drivers/acpi/acpi_pad.c

   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 <asm/mwait.h>
  22 #include <xen/xen.h>
  23
  24 #define ACPI_PROCESSOR_AGGREGATOR_CLASS "acpi_pad"
  25 #define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"
  26 #define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
  27 static DEFINE_MUTEX(isolated_cpus_lock);
  28 static DEFINE_MUTEX(round_robin_lock);
  29
  30 static unsigned long power_saving_mwait_eax;
  31
  32 static unsigned char tsc_detected_unstable;
  33 static unsigned char tsc_marked_unstable;
  34
  35 static void power_saving_mwait_init(void)
  36 {
  37         unsigned int eax, ebx, ecx, edx;
  38         unsigned int highest_cstate = 0;
  39         unsigned int highest_subcstate = 0;
  40         int i;
  41
  42         if (!boot_cpu_has(X86_FEATURE_MWAIT))
  43                 return;
  44         if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
  45                 return;
  46
  47         cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
  48
  49         if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
  50             !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
  51                 return;
  52
  53         edx >>= MWAIT_SUBSTATE_SIZE;
  54         for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
  55                 if (edx & MWAIT_SUBSTATE_MASK) {
  56                         highest_cstate = i;
  57                         highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
  58                 }
  59         }
  60         power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
  61                 (highest_subcstate - 1);
  62
  63 #if defined(CONFIG_X86)
  64         switch (boot_cpu_data.x86_vendor) {
  65         case X86_VENDOR_HYGON:
  66         case X86_VENDOR_AMD:
  67         case X86_VENDOR_INTEL:
  68         case X86_VENDOR_ZHAOXIN:
  69         case X86_VENDOR_CENTAUR:
  70                 /*
  71                  * AMD Fam10h TSC will tick in all
  72                  * C/P/S0/S1 states when this bit is set.
  73                  */
  74                 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
  75                         tsc_detected_unstable = 1;
  76                 break;
  77         default:
  78                 /* TSC could halt in idle */
  79                 tsc_detected_unstable = 1;
  80         }
  81 #endif
  82 }
  83
  84 static unsigned long cpu_weight[NR_CPUS];
  85 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
  86 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS);
  87 static void round_robin_cpu(unsigned int tsk_index)
  88 {
  89         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
  90         cpumask_var_t tmp;
  91         int cpu;
  92         unsigned long min_weight = -1;
  93         unsigned long preferred_cpu;
  94
  95         if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
  96                 return;
  97
  98         mutex_lock(&round_robin_lock);
  99         cpumask_clear(tmp);
 100         for_each_cpu(cpu, pad_busy_cpus)
 101                 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu));
 102         cpumask_andnot(tmp, cpu_online_mask, tmp);
 103         /* avoid HT sibilings if possible */
 104         if (cpumask_empty(tmp))
 105                 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);
 106         if (cpumask_empty(tmp)) {
 107                 mutex_unlock(&round_robin_lock);
 108                 free_cpumask_var(tmp);
 109                 return;
 110         }
 111         for_each_cpu(cpu, tmp) {
 112                 if (cpu_weight[cpu] < min_weight) {
 113                         min_weight = cpu_weight[cpu];
 114                         preferred_cpu = cpu;
 115                 }
 116         }
 117
 118         if (tsk_in_cpu[tsk_index] != -1)
 119                 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
 120         tsk_in_cpu[tsk_index] = preferred_cpu;
 121         cpumask_set_cpu(preferred_cpu, pad_busy_cpus);
 122         cpu_weight[preferred_cpu]++;
 123         mutex_unlock(&round_robin_lock);
 124
 125         set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));
 126
 127         free_cpumask_var(tmp);
 128 }
 129
 130 static void exit_round_robin(unsigned int tsk_index)
 131 {
 132         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
 133
 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         int do_sleep;
 143         unsigned int tsk_index = (unsigned long)data;
 144         u64 last_jiffies = 0;
 145
 146         sched_set_fifo_low(current);
 147
 148         while (!kthread_should_stop()) {
 149                 unsigned long expire_time;
 150
 151                 /* round robin to cpus */
 152                 expire_time = last_jiffies + round_robin_time * HZ;
 153                 if (time_before(expire_time, jiffies)) {
 154                         last_jiffies = jiffies;
 155                         round_robin_cpu(tsk_index);
 156                 }
 157
 158                 do_sleep = 0;
 159
 160                 expire_time = jiffies + HZ * (100 - idle_pct) / 100;
 161
 162                 while (!need_resched()) {
 163                         if (tsc_detected_unstable && !tsc_marked_unstable) {
 164                                 /* TSC could halt in idle, so notify users */
 165                                 mark_tsc_unstable("TSC halts in idle");
 166                                 tsc_marked_unstable = 1;
 167                         }
 168                         local_irq_disable();
 169
 170                         perf_lopwr_cb(true);
 171
 172                         tick_broadcast_enable();
 173                         tick_broadcast_enter();
 174                         stop_critical_timings();
 175
 176                         mwait_idle_with_hints(power_saving_mwait_eax, 1);
 177
 178                         start_critical_timings();
 179                         tick_broadcast_exit();
 180
 181                         perf_lopwr_cb(false);
 182
 183                         local_irq_enable();
 184
 185                         if (time_before(expire_time, jiffies)) {
 186                                 do_sleep = 1;
 187                                 break;
 188                         }
 189                 }
 190
 191                 /*
 192                  * current sched_rt has threshold for rt task running time.
 193                  * When a rt task uses 95% CPU time, the rt thread will be
 194                  * scheduled out for 5% CPU time to not starve other tasks. But
 195                  * the mechanism only works when all CPUs have RT task running,
 196                  * as if one CPU hasn't RT task, RT task from other CPUs will
 197                  * borrow CPU time from this CPU and cause RT task use > 95%
 198                  * CPU time. To make 'avoid starvation' work, takes a nap here.
 199                  */
 200                 if (unlikely(do_sleep))
 201                         schedule_timeout_killable(HZ * idle_pct / 100);
 202
 203                 /* If an external event has set the need_resched flag, then
 204                  * we need to deal with it, or this loop will continue to
 205                  * spin without calling __mwait().
 206                  */
 207                 if (unlikely(need_resched()))
 208                         schedule();
 209         }
 210
 211         exit_round_robin(tsk_index);
 212         return 0;
 213 }
 214
 215 static struct task_struct *ps_tsks[NR_CPUS];
 216 static unsigned int ps_tsk_num;
 217 static int create_power_saving_task(void)
 218 {
 219         int rc;
 220
 221         ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread,
 222                 (void *)(unsigned long)ps_tsk_num,
 223                 "acpi_pad/%d", ps_tsk_num);
 224
 225         if (IS_ERR(ps_tsks[ps_tsk_num])) {
 226                 rc = PTR_ERR(ps_tsks[ps_tsk_num]);
 227                 ps_tsks[ps_tsk_num] = NULL;
 228         } else {
 229                 rc = 0;
 230                 ps_tsk_num++;
 231         }
 232
 233         return rc;
 234 }
 235
 236 static void destroy_power_saving_task(void)
 237 {
 238         if (ps_tsk_num > 0) {
 239                 ps_tsk_num--;
 240                 kthread_stop(ps_tsks[ps_tsk_num]);
 241                 ps_tsks[ps_tsk_num] = NULL;
 242         }
 243 }
 244
 245 static void set_power_saving_task_num(unsigned int num)
 246 {
 247         if (num > ps_tsk_num) {
 248                 while (ps_tsk_num < num) {
 249                         if (create_power_saving_task())
 250                                 return;
 251                 }
 252         } else if (num < ps_tsk_num) {
 253                 while (ps_tsk_num > num)
 254                         destroy_power_saving_task();
 255         }
 256 }
 257
 258 static void acpi_pad_idle_cpus(unsigned int num_cpus)
 259 {
 260         cpus_read_lock();
 261
 262         num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
 263         set_power_saving_task_num(num_cpus);
 264
 265         cpus_read_unlock();
 266 }
 267
 268 static uint32_t acpi_pad_idle_cpus_num(void)
 269 {
 270         return ps_tsk_num;
 271 }
 272
 273 static ssize_t rrtime_store(struct device *dev,
 274         struct device_attribute *attr, const char *buf, size_t count)
 275 {
 276         unsigned long num;
 277
 278         if (kstrtoul(buf, 0, &num))
 279                 return -EINVAL;
 280         if (num < 1 || num >= 100)
 281                 return -EINVAL;
 282         mutex_lock(&isolated_cpus_lock);
 283         round_robin_time = num;
 284         mutex_unlock(&isolated_cpus_lock);
 285         return count;
 286 }
 287
 288 static ssize_t rrtime_show(struct device *dev,
 289         struct device_attribute *attr, char *buf)
 290 {
 291         return sysfs_emit(buf, "%d\n", round_robin_time);
 292 }
 293 static DEVICE_ATTR_RW(rrtime);
 294
 295 static ssize_t idlepct_store(struct device *dev,
 296         struct device_attribute *attr, const char *buf, size_t count)
 297 {
 298         unsigned long num;
 299
 300         if (kstrtoul(buf, 0, &num))
 301                 return -EINVAL;
 302         if (num < 1 || num >= 100)
 303                 return -EINVAL;
 304         mutex_lock(&isolated_cpus_lock);
 305         idle_pct = num;
 306         mutex_unlock(&isolated_cpus_lock);
 307         return count;
 308 }
 309
 310 static ssize_t idlepct_show(struct device *dev,
 311         struct device_attribute *attr, char *buf)
 312 {
 313         return sysfs_emit(buf, "%d\n", idle_pct);
 314 }
 315 static DEVICE_ATTR_RW(idlepct);
 316
 317 static ssize_t idlecpus_store(struct device *dev,
 318         struct device_attribute *attr, const char *buf, size_t count)
 319 {
 320         unsigned long num;
 321
 322         if (kstrtoul(buf, 0, &num))
 323                 return -EINVAL;
 324         mutex_lock(&isolated_cpus_lock);
 325         acpi_pad_idle_cpus(num);
 326         mutex_unlock(&isolated_cpus_lock);
 327         return count;
 328 }
 329
 330 static ssize_t idlecpus_show(struct device *dev,
 331         struct device_attribute *attr, char *buf)
 332 {
 333         return cpumap_print_to_pagebuf(false, buf,
 334                                        to_cpumask(pad_busy_cpus_bits));
 335 }
 336
 337 static DEVICE_ATTR_RW(idlecpus);
 338
 339 static int acpi_pad_add_sysfs(struct acpi_device *device)
 340 {
 341         int result;
 342
 343         result = device_create_file(&device->dev, &dev_attr_idlecpus);
 344         if (result)
 345                 return -ENODEV;
 346         result = device_create_file(&device->dev, &dev_attr_idlepct);
 347         if (result) {
 348                 device_remove_file(&device->dev, &dev_attr_idlecpus);
 349                 return -ENODEV;
 350         }
 351         result = device_create_file(&device->dev, &dev_attr_rrtime);
 352         if (result) {
 353                 device_remove_file(&device->dev, &dev_attr_idlecpus);
 354                 device_remove_file(&device->dev, &dev_attr_idlepct);
 355                 return -ENODEV;
 356         }
 357         return 0;
 358 }
 359
 360 static void acpi_pad_remove_sysfs(struct acpi_device *device)
 361 {
 362         device_remove_file(&device->dev, &dev_attr_idlecpus);
 363         device_remove_file(&device->dev, &dev_attr_idlepct);
 364         device_remove_file(&device->dev, &dev_attr_rrtime);
 365 }
 366
 367 /*
 368  * Query firmware how many CPUs should be idle
 369  * return -1 on failure
 370  */
 371 static int acpi_pad_pur(acpi_handle handle)
 372 {
 373         struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
 374         union acpi_object *package;
 375         int num = -1;
 376
 377         if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
 378                 return num;
 379
 380         if (!buffer.length || !buffer.pointer)
 381                 return num;
 382
 383         package = buffer.pointer;
 384
 385         if (package->type == ACPI_TYPE_PACKAGE &&
 386                 package->package.count == 2 &&
 387                 package->package.elements[0].integer.value == 1) /* rev 1 */
 388
 389                 num = package->package.elements[1].integer.value;
 390
 391         kfree(buffer.pointer);
 392         return num;
 393 }
 394
 395 static void acpi_pad_handle_notify(acpi_handle handle)
 396 {
 397         int num_cpus;
 398         uint32_t idle_cpus;
 399         struct acpi_buffer param = {
 400                 .length = 4,
 401                 .pointer = (void *)&idle_cpus,
 402         };
 403
 404         mutex_lock(&isolated_cpus_lock);
 405         num_cpus = acpi_pad_pur(handle);
 406         if (num_cpus < 0) {
 407                 mutex_unlock(&isolated_cpus_lock);
 408                 return;
 409         }
 410         acpi_pad_idle_cpus(num_cpus);
 411         idle_cpus = acpi_pad_idle_cpus_num();
 412         acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, &param);
 413         mutex_unlock(&isolated_cpus_lock);
 414 }
 415
 416 static void acpi_pad_notify(acpi_handle handle, u32 event,
 417         void *data)
 418 {
 419         struct acpi_device *device = data;
 420
 421         switch (event) {
 422         case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
 423                 acpi_pad_handle_notify(handle);
 424                 acpi_bus_generate_netlink_event(device->pnp.device_class,
 425                         dev_name(&device->dev), event, 0);
 426                 break;
 427         default:
 428                 pr_warn("Unsupported event [0x%x]\n", event);
 429                 break;
 430         }
 431 }
 432
 433 static int acpi_pad_add(struct acpi_device *device)
 434 {
 435         acpi_status status;
 436
 437         strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
 438         strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
 439
 440         if (acpi_pad_add_sysfs(device))
 441                 return -ENODEV;
 442
 443         status = acpi_install_notify_handler(device->handle,
 444                 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
 445         if (ACPI_FAILURE(status)) {
 446                 acpi_pad_remove_sysfs(device);
 447                 return -ENODEV;
 448         }
 449
 450         return 0;
 451 }
 452
 453 static void acpi_pad_remove(struct acpi_device *device)
 454 {
 455         mutex_lock(&isolated_cpus_lock);
 456         acpi_pad_idle_cpus(0);
 457         mutex_unlock(&isolated_cpus_lock);
 458
 459         acpi_remove_notify_handler(device->handle,
 460                 ACPI_DEVICE_NOTIFY, acpi_pad_notify);
 461         acpi_pad_remove_sysfs(device);
 462 }
 463
 464 static const struct acpi_device_id pad_device_ids[] = {
 465         {"ACPI000C", 0},
 466         {"", 0},
 467 };
 468 MODULE_DEVICE_TABLE(acpi, pad_device_ids);
 469
 470 static struct acpi_driver acpi_pad_driver = {
 471         .name = "processor_aggregator",
 472         .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
 473         .ids = pad_device_ids,
 474         .ops = {
 475                 .add = acpi_pad_add,
 476                 .remove = acpi_pad_remove,
 477         },
 478 };
 479
 480 static int __init acpi_pad_init(void)
 481 {
 482         /* Xen ACPI PAD is used when running as Xen Dom0. */
 483         if (xen_initial_domain())
 484                 return -ENODEV;
 485
 486         power_saving_mwait_init();
 487         if (power_saving_mwait_eax == 0)
 488                 return -EINVAL;
 489
 490         return acpi_bus_register_driver(&acpi_pad_driver);
 491 }
 492
 493 static void __exit acpi_pad_exit(void)
 494 {
 495         acpi_bus_unregister_driver(&acpi_pad_driver);
 496 }
 497
 498 module_init(acpi_pad_init);
 499 module_exit(acpi_pad_exit);
 500 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>");
 501 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver");
 502 MODULE_LICENSE("GPL");