xref: /openbmc/linux/drivers/acpi/acpi_pad.c (revision c819e2cf)
1 /*
2  * acpi_pad.c ACPI Processor Aggregator Driver
3  *
4  * Copyright (c) 2009, Intel Corporation.
5  *
6  * This program is free software; you can redistribute it and/or modify it
7  * under the terms and conditions of the GNU General Public License,
8  * version 2, as published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope it will be useful, but WITHOUT
11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
13  * more details.
14  *
15  * You should have received a copy of the GNU General Public License along with
16  * this program; if not, write to the Free Software Foundation, Inc.,
17  * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
18  *
19  */
20 
21 #include <linux/kernel.h>
22 #include <linux/cpumask.h>
23 #include <linux/module.h>
24 #include <linux/init.h>
25 #include <linux/types.h>
26 #include <linux/kthread.h>
27 #include <linux/freezer.h>
28 #include <linux/cpu.h>
29 #include <linux/clockchips.h>
30 #include <linux/slab.h>
31 #include <linux/acpi.h>
32 #include <asm/mwait.h>
33 
34 #define ACPI_PROCESSOR_AGGREGATOR_CLASS	"acpi_pad"
35 #define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"
36 #define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
37 static DEFINE_MUTEX(isolated_cpus_lock);
38 static DEFINE_MUTEX(round_robin_lock);
39 
40 static unsigned long power_saving_mwait_eax;
41 
42 static unsigned char tsc_detected_unstable;
43 static unsigned char tsc_marked_unstable;
44 static unsigned char lapic_detected_unstable;
45 static unsigned char lapic_marked_unstable;
46 
47 static void power_saving_mwait_init(void)
48 {
49 	unsigned int eax, ebx, ecx, edx;
50 	unsigned int highest_cstate = 0;
51 	unsigned int highest_subcstate = 0;
52 	int i;
53 
54 	if (!boot_cpu_has(X86_FEATURE_MWAIT))
55 		return;
56 	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
57 		return;
58 
59 	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
60 
61 	if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
62 	    !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
63 		return;
64 
65 	edx >>= MWAIT_SUBSTATE_SIZE;
66 	for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
67 		if (edx & MWAIT_SUBSTATE_MASK) {
68 			highest_cstate = i;
69 			highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
70 		}
71 	}
72 	power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
73 		(highest_subcstate - 1);
74 
75 #if defined(CONFIG_X86)
76 	switch (boot_cpu_data.x86_vendor) {
77 	case X86_VENDOR_AMD:
78 	case X86_VENDOR_INTEL:
79 		/*
80 		 * AMD Fam10h TSC will tick in all
81 		 * C/P/S0/S1 states when this bit is set.
82 		 */
83 		if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
84 			tsc_detected_unstable = 1;
85 		if (!boot_cpu_has(X86_FEATURE_ARAT))
86 			lapic_detected_unstable = 1;
87 		break;
88 	default:
89 		/* TSC & LAPIC could halt in idle */
90 		tsc_detected_unstable = 1;
91 		lapic_detected_unstable = 1;
92 	}
93 #endif
94 }
95 
96 static unsigned long cpu_weight[NR_CPUS];
97 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
98 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS);
99 static void round_robin_cpu(unsigned int tsk_index)
100 {
101 	struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
102 	cpumask_var_t tmp;
103 	int cpu;
104 	unsigned long min_weight = -1;
105 	unsigned long uninitialized_var(preferred_cpu);
106 
107 	if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
108 		return;
109 
110 	mutex_lock(&round_robin_lock);
111 	cpumask_clear(tmp);
112 	for_each_cpu(cpu, pad_busy_cpus)
113 		cpumask_or(tmp, tmp, topology_thread_cpumask(cpu));
114 	cpumask_andnot(tmp, cpu_online_mask, tmp);
115 	/* avoid HT sibilings if possible */
116 	if (cpumask_empty(tmp))
117 		cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);
118 	if (cpumask_empty(tmp)) {
119 		mutex_unlock(&round_robin_lock);
120 		return;
121 	}
122 	for_each_cpu(cpu, tmp) {
123 		if (cpu_weight[cpu] < min_weight) {
124 			min_weight = cpu_weight[cpu];
125 			preferred_cpu = cpu;
126 		}
127 	}
128 
129 	if (tsk_in_cpu[tsk_index] != -1)
130 		cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
131 	tsk_in_cpu[tsk_index] = preferred_cpu;
132 	cpumask_set_cpu(preferred_cpu, pad_busy_cpus);
133 	cpu_weight[preferred_cpu]++;
134 	mutex_unlock(&round_robin_lock);
135 
136 	set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));
137 }
138 
139 static void exit_round_robin(unsigned int tsk_index)
140 {
141 	struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
142 	cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
143 	tsk_in_cpu[tsk_index] = -1;
144 }
145 
146 static unsigned int idle_pct = 5; /* percentage */
147 static unsigned int round_robin_time = 1; /* second */
148 static int power_saving_thread(void *data)
149 {
150 	struct sched_param param = {.sched_priority = 1};
151 	int do_sleep;
152 	unsigned int tsk_index = (unsigned long)data;
153 	u64 last_jiffies = 0;
154 
155 	sched_setscheduler(current, SCHED_RR, &param);
156 
157 	while (!kthread_should_stop()) {
158 		int cpu;
159 		unsigned long expire_time;
160 
161 		try_to_freeze();
162 
163 		/* round robin to cpus */
164 		expire_time = last_jiffies + round_robin_time * HZ;
165 		if (time_before(expire_time, jiffies)) {
166 			last_jiffies = jiffies;
167 			round_robin_cpu(tsk_index);
168 		}
169 
170 		do_sleep = 0;
171 
172 		expire_time = jiffies + HZ * (100 - idle_pct) / 100;
173 
174 		while (!need_resched()) {
175 			if (tsc_detected_unstable && !tsc_marked_unstable) {
176 				/* TSC could halt in idle, so notify users */
177 				mark_tsc_unstable("TSC halts in idle");
178 				tsc_marked_unstable = 1;
179 			}
180 			if (lapic_detected_unstable && !lapic_marked_unstable) {
181 				int i;
182 				/* LAPIC could halt in idle, so notify users */
183 				for_each_online_cpu(i)
184 					clockevents_notify(
185 						CLOCK_EVT_NOTIFY_BROADCAST_ON,
186 						&i);
187 				lapic_marked_unstable = 1;
188 			}
189 			local_irq_disable();
190 			cpu = smp_processor_id();
191 			if (lapic_marked_unstable)
192 				clockevents_notify(
193 					CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
194 			stop_critical_timings();
195 
196 			mwait_idle_with_hints(power_saving_mwait_eax, 1);
197 
198 			start_critical_timings();
199 			if (lapic_marked_unstable)
200 				clockevents_notify(
201 					CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
202 			local_irq_enable();
203 
204 			if (time_before(expire_time, jiffies)) {
205 				do_sleep = 1;
206 				break;
207 			}
208 		}
209 
210 		/*
211 		 * current sched_rt has threshold for rt task running time.
212 		 * When a rt task uses 95% CPU time, the rt thread will be
213 		 * scheduled out for 5% CPU time to not starve other tasks. But
214 		 * the mechanism only works when all CPUs have RT task running,
215 		 * as if one CPU hasn't RT task, RT task from other CPUs will
216 		 * borrow CPU time from this CPU and cause RT task use > 95%
217 		 * CPU time. To make 'avoid starvation' work, takes a nap here.
218 		 */
219 		if (unlikely(do_sleep))
220 			schedule_timeout_killable(HZ * idle_pct / 100);
221 
222 		/* If an external event has set the need_resched flag, then
223 		 * we need to deal with it, or this loop will continue to
224 		 * spin without calling __mwait().
225 		 */
226 		if (unlikely(need_resched()))
227 			schedule();
228 	}
229 
230 	exit_round_robin(tsk_index);
231 	return 0;
232 }
233 
234 static struct task_struct *ps_tsks[NR_CPUS];
235 static unsigned int ps_tsk_num;
236 static int create_power_saving_task(void)
237 {
238 	int rc;
239 
240 	ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread,
241 		(void *)(unsigned long)ps_tsk_num,
242 		"acpi_pad/%d", ps_tsk_num);
243 
244 	if (IS_ERR(ps_tsks[ps_tsk_num])) {
245 		rc = PTR_ERR(ps_tsks[ps_tsk_num]);
246 		ps_tsks[ps_tsk_num] = NULL;
247 	} else {
248 		rc = 0;
249 		ps_tsk_num++;
250 	}
251 
252 	return rc;
253 }
254 
255 static void destroy_power_saving_task(void)
256 {
257 	if (ps_tsk_num > 0) {
258 		ps_tsk_num--;
259 		kthread_stop(ps_tsks[ps_tsk_num]);
260 		ps_tsks[ps_tsk_num] = NULL;
261 	}
262 }
263 
264 static void set_power_saving_task_num(unsigned int num)
265 {
266 	if (num > ps_tsk_num) {
267 		while (ps_tsk_num < num) {
268 			if (create_power_saving_task())
269 				return;
270 		}
271 	} else if (num < ps_tsk_num) {
272 		while (ps_tsk_num > num)
273 			destroy_power_saving_task();
274 	}
275 }
276 
277 static void acpi_pad_idle_cpus(unsigned int num_cpus)
278 {
279 	get_online_cpus();
280 
281 	num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
282 	set_power_saving_task_num(num_cpus);
283 
284 	put_online_cpus();
285 }
286 
287 static uint32_t acpi_pad_idle_cpus_num(void)
288 {
289 	return ps_tsk_num;
290 }
291 
292 static ssize_t acpi_pad_rrtime_store(struct device *dev,
293 	struct device_attribute *attr, const char *buf, size_t count)
294 {
295 	unsigned long num;
296 	if (kstrtoul(buf, 0, &num))
297 		return -EINVAL;
298 	if (num < 1 || num >= 100)
299 		return -EINVAL;
300 	mutex_lock(&isolated_cpus_lock);
301 	round_robin_time = num;
302 	mutex_unlock(&isolated_cpus_lock);
303 	return count;
304 }
305 
306 static ssize_t acpi_pad_rrtime_show(struct device *dev,
307 	struct device_attribute *attr, char *buf)
308 {
309 	return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time);
310 }
311 static DEVICE_ATTR(rrtime, S_IRUGO|S_IWUSR,
312 	acpi_pad_rrtime_show,
313 	acpi_pad_rrtime_store);
314 
315 static ssize_t acpi_pad_idlepct_store(struct device *dev,
316 	struct device_attribute *attr, const char *buf, size_t count)
317 {
318 	unsigned long num;
319 	if (kstrtoul(buf, 0, &num))
320 		return -EINVAL;
321 	if (num < 1 || num >= 100)
322 		return -EINVAL;
323 	mutex_lock(&isolated_cpus_lock);
324 	idle_pct = num;
325 	mutex_unlock(&isolated_cpus_lock);
326 	return count;
327 }
328 
329 static ssize_t acpi_pad_idlepct_show(struct device *dev,
330 	struct device_attribute *attr, char *buf)
331 {
332 	return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct);
333 }
334 static DEVICE_ATTR(idlepct, S_IRUGO|S_IWUSR,
335 	acpi_pad_idlepct_show,
336 	acpi_pad_idlepct_store);
337 
338 static ssize_t acpi_pad_idlecpus_store(struct device *dev,
339 	struct device_attribute *attr, const char *buf, size_t count)
340 {
341 	unsigned long num;
342 	if (kstrtoul(buf, 0, &num))
343 		return -EINVAL;
344 	mutex_lock(&isolated_cpus_lock);
345 	acpi_pad_idle_cpus(num);
346 	mutex_unlock(&isolated_cpus_lock);
347 	return count;
348 }
349 
350 static ssize_t acpi_pad_idlecpus_show(struct device *dev,
351 	struct device_attribute *attr, char *buf)
352 {
353 	return cpumap_print_to_pagebuf(false, buf,
354 				       to_cpumask(pad_busy_cpus_bits));
355 }
356 
357 static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR,
358 	acpi_pad_idlecpus_show,
359 	acpi_pad_idlecpus_store);
360 
361 static int acpi_pad_add_sysfs(struct acpi_device *device)
362 {
363 	int result;
364 
365 	result = device_create_file(&device->dev, &dev_attr_idlecpus);
366 	if (result)
367 		return -ENODEV;
368 	result = device_create_file(&device->dev, &dev_attr_idlepct);
369 	if (result) {
370 		device_remove_file(&device->dev, &dev_attr_idlecpus);
371 		return -ENODEV;
372 	}
373 	result = device_create_file(&device->dev, &dev_attr_rrtime);
374 	if (result) {
375 		device_remove_file(&device->dev, &dev_attr_idlecpus);
376 		device_remove_file(&device->dev, &dev_attr_idlepct);
377 		return -ENODEV;
378 	}
379 	return 0;
380 }
381 
382 static void acpi_pad_remove_sysfs(struct acpi_device *device)
383 {
384 	device_remove_file(&device->dev, &dev_attr_idlecpus);
385 	device_remove_file(&device->dev, &dev_attr_idlepct);
386 	device_remove_file(&device->dev, &dev_attr_rrtime);
387 }
388 
389 /*
390  * Query firmware how many CPUs should be idle
391  * return -1 on failure
392  */
393 static int acpi_pad_pur(acpi_handle handle)
394 {
395 	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
396 	union acpi_object *package;
397 	int num = -1;
398 
399 	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
400 		return num;
401 
402 	if (!buffer.length || !buffer.pointer)
403 		return num;
404 
405 	package = buffer.pointer;
406 
407 	if (package->type == ACPI_TYPE_PACKAGE &&
408 		package->package.count == 2 &&
409 		package->package.elements[0].integer.value == 1) /* rev 1 */
410 
411 		num = package->package.elements[1].integer.value;
412 
413 	kfree(buffer.pointer);
414 	return num;
415 }
416 
417 static void acpi_pad_handle_notify(acpi_handle handle)
418 {
419 	int num_cpus;
420 	uint32_t idle_cpus;
421 	struct acpi_buffer param = {
422 		.length = 4,
423 		.pointer = (void *)&idle_cpus,
424 	};
425 
426 	mutex_lock(&isolated_cpus_lock);
427 	num_cpus = acpi_pad_pur(handle);
428 	if (num_cpus < 0) {
429 		mutex_unlock(&isolated_cpus_lock);
430 		return;
431 	}
432 	acpi_pad_idle_cpus(num_cpus);
433 	idle_cpus = acpi_pad_idle_cpus_num();
434 	acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, &param);
435 	mutex_unlock(&isolated_cpus_lock);
436 }
437 
438 static void acpi_pad_notify(acpi_handle handle, u32 event,
439 	void *data)
440 {
441 	struct acpi_device *device = data;
442 
443 	switch (event) {
444 	case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
445 		acpi_pad_handle_notify(handle);
446 		acpi_bus_generate_netlink_event(device->pnp.device_class,
447 			dev_name(&device->dev), event, 0);
448 		break;
449 	default:
450 		pr_warn("Unsupported event [0x%x]\n", event);
451 		break;
452 	}
453 }
454 
455 static int acpi_pad_add(struct acpi_device *device)
456 {
457 	acpi_status status;
458 
459 	strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
460 	strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
461 
462 	if (acpi_pad_add_sysfs(device))
463 		return -ENODEV;
464 
465 	status = acpi_install_notify_handler(device->handle,
466 		ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
467 	if (ACPI_FAILURE(status)) {
468 		acpi_pad_remove_sysfs(device);
469 		return -ENODEV;
470 	}
471 
472 	return 0;
473 }
474 
475 static int acpi_pad_remove(struct acpi_device *device)
476 {
477 	mutex_lock(&isolated_cpus_lock);
478 	acpi_pad_idle_cpus(0);
479 	mutex_unlock(&isolated_cpus_lock);
480 
481 	acpi_remove_notify_handler(device->handle,
482 		ACPI_DEVICE_NOTIFY, acpi_pad_notify);
483 	acpi_pad_remove_sysfs(device);
484 	return 0;
485 }
486 
487 static const struct acpi_device_id pad_device_ids[] = {
488 	{"ACPI000C", 0},
489 	{"", 0},
490 };
491 MODULE_DEVICE_TABLE(acpi, pad_device_ids);
492 
493 static struct acpi_driver acpi_pad_driver = {
494 	.name = "processor_aggregator",
495 	.class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
496 	.ids = pad_device_ids,
497 	.ops = {
498 		.add = acpi_pad_add,
499 		.remove = acpi_pad_remove,
500 	},
501 };
502 
503 static int __init acpi_pad_init(void)
504 {
505 	power_saving_mwait_init();
506 	if (power_saving_mwait_eax == 0)
507 		return -EINVAL;
508 
509 	return acpi_bus_register_driver(&acpi_pad_driver);
510 }
511 
512 static void __exit acpi_pad_exit(void)
513 {
514 	acpi_bus_unregister_driver(&acpi_pad_driver);
515 }
516 
517 module_init(acpi_pad_init);
518 module_exit(acpi_pad_exit);
519 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>");
520 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver");
521 MODULE_LICENSE("GPL");
522