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Linux/drivers/acpi/acpi_pad.c

  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  */
 16 
 17 #include <linux/kernel.h>
 18 #include <linux/cpumask.h>
 19 #include <linux/module.h>
 20 #include <linux/init.h>
 21 #include <linux/types.h>
 22 #include <linux/kthread.h>
 23 #include <linux/freezer.h>
 24 #include <linux/cpu.h>
 25 #include <linux/tick.h>
 26 #include <linux/slab.h>
 27 #include <linux/acpi.h>
 28 #include <asm/mwait.h>
 29 #include <xen/xen.h>
 30 
 31 #define ACPI_PROCESSOR_AGGREGATOR_CLASS "acpi_pad"
 32 #define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"
 33 #define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
 34 static DEFINE_MUTEX(isolated_cpus_lock);
 35 static DEFINE_MUTEX(round_robin_lock);
 36 
 37 static unsigned long power_saving_mwait_eax;
 38 
 39 static unsigned char tsc_detected_unstable;
 40 static unsigned char tsc_marked_unstable;
 41 
 42 static void power_saving_mwait_init(void)
 43 {
 44         unsigned int eax, ebx, ecx, edx;
 45         unsigned int highest_cstate = 0;
 46         unsigned int highest_subcstate = 0;
 47         int i;
 48 
 49         if (!boot_cpu_has(X86_FEATURE_MWAIT))
 50                 return;
 51         if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
 52                 return;
 53 
 54         cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
 55 
 56         if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
 57             !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
 58                 return;
 59 
 60         edx >>= MWAIT_SUBSTATE_SIZE;
 61         for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
 62                 if (edx & MWAIT_SUBSTATE_MASK) {
 63                         highest_cstate = i;
 64                         highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
 65                 }
 66         }
 67         power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
 68                 (highest_subcstate - 1);
 69 
 70 #if defined(CONFIG_X86)
 71         switch (boot_cpu_data.x86_vendor) {
 72         case X86_VENDOR_AMD:
 73         case X86_VENDOR_INTEL:
 74                 /*
 75                  * AMD Fam10h TSC will tick in all
 76                  * C/P/S0/S1 states when this bit is set.
 77                  */
 78                 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
 79                         tsc_detected_unstable = 1;
 80                 break;
 81         default:
 82                 /* TSC could halt in idle */
 83                 tsc_detected_unstable = 1;
 84         }
 85 #endif
 86 }
 87 
 88 static unsigned long cpu_weight[NR_CPUS];
 89 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
 90 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS);
 91 static void round_robin_cpu(unsigned int tsk_index)
 92 {
 93         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
 94         cpumask_var_t tmp;
 95         int cpu;
 96         unsigned long min_weight = -1;
 97         unsigned long uninitialized_var(preferred_cpu);
 98 
 99         if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
100                 return;
101 
102         mutex_lock(&round_robin_lock);
103         cpumask_clear(tmp);
104         for_each_cpu(cpu, pad_busy_cpus)
105                 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu));
106         cpumask_andnot(tmp, cpu_online_mask, tmp);
107         /* avoid HT sibilings if possible */
108         if (cpumask_empty(tmp))
109                 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);
110         if (cpumask_empty(tmp)) {
111                 mutex_unlock(&round_robin_lock);
112                 return;
113         }
114         for_each_cpu(cpu, tmp) {
115                 if (cpu_weight[cpu] < min_weight) {
116                         min_weight = cpu_weight[cpu];
117                         preferred_cpu = cpu;
118                 }
119         }
120 
121         if (tsk_in_cpu[tsk_index] != -1)
122                 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
123         tsk_in_cpu[tsk_index] = preferred_cpu;
124         cpumask_set_cpu(preferred_cpu, pad_busy_cpus);
125         cpu_weight[preferred_cpu]++;
126         mutex_unlock(&round_robin_lock);
127 
128         set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));
129 }
130 
131 static void exit_round_robin(unsigned int tsk_index)
132 {
133         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
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         struct sched_param param = {.sched_priority = 1};
143         int do_sleep;
144         unsigned int tsk_index = (unsigned long)data;
145         u64 last_jiffies = 0;
146 
147         sched_setscheduler(current, SCHED_RR, &param);
148 
149         while (!kthread_should_stop()) {
150                 unsigned long expire_time;
151 
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);
157                 }
158 
159                 do_sleep = 0;
160 
161                 expire_time = jiffies + HZ * (100 - idle_pct) / 100;
162 
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;
168                         }
169                         local_irq_disable();
170                         tick_broadcast_enable();
171                         tick_broadcast_enter();
172                         stop_critical_timings();
173 
174                         mwait_idle_with_hints(power_saving_mwait_eax, 1);
175 
176                         start_critical_timings();
177                         tick_broadcast_exit();
178                         local_irq_enable();
179 
180                         if (time_before(expire_time, jiffies)) {
181                                 do_sleep = 1;
182                                 break;
183                         }
184                 }
185 
186                 /*
187                  * current sched_rt has threshold for rt task running time.
188                  * When a rt task uses 95% CPU time, the rt thread will be
189                  * scheduled out for 5% CPU time to not starve other tasks. But
190                  * the mechanism only works when all CPUs have RT task running,
191                  * as if one CPU hasn't RT task, RT task from other CPUs will
192                  * borrow CPU time from this CPU and cause RT task use > 95%
193                  * CPU time. To make 'avoid starvation' work, takes a nap here.
194                  */
195                 if (unlikely(do_sleep))
196                         schedule_timeout_killable(HZ * idle_pct / 100);
197 
198                 /* If an external event has set the need_resched flag, then
199                  * we need to deal with it, or this loop will continue to
200                  * spin without calling __mwait().
201                  */
202                 if (unlikely(need_resched()))
203                         schedule();
204         }
205 
206         exit_round_robin(tsk_index);
207         return 0;
208 }
209 
210 static struct task_struct *ps_tsks[NR_CPUS];
211 static unsigned int ps_tsk_num;
212 static int create_power_saving_task(void)
213 {
214         int rc;
215 
216         ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread,
217                 (void *)(unsigned long)ps_tsk_num,
218                 "acpi_pad/%d", ps_tsk_num);
219 
220         if (IS_ERR(ps_tsks[ps_tsk_num])) {
221                 rc = PTR_ERR(ps_tsks[ps_tsk_num]);
222                 ps_tsks[ps_tsk_num] = NULL;
223         } else {
224                 rc = 0;
225                 ps_tsk_num++;
226         }
227 
228         return rc;
229 }
230 
231 static void destroy_power_saving_task(void)
232 {
233         if (ps_tsk_num > 0) {
234                 ps_tsk_num--;
235                 kthread_stop(ps_tsks[ps_tsk_num]);
236                 ps_tsks[ps_tsk_num] = NULL;
237         }
238 }
239 
240 static void set_power_saving_task_num(unsigned int num)
241 {
242         if (num > ps_tsk_num) {
243                 while (ps_tsk_num < num) {
244                         if (create_power_saving_task())
245                                 return;
246                 }
247         } else if (num < ps_tsk_num) {
248                 while (ps_tsk_num > num)
249                         destroy_power_saving_task();
250         }
251 }
252 
253 static void acpi_pad_idle_cpus(unsigned int num_cpus)
254 {
255         get_online_cpus();
256 
257         num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
258         set_power_saving_task_num(num_cpus);
259 
260         put_online_cpus();
261 }
262 
263 static uint32_t acpi_pad_idle_cpus_num(void)
264 {
265         return ps_tsk_num;
266 }
267 
268 static ssize_t acpi_pad_rrtime_store(struct device *dev,
269         struct device_attribute *attr, const char *buf, size_t count)
270 {
271         unsigned long num;
272         if (kstrtoul(buf, 0, &num))
273                 return -EINVAL;
274         if (num < 1 || num >= 100)
275                 return -EINVAL;
276         mutex_lock(&isolated_cpus_lock);
277         round_robin_time = num;
278         mutex_unlock(&isolated_cpus_lock);
279         return count;
280 }
281 
282 static ssize_t acpi_pad_rrtime_show(struct device *dev,
283         struct device_attribute *attr, char *buf)
284 {
285         return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time);
286 }
287 static DEVICE_ATTR(rrtime, S_IRUGO|S_IWUSR,
288         acpi_pad_rrtime_show,
289         acpi_pad_rrtime_store);
290 
291 static ssize_t acpi_pad_idlepct_store(struct device *dev,
292         struct device_attribute *attr, const char *buf, size_t count)
293 {
294         unsigned long num;
295         if (kstrtoul(buf, 0, &num))
296                 return -EINVAL;
297         if (num < 1 || num >= 100)
298                 return -EINVAL;
299         mutex_lock(&isolated_cpus_lock);
300         idle_pct = num;
301         mutex_unlock(&isolated_cpus_lock);
302         return count;
303 }
304 
305 static ssize_t acpi_pad_idlepct_show(struct device *dev,
306         struct device_attribute *attr, char *buf)
307 {
308         return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct);
309 }
310 static DEVICE_ATTR(idlepct, S_IRUGO|S_IWUSR,
311         acpi_pad_idlepct_show,
312         acpi_pad_idlepct_store);
313 
314 static ssize_t acpi_pad_idlecpus_store(struct device *dev,
315         struct device_attribute *attr, const char *buf, size_t count)
316 {
317         unsigned long num;
318         if (kstrtoul(buf, 0, &num))
319                 return -EINVAL;
320         mutex_lock(&isolated_cpus_lock);
321         acpi_pad_idle_cpus(num);
322         mutex_unlock(&isolated_cpus_lock);
323         return count;
324 }
325 
326 static ssize_t acpi_pad_idlecpus_show(struct device *dev,
327         struct device_attribute *attr, char *buf)
328 {
329         return cpumap_print_to_pagebuf(false, buf,
330                                        to_cpumask(pad_busy_cpus_bits));
331 }
332 
333 static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR,
334         acpi_pad_idlecpus_show,
335         acpi_pad_idlecpus_store);
336 
337 static int acpi_pad_add_sysfs(struct acpi_device *device)
338 {
339         int result;
340 
341         result = device_create_file(&device->dev, &dev_attr_idlecpus);
342         if (result)
343                 return -ENODEV;
344         result = device_create_file(&device->dev, &dev_attr_idlepct);
345         if (result) {
346                 device_remove_file(&device->dev, &dev_attr_idlecpus);
347                 return -ENODEV;
348         }
349         result = device_create_file(&device->dev, &dev_attr_rrtime);
350         if (result) {
351                 device_remove_file(&device->dev, &dev_attr_idlecpus);
352                 device_remove_file(&device->dev, &dev_attr_idlepct);
353                 return -ENODEV;
354         }
355         return 0;
356 }
357 
358 static void acpi_pad_remove_sysfs(struct acpi_device *device)
359 {
360         device_remove_file(&device->dev, &dev_attr_idlecpus);
361         device_remove_file(&device->dev, &dev_attr_idlepct);
362         device_remove_file(&device->dev, &dev_attr_rrtime);
363 }
364 
365 /*
366  * Query firmware how many CPUs should be idle
367  * return -1 on failure
368  */
369 static int acpi_pad_pur(acpi_handle handle)
370 {
371         struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
372         union acpi_object *package;
373         int num = -1;
374 
375         if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
376                 return num;
377 
378         if (!buffer.length || !buffer.pointer)
379                 return num;
380 
381         package = buffer.pointer;
382 
383         if (package->type == ACPI_TYPE_PACKAGE &&
384                 package->package.count == 2 &&
385                 package->package.elements[0].integer.value == 1) /* rev 1 */
386 
387                 num = package->package.elements[1].integer.value;
388 
389         kfree(buffer.pointer);
390         return num;
391 }
392 
393 static void acpi_pad_handle_notify(acpi_handle handle)
394 {
395         int num_cpus;
396         uint32_t idle_cpus;
397         struct acpi_buffer param = {
398                 .length = 4,
399                 .pointer = (void *)&idle_cpus,
400         };
401 
402         mutex_lock(&isolated_cpus_lock);
403         num_cpus = acpi_pad_pur(handle);
404         if (num_cpus < 0) {
405                 mutex_unlock(&isolated_cpus_lock);
406                 return;
407         }
408         acpi_pad_idle_cpus(num_cpus);
409         idle_cpus = acpi_pad_idle_cpus_num();
410         acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, &param);
411         mutex_unlock(&isolated_cpus_lock);
412 }
413 
414 static void acpi_pad_notify(acpi_handle handle, u32 event,
415         void *data)
416 {
417         struct acpi_device *device = data;
418 
419         switch (event) {
420         case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
421                 acpi_pad_handle_notify(handle);
422                 acpi_bus_generate_netlink_event(device->pnp.device_class,
423                         dev_name(&device->dev), event, 0);
424                 break;
425         default:
426                 pr_warn("Unsupported event [0x%x]\n", event);
427                 break;
428         }
429 }
430 
431 static int acpi_pad_add(struct acpi_device *device)
432 {
433         acpi_status status;
434 
435         strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
436         strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
437 
438         if (acpi_pad_add_sysfs(device))
439                 return -ENODEV;
440 
441         status = acpi_install_notify_handler(device->handle,
442                 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
443         if (ACPI_FAILURE(status)) {
444                 acpi_pad_remove_sysfs(device);
445                 return -ENODEV;
446         }
447 
448         return 0;
449 }
450 
451 static int acpi_pad_remove(struct acpi_device *device)
452 {
453         mutex_lock(&isolated_cpus_lock);
454         acpi_pad_idle_cpus(0);
455         mutex_unlock(&isolated_cpus_lock);
456 
457         acpi_remove_notify_handler(device->handle,
458                 ACPI_DEVICE_NOTIFY, acpi_pad_notify);
459         acpi_pad_remove_sysfs(device);
460         return 0;
461 }
462 
463 static const struct acpi_device_id pad_device_ids[] = {
464         {"ACPI000C", 0},
465         {"", 0},
466 };
467 MODULE_DEVICE_TABLE(acpi, pad_device_ids);
468 
469 static struct acpi_driver acpi_pad_driver = {
470         .name = "processor_aggregator",
471         .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
472         .ids = pad_device_ids,
473         .ops = {
474                 .add = acpi_pad_add,
475                 .remove = acpi_pad_remove,
476         },
477 };
478 
479 static int __init acpi_pad_init(void)
480 {
481         /* Xen ACPI PAD is used when running as Xen Dom0. */
482         if (xen_initial_domain())
483                 return -ENODEV;
484 
485         power_saving_mwait_init();
486         if (power_saving_mwait_eax == 0)
487                 return -EINVAL;
488 
489         return acpi_bus_register_driver(&acpi_pad_driver);
490 }
491 
492 static void __exit acpi_pad_exit(void)
493 {
494         acpi_bus_unregister_driver(&acpi_pad_driver);
495 }
496 
497 module_init(acpi_pad_init);
498 module_exit(acpi_pad_exit);
499 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>");
500 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver");
501 MODULE_LICENSE("GPL");
502 

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