1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * System Control and Management Interface (SCMI) Message Protocol bus layer
4  *
5  * Copyright (C) 2018-2021 ARM Ltd.
6  */
7 
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 
10 #include <linux/atomic.h>
11 #include <linux/types.h>
12 #include <linux/module.h>
13 #include <linux/of.h>
14 #include <linux/kernel.h>
15 #include <linux/slab.h>
16 #include <linux/device.h>
17 
18 #include "common.h"
19 
20 #define SCMI_UEVENT_MODALIAS_FMT	"%s:%02x:%s"
21 
22 BLOCKING_NOTIFIER_HEAD(scmi_requested_devices_nh);
23 EXPORT_SYMBOL_GPL(scmi_requested_devices_nh);
24 
25 static DEFINE_IDA(scmi_bus_id);
26 
27 static DEFINE_IDR(scmi_requested_devices);
28 /* Protect access to scmi_requested_devices */
29 static DEFINE_MUTEX(scmi_requested_devices_mtx);
30 
31 struct scmi_requested_dev {
32 	const struct scmi_device_id *id_table;
33 	struct list_head node;
34 };
35 
36 /* Track globally the creation of SCMI SystemPower related devices */
37 static atomic_t scmi_syspower_registered = ATOMIC_INIT(0);
38 
39 /**
40  * scmi_protocol_device_request  - Helper to request a device
41  *
42  * @id_table: A protocol/name pair descriptor for the device to be created.
43  *
44  * This helper let an SCMI driver request specific devices identified by the
45  * @id_table to be created for each active SCMI instance.
46  *
47  * The requested device name MUST NOT be already existent for this protocol;
48  * at first the freshly requested @id_table is annotated in the IDR table
49  * @scmi_requested_devices and then the requested device is advertised to any
50  * registered party via the @scmi_requested_devices_nh notification chain.
51  *
52  * Return: 0 on Success
53  */
scmi_protocol_device_request(const struct scmi_device_id * id_table)54 static int scmi_protocol_device_request(const struct scmi_device_id *id_table)
55 {
56 	int ret = 0;
57 	struct list_head *head, *phead = NULL;
58 	struct scmi_requested_dev *rdev;
59 
60 	pr_debug("Requesting SCMI device (%s) for protocol %x\n",
61 		 id_table->name, id_table->protocol_id);
62 
63 	if (IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT) &&
64 	    !IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX)) {
65 		pr_warn("SCMI Raw mode active. Rejecting '%s'/0x%02X\n",
66 			id_table->name, id_table->protocol_id);
67 		return -EINVAL;
68 	}
69 
70 	/*
71 	 * Find the matching protocol rdev list and then search of any
72 	 * existent equally named device...fails if any duplicate found.
73 	 */
74 	mutex_lock(&scmi_requested_devices_mtx);
75 	phead = idr_find(&scmi_requested_devices, id_table->protocol_id);
76 	if (phead) {
77 		head = phead;
78 		list_for_each_entry(rdev, head, node) {
79 			if (!strcmp(rdev->id_table->name, id_table->name)) {
80 				pr_err("Ignoring duplicate request [%d] %s\n",
81 				       rdev->id_table->protocol_id,
82 				       rdev->id_table->name);
83 				ret = -EINVAL;
84 				goto out;
85 			}
86 		}
87 	}
88 
89 	/*
90 	 * No duplicate found for requested id_table, so let's create a new
91 	 * requested device entry for this new valid request.
92 	 */
93 	rdev = kzalloc(sizeof(*rdev), GFP_KERNEL);
94 	if (!rdev) {
95 		ret = -ENOMEM;
96 		goto out;
97 	}
98 	rdev->id_table = id_table;
99 
100 	/*
101 	 * Append the new requested device table descriptor to the head of the
102 	 * related protocol list, eventually creating such head if not already
103 	 * there.
104 	 */
105 	if (!phead) {
106 		phead = kzalloc(sizeof(*phead), GFP_KERNEL);
107 		if (!phead) {
108 			kfree(rdev);
109 			ret = -ENOMEM;
110 			goto out;
111 		}
112 		INIT_LIST_HEAD(phead);
113 
114 		ret = idr_alloc(&scmi_requested_devices, (void *)phead,
115 				id_table->protocol_id,
116 				id_table->protocol_id + 1, GFP_KERNEL);
117 		if (ret != id_table->protocol_id) {
118 			pr_err("Failed to save SCMI device - ret:%d\n", ret);
119 			kfree(rdev);
120 			kfree(phead);
121 			ret = -EINVAL;
122 			goto out;
123 		}
124 		ret = 0;
125 	}
126 	list_add(&rdev->node, phead);
127 
128 out:
129 	mutex_unlock(&scmi_requested_devices_mtx);
130 
131 	if (!ret)
132 		blocking_notifier_call_chain(&scmi_requested_devices_nh,
133 					     SCMI_BUS_NOTIFY_DEVICE_REQUEST,
134 					     (void *)rdev->id_table);
135 
136 	return ret;
137 }
138 
scmi_protocol_table_register(const struct scmi_device_id * id_table)139 static int scmi_protocol_table_register(const struct scmi_device_id *id_table)
140 {
141 	int ret = 0;
142 	const struct scmi_device_id *entry;
143 
144 	for (entry = id_table; entry->name && ret == 0; entry++)
145 		ret = scmi_protocol_device_request(entry);
146 
147 	return ret;
148 }
149 
150 /**
151  * scmi_protocol_device_unrequest  - Helper to unrequest a device
152  *
153  * @id_table: A protocol/name pair descriptor for the device to be unrequested.
154  *
155  * The unrequested device, described by the provided id_table, is at first
156  * removed from the IDR @scmi_requested_devices and then the removal is
157  * advertised to any registered party via the @scmi_requested_devices_nh
158  * notification chain.
159  */
scmi_protocol_device_unrequest(const struct scmi_device_id * id_table)160 static void scmi_protocol_device_unrequest(const struct scmi_device_id *id_table)
161 {
162 	struct list_head *phead;
163 
164 	pr_debug("Unrequesting SCMI device (%s) for protocol %x\n",
165 		 id_table->name, id_table->protocol_id);
166 
167 	mutex_lock(&scmi_requested_devices_mtx);
168 	phead = idr_find(&scmi_requested_devices, id_table->protocol_id);
169 	if (phead) {
170 		struct scmi_requested_dev *victim, *tmp;
171 
172 		list_for_each_entry_safe(victim, tmp, phead, node) {
173 			if (!strcmp(victim->id_table->name, id_table->name)) {
174 				list_del(&victim->node);
175 
176 				mutex_unlock(&scmi_requested_devices_mtx);
177 				blocking_notifier_call_chain(&scmi_requested_devices_nh,
178 							     SCMI_BUS_NOTIFY_DEVICE_UNREQUEST,
179 							     (void *)victim->id_table);
180 				kfree(victim);
181 				mutex_lock(&scmi_requested_devices_mtx);
182 				break;
183 			}
184 		}
185 
186 		if (list_empty(phead)) {
187 			idr_remove(&scmi_requested_devices,
188 				   id_table->protocol_id);
189 			kfree(phead);
190 		}
191 	}
192 	mutex_unlock(&scmi_requested_devices_mtx);
193 }
194 
195 static void
scmi_protocol_table_unregister(const struct scmi_device_id * id_table)196 scmi_protocol_table_unregister(const struct scmi_device_id *id_table)
197 {
198 	const struct scmi_device_id *entry;
199 
200 	for (entry = id_table; entry->name; entry++)
201 		scmi_protocol_device_unrequest(entry);
202 }
203 
204 static const struct scmi_device_id *
scmi_dev_match_id(struct scmi_device * scmi_dev,const struct scmi_driver * scmi_drv)205 scmi_dev_match_id(struct scmi_device *scmi_dev, const struct scmi_driver *scmi_drv)
206 {
207 	const struct scmi_device_id *id = scmi_drv->id_table;
208 
209 	if (!id)
210 		return NULL;
211 
212 	for (; id->protocol_id; id++)
213 		if (id->protocol_id == scmi_dev->protocol_id) {
214 			if (!id->name)
215 				return id;
216 			else if (!strcmp(id->name, scmi_dev->name))
217 				return id;
218 		}
219 
220 	return NULL;
221 }
222 
scmi_dev_match(struct device * dev,const struct device_driver * drv)223 static int scmi_dev_match(struct device *dev, const struct device_driver *drv)
224 {
225 	const struct scmi_driver *scmi_drv = to_scmi_driver(drv);
226 	struct scmi_device *scmi_dev = to_scmi_dev(dev);
227 	const struct scmi_device_id *id;
228 
229 	id = scmi_dev_match_id(scmi_dev, scmi_drv);
230 	if (id)
231 		return 1;
232 
233 	return 0;
234 }
235 
scmi_match_by_id_table(struct device * dev,const void * data)236 static int scmi_match_by_id_table(struct device *dev, const void *data)
237 {
238 	struct scmi_device *sdev = to_scmi_dev(dev);
239 	const struct scmi_device_id *id_table = data;
240 
241 	return sdev->protocol_id == id_table->protocol_id &&
242 		(id_table->name && !strcmp(sdev->name, id_table->name));
243 }
244 
scmi_child_dev_find(struct device * parent,int prot_id,const char * name)245 static struct scmi_device *scmi_child_dev_find(struct device *parent,
246 					       int prot_id, const char *name)
247 {
248 	struct scmi_device_id id_table;
249 	struct device *dev;
250 
251 	id_table.protocol_id = prot_id;
252 	id_table.name = name;
253 
254 	dev = device_find_child(parent, &id_table, scmi_match_by_id_table);
255 	if (!dev)
256 		return NULL;
257 
258 	/* Drop the refcnt bumped implicitly by device_find_child */
259 	put_device(dev);
260 
261 	return to_scmi_dev(dev);
262 }
263 
scmi_dev_probe(struct device * dev)264 static int scmi_dev_probe(struct device *dev)
265 {
266 	struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);
267 	struct scmi_device *scmi_dev = to_scmi_dev(dev);
268 
269 	if (!scmi_dev->handle)
270 		return -EPROBE_DEFER;
271 
272 	return scmi_drv->probe(scmi_dev);
273 }
274 
scmi_dev_remove(struct device * dev)275 static void scmi_dev_remove(struct device *dev)
276 {
277 	struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);
278 	struct scmi_device *scmi_dev = to_scmi_dev(dev);
279 
280 	if (scmi_drv->remove)
281 		scmi_drv->remove(scmi_dev);
282 }
283 
scmi_device_uevent(const struct device * dev,struct kobj_uevent_env * env)284 static int scmi_device_uevent(const struct device *dev, struct kobj_uevent_env *env)
285 {
286 	const struct scmi_device *scmi_dev = to_scmi_dev(dev);
287 
288 	return add_uevent_var(env, "MODALIAS=" SCMI_UEVENT_MODALIAS_FMT,
289 			      dev_name(&scmi_dev->dev), scmi_dev->protocol_id,
290 			      scmi_dev->name);
291 }
292 
modalias_show(struct device * dev,struct device_attribute * attr,char * buf)293 static ssize_t modalias_show(struct device *dev,
294 			     struct device_attribute *attr, char *buf)
295 {
296 	struct scmi_device *scmi_dev = to_scmi_dev(dev);
297 
298 	return sysfs_emit(buf, SCMI_UEVENT_MODALIAS_FMT,
299 			  dev_name(&scmi_dev->dev), scmi_dev->protocol_id,
300 			  scmi_dev->name);
301 }
302 static DEVICE_ATTR_RO(modalias);
303 
protocol_id_show(struct device * dev,struct device_attribute * attr,char * buf)304 static ssize_t protocol_id_show(struct device *dev,
305 				 struct device_attribute *attr, char *buf)
306 {
307 	struct scmi_device *scmi_dev = to_scmi_dev(dev);
308 
309 	return sprintf(buf, "0x%02x\n", scmi_dev->protocol_id);
310 }
311 static DEVICE_ATTR_RO(protocol_id);
312 
name_show(struct device * dev,struct device_attribute * attr,char * buf)313 static ssize_t name_show(struct device *dev, struct device_attribute *attr,
314 			 char *buf)
315 {
316 	struct scmi_device *scmi_dev = to_scmi_dev(dev);
317 
318 	return sprintf(buf, "%s\n", scmi_dev->name);
319 }
320 static DEVICE_ATTR_RO(name);
321 
322 static struct attribute *scmi_device_attributes_attrs[] = {
323 	&dev_attr_protocol_id.attr,
324 	&dev_attr_name.attr,
325 	&dev_attr_modalias.attr,
326 	NULL,
327 };
328 ATTRIBUTE_GROUPS(scmi_device_attributes);
329 
330 const struct bus_type scmi_bus_type = {
331 	.name =	"scmi_protocol",
332 	.match = scmi_dev_match,
333 	.probe = scmi_dev_probe,
334 	.remove = scmi_dev_remove,
335 	.uevent	= scmi_device_uevent,
336 	.dev_groups = scmi_device_attributes_groups,
337 };
338 EXPORT_SYMBOL_GPL(scmi_bus_type);
339 
scmi_driver_register(struct scmi_driver * driver,struct module * owner,const char * mod_name)340 int scmi_driver_register(struct scmi_driver *driver, struct module *owner,
341 			 const char *mod_name)
342 {
343 	int retval;
344 
345 	if (!driver->probe)
346 		return -EINVAL;
347 
348 	retval = scmi_protocol_table_register(driver->id_table);
349 	if (retval)
350 		return retval;
351 
352 	driver->driver.bus = &scmi_bus_type;
353 	driver->driver.name = driver->name;
354 	driver->driver.owner = owner;
355 	driver->driver.mod_name = mod_name;
356 
357 	retval = driver_register(&driver->driver);
358 	if (!retval)
359 		pr_debug("Registered new scmi driver %s\n", driver->name);
360 
361 	return retval;
362 }
363 EXPORT_SYMBOL_GPL(scmi_driver_register);
364 
scmi_driver_unregister(struct scmi_driver * driver)365 void scmi_driver_unregister(struct scmi_driver *driver)
366 {
367 	driver_unregister(&driver->driver);
368 	scmi_protocol_table_unregister(driver->id_table);
369 }
370 EXPORT_SYMBOL_GPL(scmi_driver_unregister);
371 
scmi_device_release(struct device * dev)372 static void scmi_device_release(struct device *dev)
373 {
374 	struct scmi_device *scmi_dev = to_scmi_dev(dev);
375 
376 	kfree_const(scmi_dev->name);
377 	kfree(scmi_dev);
378 }
379 
__scmi_device_destroy(struct scmi_device * scmi_dev)380 static void __scmi_device_destroy(struct scmi_device *scmi_dev)
381 {
382 	pr_debug("(%s) Destroying SCMI device '%s' for protocol 0x%x (%s)\n",
383 		 of_node_full_name(scmi_dev->dev.parent->of_node),
384 		 dev_name(&scmi_dev->dev), scmi_dev->protocol_id,
385 		 scmi_dev->name);
386 
387 	if (scmi_dev->protocol_id == SCMI_PROTOCOL_SYSTEM)
388 		atomic_set(&scmi_syspower_registered, 0);
389 
390 	ida_free(&scmi_bus_id, scmi_dev->id);
391 	device_unregister(&scmi_dev->dev);
392 }
393 
394 static struct scmi_device *
__scmi_device_create(struct device_node * np,struct device * parent,int protocol,const char * name)395 __scmi_device_create(struct device_node *np, struct device *parent,
396 		     int protocol, const char *name)
397 {
398 	int id, retval;
399 	struct scmi_device *scmi_dev;
400 
401 	/*
402 	 * If the same protocol/name device already exist under the same parent
403 	 * (i.e. SCMI instance) just return the existent device.
404 	 * This avoids any race between the SCMI driver, creating devices for
405 	 * each DT defined protocol at probe time, and the concurrent
406 	 * registration of SCMI drivers.
407 	 */
408 	scmi_dev = scmi_child_dev_find(parent, protocol, name);
409 	if (scmi_dev)
410 		return scmi_dev;
411 
412 	/*
413 	 * Ignore any possible subsequent failures while creating the device
414 	 * since we are doomed anyway at that point; not using a mutex which
415 	 * spans across this whole function to keep things simple and to avoid
416 	 * to serialize all the __scmi_device_create calls across possibly
417 	 * different SCMI server instances (parent)
418 	 */
419 	if (protocol == SCMI_PROTOCOL_SYSTEM &&
420 	    atomic_cmpxchg(&scmi_syspower_registered, 0, 1)) {
421 		dev_warn(parent,
422 			 "SCMI SystemPower protocol device must be unique !\n");
423 		return NULL;
424 	}
425 
426 	scmi_dev = kzalloc(sizeof(*scmi_dev), GFP_KERNEL);
427 	if (!scmi_dev)
428 		return NULL;
429 
430 	scmi_dev->name = kstrdup_const(name ?: "unknown", GFP_KERNEL);
431 	if (!scmi_dev->name) {
432 		kfree(scmi_dev);
433 		return NULL;
434 	}
435 
436 	id = ida_alloc_min(&scmi_bus_id, 1, GFP_KERNEL);
437 	if (id < 0) {
438 		kfree_const(scmi_dev->name);
439 		kfree(scmi_dev);
440 		return NULL;
441 	}
442 
443 	scmi_dev->id = id;
444 	scmi_dev->protocol_id = protocol;
445 	scmi_dev->dev.parent = parent;
446 	device_set_node(&scmi_dev->dev, of_fwnode_handle(np));
447 	scmi_dev->dev.bus = &scmi_bus_type;
448 	scmi_dev->dev.release = scmi_device_release;
449 	dev_set_name(&scmi_dev->dev, "scmi_dev.%d", id);
450 
451 	retval = device_register(&scmi_dev->dev);
452 	if (retval)
453 		goto put_dev;
454 
455 	pr_debug("(%s) Created SCMI device '%s' for protocol 0x%x (%s)\n",
456 		 of_node_full_name(parent->of_node),
457 		 dev_name(&scmi_dev->dev), protocol, name);
458 
459 	return scmi_dev;
460 put_dev:
461 	put_device(&scmi_dev->dev);
462 	ida_free(&scmi_bus_id, id);
463 	return NULL;
464 }
465 
466 /**
467  * scmi_device_create  - A method to create one or more SCMI devices
468  *
469  * @np: A reference to the device node to use for the new device(s)
470  * @parent: The parent device to use identifying a specific SCMI instance
471  * @protocol: The SCMI protocol to be associated with this device
472  * @name: The requested-name of the device to be created; this is optional
473  *	  and if no @name is provided, all the devices currently known to
474  *	  be requested on the SCMI bus for @protocol will be created.
475  *
476  * This method can be invoked to create a single well-defined device (like
477  * a transport device or a device requested by an SCMI driver loaded after
478  * the core SCMI stack has been probed), or to create all the devices currently
479  * known to have been requested by the loaded SCMI drivers for a specific
480  * protocol (typically during SCMI core protocol enumeration at probe time).
481  *
482  * Return: The created device (or one of them if @name was NOT provided and
483  *	   multiple devices were created) or NULL if no device was created;
484  *	   note that NULL indicates an error ONLY in case a specific @name
485  *	   was provided: when @name param was not provided, a number of devices
486  *	   could have been potentially created for a whole protocol, unless no
487  *	   device was found to have been requested for that specific protocol.
488  */
scmi_device_create(struct device_node * np,struct device * parent,int protocol,const char * name)489 struct scmi_device *scmi_device_create(struct device_node *np,
490 				       struct device *parent, int protocol,
491 				       const char *name)
492 {
493 	struct list_head *phead;
494 	struct scmi_requested_dev *rdev;
495 	struct scmi_device *scmi_dev = NULL;
496 
497 	if (name)
498 		return __scmi_device_create(np, parent, protocol, name);
499 
500 	mutex_lock(&scmi_requested_devices_mtx);
501 	phead = idr_find(&scmi_requested_devices, protocol);
502 	/* Nothing to do. */
503 	if (!phead) {
504 		mutex_unlock(&scmi_requested_devices_mtx);
505 		return NULL;
506 	}
507 
508 	/* Walk the list of requested devices for protocol and create them */
509 	list_for_each_entry(rdev, phead, node) {
510 		struct scmi_device *sdev;
511 
512 		sdev = __scmi_device_create(np, parent,
513 					    rdev->id_table->protocol_id,
514 					    rdev->id_table->name);
515 		/* Report errors and carry on... */
516 		if (sdev)
517 			scmi_dev = sdev;
518 		else
519 			pr_err("(%s) Failed to create device for protocol 0x%x (%s)\n",
520 			       of_node_full_name(parent->of_node),
521 			       rdev->id_table->protocol_id,
522 			       rdev->id_table->name);
523 	}
524 	mutex_unlock(&scmi_requested_devices_mtx);
525 
526 	return scmi_dev;
527 }
528 EXPORT_SYMBOL_GPL(scmi_device_create);
529 
scmi_device_destroy(struct device * parent,int protocol,const char * name)530 void scmi_device_destroy(struct device *parent, int protocol, const char *name)
531 {
532 	struct scmi_device *scmi_dev;
533 
534 	scmi_dev = scmi_child_dev_find(parent, protocol, name);
535 	if (scmi_dev)
536 		__scmi_device_destroy(scmi_dev);
537 }
538 EXPORT_SYMBOL_GPL(scmi_device_destroy);
539 
__scmi_devices_unregister(struct device * dev,void * data)540 static int __scmi_devices_unregister(struct device *dev, void *data)
541 {
542 	struct scmi_device *scmi_dev = to_scmi_dev(dev);
543 
544 	__scmi_device_destroy(scmi_dev);
545 	return 0;
546 }
547 
scmi_devices_unregister(void)548 static void scmi_devices_unregister(void)
549 {
550 	bus_for_each_dev(&scmi_bus_type, NULL, NULL, __scmi_devices_unregister);
551 }
552 
scmi_bus_init(void)553 static int __init scmi_bus_init(void)
554 {
555 	int retval;
556 
557 	retval = bus_register(&scmi_bus_type);
558 	if (retval)
559 		pr_err("SCMI protocol bus register failed (%d)\n", retval);
560 
561 	pr_info("SCMI protocol bus registered\n");
562 
563 	return retval;
564 }
565 subsys_initcall(scmi_bus_init);
566 
scmi_bus_exit(void)567 static void __exit scmi_bus_exit(void)
568 {
569 	/*
570 	 * Destroy all remaining devices: just in case the drivers were
571 	 * manually unbound and at first and then the modules unloaded.
572 	 */
573 	scmi_devices_unregister();
574 	bus_unregister(&scmi_bus_type);
575 	ida_destroy(&scmi_bus_id);
576 }
577 module_exit(scmi_bus_exit);
578 
579 MODULE_ALIAS("scmi-core");
580 MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
581 MODULE_DESCRIPTION("ARM SCMI protocol bus");
582 MODULE_LICENSE("GPL");
583