2 * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver
4 * Created by: Nicolas Pitre, March 2012
5 * Copyright: (C) 2012-2013 Linaro Limited
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
12 #include <linux/atomic.h>
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/sched.h>
17 #include <linux/interrupt.h>
18 #include <linux/cpu_pm.h>
19 #include <linux/cpu.h>
20 #include <linux/cpumask.h>
21 #include <linux/kthread.h>
22 #include <linux/wait.h>
23 #include <linux/clockchips.h>
24 #include <linux/hrtimer.h>
25 #include <linux/tick.h>
26 #include <linux/notifier.h>
28 #include <linux/mutex.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>
35 #include <asm/smp_plat.h>
36 #include <asm/suspend.h>
38 #include <asm/bL_switcher.h>
42 * Use our own MPIDR accessors as the generic ones in asm/cputype.h have
43 * __attribute_const__ and we don't want the compiler to assume any
44 * constness here as the value _does_ change along some code paths.
47 static int read_mpidr(void)
50 asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (id
));
51 return id
& MPIDR_HWID_BITMASK
;
55 * bL switcher core code.
58 static void bL_do_switch(void *_arg
)
60 unsigned ib_mpidr
, ib_cpu
, ib_cluster
;
61 long volatile handshake
, **handshake_ptr
= _arg
;
63 pr_debug("%s\n", __func__
);
65 ib_mpidr
= cpu_logical_map(smp_processor_id());
66 ib_cpu
= MPIDR_AFFINITY_LEVEL(ib_mpidr
, 0);
67 ib_cluster
= MPIDR_AFFINITY_LEVEL(ib_mpidr
, 1);
69 /* Advertise our handshake location */
72 *handshake_ptr
= &handshake
;
77 * Our state has been saved at this point. Let's release our
80 mcpm_set_entry_vector(ib_cpu
, ib_cluster
, cpu_resume
);
84 * From this point, we must assume that our counterpart CPU might
85 * have taken over in its parallel world already, as if execution
86 * just returned from cpu_suspend(). It is therefore important to
87 * be very careful not to make any change the other guy is not
88 * expecting. This is why we need stack isolation.
90 * Fancy under cover tasks could be performed here. For now
95 * Let's wait until our inbound is alive.
102 /* Let's put ourself down. */
103 mcpm_cpu_power_down();
105 /* should never get here */
110 * Stack isolation. To ensure 'current' remains valid, we just use another
111 * piece of our thread's stack space which should be fairly lightly used.
112 * The selected area starts just above the thread_info structure located
113 * at the very bottom of the stack, aligned to a cache line, and indexed
114 * with the cluster number.
116 #define STACK_SIZE 512
117 extern void call_with_stack(void (*fn
)(void *), void *arg
, void *sp
);
118 static int bL_switchpoint(unsigned long _arg
)
120 unsigned int mpidr
= read_mpidr();
121 unsigned int clusterid
= MPIDR_AFFINITY_LEVEL(mpidr
, 1);
122 void *stack
= current_thread_info() + 1;
123 stack
= PTR_ALIGN(stack
, L1_CACHE_BYTES
);
124 stack
+= clusterid
* STACK_SIZE
+ STACK_SIZE
;
125 call_with_stack(bL_do_switch
, (void *)_arg
, stack
);
130 * Generic switcher interface
133 static unsigned int bL_gic_id
[MAX_CPUS_PER_CLUSTER
][MAX_NR_CLUSTERS
];
134 static int bL_switcher_cpu_pairing
[NR_CPUS
];
137 * bL_switch_to - Switch to a specific cluster for the current CPU
138 * @new_cluster_id: the ID of the cluster to switch to.
140 * This function must be called on the CPU to be switched.
141 * Returns 0 on success, else a negative status code.
143 static int bL_switch_to(unsigned int new_cluster_id
)
145 unsigned int mpidr
, this_cpu
, that_cpu
;
146 unsigned int ob_mpidr
, ob_cpu
, ob_cluster
, ib_mpidr
, ib_cpu
, ib_cluster
;
147 struct tick_device
*tdev
;
148 enum clock_event_mode tdev_mode
;
149 long volatile *handshake_ptr
;
152 this_cpu
= smp_processor_id();
153 ob_mpidr
= read_mpidr();
154 ob_cpu
= MPIDR_AFFINITY_LEVEL(ob_mpidr
, 0);
155 ob_cluster
= MPIDR_AFFINITY_LEVEL(ob_mpidr
, 1);
156 BUG_ON(cpu_logical_map(this_cpu
) != ob_mpidr
);
158 if (new_cluster_id
== ob_cluster
)
161 that_cpu
= bL_switcher_cpu_pairing
[this_cpu
];
162 ib_mpidr
= cpu_logical_map(that_cpu
);
163 ib_cpu
= MPIDR_AFFINITY_LEVEL(ib_mpidr
, 0);
164 ib_cluster
= MPIDR_AFFINITY_LEVEL(ib_mpidr
, 1);
166 pr_debug("before switch: CPU %d MPIDR %#x -> %#x\n",
167 this_cpu
, ob_mpidr
, ib_mpidr
);
169 /* Close the gate for our entry vectors */
170 mcpm_set_entry_vector(ob_cpu
, ob_cluster
, NULL
);
171 mcpm_set_entry_vector(ib_cpu
, ib_cluster
, NULL
);
174 * Let's wake up the inbound CPU now in case it requires some delay
175 * to come online, but leave it gated in our entry vector code.
177 ret
= mcpm_cpu_power_up(ib_cpu
, ib_cluster
);
179 pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__
, ret
);
184 * From this point we are entering the switch critical zone
185 * and can't take any interrupts anymore.
190 /* redirect GIC's SGIs to our counterpart */
191 gic_migrate_target(bL_gic_id
[ib_cpu
][ib_cluster
]);
194 * Raise a SGI on the inbound CPU to make sure it doesn't stall
195 * in a possible WFI, such as in mcpm_power_down().
197 arch_send_wakeup_ipi_mask(cpumask_of(this_cpu
));
199 tdev
= tick_get_device(this_cpu
);
200 if (tdev
&& !cpumask_equal(tdev
->evtdev
->cpumask
, cpumask_of(this_cpu
)))
203 tdev_mode
= tdev
->evtdev
->mode
;
204 clockevents_set_mode(tdev
->evtdev
, CLOCK_EVT_MODE_SHUTDOWN
);
207 ret
= cpu_pm_enter();
209 /* we can not tolerate errors at this point */
211 panic("%s: cpu_pm_enter() returned %d\n", __func__
, ret
);
213 /* Swap the physical CPUs in the logical map for this logical CPU. */
214 cpu_logical_map(this_cpu
) = ib_mpidr
;
215 cpu_logical_map(that_cpu
) = ob_mpidr
;
217 /* Let's do the actual CPU switch. */
218 ret
= cpu_suspend((unsigned long)&handshake_ptr
, bL_switchpoint
);
220 panic("%s: cpu_suspend() returned %d\n", __func__
, ret
);
222 /* We are executing on the inbound CPU at this point */
223 mpidr
= read_mpidr();
224 pr_debug("after switch: CPU %d MPIDR %#x\n", this_cpu
, mpidr
);
225 BUG_ON(mpidr
!= ib_mpidr
);
227 mcpm_cpu_powered_up();
232 clockevents_set_mode(tdev
->evtdev
, tdev_mode
);
233 clockevents_program_event(tdev
->evtdev
,
234 tdev
->evtdev
->next_event
, 1);
244 pr_err("%s exiting with error %d\n", __func__
, ret
);
250 struct task_struct
*task
;
251 wait_queue_head_t wq
;
253 struct completion started
;
254 bL_switch_completion_handler completer
;
255 void *completer_cookie
;
258 static struct bL_thread bL_threads
[NR_CPUS
];
260 static int bL_switcher_thread(void *arg
)
262 struct bL_thread
*t
= arg
;
263 struct sched_param param
= { .sched_priority
= 1 };
265 bL_switch_completion_handler completer
;
266 void *completer_cookie
;
268 sched_setscheduler_nocheck(current
, SCHED_FIFO
, ¶m
);
269 complete(&t
->started
);
272 if (signal_pending(current
))
273 flush_signals(current
);
274 wait_event_interruptible(t
->wq
,
275 t
->wanted_cluster
!= -1 ||
276 kthread_should_stop());
279 cluster
= t
->wanted_cluster
;
280 completer
= t
->completer
;
281 completer_cookie
= t
->completer_cookie
;
282 t
->wanted_cluster
= -1;
284 spin_unlock(&t
->lock
);
287 bL_switch_to(cluster
);
290 completer(completer_cookie
);
292 } while (!kthread_should_stop());
297 static struct task_struct
*bL_switcher_thread_create(int cpu
, void *arg
)
299 struct task_struct
*task
;
301 task
= kthread_create_on_node(bL_switcher_thread
, arg
,
302 cpu_to_node(cpu
), "kswitcher_%d", cpu
);
304 kthread_bind(task
, cpu
);
305 wake_up_process(task
);
307 pr_err("%s failed for CPU %d\n", __func__
, cpu
);
312 * bL_switch_request_cb - Switch to a specific cluster for the given CPU,
313 * with completion notification via a callback
315 * @cpu: the CPU to switch
316 * @new_cluster_id: the ID of the cluster to switch to.
317 * @completer: switch completion callback. if non-NULL,
318 * @completer(@completer_cookie) will be called on completion of
319 * the switch, in non-atomic context.
320 * @completer_cookie: opaque context argument for @completer.
322 * This function causes a cluster switch on the given CPU by waking up
323 * the appropriate switcher thread. This function may or may not return
324 * before the switch has occurred.
326 * If a @completer callback function is supplied, it will be called when
327 * the switch is complete. This can be used to determine asynchronously
328 * when the switch is complete, regardless of when bL_switch_request()
329 * returns. When @completer is supplied, no new switch request is permitted
330 * for the affected CPU until after the switch is complete, and @completer
333 int bL_switch_request_cb(unsigned int cpu
, unsigned int new_cluster_id
,
334 bL_switch_completion_handler completer
,
335 void *completer_cookie
)
339 if (cpu
>= ARRAY_SIZE(bL_threads
)) {
340 pr_err("%s: cpu %d out of bounds\n", __func__
, cpu
);
344 t
= &bL_threads
[cpu
];
347 return PTR_ERR(t
->task
);
353 spin_unlock(&t
->lock
);
356 t
->completer
= completer
;
357 t
->completer_cookie
= completer_cookie
;
358 t
->wanted_cluster
= new_cluster_id
;
359 spin_unlock(&t
->lock
);
363 EXPORT_SYMBOL_GPL(bL_switch_request_cb
);
366 * Activation and configuration code.
369 static DEFINE_MUTEX(bL_switcher_activation_lock
);
370 static BLOCKING_NOTIFIER_HEAD(bL_activation_notifier
);
371 static unsigned int bL_switcher_active
;
372 static unsigned int bL_switcher_cpu_original_cluster
[NR_CPUS
];
373 static cpumask_t bL_switcher_removed_logical_cpus
;
375 int bL_switcher_register_notifier(struct notifier_block
*nb
)
377 return blocking_notifier_chain_register(&bL_activation_notifier
, nb
);
379 EXPORT_SYMBOL_GPL(bL_switcher_register_notifier
);
381 int bL_switcher_unregister_notifier(struct notifier_block
*nb
)
383 return blocking_notifier_chain_unregister(&bL_activation_notifier
, nb
);
385 EXPORT_SYMBOL_GPL(bL_switcher_unregister_notifier
);
387 static int bL_activation_notify(unsigned long val
)
391 ret
= blocking_notifier_call_chain(&bL_activation_notifier
, val
, NULL
);
392 if (ret
& NOTIFY_STOP_MASK
)
393 pr_err("%s: notifier chain failed with status 0x%x\n",
395 return notifier_to_errno(ret
);
398 static void bL_switcher_restore_cpus(void)
402 for_each_cpu(i
, &bL_switcher_removed_logical_cpus
)
406 static int bL_switcher_halve_cpus(void)
408 int i
, j
, cluster_0
, gic_id
, ret
;
409 unsigned int cpu
, cluster
, mask
;
410 cpumask_t available_cpus
;
412 /* First pass to validate what we have */
414 for_each_online_cpu(i
) {
415 cpu
= MPIDR_AFFINITY_LEVEL(cpu_logical_map(i
), 0);
416 cluster
= MPIDR_AFFINITY_LEVEL(cpu_logical_map(i
), 1);
418 pr_err("%s: only dual cluster systems are supported\n", __func__
);
421 if (WARN_ON(cpu
>= MAX_CPUS_PER_CLUSTER
))
423 mask
|= (1 << cluster
);
426 pr_err("%s: no CPU pairing possible\n", __func__
);
431 * Now let's do the pairing. We match each CPU with another CPU
432 * from a different cluster. To get a uniform scheduling behavior
433 * without fiddling with CPU topology and compute capacity data,
434 * we'll use logical CPUs initially belonging to the same cluster.
436 memset(bL_switcher_cpu_pairing
, -1, sizeof(bL_switcher_cpu_pairing
));
437 cpumask_copy(&available_cpus
, cpu_online_mask
);
439 for_each_cpu(i
, &available_cpus
) {
441 cluster
= MPIDR_AFFINITY_LEVEL(cpu_logical_map(i
), 1);
444 if (cluster
!= cluster_0
)
446 cpumask_clear_cpu(i
, &available_cpus
);
447 for_each_cpu(j
, &available_cpus
) {
448 cluster
= MPIDR_AFFINITY_LEVEL(cpu_logical_map(j
), 1);
450 * Let's remember the last match to create "odd"
451 * pairings on purpose in order for other code not
452 * to assume any relation between physical and
453 * logical CPU numbers.
455 if (cluster
!= cluster_0
)
459 bL_switcher_cpu_pairing
[i
] = match
;
460 cpumask_clear_cpu(match
, &available_cpus
);
461 pr_info("CPU%d paired with CPU%d\n", i
, match
);
466 * Now we disable the unwanted CPUs i.e. everything that has no
467 * pairing information (that includes the pairing counterparts).
469 cpumask_clear(&bL_switcher_removed_logical_cpus
);
470 for_each_online_cpu(i
) {
471 cpu
= MPIDR_AFFINITY_LEVEL(cpu_logical_map(i
), 0);
472 cluster
= MPIDR_AFFINITY_LEVEL(cpu_logical_map(i
), 1);
474 /* Let's take note of the GIC ID for this CPU */
475 gic_id
= gic_get_cpu_id(i
);
477 pr_err("%s: bad GIC ID for CPU %d\n", __func__
, i
);
478 bL_switcher_restore_cpus();
481 bL_gic_id
[cpu
][cluster
] = gic_id
;
482 pr_info("GIC ID for CPU %u cluster %u is %u\n",
483 cpu
, cluster
, gic_id
);
485 if (bL_switcher_cpu_pairing
[i
] != -1) {
486 bL_switcher_cpu_original_cluster
[i
] = cluster
;
492 bL_switcher_restore_cpus();
495 cpumask_set_cpu(i
, &bL_switcher_removed_logical_cpus
);
501 static int bL_switcher_enable(void)
505 mutex_lock(&bL_switcher_activation_lock
);
506 cpu_hotplug_driver_lock();
507 if (bL_switcher_active
) {
508 cpu_hotplug_driver_unlock();
509 mutex_unlock(&bL_switcher_activation_lock
);
513 pr_info("big.LITTLE switcher initializing\n");
515 ret
= bL_activation_notify(BL_NOTIFY_PRE_ENABLE
);
519 ret
= bL_switcher_halve_cpus();
523 for_each_online_cpu(cpu
) {
524 struct bL_thread
*t
= &bL_threads
[cpu
];
525 spin_lock_init(&t
->lock
);
526 init_waitqueue_head(&t
->wq
);
527 init_completion(&t
->started
);
528 t
->wanted_cluster
= -1;
529 t
->task
= bL_switcher_thread_create(cpu
, t
);
532 bL_switcher_active
= 1;
533 bL_activation_notify(BL_NOTIFY_POST_ENABLE
);
534 pr_info("big.LITTLE switcher initialized\n");
538 pr_warn("big.LITTLE switcher initialization failed\n");
539 bL_activation_notify(BL_NOTIFY_POST_DISABLE
);
542 cpu_hotplug_driver_unlock();
543 mutex_unlock(&bL_switcher_activation_lock
);
549 static void bL_switcher_disable(void)
551 unsigned int cpu
, cluster
;
553 struct task_struct
*task
;
555 mutex_lock(&bL_switcher_activation_lock
);
556 cpu_hotplug_driver_lock();
558 if (!bL_switcher_active
)
561 if (bL_activation_notify(BL_NOTIFY_PRE_DISABLE
) != 0) {
562 bL_activation_notify(BL_NOTIFY_POST_ENABLE
);
566 bL_switcher_active
= 0;
569 * To deactivate the switcher, we must shut down the switcher
570 * threads to prevent any other requests from being accepted.
571 * Then, if the final cluster for given logical CPU is not the
572 * same as the original one, we'll recreate a switcher thread
573 * just for the purpose of switching the CPU back without any
574 * possibility for interference from external requests.
576 for_each_online_cpu(cpu
) {
577 t
= &bL_threads
[cpu
];
580 if (!task
|| IS_ERR(task
))
583 /* no more switch may happen on this CPU at this point */
584 cluster
= MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu
), 1);
585 if (cluster
== bL_switcher_cpu_original_cluster
[cpu
])
587 init_completion(&t
->started
);
588 t
->wanted_cluster
= bL_switcher_cpu_original_cluster
[cpu
];
589 task
= bL_switcher_thread_create(cpu
, t
);
591 wait_for_completion(&t
->started
);
593 cluster
= MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu
), 1);
594 if (cluster
== bL_switcher_cpu_original_cluster
[cpu
])
597 /* If execution gets here, we're in trouble. */
598 pr_crit("%s: unable to restore original cluster for CPU %d\n",
600 pr_crit("%s: CPU %d can't be restored\n",
601 __func__
, bL_switcher_cpu_pairing
[cpu
]);
602 cpumask_clear_cpu(bL_switcher_cpu_pairing
[cpu
],
603 &bL_switcher_removed_logical_cpus
);
606 bL_switcher_restore_cpus();
607 bL_activation_notify(BL_NOTIFY_POST_DISABLE
);
610 cpu_hotplug_driver_unlock();
611 mutex_unlock(&bL_switcher_activation_lock
);
614 static ssize_t
bL_switcher_active_show(struct kobject
*kobj
,
615 struct kobj_attribute
*attr
, char *buf
)
617 return sprintf(buf
, "%u\n", bL_switcher_active
);
620 static ssize_t
bL_switcher_active_store(struct kobject
*kobj
,
621 struct kobj_attribute
*attr
, const char *buf
, size_t count
)
627 bL_switcher_disable();
631 ret
= bL_switcher_enable();
637 return (ret
>= 0) ? count
: ret
;
640 static struct kobj_attribute bL_switcher_active_attr
=
641 __ATTR(active
, 0644, bL_switcher_active_show
, bL_switcher_active_store
);
643 static struct attribute
*bL_switcher_attrs
[] = {
644 &bL_switcher_active_attr
.attr
,
648 static struct attribute_group bL_switcher_attr_group
= {
649 .attrs
= bL_switcher_attrs
,
652 static struct kobject
*bL_switcher_kobj
;
654 static int __init
bL_switcher_sysfs_init(void)
658 bL_switcher_kobj
= kobject_create_and_add("bL_switcher", kernel_kobj
);
659 if (!bL_switcher_kobj
)
661 ret
= sysfs_create_group(bL_switcher_kobj
, &bL_switcher_attr_group
);
663 kobject_put(bL_switcher_kobj
);
667 #endif /* CONFIG_SYSFS */
669 bool bL_switcher_get_enabled(void)
671 mutex_lock(&bL_switcher_activation_lock
);
673 return bL_switcher_active
;
675 EXPORT_SYMBOL_GPL(bL_switcher_get_enabled
);
677 void bL_switcher_put_enabled(void)
679 mutex_unlock(&bL_switcher_activation_lock
);
681 EXPORT_SYMBOL_GPL(bL_switcher_put_enabled
);
684 * Veto any CPU hotplug operation on those CPUs we've removed
685 * while the switcher is active.
686 * We're just not ready to deal with that given the trickery involved.
688 static int bL_switcher_hotplug_callback(struct notifier_block
*nfb
,
689 unsigned long action
, void *hcpu
)
691 if (bL_switcher_active
) {
692 int pairing
= bL_switcher_cpu_pairing
[(unsigned long)hcpu
];
693 switch (action
& 0xf) {
695 case CPU_DOWN_PREPARE
:
703 static bool no_bL_switcher
;
704 core_param(no_bL_switcher
, no_bL_switcher
, bool, 0644);
706 static int __init
bL_switcher_init(void)
710 if (MAX_NR_CLUSTERS
!= 2) {
711 pr_err("%s: only dual cluster systems are supported\n", __func__
);
715 cpu_notifier(bL_switcher_hotplug_callback
, 0);
717 if (!no_bL_switcher
) {
718 ret
= bL_switcher_enable();
724 ret
= bL_switcher_sysfs_init();
726 pr_err("%s: unable to create sysfs entry\n", __func__
);
732 late_initcall(bL_switcher_init
);