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 <linux/perf_event.h> 21 #include <linux/platform_device.h> 22 #include <asm/mwait.h> 23 #include <xen/xen.h> 24 25 #define ACPI_PROCESSOR_AGGREGATOR_CLASS "acpi_pad" 26 #define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator" 27 #define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80 28 29 #define ACPI_PROCESSOR_AGGREGATOR_STATUS_SUCCESS 0 30 #define ACPI_PROCESSOR_AGGREGATOR_STATUS_NO_ACTION 1 31 32 static DEFINE_MUTEX(isolated_cpus_lock); 33 static DEFINE_MUTEX(round_robin_lock); 34 35 static unsigned long power_saving_mwait_eax; 36 37 static unsigned char tsc_detected_unstable; 38 static unsigned char tsc_marked_unstable; 39 40 static void power_saving_mwait_init(void) 41 { 42 unsigned int eax, ebx, ecx, edx; 43 unsigned int highest_cstate = 0; 44 unsigned int highest_subcstate = 0; 45 int i; 46 47 if (!boot_cpu_has(X86_FEATURE_MWAIT)) 48 return; 49 if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) 50 return; 51 52 cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); 53 54 if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) || 55 !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) 56 return; 57 58 edx >>= MWAIT_SUBSTATE_SIZE; 59 for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { 60 if (edx & MWAIT_SUBSTATE_MASK) { 61 highest_cstate = i; 62 highest_subcstate = edx & MWAIT_SUBSTATE_MASK; 63 } 64 } 65 power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | 66 (highest_subcstate - 1); 67 68 #if defined(CONFIG_X86) 69 switch (boot_cpu_data.x86_vendor) { 70 case X86_VENDOR_HYGON: 71 case X86_VENDOR_AMD: 72 case X86_VENDOR_INTEL: 73 case X86_VENDOR_ZHAOXIN: 74 case X86_VENDOR_CENTAUR: 75 /* 76 * AMD Fam10h TSC will tick in all 77 * C/P/S0/S1 states when this bit is set. 78 */ 79 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) 80 tsc_detected_unstable = 1; 81 break; 82 default: 83 /* TSC could halt in idle */ 84 tsc_detected_unstable = 1; 85 } 86 #endif 87 } 88 89 static unsigned long cpu_weight[NR_CPUS]; 90 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1}; 91 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS); 92 static void round_robin_cpu(unsigned int tsk_index) 93 { 94 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); 95 cpumask_var_t tmp; 96 int cpu; 97 unsigned long min_weight = -1; 98 unsigned long preferred_cpu; 99 100 if (!alloc_cpumask_var(&tmp, GFP_KERNEL)) 101 return; 102 103 mutex_lock(&round_robin_lock); 104 cpumask_clear(tmp); 105 for_each_cpu(cpu, pad_busy_cpus) 106 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu)); 107 cpumask_andnot(tmp, cpu_online_mask, tmp); 108 /* avoid HT siblings if possible */ 109 if (cpumask_empty(tmp)) 110 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus); 111 if (cpumask_empty(tmp)) { 112 mutex_unlock(&round_robin_lock); 113 free_cpumask_var(tmp); 114 return; 115 } 116 for_each_cpu(cpu, tmp) { 117 if (cpu_weight[cpu] < min_weight) { 118 min_weight = cpu_weight[cpu]; 119 preferred_cpu = cpu; 120 } 121 } 122 123 if (tsk_in_cpu[tsk_index] != -1) 124 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 125 tsk_in_cpu[tsk_index] = preferred_cpu; 126 cpumask_set_cpu(preferred_cpu, pad_busy_cpus); 127 cpu_weight[preferred_cpu]++; 128 mutex_unlock(&round_robin_lock); 129 130 set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu)); 131 132 free_cpumask_var(tmp); 133 } 134 135 static void exit_round_robin(unsigned int tsk_index) 136 { 137 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); 138 139 if (tsk_in_cpu[tsk_index] != -1) { 140 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 141 tsk_in_cpu[tsk_index] = -1; 142 } 143 } 144 145 static unsigned int idle_pct = 5; /* percentage */ 146 static unsigned int round_robin_time = 1; /* second */ 147 static int power_saving_thread(void *data) 148 { 149 int do_sleep; 150 unsigned int tsk_index = (unsigned long)data; 151 u64 last_jiffies = 0; 152 153 sched_set_fifo_low(current); 154 155 while (!kthread_should_stop()) { 156 unsigned long expire_time; 157 158 /* round robin to cpus */ 159 expire_time = last_jiffies + round_robin_time * HZ; 160 if (time_before(expire_time, jiffies)) { 161 last_jiffies = jiffies; 162 round_robin_cpu(tsk_index); 163 } 164 165 do_sleep = 0; 166 167 expire_time = jiffies + HZ * (100 - idle_pct) / 100; 168 169 while (!need_resched()) { 170 if (tsc_detected_unstable && !tsc_marked_unstable) { 171 /* TSC could halt in idle, so notify users */ 172 mark_tsc_unstable("TSC halts in idle"); 173 tsc_marked_unstable = 1; 174 } 175 local_irq_disable(); 176 177 perf_lopwr_cb(true); 178 179 tick_broadcast_enable(); 180 tick_broadcast_enter(); 181 stop_critical_timings(); 182 183 mwait_idle_with_hints(power_saving_mwait_eax, 1); 184 185 start_critical_timings(); 186 tick_broadcast_exit(); 187 188 perf_lopwr_cb(false); 189 190 local_irq_enable(); 191 192 if (time_before(expire_time, jiffies)) { 193 do_sleep = 1; 194 break; 195 } 196 } 197 198 /* 199 * current sched_rt has threshold for rt task running time. 200 * When a rt task uses 95% CPU time, the rt thread will be 201 * scheduled out for 5% CPU time to not starve other tasks. But 202 * the mechanism only works when all CPUs have RT task running, 203 * as if one CPU hasn't RT task, RT task from other CPUs will 204 * borrow CPU time from this CPU and cause RT task use > 95% 205 * CPU time. To make 'avoid starvation' work, takes a nap here. 206 */ 207 if (unlikely(do_sleep)) 208 schedule_timeout_killable(HZ * idle_pct / 100); 209 210 /* If an external event has set the need_resched flag, then 211 * we need to deal with it, or this loop will continue to 212 * spin without calling __mwait(). 213 */ 214 if (unlikely(need_resched())) 215 schedule(); 216 } 217 218 exit_round_robin(tsk_index); 219 return 0; 220 } 221 222 static struct task_struct *ps_tsks[NR_CPUS]; 223 static unsigned int ps_tsk_num; 224 static int create_power_saving_task(void) 225 { 226 int rc; 227 228 ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread, 229 (void *)(unsigned long)ps_tsk_num, 230 "acpi_pad/%d", ps_tsk_num); 231 232 if (IS_ERR(ps_tsks[ps_tsk_num])) { 233 rc = PTR_ERR(ps_tsks[ps_tsk_num]); 234 ps_tsks[ps_tsk_num] = NULL; 235 } else { 236 rc = 0; 237 ps_tsk_num++; 238 } 239 240 return rc; 241 } 242 243 static void destroy_power_saving_task(void) 244 { 245 if (ps_tsk_num > 0) { 246 ps_tsk_num--; 247 kthread_stop(ps_tsks[ps_tsk_num]); 248 ps_tsks[ps_tsk_num] = NULL; 249 } 250 } 251 252 static void set_power_saving_task_num(unsigned int num) 253 { 254 if (num > ps_tsk_num) { 255 while (ps_tsk_num < num) { 256 if (create_power_saving_task()) 257 return; 258 } 259 } else if (num < ps_tsk_num) { 260 while (ps_tsk_num > num) 261 destroy_power_saving_task(); 262 } 263 } 264 265 static void acpi_pad_idle_cpus(unsigned int num_cpus) 266 { 267 cpus_read_lock(); 268 269 num_cpus = min_t(unsigned int, num_cpus, num_online_cpus()); 270 set_power_saving_task_num(num_cpus); 271 272 cpus_read_unlock(); 273 } 274 275 static uint32_t acpi_pad_idle_cpus_num(void) 276 { 277 return ps_tsk_num; 278 } 279 280 static ssize_t rrtime_store(struct device *dev, 281 struct device_attribute *attr, const char *buf, size_t count) 282 { 283 unsigned long num; 284 285 if (kstrtoul(buf, 0, &num)) 286 return -EINVAL; 287 if (num < 1 || num >= 100) 288 return -EINVAL; 289 mutex_lock(&isolated_cpus_lock); 290 round_robin_time = num; 291 mutex_unlock(&isolated_cpus_lock); 292 return count; 293 } 294 295 static ssize_t rrtime_show(struct device *dev, 296 struct device_attribute *attr, char *buf) 297 { 298 return sysfs_emit(buf, "%d\n", round_robin_time); 299 } 300 static DEVICE_ATTR_RW(rrtime); 301 302 static ssize_t idlepct_store(struct device *dev, 303 struct device_attribute *attr, const char *buf, size_t count) 304 { 305 unsigned long num; 306 307 if (kstrtoul(buf, 0, &num)) 308 return -EINVAL; 309 if (num < 1 || num >= 100) 310 return -EINVAL; 311 mutex_lock(&isolated_cpus_lock); 312 idle_pct = num; 313 mutex_unlock(&isolated_cpus_lock); 314 return count; 315 } 316 317 static ssize_t idlepct_show(struct device *dev, 318 struct device_attribute *attr, char *buf) 319 { 320 return sysfs_emit(buf, "%d\n", idle_pct); 321 } 322 static DEVICE_ATTR_RW(idlepct); 323 324 static ssize_t idlecpus_store(struct device *dev, 325 struct device_attribute *attr, const char *buf, size_t count) 326 { 327 unsigned long num; 328 329 if (kstrtoul(buf, 0, &num)) 330 return -EINVAL; 331 mutex_lock(&isolated_cpus_lock); 332 acpi_pad_idle_cpus(num); 333 mutex_unlock(&isolated_cpus_lock); 334 return count; 335 } 336 337 static ssize_t idlecpus_show(struct device *dev, 338 struct device_attribute *attr, char *buf) 339 { 340 return cpumap_print_to_pagebuf(false, buf, 341 to_cpumask(pad_busy_cpus_bits)); 342 } 343 344 static DEVICE_ATTR_RW(idlecpus); 345 346 static struct attribute *acpi_pad_attrs[] = { 347 &dev_attr_idlecpus.attr, 348 &dev_attr_idlepct.attr, 349 &dev_attr_rrtime.attr, 350 NULL 351 }; 352 353 ATTRIBUTE_GROUPS(acpi_pad); 354 355 /* 356 * Query firmware how many CPUs should be idle 357 * return -1 on failure 358 */ 359 static int acpi_pad_pur(acpi_handle handle) 360 { 361 struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL}; 362 union acpi_object *package; 363 int num = -1; 364 365 if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer))) 366 return num; 367 368 if (!buffer.length || !buffer.pointer) 369 return num; 370 371 package = buffer.pointer; 372 373 if (package->type == ACPI_TYPE_PACKAGE && 374 package->package.count == 2 && 375 package->package.elements[0].integer.value == 1) /* rev 1 */ 376 377 num = package->package.elements[1].integer.value; 378 379 kfree(buffer.pointer); 380 return num; 381 } 382 383 static void acpi_pad_handle_notify(acpi_handle handle) 384 { 385 int num_cpus; 386 uint32_t idle_cpus; 387 struct acpi_buffer param = { 388 .length = 4, 389 .pointer = (void *)&idle_cpus, 390 }; 391 u32 status; 392 393 mutex_lock(&isolated_cpus_lock); 394 num_cpus = acpi_pad_pur(handle); 395 if (num_cpus < 0) { 396 /* The ACPI specification says that if no action was performed when 397 * processing the _PUR object, _OST should still be evaluated, albeit 398 * with a different status code. 399 */ 400 status = ACPI_PROCESSOR_AGGREGATOR_STATUS_NO_ACTION; 401 } else { 402 status = ACPI_PROCESSOR_AGGREGATOR_STATUS_SUCCESS; 403 acpi_pad_idle_cpus(num_cpus); 404 } 405 406 idle_cpus = acpi_pad_idle_cpus_num(); 407 acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, status, ¶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 *adev = data; 415 416 switch (event) { 417 case ACPI_PROCESSOR_AGGREGATOR_NOTIFY: 418 acpi_pad_handle_notify(handle); 419 acpi_bus_generate_netlink_event(adev->pnp.device_class, 420 dev_name(&adev->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_probe(struct platform_device *pdev) 429 { 430 struct acpi_device *adev = ACPI_COMPANION(&pdev->dev); 431 acpi_status status; 432 433 strscpy(acpi_device_name(adev), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME); 434 strscpy(acpi_device_class(adev), ACPI_PROCESSOR_AGGREGATOR_CLASS); 435 436 status = acpi_install_notify_handler(adev->handle, 437 ACPI_DEVICE_NOTIFY, acpi_pad_notify, adev); 438 439 if (ACPI_FAILURE(status)) 440 return -ENODEV; 441 442 return 0; 443 } 444 445 static void acpi_pad_remove(struct platform_device *pdev) 446 { 447 struct acpi_device *adev = ACPI_COMPANION(&pdev->dev); 448 449 mutex_lock(&isolated_cpus_lock); 450 acpi_pad_idle_cpus(0); 451 mutex_unlock(&isolated_cpus_lock); 452 453 acpi_remove_notify_handler(adev->handle, 454 ACPI_DEVICE_NOTIFY, acpi_pad_notify); 455 } 456 457 static const struct acpi_device_id pad_device_ids[] = { 458 {"ACPI000C", 0}, 459 {"", 0}, 460 }; 461 MODULE_DEVICE_TABLE(acpi, pad_device_ids); 462 463 static struct platform_driver acpi_pad_driver = { 464 .probe = acpi_pad_probe, 465 .remove_new = acpi_pad_remove, 466 .driver = { 467 .dev_groups = acpi_pad_groups, 468 .name = "processor_aggregator", 469 .acpi_match_table = pad_device_ids, 470 }, 471 }; 472 473 static int __init acpi_pad_init(void) 474 { 475 /* Xen ACPI PAD is used when running as Xen Dom0. */ 476 if (xen_initial_domain()) 477 return -ENODEV; 478 479 power_saving_mwait_init(); 480 if (power_saving_mwait_eax == 0) 481 return -EINVAL; 482 483 return platform_driver_register(&acpi_pad_driver); 484 } 485 486 static void __exit acpi_pad_exit(void) 487 { 488 platform_driver_unregister(&acpi_pad_driver); 489 } 490 491 module_init(acpi_pad_init); 492 module_exit(acpi_pad_exit); 493 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>"); 494 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver"); 495 MODULE_LICENSE("GPL"); 496