1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver 4 * 5 * Created by: Nicolas Pitre, March 2012 6 * Copyright: (C) 2012-2013 Linaro Limited 7 */ 8 9 #include <linux/atomic.h> 10 #include <linux/init.h> 11 #include <linux/kernel.h> 12 #include <linux/module.h> 13 #include <linux/sched/signal.h> 14 #include <uapi/linux/sched/types.h> 15 #include <linux/interrupt.h> 16 #include <linux/cpu_pm.h> 17 #include <linux/cpu.h> 18 #include <linux/cpumask.h> 19 #include <linux/kthread.h> 20 #include <linux/wait.h> 21 #include <linux/time.h> 22 #include <linux/clockchips.h> 23 #include <linux/hrtimer.h> 24 #include <linux/tick.h> 25 #include <linux/notifier.h> 26 #include <linux/mm.h> 27 #include <linux/mutex.h> 28 #include <linux/smp.h> 29 #include <linux/spinlock.h> 30 #include <linux/string.h> 31 #include <linux/sysfs.h> 32 #include <linux/irqchip/arm-gic.h> 33 #include <linux/moduleparam.h> 34 35 #include <asm/smp_plat.h> 36 #include <asm/cputype.h> 37 #include <asm/suspend.h> 38 #include <asm/mcpm.h> 39 #include <asm/bL_switcher.h> 40 41 #define CREATE_TRACE_POINTS 42 #include <trace/events/power_cpu_migrate.h> 43 44 45 /* 46 * Use our own MPIDR accessors as the generic ones in asm/cputype.h have 47 * __attribute_const__ and we don't want the compiler to assume any 48 * constness here as the value _does_ change along some code paths. 49 */ 50 51 static int read_mpidr(void) 52 { 53 unsigned int id; 54 asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (id)); 55 return id & MPIDR_HWID_BITMASK; 56 } 57 58 /* 59 * bL switcher core code. 60 */ 61 62 static void bL_do_switch(void *_arg) 63 { 64 unsigned ib_mpidr, ib_cpu, ib_cluster; 65 long volatile handshake, **handshake_ptr = _arg; 66 67 pr_debug("%s\n", __func__); 68 69 ib_mpidr = cpu_logical_map(smp_processor_id()); 70 ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0); 71 ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1); 72 73 /* Advertise our handshake location */ 74 if (handshake_ptr) { 75 handshake = 0; 76 *handshake_ptr = &handshake; 77 } else 78 handshake = -1; 79 80 /* 81 * Our state has been saved at this point. Let's release our 82 * inbound CPU. 83 */ 84 mcpm_set_entry_vector(ib_cpu, ib_cluster, cpu_resume); 85 sev(); 86 87 /* 88 * From this point, we must assume that our counterpart CPU might 89 * have taken over in its parallel world already, as if execution 90 * just returned from cpu_suspend(). It is therefore important to 91 * be very careful not to make any change the other guy is not 92 * expecting. This is why we need stack isolation. 93 * 94 * Fancy under cover tasks could be performed here. For now 95 * we have none. 96 */ 97 98 /* 99 * Let's wait until our inbound is alive. 100 */ 101 while (!handshake) { 102 wfe(); 103 smp_mb(); 104 } 105 106 /* Let's put ourself down. */ 107 mcpm_cpu_power_down(); 108 109 /* should never get here */ 110 BUG(); 111 } 112 113 /* 114 * Stack isolation. To ensure 'current' remains valid, we just use another 115 * piece of our thread's stack space which should be fairly lightly used. 116 * The selected area starts just above the thread_info structure located 117 * at the very bottom of the stack, aligned to a cache line, and indexed 118 * with the cluster number. 119 */ 120 #define STACK_SIZE 512 121 extern void call_with_stack(void (*fn)(void *), void *arg, void *sp); 122 static int bL_switchpoint(unsigned long _arg) 123 { 124 unsigned int mpidr = read_mpidr(); 125 unsigned int clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1); 126 void *stack = current_thread_info() + 1; 127 stack = PTR_ALIGN(stack, L1_CACHE_BYTES); 128 stack += clusterid * STACK_SIZE + STACK_SIZE; 129 call_with_stack(bL_do_switch, (void *)_arg, stack); 130 BUG(); 131 } 132 133 /* 134 * Generic switcher interface 135 */ 136 137 static unsigned int bL_gic_id[MAX_CPUS_PER_CLUSTER][MAX_NR_CLUSTERS]; 138 static int bL_switcher_cpu_pairing[NR_CPUS]; 139 140 /* 141 * bL_switch_to - Switch to a specific cluster for the current CPU 142 * @new_cluster_id: the ID of the cluster to switch to. 143 * 144 * This function must be called on the CPU to be switched. 145 * Returns 0 on success, else a negative status code. 146 */ 147 static int bL_switch_to(unsigned int new_cluster_id) 148 { 149 unsigned int mpidr, this_cpu, that_cpu; 150 unsigned int ob_mpidr, ob_cpu, ob_cluster, ib_mpidr, ib_cpu, ib_cluster; 151 struct completion inbound_alive; 152 long volatile *handshake_ptr; 153 int ipi_nr, ret; 154 155 this_cpu = smp_processor_id(); 156 ob_mpidr = read_mpidr(); 157 ob_cpu = MPIDR_AFFINITY_LEVEL(ob_mpidr, 0); 158 ob_cluster = MPIDR_AFFINITY_LEVEL(ob_mpidr, 1); 159 BUG_ON(cpu_logical_map(this_cpu) != ob_mpidr); 160 161 if (new_cluster_id == ob_cluster) 162 return 0; 163 164 that_cpu = bL_switcher_cpu_pairing[this_cpu]; 165 ib_mpidr = cpu_logical_map(that_cpu); 166 ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0); 167 ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1); 168 169 pr_debug("before switch: CPU %d MPIDR %#x -> %#x\n", 170 this_cpu, ob_mpidr, ib_mpidr); 171 172 this_cpu = smp_processor_id(); 173 174 /* Close the gate for our entry vectors */ 175 mcpm_set_entry_vector(ob_cpu, ob_cluster, NULL); 176 mcpm_set_entry_vector(ib_cpu, ib_cluster, NULL); 177 178 /* Install our "inbound alive" notifier. */ 179 init_completion(&inbound_alive); 180 ipi_nr = register_ipi_completion(&inbound_alive, this_cpu); 181 ipi_nr |= ((1 << 16) << bL_gic_id[ob_cpu][ob_cluster]); 182 mcpm_set_early_poke(ib_cpu, ib_cluster, gic_get_sgir_physaddr(), ipi_nr); 183 184 /* 185 * Let's wake up the inbound CPU now in case it requires some delay 186 * to come online, but leave it gated in our entry vector code. 187 */ 188 ret = mcpm_cpu_power_up(ib_cpu, ib_cluster); 189 if (ret) { 190 pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__, ret); 191 return ret; 192 } 193 194 /* 195 * Raise a SGI on the inbound CPU to make sure it doesn't stall 196 * in a possible WFI, such as in bL_power_down(). 197 */ 198 gic_send_sgi(bL_gic_id[ib_cpu][ib_cluster], 0); 199 200 /* 201 * Wait for the inbound to come up. This allows for other 202 * tasks to be scheduled in the mean time. 203 */ 204 wait_for_completion(&inbound_alive); 205 mcpm_set_early_poke(ib_cpu, ib_cluster, 0, 0); 206 207 /* 208 * From this point we are entering the switch critical zone 209 * and can't take any interrupts anymore. 210 */ 211 local_irq_disable(); 212 local_fiq_disable(); 213 trace_cpu_migrate_begin(ktime_get_real_ns(), ob_mpidr); 214 215 /* redirect GIC's SGIs to our counterpart */ 216 gic_migrate_target(bL_gic_id[ib_cpu][ib_cluster]); 217 218 tick_suspend_local(); 219 220 ret = cpu_pm_enter(); 221 222 /* we can not tolerate errors at this point */ 223 if (ret) 224 panic("%s: cpu_pm_enter() returned %d\n", __func__, ret); 225 226 /* Swap the physical CPUs in the logical map for this logical CPU. */ 227 cpu_logical_map(this_cpu) = ib_mpidr; 228 cpu_logical_map(that_cpu) = ob_mpidr; 229 230 /* Let's do the actual CPU switch. */ 231 ret = cpu_suspend((unsigned long)&handshake_ptr, bL_switchpoint); 232 if (ret > 0) 233 panic("%s: cpu_suspend() returned %d\n", __func__, ret); 234 235 /* We are executing on the inbound CPU at this point */ 236 mpidr = read_mpidr(); 237 pr_debug("after switch: CPU %d MPIDR %#x\n", this_cpu, mpidr); 238 BUG_ON(mpidr != ib_mpidr); 239 240 mcpm_cpu_powered_up(); 241 242 ret = cpu_pm_exit(); 243 244 tick_resume_local(); 245 246 trace_cpu_migrate_finish(ktime_get_real_ns(), ib_mpidr); 247 local_fiq_enable(); 248 local_irq_enable(); 249 250 *handshake_ptr = 1; 251 dsb_sev(); 252 253 if (ret) 254 pr_err("%s exiting with error %d\n", __func__, ret); 255 return ret; 256 } 257 258 struct bL_thread { 259 spinlock_t lock; 260 struct task_struct *task; 261 wait_queue_head_t wq; 262 int wanted_cluster; 263 struct completion started; 264 bL_switch_completion_handler completer; 265 void *completer_cookie; 266 }; 267 268 static struct bL_thread bL_threads[NR_CPUS]; 269 270 static int bL_switcher_thread(void *arg) 271 { 272 struct bL_thread *t = arg; 273 struct sched_param param = { .sched_priority = 1 }; 274 int cluster; 275 bL_switch_completion_handler completer; 276 void *completer_cookie; 277 278 sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m); 279 complete(&t->started); 280 281 do { 282 if (signal_pending(current)) 283 flush_signals(current); 284 wait_event_interruptible(t->wq, 285 t->wanted_cluster != -1 || 286 kthread_should_stop()); 287 288 spin_lock(&t->lock); 289 cluster = t->wanted_cluster; 290 completer = t->completer; 291 completer_cookie = t->completer_cookie; 292 t->wanted_cluster = -1; 293 t->completer = NULL; 294 spin_unlock(&t->lock); 295 296 if (cluster != -1) { 297 bL_switch_to(cluster); 298 299 if (completer) 300 completer(completer_cookie); 301 } 302 } while (!kthread_should_stop()); 303 304 return 0; 305 } 306 307 static struct task_struct *bL_switcher_thread_create(int cpu, void *arg) 308 { 309 struct task_struct *task; 310 311 task = kthread_create_on_node(bL_switcher_thread, arg, 312 cpu_to_node(cpu), "kswitcher_%d", cpu); 313 if (!IS_ERR(task)) { 314 kthread_bind(task, cpu); 315 wake_up_process(task); 316 } else 317 pr_err("%s failed for CPU %d\n", __func__, cpu); 318 return task; 319 } 320 321 /* 322 * bL_switch_request_cb - Switch to a specific cluster for the given CPU, 323 * with completion notification via a callback 324 * 325 * @cpu: the CPU to switch 326 * @new_cluster_id: the ID of the cluster to switch to. 327 * @completer: switch completion callback. if non-NULL, 328 * @completer(@completer_cookie) will be called on completion of 329 * the switch, in non-atomic context. 330 * @completer_cookie: opaque context argument for @completer. 331 * 332 * This function causes a cluster switch on the given CPU by waking up 333 * the appropriate switcher thread. This function may or may not return 334 * before the switch has occurred. 335 * 336 * If a @completer callback function is supplied, it will be called when 337 * the switch is complete. This can be used to determine asynchronously 338 * when the switch is complete, regardless of when bL_switch_request() 339 * returns. When @completer is supplied, no new switch request is permitted 340 * for the affected CPU until after the switch is complete, and @completer 341 * has returned. 342 */ 343 int bL_switch_request_cb(unsigned int cpu, unsigned int new_cluster_id, 344 bL_switch_completion_handler completer, 345 void *completer_cookie) 346 { 347 struct bL_thread *t; 348 349 if (cpu >= ARRAY_SIZE(bL_threads)) { 350 pr_err("%s: cpu %d out of bounds\n", __func__, cpu); 351 return -EINVAL; 352 } 353 354 t = &bL_threads[cpu]; 355 356 if (IS_ERR(t->task)) 357 return PTR_ERR(t->task); 358 if (!t->task) 359 return -ESRCH; 360 361 spin_lock(&t->lock); 362 if (t->completer) { 363 spin_unlock(&t->lock); 364 return -EBUSY; 365 } 366 t->completer = completer; 367 t->completer_cookie = completer_cookie; 368 t->wanted_cluster = new_cluster_id; 369 spin_unlock(&t->lock); 370 wake_up(&t->wq); 371 return 0; 372 } 373 EXPORT_SYMBOL_GPL(bL_switch_request_cb); 374 375 /* 376 * Activation and configuration code. 377 */ 378 379 static DEFINE_MUTEX(bL_switcher_activation_lock); 380 static BLOCKING_NOTIFIER_HEAD(bL_activation_notifier); 381 static unsigned int bL_switcher_active; 382 static unsigned int bL_switcher_cpu_original_cluster[NR_CPUS]; 383 static cpumask_t bL_switcher_removed_logical_cpus; 384 385 int bL_switcher_register_notifier(struct notifier_block *nb) 386 { 387 return blocking_notifier_chain_register(&bL_activation_notifier, nb); 388 } 389 EXPORT_SYMBOL_GPL(bL_switcher_register_notifier); 390 391 int bL_switcher_unregister_notifier(struct notifier_block *nb) 392 { 393 return blocking_notifier_chain_unregister(&bL_activation_notifier, nb); 394 } 395 EXPORT_SYMBOL_GPL(bL_switcher_unregister_notifier); 396 397 static int bL_activation_notify(unsigned long val) 398 { 399 int ret; 400 401 ret = blocking_notifier_call_chain(&bL_activation_notifier, val, NULL); 402 if (ret & NOTIFY_STOP_MASK) 403 pr_err("%s: notifier chain failed with status 0x%x\n", 404 __func__, ret); 405 return notifier_to_errno(ret); 406 } 407 408 static void bL_switcher_restore_cpus(void) 409 { 410 int i; 411 412 for_each_cpu(i, &bL_switcher_removed_logical_cpus) { 413 struct device *cpu_dev = get_cpu_device(i); 414 int ret = device_online(cpu_dev); 415 if (ret) 416 dev_err(cpu_dev, "switcher: unable to restore CPU\n"); 417 } 418 } 419 420 static int bL_switcher_halve_cpus(void) 421 { 422 int i, j, cluster_0, gic_id, ret; 423 unsigned int cpu, cluster, mask; 424 cpumask_t available_cpus; 425 426 /* First pass to validate what we have */ 427 mask = 0; 428 for_each_online_cpu(i) { 429 cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0); 430 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1); 431 if (cluster >= 2) { 432 pr_err("%s: only dual cluster systems are supported\n", __func__); 433 return -EINVAL; 434 } 435 if (WARN_ON(cpu >= MAX_CPUS_PER_CLUSTER)) 436 return -EINVAL; 437 mask |= (1 << cluster); 438 } 439 if (mask != 3) { 440 pr_err("%s: no CPU pairing possible\n", __func__); 441 return -EINVAL; 442 } 443 444 /* 445 * Now let's do the pairing. We match each CPU with another CPU 446 * from a different cluster. To get a uniform scheduling behavior 447 * without fiddling with CPU topology and compute capacity data, 448 * we'll use logical CPUs initially belonging to the same cluster. 449 */ 450 memset(bL_switcher_cpu_pairing, -1, sizeof(bL_switcher_cpu_pairing)); 451 cpumask_copy(&available_cpus, cpu_online_mask); 452 cluster_0 = -1; 453 for_each_cpu(i, &available_cpus) { 454 int match = -1; 455 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1); 456 if (cluster_0 == -1) 457 cluster_0 = cluster; 458 if (cluster != cluster_0) 459 continue; 460 cpumask_clear_cpu(i, &available_cpus); 461 for_each_cpu(j, &available_cpus) { 462 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(j), 1); 463 /* 464 * Let's remember the last match to create "odd" 465 * pairings on purpose in order for other code not 466 * to assume any relation between physical and 467 * logical CPU numbers. 468 */ 469 if (cluster != cluster_0) 470 match = j; 471 } 472 if (match != -1) { 473 bL_switcher_cpu_pairing[i] = match; 474 cpumask_clear_cpu(match, &available_cpus); 475 pr_info("CPU%d paired with CPU%d\n", i, match); 476 } 477 } 478 479 /* 480 * Now we disable the unwanted CPUs i.e. everything that has no 481 * pairing information (that includes the pairing counterparts). 482 */ 483 cpumask_clear(&bL_switcher_removed_logical_cpus); 484 for_each_online_cpu(i) { 485 cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0); 486 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1); 487 488 /* Let's take note of the GIC ID for this CPU */ 489 gic_id = gic_get_cpu_id(i); 490 if (gic_id < 0) { 491 pr_err("%s: bad GIC ID for CPU %d\n", __func__, i); 492 bL_switcher_restore_cpus(); 493 return -EINVAL; 494 } 495 bL_gic_id[cpu][cluster] = gic_id; 496 pr_info("GIC ID for CPU %u cluster %u is %u\n", 497 cpu, cluster, gic_id); 498 499 if (bL_switcher_cpu_pairing[i] != -1) { 500 bL_switcher_cpu_original_cluster[i] = cluster; 501 continue; 502 } 503 504 ret = device_offline(get_cpu_device(i)); 505 if (ret) { 506 bL_switcher_restore_cpus(); 507 return ret; 508 } 509 cpumask_set_cpu(i, &bL_switcher_removed_logical_cpus); 510 } 511 512 return 0; 513 } 514 515 /* Determine the logical CPU a given physical CPU is grouped on. */ 516 int bL_switcher_get_logical_index(u32 mpidr) 517 { 518 int cpu; 519 520 if (!bL_switcher_active) 521 return -EUNATCH; 522 523 mpidr &= MPIDR_HWID_BITMASK; 524 for_each_online_cpu(cpu) { 525 int pairing = bL_switcher_cpu_pairing[cpu]; 526 if (pairing == -1) 527 continue; 528 if ((mpidr == cpu_logical_map(cpu)) || 529 (mpidr == cpu_logical_map(pairing))) 530 return cpu; 531 } 532 return -EINVAL; 533 } 534 535 static void bL_switcher_trace_trigger_cpu(void *__always_unused info) 536 { 537 trace_cpu_migrate_current(ktime_get_real_ns(), read_mpidr()); 538 } 539 540 int bL_switcher_trace_trigger(void) 541 { 542 int ret; 543 544 preempt_disable(); 545 546 bL_switcher_trace_trigger_cpu(NULL); 547 ret = smp_call_function(bL_switcher_trace_trigger_cpu, NULL, true); 548 549 preempt_enable(); 550 551 return ret; 552 } 553 EXPORT_SYMBOL_GPL(bL_switcher_trace_trigger); 554 555 static int bL_switcher_enable(void) 556 { 557 int cpu, ret; 558 559 mutex_lock(&bL_switcher_activation_lock); 560 lock_device_hotplug(); 561 if (bL_switcher_active) { 562 unlock_device_hotplug(); 563 mutex_unlock(&bL_switcher_activation_lock); 564 return 0; 565 } 566 567 pr_info("big.LITTLE switcher initializing\n"); 568 569 ret = bL_activation_notify(BL_NOTIFY_PRE_ENABLE); 570 if (ret) 571 goto error; 572 573 ret = bL_switcher_halve_cpus(); 574 if (ret) 575 goto error; 576 577 bL_switcher_trace_trigger(); 578 579 for_each_online_cpu(cpu) { 580 struct bL_thread *t = &bL_threads[cpu]; 581 spin_lock_init(&t->lock); 582 init_waitqueue_head(&t->wq); 583 init_completion(&t->started); 584 t->wanted_cluster = -1; 585 t->task = bL_switcher_thread_create(cpu, t); 586 } 587 588 bL_switcher_active = 1; 589 bL_activation_notify(BL_NOTIFY_POST_ENABLE); 590 pr_info("big.LITTLE switcher initialized\n"); 591 goto out; 592 593 error: 594 pr_warn("big.LITTLE switcher initialization failed\n"); 595 bL_activation_notify(BL_NOTIFY_POST_DISABLE); 596 597 out: 598 unlock_device_hotplug(); 599 mutex_unlock(&bL_switcher_activation_lock); 600 return ret; 601 } 602 603 #ifdef CONFIG_SYSFS 604 605 static void bL_switcher_disable(void) 606 { 607 unsigned int cpu, cluster; 608 struct bL_thread *t; 609 struct task_struct *task; 610 611 mutex_lock(&bL_switcher_activation_lock); 612 lock_device_hotplug(); 613 614 if (!bL_switcher_active) 615 goto out; 616 617 if (bL_activation_notify(BL_NOTIFY_PRE_DISABLE) != 0) { 618 bL_activation_notify(BL_NOTIFY_POST_ENABLE); 619 goto out; 620 } 621 622 bL_switcher_active = 0; 623 624 /* 625 * To deactivate the switcher, we must shut down the switcher 626 * threads to prevent any other requests from being accepted. 627 * Then, if the final cluster for given logical CPU is not the 628 * same as the original one, we'll recreate a switcher thread 629 * just for the purpose of switching the CPU back without any 630 * possibility for interference from external requests. 631 */ 632 for_each_online_cpu(cpu) { 633 t = &bL_threads[cpu]; 634 task = t->task; 635 t->task = NULL; 636 if (!task || IS_ERR(task)) 637 continue; 638 kthread_stop(task); 639 /* no more switch may happen on this CPU at this point */ 640 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1); 641 if (cluster == bL_switcher_cpu_original_cluster[cpu]) 642 continue; 643 init_completion(&t->started); 644 t->wanted_cluster = bL_switcher_cpu_original_cluster[cpu]; 645 task = bL_switcher_thread_create(cpu, t); 646 if (!IS_ERR(task)) { 647 wait_for_completion(&t->started); 648 kthread_stop(task); 649 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1); 650 if (cluster == bL_switcher_cpu_original_cluster[cpu]) 651 continue; 652 } 653 /* If execution gets here, we're in trouble. */ 654 pr_crit("%s: unable to restore original cluster for CPU %d\n", 655 __func__, cpu); 656 pr_crit("%s: CPU %d can't be restored\n", 657 __func__, bL_switcher_cpu_pairing[cpu]); 658 cpumask_clear_cpu(bL_switcher_cpu_pairing[cpu], 659 &bL_switcher_removed_logical_cpus); 660 } 661 662 bL_switcher_restore_cpus(); 663 bL_switcher_trace_trigger(); 664 665 bL_activation_notify(BL_NOTIFY_POST_DISABLE); 666 667 out: 668 unlock_device_hotplug(); 669 mutex_unlock(&bL_switcher_activation_lock); 670 } 671 672 static ssize_t bL_switcher_active_show(struct kobject *kobj, 673 struct kobj_attribute *attr, char *buf) 674 { 675 return sprintf(buf, "%u\n", bL_switcher_active); 676 } 677 678 static ssize_t bL_switcher_active_store(struct kobject *kobj, 679 struct kobj_attribute *attr, const char *buf, size_t count) 680 { 681 int ret; 682 683 switch (buf[0]) { 684 case '0': 685 bL_switcher_disable(); 686 ret = 0; 687 break; 688 case '1': 689 ret = bL_switcher_enable(); 690 break; 691 default: 692 ret = -EINVAL; 693 } 694 695 return (ret >= 0) ? count : ret; 696 } 697 698 static ssize_t bL_switcher_trace_trigger_store(struct kobject *kobj, 699 struct kobj_attribute *attr, const char *buf, size_t count) 700 { 701 int ret = bL_switcher_trace_trigger(); 702 703 return ret ? ret : count; 704 } 705 706 static struct kobj_attribute bL_switcher_active_attr = 707 __ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store); 708 709 static struct kobj_attribute bL_switcher_trace_trigger_attr = 710 __ATTR(trace_trigger, 0200, NULL, bL_switcher_trace_trigger_store); 711 712 static struct attribute *bL_switcher_attrs[] = { 713 &bL_switcher_active_attr.attr, 714 &bL_switcher_trace_trigger_attr.attr, 715 NULL, 716 }; 717 718 static struct attribute_group bL_switcher_attr_group = { 719 .attrs = bL_switcher_attrs, 720 }; 721 722 static struct kobject *bL_switcher_kobj; 723 724 static int __init bL_switcher_sysfs_init(void) 725 { 726 int ret; 727 728 bL_switcher_kobj = kobject_create_and_add("bL_switcher", kernel_kobj); 729 if (!bL_switcher_kobj) 730 return -ENOMEM; 731 ret = sysfs_create_group(bL_switcher_kobj, &bL_switcher_attr_group); 732 if (ret) 733 kobject_put(bL_switcher_kobj); 734 return ret; 735 } 736 737 #endif /* CONFIG_SYSFS */ 738 739 bool bL_switcher_get_enabled(void) 740 { 741 mutex_lock(&bL_switcher_activation_lock); 742 743 return bL_switcher_active; 744 } 745 EXPORT_SYMBOL_GPL(bL_switcher_get_enabled); 746 747 void bL_switcher_put_enabled(void) 748 { 749 mutex_unlock(&bL_switcher_activation_lock); 750 } 751 EXPORT_SYMBOL_GPL(bL_switcher_put_enabled); 752 753 /* 754 * Veto any CPU hotplug operation on those CPUs we've removed 755 * while the switcher is active. 756 * We're just not ready to deal with that given the trickery involved. 757 */ 758 static int bL_switcher_cpu_pre(unsigned int cpu) 759 { 760 int pairing; 761 762 if (!bL_switcher_active) 763 return 0; 764 765 pairing = bL_switcher_cpu_pairing[cpu]; 766 767 if (pairing == -1) 768 return -EINVAL; 769 return 0; 770 } 771 772 static bool no_bL_switcher; 773 core_param(no_bL_switcher, no_bL_switcher, bool, 0644); 774 775 static int __init bL_switcher_init(void) 776 { 777 int ret; 778 779 if (!mcpm_is_available()) 780 return -ENODEV; 781 782 cpuhp_setup_state_nocalls(CPUHP_ARM_BL_PREPARE, "arm/bl:prepare", 783 bL_switcher_cpu_pre, NULL); 784 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "arm/bl:predown", 785 NULL, bL_switcher_cpu_pre); 786 if (ret < 0) { 787 cpuhp_remove_state_nocalls(CPUHP_ARM_BL_PREPARE); 788 pr_err("bL_switcher: Failed to allocate a hotplug state\n"); 789 return ret; 790 } 791 if (!no_bL_switcher) { 792 ret = bL_switcher_enable(); 793 if (ret) 794 return ret; 795 } 796 797 #ifdef CONFIG_SYSFS 798 ret = bL_switcher_sysfs_init(); 799 if (ret) 800 pr_err("%s: unable to create sysfs entry\n", __func__); 801 #endif 802 803 return 0; 804 } 805 806 late_initcall(bL_switcher_init); 807