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 <asm/mwait.h>
22 #include <xen/xen.h>
23
24 #define ACPI_PROCESSOR_AGGREGATOR_CLASS "acpi_pad"
25 #define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"
26 #define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
27 static DEFINE_MUTEX(isolated_cpus_lock);
28 static DEFINE_MUTEX(round_robin_lock);
29
30 static unsigned long power_saving_mwait_eax;
31
32 static unsigned char tsc_detected_unstable;
33 static unsigned char tsc_marked_unstable;
34
power_saving_mwait_init(void)35 static void power_saving_mwait_init(void)
36 {
37 unsigned int eax, ebx, ecx, edx;
38 unsigned int highest_cstate = 0;
39 unsigned int highest_subcstate = 0;
40 int i;
41
42 if (!boot_cpu_has(X86_FEATURE_MWAIT))
43 return;
44 if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
45 return;
46
47 cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
48
49 if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
50 !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
51 return;
52
53 edx >>= MWAIT_SUBSTATE_SIZE;
54 for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
55 if (edx & MWAIT_SUBSTATE_MASK) {
56 highest_cstate = i;
57 highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
58 }
59 }
60 power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
61 (highest_subcstate - 1);
62
63 #if defined(CONFIG_X86)
64 switch (boot_cpu_data.x86_vendor) {
65 case X86_VENDOR_HYGON:
66 case X86_VENDOR_AMD:
67 case X86_VENDOR_INTEL:
68 case X86_VENDOR_ZHAOXIN:
69 case X86_VENDOR_CENTAUR:
70 /*
71 * AMD Fam10h TSC will tick in all
72 * C/P/S0/S1 states when this bit is set.
73 */
74 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
75 tsc_detected_unstable = 1;
76 break;
77 default:
78 /* TSC could halt in idle */
79 tsc_detected_unstable = 1;
80 }
81 #endif
82 }
83
84 static unsigned long cpu_weight[NR_CPUS];
85 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
86 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS);
round_robin_cpu(unsigned int tsk_index)87 static void round_robin_cpu(unsigned int tsk_index)
88 {
89 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
90 cpumask_var_t tmp;
91 int cpu;
92 unsigned long min_weight = -1;
93 unsigned long preferred_cpu;
94
95 if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
96 return;
97
98 mutex_lock(&round_robin_lock);
99 cpumask_clear(tmp);
100 for_each_cpu(cpu, pad_busy_cpus)
101 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu));
102 cpumask_andnot(tmp, cpu_online_mask, tmp);
103 /* avoid HT sibilings if possible */
104 if (cpumask_empty(tmp))
105 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);
106 if (cpumask_empty(tmp)) {
107 mutex_unlock(&round_robin_lock);
108 free_cpumask_var(tmp);
109 return;
110 }
111 for_each_cpu(cpu, tmp) {
112 if (cpu_weight[cpu] < min_weight) {
113 min_weight = cpu_weight[cpu];
114 preferred_cpu = cpu;
115 }
116 }
117
118 if (tsk_in_cpu[tsk_index] != -1)
119 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
120 tsk_in_cpu[tsk_index] = preferred_cpu;
121 cpumask_set_cpu(preferred_cpu, pad_busy_cpus);
122 cpu_weight[preferred_cpu]++;
123 mutex_unlock(&round_robin_lock);
124
125 set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));
126
127 free_cpumask_var(tmp);
128 }
129
exit_round_robin(unsigned int tsk_index)130 static void exit_round_robin(unsigned int tsk_index)
131 {
132 struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
133
134 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
135 tsk_in_cpu[tsk_index] = -1;
136 }
137
138 static unsigned int idle_pct = 5; /* percentage */
139 static unsigned int round_robin_time = 1; /* second */
power_saving_thread(void * data)140 static int power_saving_thread(void *data)
141 {
142 int do_sleep;
143 unsigned int tsk_index = (unsigned long)data;
144 u64 last_jiffies = 0;
145
146 sched_set_fifo_low(current);
147
148 while (!kthread_should_stop()) {
149 unsigned long expire_time;
150
151 /* round robin to cpus */
152 expire_time = last_jiffies + round_robin_time * HZ;
153 if (time_before(expire_time, jiffies)) {
154 last_jiffies = jiffies;
155 round_robin_cpu(tsk_index);
156 }
157
158 do_sleep = 0;
159
160 expire_time = jiffies + HZ * (100 - idle_pct) / 100;
161
162 while (!need_resched()) {
163 if (tsc_detected_unstable && !tsc_marked_unstable) {
164 /* TSC could halt in idle, so notify users */
165 mark_tsc_unstable("TSC halts in idle");
166 tsc_marked_unstable = 1;
167 }
168 local_irq_disable();
169
170 perf_lopwr_cb(true);
171
172 tick_broadcast_enable();
173 tick_broadcast_enter();
174 stop_critical_timings();
175
176 mwait_idle_with_hints(power_saving_mwait_eax, 1);
177
178 start_critical_timings();
179 tick_broadcast_exit();
180
181 perf_lopwr_cb(false);
182
183 local_irq_enable();
184
185 if (time_before(expire_time, jiffies)) {
186 do_sleep = 1;
187 break;
188 }
189 }
190
191 /*
192 * current sched_rt has threshold for rt task running time.
193 * When a rt task uses 95% CPU time, the rt thread will be
194 * scheduled out for 5% CPU time to not starve other tasks. But
195 * the mechanism only works when all CPUs have RT task running,
196 * as if one CPU hasn't RT task, RT task from other CPUs will
197 * borrow CPU time from this CPU and cause RT task use > 95%
198 * CPU time. To make 'avoid starvation' work, takes a nap here.
199 */
200 if (unlikely(do_sleep))
201 schedule_timeout_killable(HZ * idle_pct / 100);
202
203 /* If an external event has set the need_resched flag, then
204 * we need to deal with it, or this loop will continue to
205 * spin without calling __mwait().
206 */
207 if (unlikely(need_resched()))
208 schedule();
209 }
210
211 exit_round_robin(tsk_index);
212 return 0;
213 }
214
215 static struct task_struct *ps_tsks[NR_CPUS];
216 static unsigned int ps_tsk_num;
create_power_saving_task(void)217 static int create_power_saving_task(void)
218 {
219 int rc;
220
221 ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread,
222 (void *)(unsigned long)ps_tsk_num,
223 "acpi_pad/%d", ps_tsk_num);
224
225 if (IS_ERR(ps_tsks[ps_tsk_num])) {
226 rc = PTR_ERR(ps_tsks[ps_tsk_num]);
227 ps_tsks[ps_tsk_num] = NULL;
228 } else {
229 rc = 0;
230 ps_tsk_num++;
231 }
232
233 return rc;
234 }
235
destroy_power_saving_task(void)236 static void destroy_power_saving_task(void)
237 {
238 if (ps_tsk_num > 0) {
239 ps_tsk_num--;
240 kthread_stop(ps_tsks[ps_tsk_num]);
241 ps_tsks[ps_tsk_num] = NULL;
242 }
243 }
244
set_power_saving_task_num(unsigned int num)245 static void set_power_saving_task_num(unsigned int num)
246 {
247 if (num > ps_tsk_num) {
248 while (ps_tsk_num < num) {
249 if (create_power_saving_task())
250 return;
251 }
252 } else if (num < ps_tsk_num) {
253 while (ps_tsk_num > num)
254 destroy_power_saving_task();
255 }
256 }
257
acpi_pad_idle_cpus(unsigned int num_cpus)258 static void acpi_pad_idle_cpus(unsigned int num_cpus)
259 {
260 cpus_read_lock();
261
262 num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
263 set_power_saving_task_num(num_cpus);
264
265 cpus_read_unlock();
266 }
267
acpi_pad_idle_cpus_num(void)268 static uint32_t acpi_pad_idle_cpus_num(void)
269 {
270 return ps_tsk_num;
271 }
272
rrtime_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)273 static ssize_t rrtime_store(struct device *dev,
274 struct device_attribute *attr, const char *buf, size_t count)
275 {
276 unsigned long num;
277
278 if (kstrtoul(buf, 0, &num))
279 return -EINVAL;
280 if (num < 1 || num >= 100)
281 return -EINVAL;
282 mutex_lock(&isolated_cpus_lock);
283 round_robin_time = num;
284 mutex_unlock(&isolated_cpus_lock);
285 return count;
286 }
287
rrtime_show(struct device * dev,struct device_attribute * attr,char * buf)288 static ssize_t rrtime_show(struct device *dev,
289 struct device_attribute *attr, char *buf)
290 {
291 return sysfs_emit(buf, "%d\n", round_robin_time);
292 }
293 static DEVICE_ATTR_RW(rrtime);
294
idlepct_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)295 static ssize_t idlepct_store(struct device *dev,
296 struct device_attribute *attr, const char *buf, size_t count)
297 {
298 unsigned long num;
299
300 if (kstrtoul(buf, 0, &num))
301 return -EINVAL;
302 if (num < 1 || num >= 100)
303 return -EINVAL;
304 mutex_lock(&isolated_cpus_lock);
305 idle_pct = num;
306 mutex_unlock(&isolated_cpus_lock);
307 return count;
308 }
309
idlepct_show(struct device * dev,struct device_attribute * attr,char * buf)310 static ssize_t idlepct_show(struct device *dev,
311 struct device_attribute *attr, char *buf)
312 {
313 return sysfs_emit(buf, "%d\n", idle_pct);
314 }
315 static DEVICE_ATTR_RW(idlepct);
316
idlecpus_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)317 static ssize_t idlecpus_store(struct device *dev,
318 struct device_attribute *attr, const char *buf, size_t count)
319 {
320 unsigned long num;
321
322 if (kstrtoul(buf, 0, &num))
323 return -EINVAL;
324 mutex_lock(&isolated_cpus_lock);
325 acpi_pad_idle_cpus(num);
326 mutex_unlock(&isolated_cpus_lock);
327 return count;
328 }
329
idlecpus_show(struct device * dev,struct device_attribute * attr,char * buf)330 static ssize_t idlecpus_show(struct device *dev,
331 struct device_attribute *attr, char *buf)
332 {
333 return cpumap_print_to_pagebuf(false, buf,
334 to_cpumask(pad_busy_cpus_bits));
335 }
336
337 static DEVICE_ATTR_RW(idlecpus);
338
acpi_pad_add_sysfs(struct acpi_device * device)339 static int acpi_pad_add_sysfs(struct acpi_device *device)
340 {
341 int result;
342
343 result = device_create_file(&device->dev, &dev_attr_idlecpus);
344 if (result)
345 return -ENODEV;
346 result = device_create_file(&device->dev, &dev_attr_idlepct);
347 if (result) {
348 device_remove_file(&device->dev, &dev_attr_idlecpus);
349 return -ENODEV;
350 }
351 result = device_create_file(&device->dev, &dev_attr_rrtime);
352 if (result) {
353 device_remove_file(&device->dev, &dev_attr_idlecpus);
354 device_remove_file(&device->dev, &dev_attr_idlepct);
355 return -ENODEV;
356 }
357 return 0;
358 }
359
acpi_pad_remove_sysfs(struct acpi_device * device)360 static void acpi_pad_remove_sysfs(struct acpi_device *device)
361 {
362 device_remove_file(&device->dev, &dev_attr_idlecpus);
363 device_remove_file(&device->dev, &dev_attr_idlepct);
364 device_remove_file(&device->dev, &dev_attr_rrtime);
365 }
366
367 /*
368 * Query firmware how many CPUs should be idle
369 * return -1 on failure
370 */
acpi_pad_pur(acpi_handle handle)371 static int acpi_pad_pur(acpi_handle handle)
372 {
373 struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
374 union acpi_object *package;
375 int num = -1;
376
377 if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
378 return num;
379
380 if (!buffer.length || !buffer.pointer)
381 return num;
382
383 package = buffer.pointer;
384
385 if (package->type == ACPI_TYPE_PACKAGE &&
386 package->package.count == 2 &&
387 package->package.elements[0].integer.value == 1) /* rev 1 */
388
389 num = package->package.elements[1].integer.value;
390
391 kfree(buffer.pointer);
392 return num;
393 }
394
acpi_pad_handle_notify(acpi_handle handle)395 static void acpi_pad_handle_notify(acpi_handle handle)
396 {
397 int num_cpus;
398 uint32_t idle_cpus;
399 struct acpi_buffer param = {
400 .length = 4,
401 .pointer = (void *)&idle_cpus,
402 };
403
404 mutex_lock(&isolated_cpus_lock);
405 num_cpus = acpi_pad_pur(handle);
406 if (num_cpus < 0) {
407 mutex_unlock(&isolated_cpus_lock);
408 return;
409 }
410 acpi_pad_idle_cpus(num_cpus);
411 idle_cpus = acpi_pad_idle_cpus_num();
412 acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, ¶m);
413 mutex_unlock(&isolated_cpus_lock);
414 }
415
acpi_pad_notify(acpi_handle handle,u32 event,void * data)416 static void acpi_pad_notify(acpi_handle handle, u32 event,
417 void *data)
418 {
419 struct acpi_device *device = data;
420
421 switch (event) {
422 case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
423 acpi_pad_handle_notify(handle);
424 acpi_bus_generate_netlink_event(device->pnp.device_class,
425 dev_name(&device->dev), event, 0);
426 break;
427 default:
428 pr_warn("Unsupported event [0x%x]\n", event);
429 break;
430 }
431 }
432
acpi_pad_add(struct acpi_device * device)433 static int acpi_pad_add(struct acpi_device *device)
434 {
435 acpi_status status;
436
437 strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
438 strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
439
440 if (acpi_pad_add_sysfs(device))
441 return -ENODEV;
442
443 status = acpi_install_notify_handler(device->handle,
444 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
445 if (ACPI_FAILURE(status)) {
446 acpi_pad_remove_sysfs(device);
447 return -ENODEV;
448 }
449
450 return 0;
451 }
452
acpi_pad_remove(struct acpi_device * device)453 static void acpi_pad_remove(struct acpi_device *device)
454 {
455 mutex_lock(&isolated_cpus_lock);
456 acpi_pad_idle_cpus(0);
457 mutex_unlock(&isolated_cpus_lock);
458
459 acpi_remove_notify_handler(device->handle,
460 ACPI_DEVICE_NOTIFY, acpi_pad_notify);
461 acpi_pad_remove_sysfs(device);
462 }
463
464 static const struct acpi_device_id pad_device_ids[] = {
465 {"ACPI000C", 0},
466 {"", 0},
467 };
468 MODULE_DEVICE_TABLE(acpi, pad_device_ids);
469
470 static struct acpi_driver acpi_pad_driver = {
471 .name = "processor_aggregator",
472 .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
473 .ids = pad_device_ids,
474 .ops = {
475 .add = acpi_pad_add,
476 .remove = acpi_pad_remove,
477 },
478 };
479
acpi_pad_init(void)480 static int __init acpi_pad_init(void)
481 {
482 /* Xen ACPI PAD is used when running as Xen Dom0. */
483 if (xen_initial_domain())
484 return -ENODEV;
485
486 power_saving_mwait_init();
487 if (power_saving_mwait_eax == 0)
488 return -EINVAL;
489
490 return acpi_bus_register_driver(&acpi_pad_driver);
491 }
492
acpi_pad_exit(void)493 static void __exit acpi_pad_exit(void)
494 {
495 acpi_bus_unregister_driver(&acpi_pad_driver);
496 }
497
498 module_init(acpi_pad_init);
499 module_exit(acpi_pad_exit);
500 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>");
501 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver");
502 MODULE_LICENSE("GPL");
503