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                 /*
  70                  * AMD Fam10h TSC will tick in all
  71                  * C/P/S0/S1 states when this bit is set.
  72                  */
  73                 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
  74                         tsc_detected_unstable = 1;
  75                 break;
  76         default:
  77                 /* TSC could halt in idle */
  78                 tsc_detected_unstable = 1;
  79         }
  80 #endif
  81 }
  82
  83 static unsigned long cpu_weight[NR_CPUS];
  84 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
  85 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS);
  86 static void round_robin_cpu(unsigned int tsk_index)
  87 {
  88         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
  89         cpumask_var_t tmp;
  90         int cpu;
  91         unsigned long min_weight = -1;
  92         unsigned long preferred_cpu;
  93
  94         if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
  95                 return;
  96
  97         mutex_lock(&round_robin_lock);
  98         cpumask_clear(tmp);
  99         for_each_cpu(cpu, pad_busy_cpus)
 100                 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu));
 101         cpumask_andnot(tmp, cpu_online_mask, tmp);
 102         /* avoid HT sibilings if possible */
 103         if (cpumask_empty(tmp))
 104                 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);
 105         if (cpumask_empty(tmp)) {
 106                 mutex_unlock(&round_robin_lock);
 107                 free_cpumask_var(tmp);
 108                 return;
 109         }
 110         for_each_cpu(cpu, tmp) {
 111                 if (cpu_weight[cpu] < min_weight) {
 112                         min_weight = cpu_weight[cpu];
 113                         preferred_cpu = cpu;
 114                 }
 115         }
 116
 117         if (tsk_in_cpu[tsk_index] != -1)
 118                 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
 119         tsk_in_cpu[tsk_index] = preferred_cpu;
 120         cpumask_set_cpu(preferred_cpu, pad_busy_cpus);
 121         cpu_weight[preferred_cpu]++;
 122         mutex_unlock(&round_robin_lock);
 123
 124         set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));
 125
 126         free_cpumask_var(tmp);
 127 }
 128
 129 static void exit_round_robin(unsigned int tsk_index)
 130 {
 131         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
 132
 133         cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
 134         tsk_in_cpu[tsk_index] = -1;
 135 }
 136
 137 static unsigned int idle_pct = 5; /* percentage */
 138 static unsigned int round_robin_time = 1; /* second */
 139 static int power_saving_thread(void *data)
 140 {
 141         int do_sleep;
 142         unsigned int tsk_index = (unsigned long)data;
 143         u64 last_jiffies = 0;
 144
 145         sched_set_fifo_low(current);
 146
 147         while (!kthread_should_stop()) {
 148                 unsigned long expire_time;
 149
 150                 /* round robin to cpus */
 151                 expire_time = last_jiffies + round_robin_time * HZ;
 152                 if (time_before(expire_time, jiffies)) {
 153                         last_jiffies = jiffies;
 154                         round_robin_cpu(tsk_index);
 155                 }
 156
 157                 do_sleep = 0;
 158
 159                 expire_time = jiffies + HZ * (100 - idle_pct) / 100;
 160
 161                 while (!need_resched()) {
 162                         if (tsc_detected_unstable && !tsc_marked_unstable) {
 163                                 /* TSC could halt in idle, so notify users */
 164                                 mark_tsc_unstable("TSC halts in idle");
 165                                 tsc_marked_unstable = 1;
 166                         }
 167                         local_irq_disable();
 168
 169                         perf_lopwr_cb(true);
 170
 171                         tick_broadcast_enable();
 172                         tick_broadcast_enter();
 173                         stop_critical_timings();
 174
 175                         mwait_idle_with_hints(power_saving_mwait_eax, 1);
 176
 177                         start_critical_timings();
 178                         tick_broadcast_exit();
 179
 180                         perf_lopwr_cb(false);
 181
 182                         local_irq_enable();
 183
 184                         if (time_before(expire_time, jiffies)) {
 185                                 do_sleep = 1;
 186                                 break;
 187                         }
 188                 }
 189
 190                 /*
 191                  * current sched_rt has threshold for rt task running time.
 192                  * When a rt task uses 95% CPU time, the rt thread will be
 193                  * scheduled out for 5% CPU time to not starve other tasks. But
 194                  * the mechanism only works when all CPUs have RT task running,
 195                  * as if one CPU hasn't RT task, RT task from other CPUs will
 196                  * borrow CPU time from this CPU and cause RT task use > 95%
 197                  * CPU time. To make 'avoid starvation' work, takes a nap here.
 198                  */
 199                 if (unlikely(do_sleep))
 200                         schedule_timeout_killable(HZ * idle_pct / 100);
 201
 202                 /* If an external event has set the need_resched flag, then
 203                  * we need to deal with it, or this loop will continue to
 204                  * spin without calling __mwait().
 205                  */
 206                 if (unlikely(need_resched()))
 207                         schedule();
 208         }
 209
 210         exit_round_robin(tsk_index);
 211         return 0;
 212 }
 213
 214 static struct task_struct *ps_tsks[NR_CPUS];
 215 static unsigned int ps_tsk_num;
 216 static int create_power_saving_task(void)
 217 {
 218         int rc;
 219
 220         ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread,
 221                 (void *)(unsigned long)ps_tsk_num,
 222                 "acpi_pad/%d", ps_tsk_num);
 223
 224         if (IS_ERR(ps_tsks[ps_tsk_num])) {
 225                 rc = PTR_ERR(ps_tsks[ps_tsk_num]);
 226                 ps_tsks[ps_tsk_num] = NULL;
 227         } else {
 228                 rc = 0;
 229                 ps_tsk_num++;
 230         }
 231
 232         return rc;
 233 }
 234
 235 static void destroy_power_saving_task(void)
 236 {
 237         if (ps_tsk_num > 0) {
 238                 ps_tsk_num--;
 239                 kthread_stop(ps_tsks[ps_tsk_num]);
 240                 ps_tsks[ps_tsk_num] = NULL;
 241         }
 242 }
 243
 244 static void set_power_saving_task_num(unsigned int num)
 245 {
 246         if (num > ps_tsk_num) {
 247                 while (ps_tsk_num < num) {
 248                         if (create_power_saving_task())
 249                                 return;
 250                 }
 251         } else if (num < ps_tsk_num) {
 252                 while (ps_tsk_num > num)
 253                         destroy_power_saving_task();
 254         }
 255 }
 256
 257 static void acpi_pad_idle_cpus(unsigned int num_cpus)
 258 {
 259         cpus_read_lock();
 260
 261         num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
 262         set_power_saving_task_num(num_cpus);
 263
 264         cpus_read_unlock();
 265 }
 266
 267 static uint32_t acpi_pad_idle_cpus_num(void)
 268 {
 269         return ps_tsk_num;
 270 }
 271
 272 static ssize_t rrtime_store(struct device *dev,
 273         struct device_attribute *attr, const char *buf, size_t count)
 274 {
 275         unsigned long num;
 276
 277         if (kstrtoul(buf, 0, &num))
 278                 return -EINVAL;
 279         if (num < 1 || num >= 100)
 280                 return -EINVAL;
 281         mutex_lock(&isolated_cpus_lock);
 282         round_robin_time = num;
 283         mutex_unlock(&isolated_cpus_lock);
 284         return count;
 285 }
 286
 287 static ssize_t rrtime_show(struct device *dev,
 288         struct device_attribute *attr, char *buf)
 289 {
 290         return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time);
 291 }
 292 static DEVICE_ATTR_RW(rrtime);
 293
 294 static ssize_t idlepct_store(struct device *dev,
 295         struct device_attribute *attr, const char *buf, size_t count)
 296 {
 297         unsigned long num;
 298
 299         if (kstrtoul(buf, 0, &num))
 300                 return -EINVAL;
 301         if (num < 1 || num >= 100)
 302                 return -EINVAL;
 303         mutex_lock(&isolated_cpus_lock);
 304         idle_pct = num;
 305         mutex_unlock(&isolated_cpus_lock);
 306         return count;
 307 }
 308
 309 static ssize_t idlepct_show(struct device *dev,
 310         struct device_attribute *attr, char *buf)
 311 {
 312         return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct);
 313 }
 314 static DEVICE_ATTR_RW(idlepct);
 315
 316 static ssize_t idlecpus_store(struct device *dev,
 317         struct device_attribute *attr, const char *buf, size_t count)
 318 {
 319         unsigned long num;
 320
 321         if (kstrtoul(buf, 0, &num))
 322                 return -EINVAL;
 323         mutex_lock(&isolated_cpus_lock);
 324         acpi_pad_idle_cpus(num);
 325         mutex_unlock(&isolated_cpus_lock);
 326         return count;
 327 }
 328
 329 static ssize_t idlecpus_show(struct device *dev,
 330         struct device_attribute *attr, char *buf)
 331 {
 332         return cpumap_print_to_pagebuf(false, buf,
 333                                        to_cpumask(pad_busy_cpus_bits));
 334 }
 335
 336 static DEVICE_ATTR_RW(idlecpus);
 337
 338 static int acpi_pad_add_sysfs(struct acpi_device *device)
 339 {
 340         int result;
 341
 342         result = device_create_file(&device->dev, &dev_attr_idlecpus);
 343         if (result)
 344                 return -ENODEV;
 345         result = device_create_file(&device->dev, &dev_attr_idlepct);
 346         if (result) {
 347                 device_remove_file(&device->dev, &dev_attr_idlecpus);
 348                 return -ENODEV;
 349         }
 350         result = device_create_file(&device->dev, &dev_attr_rrtime);
 351         if (result) {
 352                 device_remove_file(&device->dev, &dev_attr_idlecpus);
 353                 device_remove_file(&device->dev, &dev_attr_idlepct);
 354                 return -ENODEV;
 355         }
 356         return 0;
 357 }
 358
 359 static void acpi_pad_remove_sysfs(struct acpi_device *device)
 360 {
 361         device_remove_file(&device->dev, &dev_attr_idlecpus);
 362         device_remove_file(&device->dev, &dev_attr_idlepct);
 363         device_remove_file(&device->dev, &dev_attr_rrtime);
 364 }
 365
 366 /*
 367  * Query firmware how many CPUs should be idle
 368  * return -1 on failure
 369  */
 370 static int acpi_pad_pur(acpi_handle handle)
 371 {
 372         struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
 373         union acpi_object *package;
 374         int num = -1;
 375
 376         if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
 377                 return num;
 378
 379         if (!buffer.length || !buffer.pointer)
 380                 return num;
 381
 382         package = buffer.pointer;
 383
 384         if (package->type == ACPI_TYPE_PACKAGE &&
 385                 package->package.count == 2 &&
 386                 package->package.elements[0].integer.value == 1) /* rev 1 */
 387
 388                 num = package->package.elements[1].integer.value;
 389
 390         kfree(buffer.pointer);
 391         return num;
 392 }
 393
 394 static void acpi_pad_handle_notify(acpi_handle handle)
 395 {
 396         int num_cpus;
 397         uint32_t idle_cpus;
 398         struct acpi_buffer param = {
 399                 .length = 4,
 400                 .pointer = (void *)&idle_cpus,
 401         };
 402
 403         mutex_lock(&isolated_cpus_lock);
 404         num_cpus = acpi_pad_pur(handle);
 405         if (num_cpus < 0) {
 406                 mutex_unlock(&isolated_cpus_lock);
 407                 return;
 408         }
 409         acpi_pad_idle_cpus(num_cpus);
 410         idle_cpus = acpi_pad_idle_cpus_num();
 411         acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, &param);
 412         mutex_unlock(&isolated_cpus_lock);
 413 }
 414
 415 static void acpi_pad_notify(acpi_handle handle, u32 event,
 416         void *data)
 417 {
 418         struct acpi_device *device = data;
 419
 420         switch (event) {
 421         case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
 422                 acpi_pad_handle_notify(handle);
 423                 acpi_bus_generate_netlink_event(device->pnp.device_class,
 424                         dev_name(&device->dev), event, 0);
 425                 break;
 426         default:
 427                 pr_warn("Unsupported event [0x%x]\n", event);
 428                 break;
 429         }
 430 }
 431
 432 static int acpi_pad_add(struct acpi_device *device)
 433 {
 434         acpi_status status;
 435
 436         strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
 437         strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
 438
 439         if (acpi_pad_add_sysfs(device))
 440                 return -ENODEV;
 441
 442         status = acpi_install_notify_handler(device->handle,
 443                 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
 444         if (ACPI_FAILURE(status)) {
 445                 acpi_pad_remove_sysfs(device);
 446                 return -ENODEV;
 447         }
 448
 449         return 0;
 450 }
 451
 452 static int acpi_pad_remove(struct acpi_device *device)
 453 {
 454         mutex_lock(&isolated_cpus_lock);
 455         acpi_pad_idle_cpus(0);
 456         mutex_unlock(&isolated_cpus_lock);
 457
 458         acpi_remove_notify_handler(device->handle,
 459                 ACPI_DEVICE_NOTIFY, acpi_pad_notify);
 460         acpi_pad_remove_sysfs(device);
 461         return 0;
 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");