xref: /openbmc/linux/drivers/acpi/acpi_pad.c (revision b72f301c)
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 
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);
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 
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 */
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;
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 
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 
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 
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 
268 static uint32_t acpi_pad_idle_cpus_num(void)
269 {
270 	return ps_tsk_num;
271 }
272 
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 
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 
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 
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 
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 
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 
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 
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  */
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 
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, &param);
413 	mutex_unlock(&isolated_cpus_lock);
414 }
415 
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 
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 
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 
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 
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