xref: /linux/drivers/acpi/acpi_pad.c (revision 3fd6c59042dbba50391e30862beac979491145fe)
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 
power_saving_mwait_init(void)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);
round_robin_cpu(unsigned int tsk_index)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 
exit_round_robin(unsigned int tsk_index)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 */
power_saving_thread(void * data)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;
create_power_saving_task(void)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 
destroy_power_saving_task(void)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 
set_power_saving_task_num(unsigned int num)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 
acpi_pad_idle_cpus(unsigned int num_cpus)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 
acpi_pad_idle_cpus_num(void)275 static uint32_t acpi_pad_idle_cpus_num(void)
276 {
277 	return ps_tsk_num;
278 }
279 
rrtime_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)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 
rrtime_show(struct device * dev,struct device_attribute * attr,char * buf)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 
idlepct_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)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 
idlepct_show(struct device * dev,struct device_attribute * attr,char * buf)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 
idlecpus_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)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 
idlecpus_show(struct device * dev,struct device_attribute * attr,char * buf)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  */
acpi_pad_pur(acpi_handle handle)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 
acpi_pad_handle_notify(acpi_handle handle)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 
acpi_pad_notify(acpi_handle handle,u32 event,void * data)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 
acpi_pad_probe(struct platform_device * pdev)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 
acpi_pad_remove(struct platform_device * pdev)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 
acpi_pad_init(void)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 
acpi_pad_exit(void)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");
496