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 static DEFINE_MUTEX(isolated_cpus_lock); 29 static DEFINE_MUTEX(round_robin_lock); 30 31 static unsigned long power_saving_mwait_eax; 32 33 static unsigned char tsc_detected_unstable; 34 static unsigned char tsc_marked_unstable; 35 36 static void power_saving_mwait_init(void) 37 { 38 unsigned int eax, ebx, ecx, edx; 39 unsigned int highest_cstate = 0; 40 unsigned int highest_subcstate = 0; 41 int i; 42 43 if (!boot_cpu_has(X86_FEATURE_MWAIT)) 44 return; 45 if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) 46 return; 47 48 cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); 49 50 if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) || 51 !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) 52 return; 53 54 edx >>= MWAIT_SUBSTATE_SIZE; 55 for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { 56 if (edx & MWAIT_SUBSTATE_MASK) { 57 highest_cstate = i; 58 highest_subcstate = edx & MWAIT_SUBSTATE_MASK; 59 } 60 } 61 power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | 62 (highest_subcstate - 1); 63 64 #if defined(CONFIG_X86) 65 switch (boot_cpu_data.x86_vendor) { 66 case X86_VENDOR_HYGON: 67 case X86_VENDOR_AMD: 68 case X86_VENDOR_INTEL: 69 case X86_VENDOR_ZHAOXIN: 70 case X86_VENDOR_CENTAUR: 71 /* 72 * AMD Fam10h TSC will tick in all 73 * C/P/S0/S1 states when this bit is set. 74 */ 75 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) 76 tsc_detected_unstable = 1; 77 break; 78 default: 79 /* TSC could halt in idle */ 80 tsc_detected_unstable = 1; 81 } 82 #endif 83 } 84 85 static unsigned long cpu_weight[NR_CPUS]; 86 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1}; 87 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS); 88 static void round_robin_cpu(unsigned int tsk_index) 89 { 90 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits); 91 cpumask_var_t tmp; 92 int cpu; 93 unsigned long min_weight = -1; 94 unsigned long preferred_cpu; 95 96 if (!alloc_cpumask_var(&tmp, GFP_KERNEL)) 97 return; 98 99 mutex_lock(&round_robin_lock); 100 cpumask_clear(tmp); 101 for_each_cpu(cpu, pad_busy_cpus) 102 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu)); 103 cpumask_andnot(tmp, cpu_online_mask, tmp); 104 /* avoid HT siblings if possible */ 105 if (cpumask_empty(tmp)) 106 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus); 107 if (cpumask_empty(tmp)) { 108 mutex_unlock(&round_robin_lock); 109 free_cpumask_var(tmp); 110 return; 111 } 112 for_each_cpu(cpu, tmp) { 113 if (cpu_weight[cpu] < min_weight) { 114 min_weight = cpu_weight[cpu]; 115 preferred_cpu = cpu; 116 } 117 } 118 119 if (tsk_in_cpu[tsk_index] != -1) 120 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 121 tsk_in_cpu[tsk_index] = preferred_cpu; 122 cpumask_set_cpu(preferred_cpu, pad_busy_cpus); 123 cpu_weight[preferred_cpu]++; 124 mutex_unlock(&round_robin_lock); 125 126 set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu)); 127 128 free_cpumask_var(tmp); 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); 134 135 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus); 136 tsk_in_cpu[tsk_index] = -1; 137 } 138 139 static unsigned int idle_pct = 5; /* percentage */ 140 static unsigned int round_robin_time = 1; /* second */ 141 static int power_saving_thread(void *data) 142 { 143 int do_sleep; 144 unsigned int tsk_index = (unsigned long)data; 145 u64 last_jiffies = 0; 146 147 sched_set_fifo_low(current); 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(); 170 171 perf_lopwr_cb(true); 172 173 tick_broadcast_enable(); 174 tick_broadcast_enter(); 175 stop_critical_timings(); 176 177 mwait_idle_with_hints(power_saving_mwait_eax, 1); 178 179 start_critical_timings(); 180 tick_broadcast_exit(); 181 182 perf_lopwr_cb(false); 183 184 local_irq_enable(); 185 186 if (time_before(expire_time, jiffies)) { 187 do_sleep = 1; 188 break; 189 } 190 } 191 192 /* 193 * current sched_rt has threshold for rt task running time. 194 * When a rt task uses 95% CPU time, the rt thread will be 195 * scheduled out for 5% CPU time to not starve other tasks. But 196 * the mechanism only works when all CPUs have RT task running, 197 * as if one CPU hasn't RT task, RT task from other CPUs will 198 * borrow CPU time from this CPU and cause RT task use > 95% 199 * CPU time. To make 'avoid starvation' work, takes a nap here. 200 */ 201 if (unlikely(do_sleep)) 202 schedule_timeout_killable(HZ * idle_pct / 100); 203 204 /* If an external event has set the need_resched flag, then 205 * we need to deal with it, or this loop will continue to 206 * spin without calling __mwait(). 207 */ 208 if (unlikely(need_resched())) 209 schedule(); 210 } 211 212 exit_round_robin(tsk_index); 213 return 0; 214 } 215 216 static struct task_struct *ps_tsks[NR_CPUS]; 217 static unsigned int ps_tsk_num; 218 static int create_power_saving_task(void) 219 { 220 int rc; 221 222 ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread, 223 (void *)(unsigned long)ps_tsk_num, 224 "acpi_pad/%d", ps_tsk_num); 225 226 if (IS_ERR(ps_tsks[ps_tsk_num])) { 227 rc = PTR_ERR(ps_tsks[ps_tsk_num]); 228 ps_tsks[ps_tsk_num] = NULL; 229 } else { 230 rc = 0; 231 ps_tsk_num++; 232 } 233 234 return rc; 235 } 236 237 static void destroy_power_saving_task(void) 238 { 239 if (ps_tsk_num > 0) { 240 ps_tsk_num--; 241 kthread_stop(ps_tsks[ps_tsk_num]); 242 ps_tsks[ps_tsk_num] = NULL; 243 } 244 } 245 246 static void set_power_saving_task_num(unsigned int num) 247 { 248 if (num > ps_tsk_num) { 249 while (ps_tsk_num < num) { 250 if (create_power_saving_task()) 251 return; 252 } 253 } else if (num < ps_tsk_num) { 254 while (ps_tsk_num > num) 255 destroy_power_saving_task(); 256 } 257 } 258 259 static void acpi_pad_idle_cpus(unsigned int num_cpus) 260 { 261 cpus_read_lock(); 262 263 num_cpus = min_t(unsigned int, num_cpus, num_online_cpus()); 264 set_power_saving_task_num(num_cpus); 265 266 cpus_read_unlock(); 267 } 268 269 static uint32_t acpi_pad_idle_cpus_num(void) 270 { 271 return ps_tsk_num; 272 } 273 274 static ssize_t rrtime_store(struct device *dev, 275 struct device_attribute *attr, const char *buf, size_t count) 276 { 277 unsigned long num; 278 279 if (kstrtoul(buf, 0, &num)) 280 return -EINVAL; 281 if (num < 1 || num >= 100) 282 return -EINVAL; 283 mutex_lock(&isolated_cpus_lock); 284 round_robin_time = num; 285 mutex_unlock(&isolated_cpus_lock); 286 return count; 287 } 288 289 static ssize_t rrtime_show(struct device *dev, 290 struct device_attribute *attr, char *buf) 291 { 292 return sysfs_emit(buf, "%d\n", round_robin_time); 293 } 294 static DEVICE_ATTR_RW(rrtime); 295 296 static ssize_t idlepct_store(struct device *dev, 297 struct device_attribute *attr, const char *buf, size_t count) 298 { 299 unsigned long num; 300 301 if (kstrtoul(buf, 0, &num)) 302 return -EINVAL; 303 if (num < 1 || num >= 100) 304 return -EINVAL; 305 mutex_lock(&isolated_cpus_lock); 306 idle_pct = num; 307 mutex_unlock(&isolated_cpus_lock); 308 return count; 309 } 310 311 static ssize_t idlepct_show(struct device *dev, 312 struct device_attribute *attr, char *buf) 313 { 314 return sysfs_emit(buf, "%d\n", idle_pct); 315 } 316 static DEVICE_ATTR_RW(idlepct); 317 318 static ssize_t idlecpus_store(struct device *dev, 319 struct device_attribute *attr, const char *buf, size_t count) 320 { 321 unsigned long num; 322 323 if (kstrtoul(buf, 0, &num)) 324 return -EINVAL; 325 mutex_lock(&isolated_cpus_lock); 326 acpi_pad_idle_cpus(num); 327 mutex_unlock(&isolated_cpus_lock); 328 return count; 329 } 330 331 static ssize_t idlecpus_show(struct device *dev, 332 struct device_attribute *attr, char *buf) 333 { 334 return cpumap_print_to_pagebuf(false, buf, 335 to_cpumask(pad_busy_cpus_bits)); 336 } 337 338 static DEVICE_ATTR_RW(idlecpus); 339 340 static struct attribute *acpi_pad_attrs[] = { 341 &dev_attr_idlecpus.attr, 342 &dev_attr_idlepct.attr, 343 &dev_attr_rrtime.attr, 344 NULL 345 }; 346 347 ATTRIBUTE_GROUPS(acpi_pad); 348 349 /* 350 * Query firmware how many CPUs should be idle 351 * return -1 on failure 352 */ 353 static int acpi_pad_pur(acpi_handle handle) 354 { 355 struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL}; 356 union acpi_object *package; 357 int num = -1; 358 359 if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer))) 360 return num; 361 362 if (!buffer.length || !buffer.pointer) 363 return num; 364 365 package = buffer.pointer; 366 367 if (package->type == ACPI_TYPE_PACKAGE && 368 package->package.count == 2 && 369 package->package.elements[0].integer.value == 1) /* rev 1 */ 370 371 num = package->package.elements[1].integer.value; 372 373 kfree(buffer.pointer); 374 return num; 375 } 376 377 static void acpi_pad_handle_notify(acpi_handle handle) 378 { 379 int num_cpus; 380 uint32_t idle_cpus; 381 struct acpi_buffer param = { 382 .length = 4, 383 .pointer = (void *)&idle_cpus, 384 }; 385 386 mutex_lock(&isolated_cpus_lock); 387 num_cpus = acpi_pad_pur(handle); 388 if (num_cpus < 0) { 389 mutex_unlock(&isolated_cpus_lock); 390 return; 391 } 392 acpi_pad_idle_cpus(num_cpus); 393 idle_cpus = acpi_pad_idle_cpus_num(); 394 acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, ¶m); 395 mutex_unlock(&isolated_cpus_lock); 396 } 397 398 static void acpi_pad_notify(acpi_handle handle, u32 event, 399 void *data) 400 { 401 struct acpi_device *adev = data; 402 403 switch (event) { 404 case ACPI_PROCESSOR_AGGREGATOR_NOTIFY: 405 acpi_pad_handle_notify(handle); 406 acpi_bus_generate_netlink_event(adev->pnp.device_class, 407 dev_name(&adev->dev), event, 0); 408 break; 409 default: 410 pr_warn("Unsupported event [0x%x]\n", event); 411 break; 412 } 413 } 414 415 static int acpi_pad_probe(struct platform_device *pdev) 416 { 417 struct acpi_device *adev = ACPI_COMPANION(&pdev->dev); 418 acpi_status status; 419 420 strcpy(acpi_device_name(adev), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME); 421 strcpy(acpi_device_class(adev), ACPI_PROCESSOR_AGGREGATOR_CLASS); 422 423 status = acpi_install_notify_handler(adev->handle, 424 ACPI_DEVICE_NOTIFY, acpi_pad_notify, adev); 425 426 if (ACPI_FAILURE(status)) 427 return -ENODEV; 428 429 return 0; 430 } 431 432 static void acpi_pad_remove(struct platform_device *pdev) 433 { 434 struct acpi_device *adev = ACPI_COMPANION(&pdev->dev); 435 436 mutex_lock(&isolated_cpus_lock); 437 acpi_pad_idle_cpus(0); 438 mutex_unlock(&isolated_cpus_lock); 439 440 acpi_remove_notify_handler(adev->handle, 441 ACPI_DEVICE_NOTIFY, acpi_pad_notify); 442 } 443 444 static const struct acpi_device_id pad_device_ids[] = { 445 {"ACPI000C", 0}, 446 {"", 0}, 447 }; 448 MODULE_DEVICE_TABLE(acpi, pad_device_ids); 449 450 static struct platform_driver acpi_pad_driver = { 451 .probe = acpi_pad_probe, 452 .remove_new = acpi_pad_remove, 453 .driver = { 454 .dev_groups = acpi_pad_groups, 455 .name = "processor_aggregator", 456 .acpi_match_table = pad_device_ids, 457 }, 458 }; 459 460 static int __init acpi_pad_init(void) 461 { 462 /* Xen ACPI PAD is used when running as Xen Dom0. */ 463 if (xen_initial_domain()) 464 return -ENODEV; 465 466 power_saving_mwait_init(); 467 if (power_saving_mwait_eax == 0) 468 return -EINVAL; 469 470 return platform_driver_register(&acpi_pad_driver); 471 } 472 473 static void __exit acpi_pad_exit(void) 474 { 475 platform_driver_unregister(&acpi_pad_driver); 476 } 477 478 module_init(acpi_pad_init); 479 module_exit(acpi_pad_exit); 480 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>"); 481 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver"); 482 MODULE_LICENSE("GPL"); 483