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