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 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, &param);
 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");