_tsk_num++; 226 } 227 228 return rc; 229 } 230 231 static void destroy_power_saving_task(void) 232 { 233 if (ps_tsk_num > 0) { 234 ps_tsk_num--; 235 kthread_stop(ps_tsks[ps_tsk_num]); 236 ps_tsks[ps_tsk_num] = NULL; 237 } 238 } 239 240 static void set_power_saving_task_num(unsigned int num) 241 { 242 if (num > ps_tsk_num) { 243 while (ps_tsk_num < num) { 244 if (create_power_saving_task()) 245 return; 246 } 247 } else if (num < ps_tsk_num) { 248 while (ps_tsk_num > num) 249 destroy_power_saving_task(); 250 } 251 } 252 253 static void acpi_pad_idle_cpus(unsigned int num_cpus) 254 { 255 get_online_cpus(); 256 257 num_cpus = min_t(unsigned int, num_cpus, num_online_cpus()); 258 set_power_saving_task_num(num_cpus); 259 260 put_online_cpus(); 261 } 262 263 static uint32_t acpi_pad_idle_cpus_num(void) 264 { 265 return ps_tsk_num; 266 } 267 268 static ssize_t acpi_pad_rrtime_store(struct device *dev, 269 struct device_attribute *attr, const char *buf, size_t count) 270 { 271 unsigned long num; 272 if (kstrtoul(buf, 0, &num)) 273 return -EINVAL; 274 if (num < 1 || num >= 100) 275 return -EINVAL; 276 mutex_lock(&isolated_cpus_lock); 277 round_robin_time = num; 278 mutex_unlock(&isolated_cpus_lock); 279 return count; 280 } 281 282 static ssize_t acpi_pad_rrtime_show(struct device *dev, 283 struct device_attribute *attr, char *buf) 284 { 285 return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time); 286 } 287 static DEVICE_ATTR(rrtime, S_IRUGO|S_IWUSR, 288 acpi_pad_rrtime_show, 289 acpi_pad_rrtime_store); 290 291 static ssize_t acpi_pad_idlepct_store(struct device *dev, 292 struct device_attribute *attr, const char *buf, size_t count) 293 { 294 unsigned long num; 295 if (kstrtoul(buf, 0, &num)) 296 return -EINVAL; 297 if (num < 1 || num >= 100) 298 return -EINVAL; 299 mutex_lock(&isolated_cpus_lock); 300 idle_pct = num; 301 mutex_unlock(&isolated_cpus_lock); 302 return count; 303 } 304 305 static ssize_t acpi_pad_idlepct_show(struct device *dev, 306 struct device_attribute *attr, char *buf) 307 { 308 return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct); 309 } 310 static DEVICE_ATTR(idlepct, S_IRUGO|S_IWUSR, 311 acpi_pad_idlepct_show, 312 acpi_pad_idlepct_store); 313 314 static ssize_t acpi_pad_idlecpus_store(struct device *dev, 315 struct device_attribute *attr, const char *buf, size_t count) 316 { 317 unsigned long num; 318 if (kstrtoul(buf, 0, &num)) 319 return -EINVAL; 320 mutex_lock(&isolated_cpus_lock); 321 acpi_pad_idle_cpus(num); 322 mutex_unlock(&isolated_cpus_lock); 323 return count; 324 } 325 326 static ssize_t acpi_pad_idlecpus_show(struct device *dev, 327 struct device_attribute *attr, char *buf) 328 { 329 return cpumap_print_to_pagebuf(false, buf, 330 to_cpumask(pad_busy_cpus_bits)); 331 } 332 333 static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR, 334 acpi_pad_idlecpus_show, 335 acpi_pad_idlecpus_store); 336 337 static int acpi_pad_add_sysfs(struct acpi_device *device) 338 { 339 int result; 340 341 result = device_create_file(&device->dev, &dev_attr_idlecpus); 342 if (result) 343 return -ENODEV; 344 result = device_create_file(&device->dev, &dev_attr_idlepct); 345 if (result) { 346 device_remove_file(&device->dev, &dev_attr_idlecpus); 347 return -ENODEV; 348 } 349 result = device_create_file(&device->dev, &dev_attr_rrtime); 350 if (result) { 351 device_remove_file(&device->dev, &dev_attr_idlecpus); 352 device_remove_file(&device->dev, &dev_attr_idlepct); 353 return -ENODEV; 354 } 355 return 0; 356 } 357 358 static void acpi_pad_remove_sysfs(struct acpi_device *device) 359 { 360 device_remove_file(&device->dev, &dev_attr_idlecpus); 361 device_remove_file(&device->dev, &dev_attr_idlepct); 362 device_remove_file(&device->dev, &dev_attr_rrtime); 363 } 364 365 /* 366 * Query firmware how many CPUs should be idle 367 * return -1 on failure 368 */ 369 static int acpi_pad_pur(acpi_handle handle) 370 { 371 struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL}; 372 union acpi_object *package; 373 int num = -1; 374 375 if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer))) 376 return num; 377 378 if (!buffer.length || !buffer.pointer) 379 return num; 380 381 package = buffer.pointer; 382 383 if (package->type == ACPI_TYPE_PACKAGE && 384 package->package.count == 2 && 385 package->package.elements[0].integer.value == 1) /* rev 1 */ 386 387 num = package->package.elements[1].integer.value; 388 389 kfree(buffer.pointer); 390 return num; 391 } 392 393 static void acpi_pad_handle_notify(acpi_handle handle) 394 { 395 int num_cpus; 396 uint32_t idle_cpus; 397 struct acpi_buffer param = { 398 .length = 4, 399 .pointer = (void *)&idle_cpus, 400 }; 401 402 mutex_lock(&isolated_cpus_lock); 403 num_cpus = acpi_pad_pur(handle); 404 if (num_cpus < 0) { 405 mutex_unlock(&isolated_cpus_lock); 406 return; 407 } 408 acpi_pad_idle_cpus(num_cpus); 409 idle_cpus = acpi_pad_idle_cpus_num(); 410 acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, ¶m); 411 mutex_unlock(&isolated_cpus_lock); 412 } 413 414 static void acpi_pad_notify(acpi_handle handle, u32 event, 415 void *data) 416 { 417 struct acpi_device *device = data; 418 419 switch (event) { 420 case ACPI_PROCESSOR_AGGREGATOR_NOTIFY: 421 acpi_pad_handle_notify(handle); 422 acpi_bus_generate_netlink_event(device->pnp.device_class, 423 dev_name(&device->dev), event, 0); 424 break; 425 default: 426 pr_warn("Unsupported event [0x%x]\n", event); 427 break; 428 } 429 } 430 431 static int acpi_pad_add(struct acpi_device *device) 432 { 433 acpi_status status; 434 435 strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME); 436 strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS); 437 438 if (acpi_pad_add_sysfs(device)) 439 return -ENODEV; 440 441 status = acpi_install_notify_handler(device->handle, 442 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device); 443 if (ACPI_FAILURE(status)) { 444 acpi_pad_remove_sysfs(device); 445 return -ENODEV; 446 } 447 448 return 0; 449 } 450 451 static int acpi_pad_remove(struct acpi_device *device) 452 { 453 mutex_lock(&isolated_cpus_lock); 454 acpi_pad_idle_cpus(0); 455 mutex_unlock(&isolated_cpus_lock); 456 457 acpi_remove_notify_handler(device->handle, 458 ACPI_DEVICE_NOTIFY, acpi_pad_notify); 459 acpi_pad_remove_sysfs(device); 460 return 0; 461 } 462 463 static const struct acpi_device_id pad_device_ids[] = { 464 {"ACPI000C", 0}, 465 {"", 0}, 466 }; 467 MODULE_DEVICE_TABLE(acpi, pad_device_ids); 468 469 static struct acpi_driver acpi_pad_driver = { 470 .name = "processor_aggregator", 471 .class = ACPI_PROCESSOR_AGGREGATOR_CLASS, 472 .ids = pad_device_ids, 473 .ops = { 474 .add = acpi_pad_add, 475 .remove = acpi_pad_remove, 476 }, 477 }; 478 479 static int __init acpi_pad_init(void) 480 { 481 /* Xen ACPI PAD is used when running as Xen Dom0. */ 482 if (xen_initial_domain()) 483 return -ENODEV; 484 485 power_saving_mwait_init(); 486 if (power_saving_mwait_eax == 0) 487 return -EINVAL; 488 489 return acpi_bus_register_driver(&acpi_pad_driver); 490 } 491 492 static void __exit acpi_pad_exit(void) 493 { 494 acpi_bus_unregister_driver(&acpi_pad_driver); 495 } 496 497 module_init(acpi_pad_init); 498 module_exit(acpi_pad_exit); 499 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>"); 500 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver"); 501 MODULE_LICENSE("GPL"); 502