1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * acpi_pad.c ACPI Processor Aggregator Driver 4 * 5 * Copyright (c) 2009, Intel Corporation. 6 */ 7 8 #include <linux/kernel.h> 9 #include <linux/cpumask.h> 10 #include <linux/module.h> 11 #include <linux/init.h> 12 #include <linux/types.h> 13 #include <linux/kthread.h> 14 #include <uapi/linux/sched/types.h> 15 #include <linux/freezer.h> 16 #include <linux/cpu.h> 17 #include <linux/tick.h> 18 #include <linux/slab.h> 19 #include <linux/acpi.h> 20 #include <asm/mwait.h> 21 #include <xen/xen.h> 22 23 #define ACPI_PROCESSOR_AGGREGATOR_CLASS "acpi_pad" 24 #define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator" 25 #define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80 26 static DEFINE_MUTEX(isolated_cpus_lock); 27 static DEFINE_MUTEX(round_robin_lock); 28 29 static unsigned long power_saving_mwait_eax; 30 31 static unsigned char tsc_detected_unstable; 32 static unsigned char tsc_marked_unstable; 33 34 static void power_saving_mwait_init(void) 35 { 36 unsigned int eax, ebx, ecx, edx; 37 unsigned int highest_cstate = 0; 38 unsigned int highest_subcstate = 0; 39 int i; 40 41 if (!boot_cpu_has(X86_FEATURE_MWAIT)) 42 return; 43 if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) 44 return; 45 46 cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); 47 48 if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) || 49 !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) 50 return; 51 52 edx >>= MWAIT_SUBSTATE_SIZE; 53 for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { 54 if (edx & MWAIT_SUBSTATE_MASK) { 55 highest_cstate = i; 56 highest_subcstate = edx & MWAIT_SUBSTATE_MASK; 57 } 58 } 59 power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | 60 (highest_subcstate - 1); 61 62 #if defined(CONFIG_X86) 63 switch (boot_cpu_data.x86_vendor) { 64 case X86_VENDOR_HYGON: 65 case X86_VENDOR_AMD: 66 case X86_VENDOR_INTEL: 67 case X86_VENDOR_ZHAOXIN: 68 /* 69 * AMD Fam10h TSC will tick in all 70 * C/P/S0/S1 states when this bit is set. 71 */ 72 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) 73 tsc_detected_unstable = 1; 74 break; 75 default: 76 /* TSC could halt in idle */ 77 tsc_detected_unstable = 1; 78 } 79 #endif 80 } 81 82 static unsigned long cpu_weight[NR_CPUS]; 83 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1}; 84 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS); 85 static void round_robin_cpu(unsigned int tsk_index) 86 { 87 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); 88 cpumask_var_t tmp; 89 int cpu; 90 unsigned long min_weight = -1; 91 unsigned long uninitialized_var(preferred_cpu); 92 93 if (!alloc_cpumask_var(&tmp, GFP_KERNEL)) 94 return; 95 96 mutex_lock(&round_robin_lock); 97 cpumask_clear(tmp); 98 for_each_cpu(cpu, pad_busy_cpus) 99 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu)); 100 cpumask_andnot(tmp, cpu_online_mask, tmp); 101 /* avoid HT sibilings if possible */ 102 if (cpumask_empty(tmp)) 103 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus); 104 if (cpumask_empty(tmp)) { 105 mutex_unlock(&round_robin_lock); 106 free_cpumask_var(tmp); 107 return; 108 } 109 for_each_cpu(cpu, tmp) { 110 if (cpu_weight[cpu] < min_weight) { 111 min_weight = cpu_weight[cpu]; 112 preferred_cpu = cpu; 113 } 114 } 115 116 if (tsk_in_cpu[tsk_index] != -1) 117 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 118 tsk_in_cpu[tsk_index] = preferred_cpu; 119 cpumask_set_cpu(preferred_cpu, pad_busy_cpus); 120 cpu_weight[preferred_cpu]++; 121 mutex_unlock(&round_robin_lock); 122 123 set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu)); 124 125 free_cpumask_var(tmp); 126 } 127 128 static void exit_round_robin(unsigned int tsk_index) 129 { 130 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); 131 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 132 tsk_in_cpu[tsk_index] = -1; 133 } 134 135 static unsigned int idle_pct = 5; /* percentage */ 136 static unsigned int round_robin_time = 1; /* second */ 137 static int power_saving_thread(void *data) 138 { 139 struct sched_param param = {.sched_priority = 1}; 140 int do_sleep; 141 unsigned int tsk_index = (unsigned long)data; 142 u64 last_jiffies = 0; 143 144 sched_setscheduler(current, SCHED_RR, ¶m); 145 146 while (!kthread_should_stop()) { 147 unsigned long expire_time; 148 149 /* round robin to cpus */ 150 expire_time = last_jiffies + round_robin_time * HZ; 151 if (time_before(expire_time, jiffies)) { 152 last_jiffies = jiffies; 153 round_robin_cpu(tsk_index); 154 } 155 156 do_sleep = 0; 157 158 expire_time = jiffies + HZ * (100 - idle_pct) / 100; 159 160 while (!need_resched()) { 161 if (tsc_detected_unstable && !tsc_marked_unstable) { 162 /* TSC could halt in idle, so notify users */ 163 mark_tsc_unstable("TSC halts in idle"); 164 tsc_marked_unstable = 1; 165 } 166 local_irq_disable(); 167 tick_broadcast_enable(); 168 tick_broadcast_enter(); 169 stop_critical_timings(); 170 171 mwait_idle_with_hints(power_saving_mwait_eax, 1); 172 173 start_critical_timings(); 174 tick_broadcast_exit(); 175 local_irq_enable(); 176 177 if (time_before(expire_time, jiffies)) { 178 do_sleep = 1; 179 break; 180 } 181 } 182 183 /* 184 * current sched_rt has threshold for rt task running time. 185 * When a rt task uses 95% CPU time, the rt thread will be 186 * scheduled out for 5% CPU time to not starve other tasks. But 187 * the mechanism only works when all CPUs have RT task running, 188 * as if one CPU hasn't RT task, RT task from other CPUs will 189 * borrow CPU time from this CPU and cause RT task use > 95% 190 * CPU time. To make 'avoid starvation' work, takes a nap here. 191 */ 192 if (unlikely(do_sleep)) 193 schedule_timeout_killable(HZ * idle_pct / 100); 194 195 /* If an external event has set the need_resched flag, then 196 * we need to deal with it, or this loop will continue to 197 * spin without calling __mwait(). 198 */ 199 if (unlikely(need_resched())) 200 schedule(); 201 } 202 203 exit_round_robin(tsk_index); 204 return 0; 205 } 206 207 static struct task_struct *ps_tsks[NR_CPUS]; 208 static unsigned int ps_tsk_num; 209 static int create_power_saving_task(void) 210 { 211 int rc; 212 213 ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread, 214 (void *)(unsigned long)ps_tsk_num, 215 "acpi_pad/%d", ps_tsk_num); 216 217 if (IS_ERR(ps_tsks[ps_tsk_num])) { 218 rc = PTR_ERR(ps_tsks[ps_tsk_num]); 219 ps_tsks[ps_tsk_num] = NULL; 220 } else { 221 rc = 0; 222 ps_tsk_num++; 223 } 224 225 return rc; 226 } 227 228 static void destroy_power_saving_task(void) 229 { 230 if (ps_tsk_num > 0) { 231 ps_tsk_num--; 232 kthread_stop(ps_tsks[ps_tsk_num]); 233 ps_tsks[ps_tsk_num] = NULL; 234 } 235 } 236 237 static void set_power_saving_task_num(unsigned int num) 238 { 239 if (num > ps_tsk_num) { 240 while (ps_tsk_num < num) { 241 if (create_power_saving_task()) 242 return; 243 } 244 } else if (num < ps_tsk_num) { 245 while (ps_tsk_num > num) 246 destroy_power_saving_task(); 247 } 248 } 249 250 static void acpi_pad_idle_cpus(unsigned int num_cpus) 251 { 252 get_online_cpus(); 253 254 num_cpus = min_t(unsigned int, num_cpus, num_online_cpus()); 255 set_power_saving_task_num(num_cpus); 256 257 put_online_cpus(); 258 } 259 260 static uint32_t acpi_pad_idle_cpus_num(void) 261 { 262 return ps_tsk_num; 263 } 264 265 static ssize_t acpi_pad_rrtime_store(struct device *dev, 266 struct device_attribute *attr, const char *buf, size_t count) 267 { 268 unsigned long num; 269 if (kstrtoul(buf, 0, &num)) 270 return -EINVAL; 271 if (num < 1 || num >= 100) 272 return -EINVAL; 273 mutex_lock(&isolated_cpus_lock); 274 round_robin_time = num; 275 mutex_unlock(&isolated_cpus_lock); 276 return count; 277 } 278 279 static ssize_t acpi_pad_rrtime_show(struct device *dev, 280 struct device_attribute *attr, char *buf) 281 { 282 return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time); 283 } 284 static DEVICE_ATTR(rrtime, S_IRUGO|S_IWUSR, 285 acpi_pad_rrtime_show, 286 acpi_pad_rrtime_store); 287 288 static ssize_t acpi_pad_idlepct_store(struct device *dev, 289 struct device_attribute *attr, const char *buf, size_t count) 290 { 291 unsigned long num; 292 if (kstrtoul(buf, 0, &num)) 293 return -EINVAL; 294 if (num < 1 || num >= 100) 295 return -EINVAL; 296 mutex_lock(&isolated_cpus_lock); 297 idle_pct = num; 298 mutex_unlock(&isolated_cpus_lock); 299 return count; 300 } 301 302 static ssize_t acpi_pad_idlepct_show(struct device *dev, 303 struct device_attribute *attr, char *buf) 304 { 305 return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct); 306 } 307 static DEVICE_ATTR(idlepct, S_IRUGO|S_IWUSR, 308 acpi_pad_idlepct_show, 309 acpi_pad_idlepct_store); 310 311 static ssize_t acpi_pad_idlecpus_store(struct device *dev, 312 struct device_attribute *attr, const char *buf, size_t count) 313 { 314 unsigned long num; 315 if (kstrtoul(buf, 0, &num)) 316 return -EINVAL; 317 mutex_lock(&isolated_cpus_lock); 318 acpi_pad_idle_cpus(num); 319 mutex_unlock(&isolated_cpus_lock); 320 return count; 321 } 322 323 static ssize_t acpi_pad_idlecpus_show(struct device *dev, 324 struct device_attribute *attr, char *buf) 325 { 326 return cpumap_print_to_pagebuf(false, buf, 327 to_cpumask(pad_busy_cpus_bits)); 328 } 329 330 static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR, 331 acpi_pad_idlecpus_show, 332 acpi_pad_idlecpus_store); 333 334 static int acpi_pad_add_sysfs(struct acpi_device *device) 335 { 336 int result; 337 338 result = device_create_file(&device->dev, &dev_attr_idlecpus); 339 if (result) 340 return -ENODEV; 341 result = device_create_file(&device->dev, &dev_attr_idlepct); 342 if (result) { 343 device_remove_file(&device->dev, &dev_attr_idlecpus); 344 return -ENODEV; 345 } 346 result = device_create_file(&device->dev, &dev_attr_rrtime); 347 if (result) { 348 device_remove_file(&device->dev, &dev_attr_idlecpus); 349 device_remove_file(&device->dev, &dev_attr_idlepct); 350 return -ENODEV; 351 } 352 return 0; 353 } 354 355 static void acpi_pad_remove_sysfs(struct acpi_device *device) 356 { 357 device_remove_file(&device->dev, &dev_attr_idlecpus); 358 device_remove_file(&device->dev, &dev_attr_idlepct); 359 device_remove_file(&device->dev, &dev_attr_rrtime); 360 } 361 362 /* 363 * Query firmware how many CPUs should be idle 364 * return -1 on failure 365 */ 366 static int acpi_pad_pur(acpi_handle handle) 367 { 368 struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL}; 369 union acpi_object *package; 370 int num = -1; 371 372 if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer))) 373 return num; 374 375 if (!buffer.length || !buffer.pointer) 376 return num; 377 378 package = buffer.pointer; 379 380 if (package->type == ACPI_TYPE_PACKAGE && 381 package->package.count == 2 && 382 package->package.elements[0].integer.value == 1) /* rev 1 */ 383 384 num = package->package.elements[1].integer.value; 385 386 kfree(buffer.pointer); 387 return num; 388 } 389 390 static void acpi_pad_handle_notify(acpi_handle handle) 391 { 392 int num_cpus; 393 uint32_t idle_cpus; 394 struct acpi_buffer param = { 395 .length = 4, 396 .pointer = (void *)&idle_cpus, 397 }; 398 399 mutex_lock(&isolated_cpus_lock); 400 num_cpus = acpi_pad_pur(handle); 401 if (num_cpus < 0) { 402 mutex_unlock(&isolated_cpus_lock); 403 return; 404 } 405 acpi_pad_idle_cpus(num_cpus); 406 idle_cpus = acpi_pad_idle_cpus_num(); 407 acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, ¶m); 408 mutex_unlock(&isolated_cpus_lock); 409 } 410 411 static void acpi_pad_notify(acpi_handle handle, u32 event, 412 void *data) 413 { 414 struct acpi_device *device = data; 415 416 switch (event) { 417 case ACPI_PROCESSOR_AGGREGATOR_NOTIFY: 418 acpi_pad_handle_notify(handle); 419 acpi_bus_generate_netlink_event(device->pnp.device_class, 420 dev_name(&device->dev), event, 0); 421 break; 422 default: 423 pr_warn("Unsupported event [0x%x]\n", event); 424 break; 425 } 426 } 427 428 static int acpi_pad_add(struct acpi_device *device) 429 { 430 acpi_status status; 431 432 strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME); 433 strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS); 434 435 if (acpi_pad_add_sysfs(device)) 436 return -ENODEV; 437 438 status = acpi_install_notify_handler(device->handle, 439 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device); 440 if (ACPI_FAILURE(status)) { 441 acpi_pad_remove_sysfs(device); 442 return -ENODEV; 443 } 444 445 return 0; 446 } 447 448 static int acpi_pad_remove(struct acpi_device *device) 449 { 450 mutex_lock(&isolated_cpus_lock); 451 acpi_pad_idle_cpus(0); 452 mutex_unlock(&isolated_cpus_lock); 453 454 acpi_remove_notify_handler(device->handle, 455 ACPI_DEVICE_NOTIFY, acpi_pad_notify); 456 acpi_pad_remove_sysfs(device); 457 return 0; 458 } 459 460 static const struct acpi_device_id pad_device_ids[] = { 461 {"ACPI000C", 0}, 462 {"", 0}, 463 }; 464 MODULE_DEVICE_TABLE(acpi, pad_device_ids); 465 466 static struct acpi_driver acpi_pad_driver = { 467 .name = "processor_aggregator", 468 .class = ACPI_PROCESSOR_AGGREGATOR_CLASS, 469 .ids = pad_device_ids, 470 .ops = { 471 .add = acpi_pad_add, 472 .remove = acpi_pad_remove, 473 }, 474 }; 475 476 static int __init acpi_pad_init(void) 477 { 478 /* Xen ACPI PAD is used when running as Xen Dom0. */ 479 if (xen_initial_domain()) 480 return -ENODEV; 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