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 <asm/mwait.h>
  21 #include <xen/xen.h>
  22
  23 #define ACPI_PROCESSOR_AGGREGATOR_CLASS "acpi_pad"
  24 #define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"
  25 #define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
  26 static DEFINE_MUTEX(isolated_cpus_lock);
  27 static DEFINE_MUTEX(round_robin_lock);
  28
  29 static unsigned long power_saving_mwait_eax;
  30
  31 static unsigned char tsc_detected_unstable;
  32 static unsigned char tsc_marked_unstable;
  33
  34 static void power_saving_mwait_init(void)
  35 {
  36         unsigned int eax, ebx, ecx, edx;
  37         unsigned int highest_cstate = 0;
  38         unsigned int highest_subcstate = 0;
  39         int i;
  40
  41         if (!boot_cpu_has(X86_FEATURE_MWAIT))
  42                 return;
  43         if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
  44                 return;
  45
  46         cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
  47
  48         if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
  49             !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
  50                 return;
  51
  52         edx >>= MWAIT_SUBSTATE_SIZE;
  53         for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
  54                 if (edx & MWAIT_SUBSTATE_MASK) {
  55                         highest_cstate = i;
  56                         highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
  57                 }
  58         }
  59         power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
  60                 (highest_subcstate - 1);
  61
  62 #if defined(CONFIG_X86)
  63         switch (boot_cpu_data.x86_vendor) {
  64         case X86_VENDOR_HYGON:
  65         case X86_VENDOR_AMD:
  66         case X86_VENDOR_INTEL:
  67         case X86_VENDOR_ZHAOXIN:
  68                 /*
  69                  * AMD Fam10h TSC will tick in all
  70                  * C/P/S0/S1 states when this bit is set.
  71                  */
  72                 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
  73                         tsc_detected_unstable = 1;
  74                 break;
  75         default:
  76                 /* TSC could halt in idle */
  77                 tsc_detected_unstable = 1;
  78         }
  79 #endif
  80 }
  81
  82 static unsigned long cpu_weight[NR_CPUS];
  83 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
  84 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS);
  85 static void round_robin_cpu(unsigned int tsk_index)
  86 {
  87         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
  88         cpumask_var_t tmp;
  89         int cpu;
  90         unsigned long min_weight = -1;
  91         unsigned long preferred_cpu;
  92
  93         if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
  94                 return;
  95
  96         mutex_lock(&round_robin_lock);
  97         cpumask_clear(tmp);
  98         for_each_cpu(cpu, pad_busy_cpus)
  99                 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu));
 100         cpumask_andnot(tmp, cpu_online_mask, tmp);
 101         /* avoid HT sibilings if possible */
 102         if (cpumask_empty(tmp))
 103                 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);
 104         if (cpumask_empty(tmp)) {
 105                 mutex_unlock(&round_robin_lock);
 106                 free_cpumask_var(tmp);
 107                 return;
 108         }
 109         for_each_cpu(cpu, tmp) {
 110                 if (cpu_weight[cpu] < min_weight) {
 111                         min_weight = cpu_weight[cpu];
 112                         preferred_cpu = cpu;
 113                 }
 114         }
 115
 116         if (tsk_in_cpu[tsk_index] != -1)
 117                 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
 118         tsk_in_cpu[tsk_index] = preferred_cpu;
 119         cpumask_set_cpu(preferred_cpu, pad_busy_cpus);
 120         cpu_weight[preferred_cpu]++;
 121         mutex_unlock(&round_robin_lock);
 122
 123         set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));
 124
 125         free_cpumask_var(tmp);
 126 }
 127
 128 static void exit_round_robin(unsigned int tsk_index)
 129 {
 130         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
 131         cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
 132         tsk_in_cpu[tsk_index] = -1;
 133 }
 134
 135 static unsigned int idle_pct = 5; /* percentage */
 136 static unsigned int round_robin_time = 1; /* second */
 137 static int power_saving_thread(void *data)
 138 {
 139         int do_sleep;
 140         unsigned int tsk_index = (unsigned long)data;
 141         u64 last_jiffies = 0;
 142
 143         sched_set_fifo_low(current);
 144
 145         while (!kthread_should_stop()) {
 146                 unsigned long expire_time;
 147
 148                 /* round robin to cpus */
 149                 expire_time = last_jiffies + round_robin_time * HZ;
 150                 if (time_before(expire_time, jiffies)) {
 151                         last_jiffies = jiffies;
 152                         round_robin_cpu(tsk_index);
 153                 }
 154
 155                 do_sleep = 0;
 156
 157                 expire_time = jiffies + HZ * (100 - idle_pct) / 100;
 158
 159                 while (!need_resched()) {
 160                         if (tsc_detected_unstable && !tsc_marked_unstable) {
 161                                 /* TSC could halt in idle, so notify users */
 162                                 mark_tsc_unstable("TSC halts in idle");
 163                                 tsc_marked_unstable = 1;
 164                         }
 165                         local_irq_disable();
 166                         tick_broadcast_enable();
 167                         tick_broadcast_enter();
 168                         stop_critical_timings();
 169
 170                         mwait_idle_with_hints(power_saving_mwait_eax, 1);
 171
 172                         start_critical_timings();
 173                         tick_broadcast_exit();
 174                         local_irq_enable();
 175
 176                         if (time_before(expire_time, jiffies)) {
 177                                 do_sleep = 1;
 178                                 break;
 179                         }
 180                 }
 181
 182                 /*
 183                  * current sched_rt has threshold for rt task running time.
 184                  * When a rt task uses 95% CPU time, the rt thread will be
 185                  * scheduled out for 5% CPU time to not starve other tasks. But
 186                  * the mechanism only works when all CPUs have RT task running,
 187                  * as if one CPU hasn't RT task, RT task from other CPUs will
 188                  * borrow CPU time from this CPU and cause RT task use > 95%
 189                  * CPU time. To make 'avoid starvation' work, takes a nap here.
 190                  */
 191                 if (unlikely(do_sleep))
 192                         schedule_timeout_killable(HZ * idle_pct / 100);
 193
 194                 /* If an external event has set the need_resched flag, then
 195                  * we need to deal with it, or this loop will continue to
 196                  * spin without calling __mwait().
 197                  */
 198                 if (unlikely(need_resched()))
 199                         schedule();
 200         }
 201
 202         exit_round_robin(tsk_index);
 203         return 0;
 204 }
 205
 206 static struct task_struct *ps_tsks[NR_CPUS];
 207 static unsigned int ps_tsk_num;
 208 static int create_power_saving_task(void)
 209 {
 210         int rc;
 211
 212         ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread,
 213                 (void *)(unsigned long)ps_tsk_num,
 214                 "acpi_pad/%d", ps_tsk_num);
 215
 216         if (IS_ERR(ps_tsks[ps_tsk_num])) {
 217                 rc = PTR_ERR(ps_tsks[ps_tsk_num]);
 218                 ps_tsks[ps_tsk_num] = NULL;
 219         } else {
 220                 rc = 0;
 221                 ps_tsk_num++;
 222         }
 223
 224         return rc;
 225 }
 226
 227 static void destroy_power_saving_task(void)
 228 {
 229         if (ps_tsk_num > 0) {
 230                 ps_tsk_num--;
 231                 kthread_stop(ps_tsks[ps_tsk_num]);
 232                 ps_tsks[ps_tsk_num] = NULL;
 233         }
 234 }
 235
 236 static void set_power_saving_task_num(unsigned int num)
 237 {
 238         if (num > ps_tsk_num) {
 239                 while (ps_tsk_num < num) {
 240                         if (create_power_saving_task())
 241                                 return;
 242                 }
 243         } else if (num < ps_tsk_num) {
 244                 while (ps_tsk_num > num)
 245                         destroy_power_saving_task();
 246         }
 247 }
 248
 249 static void acpi_pad_idle_cpus(unsigned int num_cpus)
 250 {
 251         get_online_cpus();
 252
 253         num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
 254         set_power_saving_task_num(num_cpus);
 255
 256         put_online_cpus();
 257 }
 258
 259 static uint32_t acpi_pad_idle_cpus_num(void)
 260 {
 261         return ps_tsk_num;
 262 }
 263
 264 static ssize_t acpi_pad_rrtime_store(struct device *dev,
 265         struct device_attribute *attr, const char *buf, size_t count)
 266 {
 267         unsigned long num;
 268         if (kstrtoul(buf, 0, &num))
 269                 return -EINVAL;
 270         if (num < 1 || num >= 100)
 271                 return -EINVAL;
 272         mutex_lock(&isolated_cpus_lock);
 273         round_robin_time = num;
 274         mutex_unlock(&isolated_cpus_lock);
 275         return count;
 276 }
 277
 278 static ssize_t acpi_pad_rrtime_show(struct device *dev,
 279         struct device_attribute *attr, char *buf)
 280 {
 281         return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time);
 282 }
 283 static DEVICE_ATTR(rrtime, S_IRUGO|S_IWUSR,
 284         acpi_pad_rrtime_show,
 285         acpi_pad_rrtime_store);
 286
 287 static ssize_t acpi_pad_idlepct_store(struct device *dev,
 288         struct device_attribute *attr, const char *buf, size_t count)
 289 {
 290         unsigned long num;
 291         if (kstrtoul(buf, 0, &num))
 292                 return -EINVAL;
 293         if (num < 1 || num >= 100)
 294                 return -EINVAL;
 295         mutex_lock(&isolated_cpus_lock);
 296         idle_pct = num;
 297         mutex_unlock(&isolated_cpus_lock);
 298         return count;
 299 }
 300
 301 static ssize_t acpi_pad_idlepct_show(struct device *dev,
 302         struct device_attribute *attr, char *buf)
 303 {
 304         return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct);
 305 }
 306 static DEVICE_ATTR(idlepct, S_IRUGO|S_IWUSR,
 307         acpi_pad_idlepct_show,
 308         acpi_pad_idlepct_store);
 309
 310 static ssize_t acpi_pad_idlecpus_store(struct device *dev,
 311         struct device_attribute *attr, const char *buf, size_t count)
 312 {
 313         unsigned long num;
 314         if (kstrtoul(buf, 0, &num))
 315                 return -EINVAL;
 316         mutex_lock(&isolated_cpus_lock);
 317         acpi_pad_idle_cpus(num);
 318         mutex_unlock(&isolated_cpus_lock);
 319         return count;
 320 }
 321
 322 static ssize_t acpi_pad_idlecpus_show(struct device *dev,
 323         struct device_attribute *attr, char *buf)
 324 {
 325         return cpumap_print_to_pagebuf(false, buf,
 326                                        to_cpumask(pad_busy_cpus_bits));
 327 }
 328
 329 static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR,
 330         acpi_pad_idlecpus_show,
 331         acpi_pad_idlecpus_store);
 332
 333 static int acpi_pad_add_sysfs(struct acpi_device *device)
 334 {
 335         int result;
 336
 337         result = device_create_file(&device->dev, &dev_attr_idlecpus);
 338         if (result)
 339                 return -ENODEV;
 340         result = device_create_file(&device->dev, &dev_attr_idlepct);
 341         if (result) {
 342                 device_remove_file(&device->dev, &dev_attr_idlecpus);
 343                 return -ENODEV;
 344         }
 345         result = device_create_file(&device->dev, &dev_attr_rrtime);
 346         if (result) {
 347                 device_remove_file(&device->dev, &dev_attr_idlecpus);
 348                 device_remove_file(&device->dev, &dev_attr_idlepct);
 349                 return -ENODEV;
 350         }
 351         return 0;
 352 }
 353
 354 static void acpi_pad_remove_sysfs(struct acpi_device *device)
 355 {
 356         device_remove_file(&device->dev, &dev_attr_idlecpus);
 357         device_remove_file(&device->dev, &dev_attr_idlepct);
 358         device_remove_file(&device->dev, &dev_attr_rrtime);
 359 }
 360
 361 /*
 362  * Query firmware how many CPUs should be idle
 363  * return -1 on failure
 364  */
 365 static int acpi_pad_pur(acpi_handle handle)
 366 {
 367         struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
 368         union acpi_object *package;
 369         int num = -1;
 370
 371         if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
 372                 return num;
 373
 374         if (!buffer.length || !buffer.pointer)
 375                 return num;
 376
 377         package = buffer.pointer;
 378
 379         if (package->type == ACPI_TYPE_PACKAGE &&
 380                 package->package.count == 2 &&
 381                 package->package.elements[0].integer.value == 1) /* rev 1 */
 382
 383                 num = package->package.elements[1].integer.value;
 384
 385         kfree(buffer.pointer);
 386         return num;
 387 }
 388
 389 static void acpi_pad_handle_notify(acpi_handle handle)
 390 {
 391         int num_cpus;
 392         uint32_t idle_cpus;
 393         struct acpi_buffer param = {
 394                 .length = 4,
 395                 .pointer = (void *)&idle_cpus,
 396         };
 397
 398         mutex_lock(&isolated_cpus_lock);
 399         num_cpus = acpi_pad_pur(handle);
 400         if (num_cpus < 0) {
 401                 mutex_unlock(&isolated_cpus_lock);
 402                 return;
 403         }
 404         acpi_pad_idle_cpus(num_cpus);
 405         idle_cpus = acpi_pad_idle_cpus_num();
 406         acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, &param);
 407         mutex_unlock(&isolated_cpus_lock);
 408 }
 409
 410 static void acpi_pad_notify(acpi_handle handle, u32 event,
 411         void *data)
 412 {
 413         struct acpi_device *device = data;
 414
 415         switch (event) {
 416         case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
 417                 acpi_pad_handle_notify(handle);
 418                 acpi_bus_generate_netlink_event(device->pnp.device_class,
 419                         dev_name(&device->dev), event, 0);
 420                 break;
 421         default:
 422                 pr_warn("Unsupported event [0x%x]\n", event);
 423                 break;
 424         }
 425 }
 426
 427 static int acpi_pad_add(struct acpi_device *device)
 428 {
 429         acpi_status status;
 430
 431         strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
 432         strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
 433
 434         if (acpi_pad_add_sysfs(device))
 435                 return -ENODEV;
 436
 437         status = acpi_install_notify_handler(device->handle,
 438                 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
 439         if (ACPI_FAILURE(status)) {
 440                 acpi_pad_remove_sysfs(device);
 441                 return -ENODEV;
 442         }
 443
 444         return 0;
 445 }
 446
 447 static int acpi_pad_remove(struct acpi_device *device)
 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(device->handle,
 454                 ACPI_DEVICE_NOTIFY, acpi_pad_notify);
 455         acpi_pad_remove_sysfs(device);
 456         return 0;
 457 }
 458
 459 static const struct acpi_device_id pad_device_ids[] = {
 460         {"ACPI000C", 0},
 461         {"", 0},
 462 };
 463 MODULE_DEVICE_TABLE(acpi, pad_device_ids);
 464
 465 static struct acpi_driver acpi_pad_driver = {
 466         .name = "processor_aggregator",
 467         .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
 468         .ids = pad_device_ids,
 469         .ops = {
 470                 .add = acpi_pad_add,
 471                 .remove = acpi_pad_remove,
 472         },
 473 };
 474
 475 static int __init acpi_pad_init(void)
 476 {
 477         /* Xen ACPI PAD is used when running as Xen Dom0. */
 478         if (xen_initial_domain())
 479                 return -ENODEV;
 480
 481         power_saving_mwait_init();
 482         if (power_saving_mwait_eax == 0)
 483                 return -EINVAL;
 484
 485         return acpi_bus_register_driver(&acpi_pad_driver);
 486 }
 487
 488 static void __exit acpi_pad_exit(void)
 489 {
 490         acpi_bus_unregister_driver(&acpi_pad_driver);
 491 }
 492
 493 module_init(acpi_pad_init);
 494 module_exit(acpi_pad_exit);
 495 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>");
 496 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver");
 497 MODULE_LICENSE("GPL");