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 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 140 tsk_in_cpu[tsk_index] = -1; 141 } 142 143 static unsigned int idle_pct = 5; /* percentage */ 144 static unsigned int round_robin_time = 1; /* second */ 145 static int power_saving_thread(void *data) 146 { 147 int do_sleep; 148 unsigned int tsk_index = (unsigned long)data; 149 u64 last_jiffies = 0; 150 151 sched_set_fifo_low(current); 152 153 while (!kthread_should_stop()) { 154 unsigned long expire_time; 155 156 /* round robin to cpus */ 157 expire_time = last_jiffies + round_robin_time * HZ; 158 if (time_before(expire_time, jiffies)) { 159 last_jiffies = jiffies; 160 round_robin_cpu(tsk_index); 161 } 162 163 do_sleep = 0; 164 165 expire_time = jiffies + HZ * (100 - idle_pct) / 100; 166 167 while (!need_resched()) { 168 if (tsc_detected_unstable && !tsc_marked_unstable) { 169 /* TSC could halt in idle, so notify users */ 170 mark_tsc_unstable("TSC halts in idle"); 171 tsc_marked_unstable = 1; 172 } 173 local_irq_disable(); 174 175 perf_lopwr_cb(true); 176 177 tick_broadcast_enable(); 178 tick_broadcast_enter(); 179 stop_critical_timings(); 180 181 mwait_idle_with_hints(power_saving_mwait_eax, 1); 182 183 start_critical_timings(); 184 tick_broadcast_exit(); 185 186 perf_lopwr_cb(false); 187 188 local_irq_enable(); 189 190 if (time_before(expire_time, jiffies)) { 191 do_sleep = 1; 192 break; 193 } 194 } 195 196 /* 197 * current sched_rt has threshold for rt task running time. 198 * When a rt task uses 95% CPU time, the rt thread will be 199 * scheduled out for 5% CPU time to not starve other tasks. But 200 * the mechanism only works when all CPUs have RT task running, 201 * as if one CPU hasn't RT task, RT task from other CPUs will 202 * borrow CPU time from this CPU and cause RT task use > 95% 203 * CPU time. To make 'avoid starvation' work, takes a nap here. 204 */ 205 if (unlikely(do_sleep)) 206 schedule_timeout_killable(HZ * idle_pct / 100); 207 208 /* If an external event has set the need_resched flag, then 209 * we need to deal with it, or this loop will continue to 210 * spin without calling __mwait(). 211 */ 212 if (unlikely(need_resched())) 213 schedule(); 214 } 215 216 exit_round_robin(tsk_index); 217 return 0; 218 } 219 220 static struct task_struct *ps_tsks[NR_CPUS]; 221 static unsigned int ps_tsk_num; 222 static int create_power_saving_task(void) 223 { 224 int rc; 225 226 ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread, 227 (void *)(unsigned long)ps_tsk_num, 228 "acpi_pad/%d", ps_tsk_num); 229 230 if (IS_ERR(ps_tsks[ps_tsk_num])) { 231 rc = PTR_ERR(ps_tsks[ps_tsk_num]); 232 ps_tsks[ps_tsk_num] = NULL; 233 } else { 234 rc = 0; 235 ps_tsk_num++; 236 } 237 238 return rc; 239 } 240 241 static void destroy_power_saving_task(void) 242 { 243 if (ps_tsk_num > 0) { 244 ps_tsk_num--; 245 kthread_stop(ps_tsks[ps_tsk_num]); 246 ps_tsks[ps_tsk_num] = NULL; 247 } 248 } 249 250 static void set_power_saving_task_num(unsigned int num) 251 { 252 if (num > ps_tsk_num) { 253 while (ps_tsk_num < num) { 254 if (create_power_saving_task()) 255 return; 256 } 257 } else if (num < ps_tsk_num) { 258 while (ps_tsk_num > num) 259 destroy_power_saving_task(); 260 } 261 } 262 263 static void acpi_pad_idle_cpus(unsigned int num_cpus) 264 { 265 cpus_read_lock(); 266 267 num_cpus = min_t(unsigned int, num_cpus, num_online_cpus()); 268 set_power_saving_task_num(num_cpus); 269 270 cpus_read_unlock(); 271 } 272 273 static uint32_t acpi_pad_idle_cpus_num(void) 274 { 275 return ps_tsk_num; 276 } 277 278 static ssize_t rrtime_store(struct device *dev, 279 struct device_attribute *attr, const char *buf, size_t count) 280 { 281 unsigned long num; 282 283 if (kstrtoul(buf, 0, &num)) 284 return -EINVAL; 285 if (num < 1 || num >= 100) 286 return -EINVAL; 287 mutex_lock(&isolated_cpus_lock); 288 round_robin_time = num; 289 mutex_unlock(&isolated_cpus_lock); 290 return count; 291 } 292 293 static ssize_t rrtime_show(struct device *dev, 294 struct device_attribute *attr, char *buf) 295 { 296 return sysfs_emit(buf, "%d\n", round_robin_time); 297 } 298 static DEVICE_ATTR_RW(rrtime); 299 300 static ssize_t idlepct_store(struct device *dev, 301 struct device_attribute *attr, const char *buf, size_t count) 302 { 303 unsigned long num; 304 305 if (kstrtoul(buf, 0, &num)) 306 return -EINVAL; 307 if (num < 1 || num >= 100) 308 return -EINVAL; 309 mutex_lock(&isolated_cpus_lock); 310 idle_pct = num; 311 mutex_unlock(&isolated_cpus_lock); 312 return count; 313 } 314 315 static ssize_t idlepct_show(struct device *dev, 316 struct device_attribute *attr, char *buf) 317 { 318 return sysfs_emit(buf, "%d\n", idle_pct); 319 } 320 static DEVICE_ATTR_RW(idlepct); 321 322 static ssize_t idlecpus_store(struct device *dev, 323 struct device_attribute *attr, const char *buf, size_t count) 324 { 325 unsigned long num; 326 327 if (kstrtoul(buf, 0, &num)) 328 return -EINVAL; 329 mutex_lock(&isolated_cpus_lock); 330 acpi_pad_idle_cpus(num); 331 mutex_unlock(&isolated_cpus_lock); 332 return count; 333 } 334 335 static ssize_t idlecpus_show(struct device *dev, 336 struct device_attribute *attr, char *buf) 337 { 338 return cpumap_print_to_pagebuf(false, buf, 339 to_cpumask(pad_busy_cpus_bits)); 340 } 341 342 static DEVICE_ATTR_RW(idlecpus); 343 344 static struct attribute *acpi_pad_attrs[] = { 345 &dev_attr_idlecpus.attr, 346 &dev_attr_idlepct.attr, 347 &dev_attr_rrtime.attr, 348 NULL 349 }; 350 351 ATTRIBUTE_GROUPS(acpi_pad); 352 353 /* 354 * Query firmware how many CPUs should be idle 355 * return -1 on failure 356 */ 357 static int acpi_pad_pur(acpi_handle handle) 358 { 359 struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL}; 360 union acpi_object *package; 361 int num = -1; 362 363 if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer))) 364 return num; 365 366 if (!buffer.length || !buffer.pointer) 367 return num; 368 369 package = buffer.pointer; 370 371 if (package->type == ACPI_TYPE_PACKAGE && 372 package->package.count == 2 && 373 package->package.elements[0].integer.value == 1) /* rev 1 */ 374 375 num = package->package.elements[1].integer.value; 376 377 kfree(buffer.pointer); 378 return num; 379 } 380 381 static void acpi_pad_handle_notify(acpi_handle handle) 382 { 383 int num_cpus; 384 uint32_t idle_cpus; 385 struct acpi_buffer param = { 386 .length = 4, 387 .pointer = (void *)&idle_cpus, 388 }; 389 u32 status; 390 391 mutex_lock(&isolated_cpus_lock); 392 num_cpus = acpi_pad_pur(handle); 393 if (num_cpus < 0) { 394 /* The ACPI specification says that if no action was performed when 395 * processing the _PUR object, _OST should still be evaluated, albeit 396 * with a different status code. 397 */ 398 status = ACPI_PROCESSOR_AGGREGATOR_STATUS_NO_ACTION; 399 } else { 400 status = ACPI_PROCESSOR_AGGREGATOR_STATUS_SUCCESS; 401 acpi_pad_idle_cpus(num_cpus); 402 } 403 404 idle_cpus = acpi_pad_idle_cpus_num(); 405 acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, status, ¶m); 406 mutex_unlock(&isolated_cpus_lock); 407 } 408 409 static void acpi_pad_notify(acpi_handle handle, u32 event, 410 void *data) 411 { 412 struct acpi_device *adev = data; 413 414 switch (event) { 415 case ACPI_PROCESSOR_AGGREGATOR_NOTIFY: 416 acpi_pad_handle_notify(handle); 417 acpi_bus_generate_netlink_event(adev->pnp.device_class, 418 dev_name(&adev->dev), event, 0); 419 break; 420 default: 421 pr_warn("Unsupported event [0x%x]\n", event); 422 break; 423 } 424 } 425 426 static int acpi_pad_probe(struct platform_device *pdev) 427 { 428 struct acpi_device *adev = ACPI_COMPANION(&pdev->dev); 429 acpi_status status; 430 431 strcpy(acpi_device_name(adev), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME); 432 strcpy(acpi_device_class(adev), ACPI_PROCESSOR_AGGREGATOR_CLASS); 433 434 status = acpi_install_notify_handler(adev->handle, 435 ACPI_DEVICE_NOTIFY, acpi_pad_notify, adev); 436 437 if (ACPI_FAILURE(status)) 438 return -ENODEV; 439 440 return 0; 441 } 442 443 static void acpi_pad_remove(struct platform_device *pdev) 444 { 445 struct acpi_device *adev = ACPI_COMPANION(&pdev->dev); 446 447 mutex_lock(&isolated_cpus_lock); 448 acpi_pad_idle_cpus(0); 449 mutex_unlock(&isolated_cpus_lock); 450 451 acpi_remove_notify_handler(adev->handle, 452 ACPI_DEVICE_NOTIFY, acpi_pad_notify); 453 } 454 455 static const struct acpi_device_id pad_device_ids[] = { 456 {"ACPI000C", 0}, 457 {"", 0}, 458 }; 459 MODULE_DEVICE_TABLE(acpi, pad_device_ids); 460 461 static struct platform_driver acpi_pad_driver = { 462 .probe = acpi_pad_probe, 463 .remove_new = acpi_pad_remove, 464 .driver = { 465 .dev_groups = acpi_pad_groups, 466 .name = "processor_aggregator", 467 .acpi_match_table = pad_device_ids, 468 }, 469 }; 470 471 static int __init acpi_pad_init(void) 472 { 473 /* Xen ACPI PAD is used when running as Xen Dom0. */ 474 if (xen_initial_domain()) 475 return -ENODEV; 476 477 power_saving_mwait_init(); 478 if (power_saving_mwait_eax == 0) 479 return -EINVAL; 480 481 return platform_driver_register(&acpi_pad_driver); 482 } 483 484 static void __exit acpi_pad_exit(void) 485 { 486 platform_driver_unregister(&acpi_pad_driver); 487 } 488 489 module_init(acpi_pad_init); 490 module_exit(acpi_pad_exit); 491 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>"); 492 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver"); 493 MODULE_LICENSE("GPL"); 494