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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  * 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         int n = 0;
354         n = cpumask_scnprintf(buf, PAGE_SIZE-2, to_cpumask(pad_busy_cpus_bits));
355         buf[n++] = '\n';
356         buf[n] = '\0';
357         return n;
358 }
359 static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR,
360         acpi_pad_idlecpus_show,
361         acpi_pad_idlecpus_store);
362 
363 static int acpi_pad_add_sysfs(struct acpi_device *device)
364 {
365         int result;
366 
367         result = device_create_file(&device->dev, &dev_attr_idlecpus);
368         if (result)
369                 return -ENODEV;
370         result = device_create_file(&device->dev, &dev_attr_idlepct);
371         if (result) {
372                 device_remove_file(&device->dev, &dev_attr_idlecpus);
373                 return -ENODEV;
374         }
375         result = device_create_file(&device->dev, &dev_attr_rrtime);
376         if (result) {
377                 device_remove_file(&device->dev, &dev_attr_idlecpus);
378                 device_remove_file(&device->dev, &dev_attr_idlepct);
379                 return -ENODEV;
380         }
381         return 0;
382 }
383 
384 static void acpi_pad_remove_sysfs(struct acpi_device *device)
385 {
386         device_remove_file(&device->dev, &dev_attr_idlecpus);
387         device_remove_file(&device->dev, &dev_attr_idlepct);
388         device_remove_file(&device->dev, &dev_attr_rrtime);
389 }
390 
391 /*
392  * Query firmware how many CPUs should be idle
393  * return -1 on failure
394  */
395 static int acpi_pad_pur(acpi_handle handle)
396 {
397         struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
398         union acpi_object *package;
399         int num = -1;
400 
401         if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
402                 return num;
403 
404         if (!buffer.length || !buffer.pointer)
405                 return num;
406 
407         package = buffer.pointer;
408 
409         if (package->type == ACPI_TYPE_PACKAGE &&
410                 package->package.count == 2 &&
411                 package->package.elements[0].integer.value == 1) /* rev 1 */
412 
413                 num = package->package.elements[1].integer.value;
414 
415         kfree(buffer.pointer);
416         return num;
417 }
418 
419 static void acpi_pad_handle_notify(acpi_handle handle)
420 {
421         int num_cpus;
422         uint32_t idle_cpus;
423         struct acpi_buffer param = {
424                 .length = 4,
425                 .pointer = (void *)&idle_cpus,
426         };
427 
428         mutex_lock(&isolated_cpus_lock);
429         num_cpus = acpi_pad_pur(handle);
430         if (num_cpus < 0) {
431                 mutex_unlock(&isolated_cpus_lock);
432                 return;
433         }
434         acpi_pad_idle_cpus(num_cpus);
435         idle_cpus = acpi_pad_idle_cpus_num();
436         acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, &param);
437         mutex_unlock(&isolated_cpus_lock);
438 }
439 
440 static void acpi_pad_notify(acpi_handle handle, u32 event,
441         void *data)
442 {
443         struct acpi_device *device = data;
444 
445         switch (event) {
446         case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
447                 acpi_pad_handle_notify(handle);
448                 acpi_bus_generate_netlink_event(device->pnp.device_class,
449                         dev_name(&device->dev), event, 0);
450                 break;
451         default:
452                 pr_warn("Unsupported event [0x%x]\n", event);
453                 break;
454         }
455 }
456 
457 static int acpi_pad_add(struct acpi_device *device)
458 {
459         acpi_status status;
460 
461         strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
462         strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
463 
464         if (acpi_pad_add_sysfs(device))
465                 return -ENODEV;
466 
467         status = acpi_install_notify_handler(device->handle,
468                 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
469         if (ACPI_FAILURE(status)) {
470                 acpi_pad_remove_sysfs(device);
471                 return -ENODEV;
472         }
473 
474         return 0;
475 }
476 
477 static int acpi_pad_remove(struct acpi_device *device)
478 {
479         mutex_lock(&isolated_cpus_lock);
480         acpi_pad_idle_cpus(0);
481         mutex_unlock(&isolated_cpus_lock);
482 
483         acpi_remove_notify_handler(device->handle,
484                 ACPI_DEVICE_NOTIFY, acpi_pad_notify);
485         acpi_pad_remove_sysfs(device);
486         return 0;
487 }
488 
489 static const struct acpi_device_id pad_device_ids[] = {
490         {"ACPI000C", 0},
491         {"", 0},
492 };
493 MODULE_DEVICE_TABLE(acpi, pad_device_ids);
494 
495 static struct acpi_driver acpi_pad_driver = {
496         .name = "processor_aggregator",
497         .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
498         .ids = pad_device_ids,
499         .ops = {
500                 .add = acpi_pad_add,
501                 .remove = acpi_pad_remove,
502         },
503 };
504 
505 static int __init acpi_pad_init(void)
506 {
507         power_saving_mwait_init();
508         if (power_saving_mwait_eax == 0)
509                 return -EINVAL;
510 
511         return acpi_bus_register_driver(&acpi_pad_driver);
512 }
513 
514 static void __exit acpi_pad_exit(void)
515 {
516         acpi_bus_unregister_driver(&acpi_pad_driver);
517 }
518 
519 module_init(acpi_pad_init);
520 module_exit(acpi_pad_exit);
521 MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>");
522 MODULE_DESCRIPTION("ACPI Processor Aggregator Driver");
523 MODULE_LICENSE("GPL");
524 

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