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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/tick.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 
 45 static void power_saving_mwait_init(void)
 46 {
 47         unsigned int eax, ebx, ecx, edx;
 48         unsigned int highest_cstate = 0;
 49         unsigned int highest_subcstate = 0;
 50         int i;
 51 
 52         if (!boot_cpu_has(X86_FEATURE_MWAIT))
 53                 return;
 54         if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
 55                 return;
 56 
 57         cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
 58 
 59         if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
 60             !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
 61                 return;
 62 
 63         edx >>= MWAIT_SUBSTATE_SIZE;
 64         for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
 65                 if (edx & MWAIT_SUBSTATE_MASK) {
 66                         highest_cstate = i;
 67                         highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
 68                 }
 69         }
 70         power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
 71                 (highest_subcstate - 1);
 72 
 73 #if defined(CONFIG_X86)
 74         switch (boot_cpu_data.x86_vendor) {
 75         case X86_VENDOR_AMD:
 76         case X86_VENDOR_INTEL:
 77                 /*
 78                  * AMD Fam10h TSC will tick in all
 79                  * C/P/S0/S1 states when this bit is set.
 80                  */
 81                 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
 82                         tsc_detected_unstable = 1;
 83                 break;
 84         default:
 85                 /* TSC could halt in idle */
 86                 tsc_detected_unstable = 1;
 87         }
 88 #endif
 89 }
 90 
 91 static unsigned long cpu_weight[NR_CPUS];
 92 static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
 93 static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS);
 94 static void round_robin_cpu(unsigned int tsk_index)
 95 {
 96         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
 97         cpumask_var_t tmp;
 98         int cpu;
 99         unsigned long min_weight = -1;
100         unsigned long uninitialized_var(preferred_cpu);
101 
102         if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
103                 return;
104 
105         mutex_lock(&round_robin_lock);
106         cpumask_clear(tmp);
107         for_each_cpu(cpu, pad_busy_cpus)
108                 cpumask_or(tmp, tmp, topology_sibling_cpumask(cpu));
109         cpumask_andnot(tmp, cpu_online_mask, tmp);
110         /* avoid HT sibilings if possible */
111         if (cpumask_empty(tmp))
112                 cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);
113         if (cpumask_empty(tmp)) {
114                 mutex_unlock(&round_robin_lock);
115                 return;
116         }
117         for_each_cpu(cpu, tmp) {
118                 if (cpu_weight[cpu] < min_weight) {
119                         min_weight = cpu_weight[cpu];
120                         preferred_cpu = cpu;
121                 }
122         }
123 
124         if (tsk_in_cpu[tsk_index] != -1)
125                 cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
126         tsk_in_cpu[tsk_index] = preferred_cpu;
127         cpumask_set_cpu(preferred_cpu, pad_busy_cpus);
128         cpu_weight[preferred_cpu]++;
129         mutex_unlock(&round_robin_lock);
130 
131         set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));
132 }
133 
134 static void exit_round_robin(unsigned int tsk_index)
135 {
136         struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
137         cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
138         tsk_in_cpu[tsk_index] = -1;
139 }
140 
141 static unsigned int idle_pct = 5; /* percentage */
142 static unsigned int round_robin_time = 1; /* second */
143 static int power_saving_thread(void *data)
144 {
145         struct sched_param param = {.sched_priority = 1};
146         int do_sleep;
147         unsigned int tsk_index = (unsigned long)data;
148         u64 last_jiffies = 0;
149 
150         sched_setscheduler(current, SCHED_RR, &param);
151 
152         while (!kthread_should_stop()) {
153                 unsigned long expire_time;
154 
155                 try_to_freeze();
156 
157                 /* round robin to cpus */
158                 expire_time = last_jiffies + round_robin_time * HZ;
159                 if (time_before(expire_time, jiffies)) {
160                         last_jiffies = jiffies;
161                         round_robin_cpu(tsk_index);
162                 }
163 
164                 do_sleep = 0;
165 
166                 expire_time = jiffies + HZ * (100 - idle_pct) / 100;
167 
168                 while (!need_resched()) {
169                         if (tsc_detected_unstable && !tsc_marked_unstable) {
170                                 /* TSC could halt in idle, so notify users */
171                                 mark_tsc_unstable("TSC halts in idle");
172                                 tsc_marked_unstable = 1;
173                         }
174                         local_irq_disable();
175                         tick_broadcast_enable();
176                         tick_broadcast_enter();
177                         stop_critical_timings();
178 
179                         mwait_idle_with_hints(power_saving_mwait_eax, 1);
180 
181                         start_critical_timings();
182                         tick_broadcast_exit();
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         get_online_cpus();
261 
262         num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
263         set_power_saving_task_num(num_cpus);
264 
265         put_online_cpus();
266 }
267 
268 static uint32_t acpi_pad_idle_cpus_num(void)
269 {
270         return ps_tsk_num;
271 }
272 
273 static ssize_t acpi_pad_rrtime_store(struct device *dev,
274         struct device_attribute *attr, const char *buf, size_t count)
275 {
276         unsigned long num;
277         if (kstrtoul(buf, 0, &num))
278                 return -EINVAL;
279         if (num < 1 || num >= 100)
280                 return -EINVAL;
281         mutex_lock(&isolated_cpus_lock);
282         round_robin_time = num;
283         mutex_unlock(&isolated_cpus_lock);
284         return count;
285 }
286 
287 static ssize_t acpi_pad_rrtime_show(struct device *dev,
288         struct device_attribute *attr, char *buf)
289 {
290         return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time);
291 }
292 static DEVICE_ATTR(rrtime, S_IRUGO|S_IWUSR,
293         acpi_pad_rrtime_show,
294         acpi_pad_rrtime_store);
295 
296 static ssize_t acpi_pad_idlepct_store(struct device *dev,
297         struct device_attribute *attr, const char *buf, size_t count)
298 {
299         unsigned long num;
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 acpi_pad_idlepct_show(struct device *dev,
311         struct device_attribute *attr, char *buf)
312 {
313         return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct);
314 }
315 static DEVICE_ATTR(idlepct, S_IRUGO|S_IWUSR,
316         acpi_pad_idlepct_show,
317         acpi_pad_idlepct_store);
318 
319 static ssize_t acpi_pad_idlecpus_store(struct device *dev,
320         struct device_attribute *attr, const char *buf, size_t count)
321 {
322         unsigned long num;
323         if (kstrtoul(buf, 0, &num))
324                 return -EINVAL;
325         mutex_lock(&isolated_cpus_lock);
326         acpi_pad_idle_cpus(num);
327         mutex_unlock(&isolated_cpus_lock);
328         return count;
329 }
330 
331 static ssize_t acpi_pad_idlecpus_show(struct device *dev,
332         struct device_attribute *attr, char *buf)
333 {
334         return cpumap_print_to_pagebuf(false, buf,
335                                        to_cpumask(pad_busy_cpus_bits));
336 }
337 
338 static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR,
339         acpi_pad_idlecpus_show,
340         acpi_pad_idlecpus_store);
341 
342 static int acpi_pad_add_sysfs(struct acpi_device *device)
343 {
344         int result;
345 
346         result = device_create_file(&device->dev, &dev_attr_idlecpus);
347         if (result)
348                 return -ENODEV;
349         result = device_create_file(&device->dev, &dev_attr_idlepct);
350         if (result) {
351                 device_remove_file(&device->dev, &dev_attr_idlecpus);
352                 return -ENODEV;
353         }
354         result = device_create_file(&device->dev, &dev_attr_rrtime);
355         if (result) {
356                 device_remove_file(&device->dev, &dev_attr_idlecpus);
357                 device_remove_file(&device->dev, &dev_attr_idlepct);
358                 return -ENODEV;
359         }
360         return 0;
361 }
362 
363 static void acpi_pad_remove_sysfs(struct acpi_device *device)
364 {
365         device_remove_file(&device->dev, &dev_attr_idlecpus);
366         device_remove_file(&device->dev, &dev_attr_idlepct);
367         device_remove_file(&device->dev, &dev_attr_rrtime);
368 }
369 
370 /*
371  * Query firmware how many CPUs should be idle
372  * return -1 on failure
373  */
374 static int acpi_pad_pur(acpi_handle handle)
375 {
376         struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
377         union acpi_object *package;
378         int num = -1;
379 
380         if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
381                 return num;
382 
383         if (!buffer.length || !buffer.pointer)
384                 return num;
385 
386         package = buffer.pointer;
387 
388         if (package->type == ACPI_TYPE_PACKAGE &&
389                 package->package.count == 2 &&
390                 package->package.elements[0].integer.value == 1) /* rev 1 */
391 
392                 num = package->package.elements[1].integer.value;
393 
394         kfree(buffer.pointer);
395         return num;
396 }
397 
398 static void acpi_pad_handle_notify(acpi_handle handle)
399 {
400         int num_cpus;
401         uint32_t idle_cpus;
402         struct acpi_buffer param = {
403                 .length = 4,
404                 .pointer = (void *)&idle_cpus,
405         };
406 
407         mutex_lock(&isolated_cpus_lock);
408         num_cpus = acpi_pad_pur(handle);
409         if (num_cpus < 0) {
410                 mutex_unlock(&isolated_cpus_lock);
411                 return;
412         }
413         acpi_pad_idle_cpus(num_cpus);
414         idle_cpus = acpi_pad_idle_cpus_num();
415         acpi_evaluate_ost(handle, ACPI_PROCESSOR_AGGREGATOR_NOTIFY, 0, &param);
416         mutex_unlock(&isolated_cpus_lock);
417 }
418 
419 static void acpi_pad_notify(acpi_handle handle, u32 event,
420         void *data)
421 {
422         struct acpi_device *device = data;
423 
424         switch (event) {
425         case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
426                 acpi_pad_handle_notify(handle);
427                 acpi_bus_generate_netlink_event(device->pnp.device_class,
428                         dev_name(&device->dev), event, 0);
429                 break;
430         default:
431                 pr_warn("Unsupported event [0x%x]\n", event);
432                 break;
433         }
434 }
435 
436 static int acpi_pad_add(struct acpi_device *device)
437 {
438         acpi_status status;
439 
440         strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
441         strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
442 
443         if (acpi_pad_add_sysfs(device))
444                 return -ENODEV;
445 
446         status = acpi_install_notify_handler(device->handle,
447                 ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
448         if (ACPI_FAILURE(status)) {
449                 acpi_pad_remove_sysfs(device);
450                 return -ENODEV;
451         }
452 
453         return 0;
454 }
455 
456 static int acpi_pad_remove(struct acpi_device *device)
457 {
458         mutex_lock(&isolated_cpus_lock);
459         acpi_pad_idle_cpus(0);
460         mutex_unlock(&isolated_cpus_lock);
461 
462         acpi_remove_notify_handler(device->handle,
463                 ACPI_DEVICE_NOTIFY, acpi_pad_notify);
464         acpi_pad_remove_sysfs(device);
465         return 0;
466 }
467 
468 static const struct acpi_device_id pad_device_ids[] = {
469         {"ACPI000C", 0},
470         {"", 0},
471 };
472 MODULE_DEVICE_TABLE(acpi, pad_device_ids);
473 
474 static struct acpi_driver acpi_pad_driver = {
475         .name = "processor_aggregator",
476         .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
477         .ids = pad_device_ids,
478         .ops = {
479                 .add = acpi_pad_add,
480                 .remove = acpi_pad_remove,
481         },
482 };
483 
484 static int __init acpi_pad_init(void)
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 

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