1 // SPDX-License-Identifier: GPL-2.0-only
3 * acpi_pad.c ACPI Processor Aggregator Driver
5 * Copyright (c) 2009, Intel Corporation.
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>
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);
31 static unsigned long power_saving_mwait_eax;
33 static unsigned char tsc_detected_unstable;
34 static unsigned char tsc_marked_unstable;
36 static void power_saving_mwait_init(void)
38 unsigned int eax, ebx, ecx, edx;
39 unsigned int highest_cstate = 0;
40 unsigned int highest_subcstate = 0;
43 if (!boot_cpu_has(X86_FEATURE_MWAIT))
45 if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
48 cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
50 if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
51 !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
54 edx >>= MWAIT_SUBSTATE_SIZE;
55 for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
56 if (edx & MWAIT_SUBSTATE_MASK) {
58 highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
61 power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
62 (highest_subcstate - 1);
64 #if defined(CONFIG_X86)
65 switch (boot_cpu_data.x86_vendor) {
66 case X86_VENDOR_HYGON:
68 case X86_VENDOR_INTEL:
69 case X86_VENDOR_ZHAOXIN:
70 case X86_VENDOR_CENTAUR:
72 * AMD Fam10h TSC will tick in all
73 * C/P/S0/S1 states when this bit is set.
75 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
76 tsc_detected_unstable = 1;
79 /* TSC could halt in idle */
80 tsc_detected_unstable = 1;
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)
90 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
93 unsigned long min_weight = -1;
94 unsigned long preferred_cpu;
96 if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
99 mutex_lock(&round_robin_lock);
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);
112 for_each_cpu(cpu, tmp) {
113 if (cpu_weight[cpu] < min_weight) {
114 min_weight = cpu_weight[cpu];
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);
126 set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));
128 free_cpumask_var(tmp);
131 static void exit_round_robin(unsigned int tsk_index)
133 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
135 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
136 tsk_in_cpu[tsk_index] = -1;
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)
144 unsigned int tsk_index = (unsigned long)data;
145 u64 last_jiffies = 0;
147 sched_set_fifo_low(current);
149 while (!kthread_should_stop()) {
150 unsigned long expire_time;
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);
161 expire_time = jiffies + HZ * (100 - idle_pct) / 100;
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;
173 tick_broadcast_enable();
174 tick_broadcast_enter();
175 stop_critical_timings();
177 mwait_idle_with_hints(power_saving_mwait_eax, 1);
179 start_critical_timings();
180 tick_broadcast_exit();
182 perf_lopwr_cb(false);
186 if (time_before(expire_time, jiffies)) {
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.
201 if (unlikely(do_sleep))
202 schedule_timeout_killable(HZ * idle_pct / 100);
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().
208 if (unlikely(need_resched()))
212 exit_round_robin(tsk_index);
216 static struct task_struct *ps_tsks[NR_CPUS];
217 static unsigned int ps_tsk_num;
218 static int create_power_saving_task(void)
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);
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;
237 static void destroy_power_saving_task(void)
239 if (ps_tsk_num > 0) {
241 kthread_stop(ps_tsks[ps_tsk_num]);
242 ps_tsks[ps_tsk_num] = NULL;
246 static void set_power_saving_task_num(unsigned int num)
248 if (num > ps_tsk_num) {
249 while (ps_tsk_num < num) {
250 if (create_power_saving_task())
253 } else if (num < ps_tsk_num) {
254 while (ps_tsk_num > num)
255 destroy_power_saving_task();
259 static void acpi_pad_idle_cpus(unsigned int num_cpus)
263 num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
264 set_power_saving_task_num(num_cpus);
269 static uint32_t acpi_pad_idle_cpus_num(void)
274 static ssize_t rrtime_store(struct device *dev,
275 struct device_attribute *attr, const char *buf, size_t count)
279 if (kstrtoul(buf, 0, &num))
281 if (num < 1 || num >= 100)
283 mutex_lock(&isolated_cpus_lock);
284 round_robin_time = num;
285 mutex_unlock(&isolated_cpus_lock);
289 static ssize_t rrtime_show(struct device *dev,
290 struct device_attribute *attr, char *buf)
292 return sysfs_emit(buf, "%d\n", round_robin_time);
294 static DEVICE_ATTR_RW(rrtime);
296 static ssize_t idlepct_store(struct device *dev,
297 struct device_attribute *attr, const char *buf, size_t count)
301 if (kstrtoul(buf, 0, &num))
303 if (num < 1 || num >= 100)
305 mutex_lock(&isolated_cpus_lock);
307 mutex_unlock(&isolated_cpus_lock);
311 static ssize_t idlepct_show(struct device *dev,
312 struct device_attribute *attr, char *buf)
314 return sysfs_emit(buf, "%d\n", idle_pct);
316 static DEVICE_ATTR_RW(idlepct);
318 static ssize_t idlecpus_store(struct device *dev,
319 struct device_attribute *attr, const char *buf, size_t count)
323 if (kstrtoul(buf, 0, &num))
325 mutex_lock(&isolated_cpus_lock);
326 acpi_pad_idle_cpus(num);
327 mutex_unlock(&isolated_cpus_lock);
331 static ssize_t idlecpus_show(struct device *dev,
332 struct device_attribute *attr, char *buf)
334 return cpumap_print_to_pagebuf(false, buf,
335 to_cpumask(pad_busy_cpus_bits));
338 static DEVICE_ATTR_RW(idlecpus);
340 static struct attribute *acpi_pad_attrs[] = {
341 &dev_attr_idlecpus.attr,
342 &dev_attr_idlepct.attr,
343 &dev_attr_rrtime.attr,
347 ATTRIBUTE_GROUPS(acpi_pad);
350 * Query firmware how many CPUs should be idle
351 * return -1 on failure
353 static int acpi_pad_pur(acpi_handle handle)
355 struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
356 union acpi_object *package;
359 if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
362 if (!buffer.length || !buffer.pointer)
365 package = buffer.pointer;
367 if (package->type == ACPI_TYPE_PACKAGE &&
368 package->package.count == 2 &&
369 package->package.elements[0].integer.value == 1) /* rev 1 */
371 num = package->package.elements[1].integer.value;
373 kfree(buffer.pointer);
377 static void acpi_pad_handle_notify(acpi_handle handle)
381 struct acpi_buffer param = {
383 .pointer = (void *)&idle_cpus,
386 mutex_lock(&isolated_cpus_lock);
387 num_cpus = acpi_pad_pur(handle);
389 mutex_unlock(&isolated_cpus_lock);
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, ¶m);
395 mutex_unlock(&isolated_cpus_lock);
398 static void acpi_pad_notify(acpi_handle handle, u32 event,
401 struct acpi_device *adev = data;
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);
410 pr_warn("Unsupported event [0x%x]\n", event);
415 static int acpi_pad_probe(struct platform_device *pdev)
417 struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
420 strcpy(acpi_device_name(adev), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
421 strcpy(acpi_device_class(adev), ACPI_PROCESSOR_AGGREGATOR_CLASS);
423 status = acpi_install_notify_handler(adev->handle,
424 ACPI_DEVICE_NOTIFY, acpi_pad_notify, adev);
426 if (ACPI_FAILURE(status))
432 static void acpi_pad_remove(struct platform_device *pdev)
434 struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
436 mutex_lock(&isolated_cpus_lock);
437 acpi_pad_idle_cpus(0);
438 mutex_unlock(&isolated_cpus_lock);
440 acpi_remove_notify_handler(adev->handle,
441 ACPI_DEVICE_NOTIFY, acpi_pad_notify);
444 static const struct acpi_device_id pad_device_ids[] = {
448 MODULE_DEVICE_TABLE(acpi, pad_device_ids);
450 static struct platform_driver acpi_pad_driver = {
451 .probe = acpi_pad_probe,
452 .remove_new = acpi_pad_remove,
454 .dev_groups = acpi_pad_groups,
455 .name = "processor_aggregator",
456 .acpi_match_table = pad_device_ids,
460 static int __init acpi_pad_init(void)
462 /* Xen ACPI PAD is used when running as Xen Dom0. */
463 if (xen_initial_domain())
466 power_saving_mwait_init();
467 if (power_saving_mwait_eax == 0)
470 return platform_driver_register(&acpi_pad_driver);
473 static void __exit acpi_pad_exit(void)
475 platform_driver_unregister(&acpi_pad_driver);
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");