xref: /openbmc/linux/drivers/base/dd.c (revision e6c81cce)
1 /*
2  * drivers/base/dd.c - The core device/driver interactions.
3  *
4  * This file contains the (sometimes tricky) code that controls the
5  * interactions between devices and drivers, which primarily includes
6  * driver binding and unbinding.
7  *
8  * All of this code used to exist in drivers/base/bus.c, but was
9  * relocated to here in the name of compartmentalization (since it wasn't
10  * strictly code just for the 'struct bus_type'.
11  *
12  * Copyright (c) 2002-5 Patrick Mochel
13  * Copyright (c) 2002-3 Open Source Development Labs
14  * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
15  * Copyright (c) 2007-2009 Novell Inc.
16  *
17  * This file is released under the GPLv2
18  */
19 
20 #include <linux/device.h>
21 #include <linux/delay.h>
22 #include <linux/module.h>
23 #include <linux/kthread.h>
24 #include <linux/wait.h>
25 #include <linux/async.h>
26 #include <linux/pm_runtime.h>
27 #include <linux/pinctrl/devinfo.h>
28 
29 #include "base.h"
30 #include "power/power.h"
31 
32 /*
33  * Deferred Probe infrastructure.
34  *
35  * Sometimes driver probe order matters, but the kernel doesn't always have
36  * dependency information which means some drivers will get probed before a
37  * resource it depends on is available.  For example, an SDHCI driver may
38  * first need a GPIO line from an i2c GPIO controller before it can be
39  * initialized.  If a required resource is not available yet, a driver can
40  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
41  *
42  * Deferred probe maintains two lists of devices, a pending list and an active
43  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
44  * pending list.  A successful driver probe will trigger moving all devices
45  * from the pending to the active list so that the workqueue will eventually
46  * retry them.
47  *
48  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
49  * of the (struct device*)->p->deferred_probe pointers are manipulated
50  */
51 static DEFINE_MUTEX(deferred_probe_mutex);
52 static LIST_HEAD(deferred_probe_pending_list);
53 static LIST_HEAD(deferred_probe_active_list);
54 static struct workqueue_struct *deferred_wq;
55 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
56 
57 /*
58  * deferred_probe_work_func() - Retry probing devices in the active list.
59  */
60 static void deferred_probe_work_func(struct work_struct *work)
61 {
62 	struct device *dev;
63 	struct device_private *private;
64 	/*
65 	 * This block processes every device in the deferred 'active' list.
66 	 * Each device is removed from the active list and passed to
67 	 * bus_probe_device() to re-attempt the probe.  The loop continues
68 	 * until every device in the active list is removed and retried.
69 	 *
70 	 * Note: Once the device is removed from the list and the mutex is
71 	 * released, it is possible for the device get freed by another thread
72 	 * and cause a illegal pointer dereference.  This code uses
73 	 * get/put_device() to ensure the device structure cannot disappear
74 	 * from under our feet.
75 	 */
76 	mutex_lock(&deferred_probe_mutex);
77 	while (!list_empty(&deferred_probe_active_list)) {
78 		private = list_first_entry(&deferred_probe_active_list,
79 					typeof(*dev->p), deferred_probe);
80 		dev = private->device;
81 		list_del_init(&private->deferred_probe);
82 
83 		get_device(dev);
84 
85 		/*
86 		 * Drop the mutex while probing each device; the probe path may
87 		 * manipulate the deferred list
88 		 */
89 		mutex_unlock(&deferred_probe_mutex);
90 
91 		/*
92 		 * Force the device to the end of the dpm_list since
93 		 * the PM code assumes that the order we add things to
94 		 * the list is a good order for suspend but deferred
95 		 * probe makes that very unsafe.
96 		 */
97 		device_pm_lock();
98 		device_pm_move_last(dev);
99 		device_pm_unlock();
100 
101 		dev_dbg(dev, "Retrying from deferred list\n");
102 		bus_probe_device(dev);
103 
104 		mutex_lock(&deferred_probe_mutex);
105 
106 		put_device(dev);
107 	}
108 	mutex_unlock(&deferred_probe_mutex);
109 }
110 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
111 
112 static void driver_deferred_probe_add(struct device *dev)
113 {
114 	mutex_lock(&deferred_probe_mutex);
115 	if (list_empty(&dev->p->deferred_probe)) {
116 		dev_dbg(dev, "Added to deferred list\n");
117 		list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
118 	}
119 	mutex_unlock(&deferred_probe_mutex);
120 }
121 
122 void driver_deferred_probe_del(struct device *dev)
123 {
124 	mutex_lock(&deferred_probe_mutex);
125 	if (!list_empty(&dev->p->deferred_probe)) {
126 		dev_dbg(dev, "Removed from deferred list\n");
127 		list_del_init(&dev->p->deferred_probe);
128 	}
129 	mutex_unlock(&deferred_probe_mutex);
130 }
131 
132 static bool driver_deferred_probe_enable = false;
133 /**
134  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
135  *
136  * This functions moves all devices from the pending list to the active
137  * list and schedules the deferred probe workqueue to process them.  It
138  * should be called anytime a driver is successfully bound to a device.
139  *
140  * Note, there is a race condition in multi-threaded probe. In the case where
141  * more than one device is probing at the same time, it is possible for one
142  * probe to complete successfully while another is about to defer. If the second
143  * depends on the first, then it will get put on the pending list after the
144  * trigger event has already occured and will be stuck there.
145  *
146  * The atomic 'deferred_trigger_count' is used to determine if a successful
147  * trigger has occurred in the midst of probing a driver. If the trigger count
148  * changes in the midst of a probe, then deferred processing should be triggered
149  * again.
150  */
151 static void driver_deferred_probe_trigger(void)
152 {
153 	if (!driver_deferred_probe_enable)
154 		return;
155 
156 	/*
157 	 * A successful probe means that all the devices in the pending list
158 	 * should be triggered to be reprobed.  Move all the deferred devices
159 	 * into the active list so they can be retried by the workqueue
160 	 */
161 	mutex_lock(&deferred_probe_mutex);
162 	atomic_inc(&deferred_trigger_count);
163 	list_splice_tail_init(&deferred_probe_pending_list,
164 			      &deferred_probe_active_list);
165 	mutex_unlock(&deferred_probe_mutex);
166 
167 	/*
168 	 * Kick the re-probe thread.  It may already be scheduled, but it is
169 	 * safe to kick it again.
170 	 */
171 	queue_work(deferred_wq, &deferred_probe_work);
172 }
173 
174 /**
175  * deferred_probe_initcall() - Enable probing of deferred devices
176  *
177  * We don't want to get in the way when the bulk of drivers are getting probed.
178  * Instead, this initcall makes sure that deferred probing is delayed until
179  * late_initcall time.
180  */
181 static int deferred_probe_initcall(void)
182 {
183 	deferred_wq = create_singlethread_workqueue("deferwq");
184 	if (WARN_ON(!deferred_wq))
185 		return -ENOMEM;
186 
187 	driver_deferred_probe_enable = true;
188 	driver_deferred_probe_trigger();
189 	/* Sort as many dependencies as possible before exiting initcalls */
190 	flush_workqueue(deferred_wq);
191 	return 0;
192 }
193 late_initcall(deferred_probe_initcall);
194 
195 static void driver_bound(struct device *dev)
196 {
197 	if (klist_node_attached(&dev->p->knode_driver)) {
198 		printk(KERN_WARNING "%s: device %s already bound\n",
199 			__func__, kobject_name(&dev->kobj));
200 		return;
201 	}
202 
203 	pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
204 		 __func__, dev_name(dev));
205 
206 	klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
207 
208 	/*
209 	 * Make sure the device is no longer in one of the deferred lists and
210 	 * kick off retrying all pending devices
211 	 */
212 	driver_deferred_probe_del(dev);
213 	driver_deferred_probe_trigger();
214 
215 	if (dev->bus)
216 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
217 					     BUS_NOTIFY_BOUND_DRIVER, dev);
218 }
219 
220 static int driver_sysfs_add(struct device *dev)
221 {
222 	int ret;
223 
224 	if (dev->bus)
225 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
226 					     BUS_NOTIFY_BIND_DRIVER, dev);
227 
228 	ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
229 			  kobject_name(&dev->kobj));
230 	if (ret == 0) {
231 		ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
232 					"driver");
233 		if (ret)
234 			sysfs_remove_link(&dev->driver->p->kobj,
235 					kobject_name(&dev->kobj));
236 	}
237 	return ret;
238 }
239 
240 static void driver_sysfs_remove(struct device *dev)
241 {
242 	struct device_driver *drv = dev->driver;
243 
244 	if (drv) {
245 		sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
246 		sysfs_remove_link(&dev->kobj, "driver");
247 	}
248 }
249 
250 /**
251  * device_bind_driver - bind a driver to one device.
252  * @dev: device.
253  *
254  * Allow manual attachment of a driver to a device.
255  * Caller must have already set @dev->driver.
256  *
257  * Note that this does not modify the bus reference count
258  * nor take the bus's rwsem. Please verify those are accounted
259  * for before calling this. (It is ok to call with no other effort
260  * from a driver's probe() method.)
261  *
262  * This function must be called with the device lock held.
263  */
264 int device_bind_driver(struct device *dev)
265 {
266 	int ret;
267 
268 	ret = driver_sysfs_add(dev);
269 	if (!ret)
270 		driver_bound(dev);
271 	return ret;
272 }
273 EXPORT_SYMBOL_GPL(device_bind_driver);
274 
275 static atomic_t probe_count = ATOMIC_INIT(0);
276 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
277 
278 static int really_probe(struct device *dev, struct device_driver *drv)
279 {
280 	int ret = 0;
281 	int local_trigger_count = atomic_read(&deferred_trigger_count);
282 
283 	atomic_inc(&probe_count);
284 	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
285 		 drv->bus->name, __func__, drv->name, dev_name(dev));
286 	WARN_ON(!list_empty(&dev->devres_head));
287 
288 	dev->driver = drv;
289 
290 	/* If using pinctrl, bind pins now before probing */
291 	ret = pinctrl_bind_pins(dev);
292 	if (ret)
293 		goto probe_failed;
294 
295 	if (driver_sysfs_add(dev)) {
296 		printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
297 			__func__, dev_name(dev));
298 		goto probe_failed;
299 	}
300 
301 	if (dev->pm_domain && dev->pm_domain->activate) {
302 		ret = dev->pm_domain->activate(dev);
303 		if (ret)
304 			goto probe_failed;
305 	}
306 
307 	if (dev->bus->probe) {
308 		ret = dev->bus->probe(dev);
309 		if (ret)
310 			goto probe_failed;
311 	} else if (drv->probe) {
312 		ret = drv->probe(dev);
313 		if (ret)
314 			goto probe_failed;
315 	}
316 
317 	if (dev->pm_domain && dev->pm_domain->sync)
318 		dev->pm_domain->sync(dev);
319 
320 	driver_bound(dev);
321 	ret = 1;
322 	pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
323 		 drv->bus->name, __func__, dev_name(dev), drv->name);
324 	goto done;
325 
326 probe_failed:
327 	devres_release_all(dev);
328 	driver_sysfs_remove(dev);
329 	dev->driver = NULL;
330 	dev_set_drvdata(dev, NULL);
331 	if (dev->pm_domain && dev->pm_domain->dismiss)
332 		dev->pm_domain->dismiss(dev);
333 
334 	switch (ret) {
335 	case -EPROBE_DEFER:
336 		/* Driver requested deferred probing */
337 		dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
338 		driver_deferred_probe_add(dev);
339 		/* Did a trigger occur while probing? Need to re-trigger if yes */
340 		if (local_trigger_count != atomic_read(&deferred_trigger_count))
341 			driver_deferred_probe_trigger();
342 		break;
343 	case -ENODEV:
344 	case -ENXIO:
345 		pr_debug("%s: probe of %s rejects match %d\n",
346 			 drv->name, dev_name(dev), ret);
347 		break;
348 	default:
349 		/* driver matched but the probe failed */
350 		printk(KERN_WARNING
351 		       "%s: probe of %s failed with error %d\n",
352 		       drv->name, dev_name(dev), ret);
353 	}
354 	/*
355 	 * Ignore errors returned by ->probe so that the next driver can try
356 	 * its luck.
357 	 */
358 	ret = 0;
359 done:
360 	atomic_dec(&probe_count);
361 	wake_up(&probe_waitqueue);
362 	return ret;
363 }
364 
365 /**
366  * driver_probe_done
367  * Determine if the probe sequence is finished or not.
368  *
369  * Should somehow figure out how to use a semaphore, not an atomic variable...
370  */
371 int driver_probe_done(void)
372 {
373 	pr_debug("%s: probe_count = %d\n", __func__,
374 		 atomic_read(&probe_count));
375 	if (atomic_read(&probe_count))
376 		return -EBUSY;
377 	return 0;
378 }
379 
380 /**
381  * wait_for_device_probe
382  * Wait for device probing to be completed.
383  */
384 void wait_for_device_probe(void)
385 {
386 	/* wait for the known devices to complete their probing */
387 	wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
388 	async_synchronize_full();
389 }
390 EXPORT_SYMBOL_GPL(wait_for_device_probe);
391 
392 /**
393  * driver_probe_device - attempt to bind device & driver together
394  * @drv: driver to bind a device to
395  * @dev: device to try to bind to the driver
396  *
397  * This function returns -ENODEV if the device is not registered,
398  * 1 if the device is bound successfully and 0 otherwise.
399  *
400  * This function must be called with @dev lock held.  When called for a
401  * USB interface, @dev->parent lock must be held as well.
402  */
403 int driver_probe_device(struct device_driver *drv, struct device *dev)
404 {
405 	int ret = 0;
406 
407 	if (!device_is_registered(dev))
408 		return -ENODEV;
409 
410 	pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
411 		 drv->bus->name, __func__, dev_name(dev), drv->name);
412 
413 	pm_runtime_barrier(dev);
414 	ret = really_probe(dev, drv);
415 	pm_request_idle(dev);
416 
417 	return ret;
418 }
419 
420 static int __device_attach(struct device_driver *drv, void *data)
421 {
422 	struct device *dev = data;
423 
424 	if (!driver_match_device(drv, dev))
425 		return 0;
426 
427 	return driver_probe_device(drv, dev);
428 }
429 
430 /**
431  * device_attach - try to attach device to a driver.
432  * @dev: device.
433  *
434  * Walk the list of drivers that the bus has and call
435  * driver_probe_device() for each pair. If a compatible
436  * pair is found, break out and return.
437  *
438  * Returns 1 if the device was bound to a driver;
439  * 0 if no matching driver was found;
440  * -ENODEV if the device is not registered.
441  *
442  * When called for a USB interface, @dev->parent lock must be held.
443  */
444 int device_attach(struct device *dev)
445 {
446 	int ret = 0;
447 
448 	device_lock(dev);
449 	if (dev->driver) {
450 		if (klist_node_attached(&dev->p->knode_driver)) {
451 			ret = 1;
452 			goto out_unlock;
453 		}
454 		ret = device_bind_driver(dev);
455 		if (ret == 0)
456 			ret = 1;
457 		else {
458 			dev->driver = NULL;
459 			ret = 0;
460 		}
461 	} else {
462 		ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
463 		pm_request_idle(dev);
464 	}
465 out_unlock:
466 	device_unlock(dev);
467 	return ret;
468 }
469 EXPORT_SYMBOL_GPL(device_attach);
470 
471 static int __driver_attach(struct device *dev, void *data)
472 {
473 	struct device_driver *drv = data;
474 
475 	/*
476 	 * Lock device and try to bind to it. We drop the error
477 	 * here and always return 0, because we need to keep trying
478 	 * to bind to devices and some drivers will return an error
479 	 * simply if it didn't support the device.
480 	 *
481 	 * driver_probe_device() will spit a warning if there
482 	 * is an error.
483 	 */
484 
485 	if (!driver_match_device(drv, dev))
486 		return 0;
487 
488 	if (dev->parent)	/* Needed for USB */
489 		device_lock(dev->parent);
490 	device_lock(dev);
491 	if (!dev->driver)
492 		driver_probe_device(drv, dev);
493 	device_unlock(dev);
494 	if (dev->parent)
495 		device_unlock(dev->parent);
496 
497 	return 0;
498 }
499 
500 /**
501  * driver_attach - try to bind driver to devices.
502  * @drv: driver.
503  *
504  * Walk the list of devices that the bus has on it and try to
505  * match the driver with each one.  If driver_probe_device()
506  * returns 0 and the @dev->driver is set, we've found a
507  * compatible pair.
508  */
509 int driver_attach(struct device_driver *drv)
510 {
511 	return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
512 }
513 EXPORT_SYMBOL_GPL(driver_attach);
514 
515 /*
516  * __device_release_driver() must be called with @dev lock held.
517  * When called for a USB interface, @dev->parent lock must be held as well.
518  */
519 static void __device_release_driver(struct device *dev)
520 {
521 	struct device_driver *drv;
522 
523 	drv = dev->driver;
524 	if (drv) {
525 		pm_runtime_get_sync(dev);
526 
527 		driver_sysfs_remove(dev);
528 
529 		if (dev->bus)
530 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
531 						     BUS_NOTIFY_UNBIND_DRIVER,
532 						     dev);
533 
534 		pm_runtime_put_sync(dev);
535 
536 		if (dev->bus && dev->bus->remove)
537 			dev->bus->remove(dev);
538 		else if (drv->remove)
539 			drv->remove(dev);
540 		devres_release_all(dev);
541 		dev->driver = NULL;
542 		dev_set_drvdata(dev, NULL);
543 		if (dev->pm_domain && dev->pm_domain->dismiss)
544 			dev->pm_domain->dismiss(dev);
545 
546 		klist_remove(&dev->p->knode_driver);
547 		if (dev->bus)
548 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
549 						     BUS_NOTIFY_UNBOUND_DRIVER,
550 						     dev);
551 
552 	}
553 }
554 
555 /**
556  * device_release_driver - manually detach device from driver.
557  * @dev: device.
558  *
559  * Manually detach device from driver.
560  * When called for a USB interface, @dev->parent lock must be held.
561  */
562 void device_release_driver(struct device *dev)
563 {
564 	/*
565 	 * If anyone calls device_release_driver() recursively from
566 	 * within their ->remove callback for the same device, they
567 	 * will deadlock right here.
568 	 */
569 	device_lock(dev);
570 	__device_release_driver(dev);
571 	device_unlock(dev);
572 }
573 EXPORT_SYMBOL_GPL(device_release_driver);
574 
575 /**
576  * driver_detach - detach driver from all devices it controls.
577  * @drv: driver.
578  */
579 void driver_detach(struct device_driver *drv)
580 {
581 	struct device_private *dev_prv;
582 	struct device *dev;
583 
584 	for (;;) {
585 		spin_lock(&drv->p->klist_devices.k_lock);
586 		if (list_empty(&drv->p->klist_devices.k_list)) {
587 			spin_unlock(&drv->p->klist_devices.k_lock);
588 			break;
589 		}
590 		dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
591 				     struct device_private,
592 				     knode_driver.n_node);
593 		dev = dev_prv->device;
594 		get_device(dev);
595 		spin_unlock(&drv->p->klist_devices.k_lock);
596 
597 		if (dev->parent)	/* Needed for USB */
598 			device_lock(dev->parent);
599 		device_lock(dev);
600 		if (dev->driver == drv)
601 			__device_release_driver(dev);
602 		device_unlock(dev);
603 		if (dev->parent)
604 			device_unlock(dev->parent);
605 		put_device(dev);
606 	}
607 }
608