linux/drivers/acpi/acpi_pad.c
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   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
  26static DEFINE_MUTEX(isolated_cpus_lock);
  27static DEFINE_MUTEX(round_robin_lock);
  28
  29static unsigned long power_saving_mwait_eax;
  30
  31static unsigned char tsc_detected_unstable;
  32static unsigned char tsc_marked_unstable;
  33
  34static 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
  82static unsigned long cpu_weight[NR_CPUS];
  83static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
  84static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS);
  85static 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
 128static void exit_round_robin(unsigned int tsk_index)
 129{
 130        struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
 131
 132        cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
 133        tsk_in_cpu[tsk_index] = -1;
 134}
 135
 136static unsigned int idle_pct = 5; /* percentage */
 137static unsigned int round_robin_time = 1; /* second */
 138static int power_saving_thread(void *data)
 139{
 140        int do_sleep;
 141        unsigned int tsk_index = (unsigned long)data;
 142        u64 last_jiffies = 0;
 143
 144        sched_set_fifo_low(current);
 145
 146        while (!kthread_should_stop()) {
 147                unsigned long expire_time;
 148
 149                /* round robin to cpus */
 150                expire_time = last_jiffies + round_robin_time * HZ;
 151                if (time_before(expire_time, jiffies)) {
 152                        last_jiffies = jiffies;
 153                        round_robin_cpu(tsk_index);
 154                }
 155
 156                do_sleep = 0;
 157
 158                expire_time = jiffies + HZ * (100 - idle_pct) / 100;
 159
 160                while (!need_resched()) {
 161                        if (tsc_detected_unstable && !tsc_marked_unstable) {
 162                                /* TSC could halt in idle, so notify users */
 163                                mark_tsc_unstable("TSC halts in idle");
 164                                tsc_marked_unstable = 1;
 165                        }
 166                        local_irq_disable();
 167                        tick_broadcast_enable();
 168                        tick_broadcast_enter();
 169                        stop_critical_timings();
 170
 171                        mwait_idle_with_hints(power_saving_mwait_eax, 1);
 172
 173                        start_critical_timings();
 174                        tick_broadcast_exit();
 175                        local_irq_enable();
 176
 177                        if (time_before(expire_time, jiffies)) {
 178                                do_sleep = 1;
 179                                break;
 180                        }
 181                }
 182
 183                /*
 184                 * current sched_rt has threshold for rt task running time.
 185                 * When a rt task uses 95% CPU time, the rt thread will be
 186                 * scheduled out for 5% CPU time to not starve other tasks. But
 187                 * the mechanism only works when all CPUs have RT task running,
 188                 * as if one CPU hasn't RT task, RT task from other CPUs will
 189                 * borrow CPU time from this CPU and cause RT task use > 95%
 190                 * CPU time. To make 'avoid starvation' work, takes a nap here.
 191                 */
 192                if (unlikely(do_sleep))
 193                        schedule_timeout_killable(HZ * idle_pct / 100);
 194
 195                /* If an external event has set the need_resched flag, then
 196                 * we need to deal with it, or this loop will continue to
 197                 * spin without calling __mwait().
 198                 */
 199                if (unlikely(need_resched()))
 200                        schedule();
 201        }
 202
 203        exit_round_robin(tsk_index);
 204        return 0;
 205}
 206
 207static struct task_struct *ps_tsks[NR_CPUS];
 208static unsigned int ps_tsk_num;
 209static int create_power_saving_task(void)
 210{
 211        int rc;
 212
 213        ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread,
 214                (void *)(unsigned long)ps_tsk_num,
 215                "acpi_pad/%d", ps_tsk_num);
 216
 217        if (IS_ERR(ps_tsks[ps_tsk_num])) {
 218                rc = PTR_ERR(ps_tsks[ps_tsk_num]);
 219                ps_tsks[ps_tsk_num] = NULL;
 220        } else {
 221                rc = 0;
 222                ps_tsk_num++;
 223        }
 224
 225        return rc;
 226}
 227
 228static void destroy_power_saving_task(void)
 229{
 230        if (ps_tsk_num > 0) {
 231                ps_tsk_num--;
 232                kthread_stop(ps_tsks[ps_tsk_num]);
 233                ps_tsks[ps_tsk_num] = NULL;
 234        }
 235}
 236
 237static void set_power_saving_task_num(unsigned int num)
 238{
 239        if (num > ps_tsk_num) {
 240                while (ps_tsk_num < num) {
 241                        if (create_power_saving_task())
 242                                return;
 243                }
 244        } else if (num < ps_tsk_num) {
 245                while (ps_tsk_num > num)
 246                        destroy_power_saving_task();
 247        }
 248}
 249
 250static void acpi_pad_idle_cpus(unsigned int num_cpus)
 251{
 252        get_online_cpus();
 253
 254        num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
 255        set_power_saving_task_num(num_cpus);
 256
 257        put_online_cpus();
 258}
 259
 260static uint32_t acpi_pad_idle_cpus_num(void)
 261{
 262        return ps_tsk_num;
 263}
 264
 265static ssize_t rrtime_store(struct device *dev,
 266        struct device_attribute *attr, const char *buf, size_t count)
 267{
 268        unsigned long num;
 269
 270        if (kstrtoul(buf, 0, &num))
 271                return -EINVAL;
 272        if (num < 1 || num >= 100)
 273                return -EINVAL;
 274        mutex_lock(&isolated_cpus_lock);
 275        round_robin_time = num;
 276        mutex_unlock(&isolated_cpus_lock);
 277        return count;
 278}
 279
 280static ssize_t rrtime_show(struct device *dev,
 281        struct device_attribute *attr, char *buf)
 282{
 283        return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time);
 284}
 285static DEVICE_ATTR_RW(rrtime);
 286
 287static ssize_t idlepct_store(struct device *dev,
 288        struct device_attribute *attr, const char *buf, size_t count)
 289{
 290        unsigned long num;
 291
 292        if (kstrtoul(buf, 0, &num))
 293                return -EINVAL;
 294        if (num < 1 || num >= 100)
 295                return -EINVAL;
 296        mutex_lock(&isolated_cpus_lock);
 297        idle_pct = num;
 298        mutex_unlock(&isolated_cpus_lock);
 299        return count;
 300}
 301
 302static ssize_t idlepct_show(struct device *dev,
 303        struct device_attribute *attr, char *buf)
 304{
 305        return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct);
 306}
 307static DEVICE_ATTR_RW(idlepct);
 308
 309static ssize_t idlecpus_store(struct device *dev,
 310        struct device_attribute *attr, const char *buf, size_t count)
 311{
 312        unsigned long num;
 313
 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
 322static ssize_t 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
 329static DEVICE_ATTR_RW(idlecpus);
 330
 331static int acpi_pad_add_sysfs(struct acpi_device *device)
 332{
 333        int result;
 334
 335        result = device_create_file(&device->dev, &dev_attr_idlecpus);
 336        if (result)
 337                return -ENODEV;
 338        result = device_create_file(&device->dev, &dev_attr_idlepct);
 339        if (result) {
 340                device_remove_file(&device->dev, &dev_attr_idlecpus);
 341                return -ENODEV;
 342        }
 343        result = device_create_file(&device->dev, &dev_attr_rrtime);
 344        if (result) {
 345                device_remove_file(&device->dev, &dev_attr_idlecpus);
 346                device_remove_file(&device->dev, &dev_attr_idlepct);
 347                return -ENODEV;
 348        }
 349        return 0;
 350}
 351
 352static void acpi_pad_remove_sysfs(struct acpi_device *device)
 353{
 354        device_remove_file(&device->dev, &dev_attr_idlecpus);
 355        device_remove_file(&device->dev, &dev_attr_idlepct);
 356        device_remove_file(&device->dev, &dev_attr_rrtime);
 357}
 358
 359/*
 360 * Query firmware how many CPUs should be idle
 361 * return -1 on failure
 362 */
 363static int acpi_pad_pur(acpi_handle handle)
 364{
 365        struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
 366        union acpi_object *package;
 367        int num = -1;
 368
 369        if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
 370                return num;
 371
 372        if (!buffer.length || !buffer.pointer)
 373                return num;
 374
 375        package = buffer.pointer;
 376
 377        if (package->type == ACPI_TYPE_PACKAGE &&
 378                package->package.count == 2 &&
 379                package->package.elements[0].integer.value == 1) /* rev 1 */
 380
 381                num = package->package.elements[1].integer.value;
 382
 383        kfree(buffer.pointer);
 384        return num;
 385}
 386
 387static void acpi_pad_handle_notify(acpi_handle handle)
 388{
 389        int num_cpus;
 390        uint32_t idle_cpus;
 391        struct acpi_buffer param = {
 392                .length = 4,
 393                .pointer = (void *)&idle_cpus,
 394        };
 395
 396        mutex_lock(&isolated_cpus_lock);
 397        num_cpus = acpi_pad_pur(handle);
 398        if (num_cpus < 0) {
 399                mutex_unlock(&isolated_cpus_lock);
 400                return;
 401        }
 402        acpi_pad_idle_cpus(num_cpus);
 403        idle_cpus = acpi_pad_idle_cpus_num();
 404        acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, &param);
 405        mutex_unlock(&isolated_cpus_lock);
 406}
 407
 408static void acpi_pad_notify(acpi_handle handle, u32 event,
 409        void *data)
 410{
 411        struct acpi_device *device = data;
 412
 413        switch (event) {
 414        case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
 415                acpi_pad_handle_notify(handle);
 416                acpi_bus_generate_netlink_event(device->pnp.device_class,
 417                        dev_name(&device->dev), event, 0);
 418                break;
 419        default:
 420                pr_warn("Unsupported event [0x%x]\n", event);
 421                break;
 422        }
 423}
 424
 425static int acpi_pad_add(struct acpi_device *device)
 426{
 427        acpi_status status;
 428
 429        strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
 430        strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
 431
 432        if (acpi_pad_add_sysfs(device))
 433                return -ENODEV;
 434
 435        status = acpi_install_notify_handler(device->handle,
 436                ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
 437        if (ACPI_FAILURE(status)) {
 438                acpi_pad_remove_sysfs(device);
 439                return -ENODEV;
 440        }
 441
 442        return 0;
 443}
 444
 445static int acpi_pad_remove(struct acpi_device *device)
 446{
 447        mutex_lock(&isolated_cpus_lock);
 448        acpi_pad_idle_cpus(0);
 449        mutex_unlock(&isolated_cpus_lock);
 450
 451        acpi_remove_notify_handler(device->handle,
 452                ACPI_DEVICE_NOTIFY, acpi_pad_notify);
 453        acpi_pad_remove_sysfs(device);
 454        return 0;
 455}
 456
 457static const struct acpi_device_id pad_device_ids[] = {
 458        {"ACPI000C", 0},
 459        {"", 0},
 460};
 461MODULE_DEVICE_TABLE(acpi, pad_device_ids);
 462
 463static struct acpi_driver acpi_pad_driver = {
 464        .name = "processor_aggregator",
 465        .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
 466        .ids = pad_device_ids,
 467        .ops = {
 468                .add = acpi_pad_add,
 469                .remove = acpi_pad_remove,
 470        },
 471};
 472
 473static 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 acpi_bus_register_driver(&acpi_pad_driver);
 484}
 485
 486static void __exit acpi_pad_exit(void)
 487{
 488        acpi_bus_unregister_driver(&acpi_pad_driver);
 489}
 490
 491module_init(acpi_pad_init);
 492module_exit(acpi_pad_exit);
 493MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>");
 494MODULE_DESCRIPTION("ACPI Processor Aggregator Driver");
 495MODULE_LICENSE("GPL");
 496