1 /*
2  * Virtio-based remote processor messaging bus
3  *
4  * Copyright (C) 2011 Texas Instruments, Inc.
5  * Copyright (C) 2011 Google, Inc.
6  *
7  * Ohad Ben-Cohen <ohad@wizery.com>
8  * Brian Swetland <swetland@google.com>
9  *
10  * This software is licensed under the terms of the GNU General Public
11  * License version 2, as published by the Free Software Foundation, and
12  * may be copied, distributed, and modified under those terms.
13  *
14  * This program is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17  * GNU General Public License for more details.
18  */
19 
20 #define pr_fmt(fmt) "%s: " fmt, __func__
21 
22 #include <linux/kernel.h>
23 #include <linux/module.h>
24 #include <linux/virtio.h>
25 #include <linux/virtio_ids.h>
26 #include <linux/virtio_config.h>
27 #include <linux/scatterlist.h>
28 #include <linux/dma-mapping.h>
29 #include <linux/slab.h>
30 #include <linux/idr.h>
31 #include <linux/jiffies.h>
32 #include <linux/sched.h>
33 #include <linux/wait.h>
34 #include <linux/rpmsg.h>
35 #include <linux/mutex.h>
36 
37 /**
38  * struct virtproc_info - virtual remote processor state
39  * @vdev:	the virtio device
40  * @rvq:	rx virtqueue
41  * @svq:	tx virtqueue
42  * @rbufs:	kernel address of rx buffers
43  * @sbufs:	kernel address of tx buffers
44  * @last_sbuf:	index of last tx buffer used
45  * @bufs_dma:	dma base addr of the buffers
46  * @tx_lock:	protects svq, sbufs and sleepers, to allow concurrent senders.
47  *		sending a message might require waking up a dozing remote
48  *		processor, which involves sleeping, hence the mutex.
49  * @endpoints:	idr of local endpoints, allows fast retrieval
50  * @endpoints_lock: lock of the endpoints set
51  * @sendq:	wait queue of sending contexts waiting for a tx buffers
52  * @sleepers:	number of senders that are waiting for a tx buffer
53  * @ns_ept:	the bus's name service endpoint
54  *
55  * This structure stores the rpmsg state of a given virtio remote processor
56  * device (there might be several virtio proc devices for each physical
57  * remote processor).
58  */
59 struct virtproc_info {
60 	struct virtio_device *vdev;
61 	struct virtqueue *rvq, *svq;
62 	void *rbufs, *sbufs;
63 	int last_sbuf;
64 	dma_addr_t bufs_dma;
65 	struct mutex tx_lock;
66 	struct idr endpoints;
67 	struct mutex endpoints_lock;
68 	wait_queue_head_t sendq;
69 	atomic_t sleepers;
70 	struct rpmsg_endpoint *ns_ept;
71 };
72 
73 /**
74  * struct rpmsg_channel_info - internal channel info representation
75  * @name: name of service
76  * @src: local address
77  * @dst: destination address
78  */
79 struct rpmsg_channel_info {
80 	char name[RPMSG_NAME_SIZE];
81 	u32 src;
82 	u32 dst;
83 };
84 
85 #define to_rpmsg_channel(d) container_of(d, struct rpmsg_channel, dev)
86 #define to_rpmsg_driver(d) container_of(d, struct rpmsg_driver, drv)
87 
88 /*
89  * We're allocating 512 buffers of 512 bytes for communications, and then
90  * using the first 256 buffers for RX, and the last 256 buffers for TX.
91  *
92  * Each buffer will have 16 bytes for the msg header and 496 bytes for
93  * the payload.
94  *
95  * This will require a total space of 256KB for the buffers.
96  *
97  * We might also want to add support for user-provided buffers in time.
98  * This will allow bigger buffer size flexibility, and can also be used
99  * to achieve zero-copy messaging.
100  *
101  * Note that these numbers are purely a decision of this driver - we
102  * can change this without changing anything in the firmware of the remote
103  * processor.
104  */
105 #define RPMSG_NUM_BUFS		(512)
106 #define RPMSG_BUF_SIZE		(512)
107 #define RPMSG_TOTAL_BUF_SPACE	(RPMSG_NUM_BUFS * RPMSG_BUF_SIZE)
108 
109 /*
110  * Local addresses are dynamically allocated on-demand.
111  * We do not dynamically assign addresses from the low 1024 range,
112  * in order to reserve that address range for predefined services.
113  */
114 #define RPMSG_RESERVED_ADDRESSES	(1024)
115 
116 /* Address 53 is reserved for advertising remote services */
117 #define RPMSG_NS_ADDR			(53)
118 
119 /* sysfs show configuration fields */
120 #define rpmsg_show_attr(field, path, format_string)			\
121 static ssize_t								\
122 field##_show(struct device *dev,					\
123 			struct device_attribute *attr, char *buf)	\
124 {									\
125 	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);		\
126 									\
127 	return sprintf(buf, format_string, rpdev->path);		\
128 }
129 
130 /* for more info, see Documentation/ABI/testing/sysfs-bus-rpmsg */
131 rpmsg_show_attr(name, id.name, "%s\n");
132 rpmsg_show_attr(src, src, "0x%x\n");
133 rpmsg_show_attr(dst, dst, "0x%x\n");
134 rpmsg_show_attr(announce, announce ? "true" : "false", "%s\n");
135 
136 /*
137  * Unique (and free running) index for rpmsg devices.
138  *
139  * Yeah, we're not recycling those numbers (yet?). will be easy
140  * to change if/when we want to.
141  */
142 static unsigned int rpmsg_dev_index;
143 
modalias_show(struct device * dev,struct device_attribute * attr,char * buf)144 static ssize_t modalias_show(struct device *dev,
145 			     struct device_attribute *attr, char *buf)
146 {
147 	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
148 
149 	return sprintf(buf, RPMSG_DEVICE_MODALIAS_FMT "\n", rpdev->id.name);
150 }
151 
152 static struct device_attribute rpmsg_dev_attrs[] = {
153 	__ATTR_RO(name),
154 	__ATTR_RO(modalias),
155 	__ATTR_RO(dst),
156 	__ATTR_RO(src),
157 	__ATTR_RO(announce),
158 	__ATTR_NULL
159 };
160 
161 /* rpmsg devices and drivers are matched using the service name */
rpmsg_id_match(const struct rpmsg_channel * rpdev,const struct rpmsg_device_id * id)162 static inline int rpmsg_id_match(const struct rpmsg_channel *rpdev,
163 				  const struct rpmsg_device_id *id)
164 {
165 	return strncmp(id->name, rpdev->id.name, RPMSG_NAME_SIZE) == 0;
166 }
167 
168 /* match rpmsg channel and rpmsg driver */
rpmsg_dev_match(struct device * dev,struct device_driver * drv)169 static int rpmsg_dev_match(struct device *dev, struct device_driver *drv)
170 {
171 	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
172 	struct rpmsg_driver *rpdrv = to_rpmsg_driver(drv);
173 	const struct rpmsg_device_id *ids = rpdrv->id_table;
174 	unsigned int i;
175 
176 	for (i = 0; ids[i].name[0]; i++)
177 		if (rpmsg_id_match(rpdev, &ids[i]))
178 			return 1;
179 
180 	return 0;
181 }
182 
rpmsg_uevent(struct device * dev,struct kobj_uevent_env * env)183 static int rpmsg_uevent(struct device *dev, struct kobj_uevent_env *env)
184 {
185 	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
186 
187 	return add_uevent_var(env, "MODALIAS=" RPMSG_DEVICE_MODALIAS_FMT,
188 					rpdev->id.name);
189 }
190 
191 /**
192  * __ept_release() - deallocate an rpmsg endpoint
193  * @kref: the ept's reference count
194  *
195  * This function deallocates an ept, and is invoked when its @kref refcount
196  * drops to zero.
197  *
198  * Never invoke this function directly!
199  */
__ept_release(struct kref * kref)200 static void __ept_release(struct kref *kref)
201 {
202 	struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
203 						  refcount);
204 	/*
205 	 * At this point no one holds a reference to ept anymore,
206 	 * so we can directly free it
207 	 */
208 	kfree(ept);
209 }
210 
211 /* for more info, see below documentation of rpmsg_create_ept() */
__rpmsg_create_ept(struct virtproc_info * vrp,struct rpmsg_channel * rpdev,rpmsg_rx_cb_t cb,void * priv,u32 addr)212 static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
213 		struct rpmsg_channel *rpdev, rpmsg_rx_cb_t cb,
214 		void *priv, u32 addr)
215 {
216 	int err, tmpaddr, request;
217 	struct rpmsg_endpoint *ept;
218 	struct device *dev = rpdev ? &rpdev->dev : &vrp->vdev->dev;
219 
220 	if (!idr_pre_get(&vrp->endpoints, GFP_KERNEL))
221 		return NULL;
222 
223 	ept = kzalloc(sizeof(*ept), GFP_KERNEL);
224 	if (!ept) {
225 		dev_err(dev, "failed to kzalloc a new ept\n");
226 		return NULL;
227 	}
228 
229 	kref_init(&ept->refcount);
230 	mutex_init(&ept->cb_lock);
231 
232 	ept->rpdev = rpdev;
233 	ept->cb = cb;
234 	ept->priv = priv;
235 
236 	/* do we need to allocate a local address ? */
237 	request = addr == RPMSG_ADDR_ANY ? RPMSG_RESERVED_ADDRESSES : addr;
238 
239 	mutex_lock(&vrp->endpoints_lock);
240 
241 	/* bind the endpoint to an rpmsg address (and allocate one if needed) */
242 	err = idr_get_new_above(&vrp->endpoints, ept, request, &tmpaddr);
243 	if (err) {
244 		dev_err(dev, "idr_get_new_above failed: %d\n", err);
245 		goto free_ept;
246 	}
247 
248 	/* make sure the user's address request is fulfilled, if relevant */
249 	if (addr != RPMSG_ADDR_ANY && tmpaddr != addr) {
250 		dev_err(dev, "address 0x%x already in use\n", addr);
251 		goto rem_idr;
252 	}
253 
254 	ept->addr = tmpaddr;
255 
256 	mutex_unlock(&vrp->endpoints_lock);
257 
258 	return ept;
259 
260 rem_idr:
261 	idr_remove(&vrp->endpoints, request);
262 free_ept:
263 	mutex_unlock(&vrp->endpoints_lock);
264 	kref_put(&ept->refcount, __ept_release);
265 	return NULL;
266 }
267 
268 /**
269  * rpmsg_create_ept() - create a new rpmsg_endpoint
270  * @rpdev: rpmsg channel device
271  * @cb: rx callback handler
272  * @priv: private data for the driver's use
273  * @addr: local rpmsg address to bind with @cb
274  *
275  * Every rpmsg address in the system is bound to an rx callback (so when
276  * inbound messages arrive, they are dispatched by the rpmsg bus using the
277  * appropriate callback handler) by means of an rpmsg_endpoint struct.
278  *
279  * This function allows drivers to create such an endpoint, and by that,
280  * bind a callback, and possibly some private data too, to an rpmsg address
281  * (either one that is known in advance, or one that will be dynamically
282  * assigned for them).
283  *
284  * Simple rpmsg drivers need not call rpmsg_create_ept, because an endpoint
285  * is already created for them when they are probed by the rpmsg bus
286  * (using the rx callback provided when they registered to the rpmsg bus).
287  *
288  * So things should just work for simple drivers: they already have an
289  * endpoint, their rx callback is bound to their rpmsg address, and when
290  * relevant inbound messages arrive (i.e. messages which their dst address
291  * equals to the src address of their rpmsg channel), the driver's handler
292  * is invoked to process it.
293  *
294  * That said, more complicated drivers might do need to allocate
295  * additional rpmsg addresses, and bind them to different rx callbacks.
296  * To accomplish that, those drivers need to call this function.
297  *
298  * Drivers should provide their @rpdev channel (so the new endpoint would belong
299  * to the same remote processor their channel belongs to), an rx callback
300  * function, an optional private data (which is provided back when the
301  * rx callback is invoked), and an address they want to bind with the
302  * callback. If @addr is RPMSG_ADDR_ANY, then rpmsg_create_ept will
303  * dynamically assign them an available rpmsg address (drivers should have
304  * a very good reason why not to always use RPMSG_ADDR_ANY here).
305  *
306  * Returns a pointer to the endpoint on success, or NULL on error.
307  */
rpmsg_create_ept(struct rpmsg_channel * rpdev,rpmsg_rx_cb_t cb,void * priv,u32 addr)308 struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_channel *rpdev,
309 				rpmsg_rx_cb_t cb, void *priv, u32 addr)
310 {
311 	return __rpmsg_create_ept(rpdev->vrp, rpdev, cb, priv, addr);
312 }
313 EXPORT_SYMBOL(rpmsg_create_ept);
314 
315 /**
316  * __rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
317  * @vrp: virtproc which owns this ept
318  * @ept: endpoing to destroy
319  *
320  * An internal function which destroy an ept without assuming it is
321  * bound to an rpmsg channel. This is needed for handling the internal
322  * name service endpoint, which isn't bound to an rpmsg channel.
323  * See also __rpmsg_create_ept().
324  */
325 static void
__rpmsg_destroy_ept(struct virtproc_info * vrp,struct rpmsg_endpoint * ept)326 __rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
327 {
328 	/* make sure new inbound messages can't find this ept anymore */
329 	mutex_lock(&vrp->endpoints_lock);
330 	idr_remove(&vrp->endpoints, ept->addr);
331 	mutex_unlock(&vrp->endpoints_lock);
332 
333 	/* make sure in-flight inbound messages won't invoke cb anymore */
334 	mutex_lock(&ept->cb_lock);
335 	ept->cb = NULL;
336 	mutex_unlock(&ept->cb_lock);
337 
338 	kref_put(&ept->refcount, __ept_release);
339 }
340 
341 /**
342  * rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
343  * @ept: endpoing to destroy
344  *
345  * Should be used by drivers to destroy an rpmsg endpoint previously
346  * created with rpmsg_create_ept().
347  */
rpmsg_destroy_ept(struct rpmsg_endpoint * ept)348 void rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
349 {
350 	__rpmsg_destroy_ept(ept->rpdev->vrp, ept);
351 }
352 EXPORT_SYMBOL(rpmsg_destroy_ept);
353 
354 /*
355  * when an rpmsg driver is probed with a channel, we seamlessly create
356  * it an endpoint, binding its rx callback to a unique local rpmsg
357  * address.
358  *
359  * if we need to, we also announce about this channel to the remote
360  * processor (needed in case the driver is exposing an rpmsg service).
361  */
rpmsg_dev_probe(struct device * dev)362 static int rpmsg_dev_probe(struct device *dev)
363 {
364 	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
365 	struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
366 	struct virtproc_info *vrp = rpdev->vrp;
367 	struct rpmsg_endpoint *ept;
368 	int err;
369 
370 	ept = rpmsg_create_ept(rpdev, rpdrv->callback, NULL, rpdev->src);
371 	if (!ept) {
372 		dev_err(dev, "failed to create endpoint\n");
373 		err = -ENOMEM;
374 		goto out;
375 	}
376 
377 	rpdev->ept = ept;
378 	rpdev->src = ept->addr;
379 
380 	err = rpdrv->probe(rpdev);
381 	if (err) {
382 		dev_err(dev, "%s: failed: %d\n", __func__, err);
383 		rpmsg_destroy_ept(ept);
384 		goto out;
385 	}
386 
387 	/* need to tell remote processor's name service about this channel ? */
388 	if (rpdev->announce &&
389 			virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
390 		struct rpmsg_ns_msg nsm;
391 
392 		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
393 		nsm.addr = rpdev->src;
394 		nsm.flags = RPMSG_NS_CREATE;
395 
396 		err = rpmsg_sendto(rpdev, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
397 		if (err)
398 			dev_err(dev, "failed to announce service %d\n", err);
399 	}
400 
401 out:
402 	return err;
403 }
404 
rpmsg_dev_remove(struct device * dev)405 static int rpmsg_dev_remove(struct device *dev)
406 {
407 	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
408 	struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
409 	struct virtproc_info *vrp = rpdev->vrp;
410 	int err = 0;
411 
412 	/* tell remote processor's name service we're removing this channel */
413 	if (rpdev->announce &&
414 			virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
415 		struct rpmsg_ns_msg nsm;
416 
417 		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
418 		nsm.addr = rpdev->src;
419 		nsm.flags = RPMSG_NS_DESTROY;
420 
421 		err = rpmsg_sendto(rpdev, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
422 		if (err)
423 			dev_err(dev, "failed to announce service %d\n", err);
424 	}
425 
426 	rpdrv->remove(rpdev);
427 
428 	rpmsg_destroy_ept(rpdev->ept);
429 
430 	return err;
431 }
432 
433 static struct bus_type rpmsg_bus = {
434 	.name		= "rpmsg",
435 	.match		= rpmsg_dev_match,
436 	.dev_attrs	= rpmsg_dev_attrs,
437 	.uevent		= rpmsg_uevent,
438 	.probe		= rpmsg_dev_probe,
439 	.remove		= rpmsg_dev_remove,
440 };
441 
442 /**
443  * register_rpmsg_driver() - register an rpmsg driver with the rpmsg bus
444  * @rpdrv: pointer to a struct rpmsg_driver
445  *
446  * Returns 0 on success, and an appropriate error value on failure.
447  */
register_rpmsg_driver(struct rpmsg_driver * rpdrv)448 int register_rpmsg_driver(struct rpmsg_driver *rpdrv)
449 {
450 	rpdrv->drv.bus = &rpmsg_bus;
451 	return driver_register(&rpdrv->drv);
452 }
453 EXPORT_SYMBOL(register_rpmsg_driver);
454 
455 /**
456  * unregister_rpmsg_driver() - unregister an rpmsg driver from the rpmsg bus
457  * @rpdrv: pointer to a struct rpmsg_driver
458  *
459  * Returns 0 on success, and an appropriate error value on failure.
460  */
unregister_rpmsg_driver(struct rpmsg_driver * rpdrv)461 void unregister_rpmsg_driver(struct rpmsg_driver *rpdrv)
462 {
463 	driver_unregister(&rpdrv->drv);
464 }
465 EXPORT_SYMBOL(unregister_rpmsg_driver);
466 
rpmsg_release_device(struct device * dev)467 static void rpmsg_release_device(struct device *dev)
468 {
469 	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
470 
471 	kfree(rpdev);
472 }
473 
474 /*
475  * match an rpmsg channel with a channel info struct.
476  * this is used to make sure we're not creating rpmsg devices for channels
477  * that already exist.
478  */
rpmsg_channel_match(struct device * dev,void * data)479 static int rpmsg_channel_match(struct device *dev, void *data)
480 {
481 	struct rpmsg_channel_info *chinfo = data;
482 	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
483 
484 	if (chinfo->src != RPMSG_ADDR_ANY && chinfo->src != rpdev->src)
485 		return 0;
486 
487 	if (chinfo->dst != RPMSG_ADDR_ANY && chinfo->dst != rpdev->dst)
488 		return 0;
489 
490 	if (strncmp(chinfo->name, rpdev->id.name, RPMSG_NAME_SIZE))
491 		return 0;
492 
493 	/* found a match ! */
494 	return 1;
495 }
496 
497 /*
498  * create an rpmsg channel using its name and address info.
499  * this function will be used to create both static and dynamic
500  * channels.
501  */
rpmsg_create_channel(struct virtproc_info * vrp,struct rpmsg_channel_info * chinfo)502 static struct rpmsg_channel *rpmsg_create_channel(struct virtproc_info *vrp,
503 				struct rpmsg_channel_info *chinfo)
504 {
505 	struct rpmsg_channel *rpdev;
506 	struct device *tmp, *dev = &vrp->vdev->dev;
507 	int ret;
508 
509 	/* make sure a similar channel doesn't already exist */
510 	tmp = device_find_child(dev, chinfo, rpmsg_channel_match);
511 	if (tmp) {
512 		/* decrement the matched device's refcount back */
513 		put_device(tmp);
514 		dev_err(dev, "channel %s:%x:%x already exist\n",
515 				chinfo->name, chinfo->src, chinfo->dst);
516 		return NULL;
517 	}
518 
519 	rpdev = kzalloc(sizeof(struct rpmsg_channel), GFP_KERNEL);
520 	if (!rpdev) {
521 		pr_err("kzalloc failed\n");
522 		return NULL;
523 	}
524 
525 	rpdev->vrp = vrp;
526 	rpdev->src = chinfo->src;
527 	rpdev->dst = chinfo->dst;
528 
529 	/*
530 	 * rpmsg server channels has predefined local address (for now),
531 	 * and their existence needs to be announced remotely
532 	 */
533 	rpdev->announce = rpdev->src != RPMSG_ADDR_ANY ? true : false;
534 
535 	strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE);
536 
537 	/* very simple device indexing plumbing which is enough for now */
538 	dev_set_name(&rpdev->dev, "rpmsg%d", rpmsg_dev_index++);
539 
540 	rpdev->dev.parent = &vrp->vdev->dev;
541 	rpdev->dev.bus = &rpmsg_bus;
542 	rpdev->dev.release = rpmsg_release_device;
543 
544 	ret = device_register(&rpdev->dev);
545 	if (ret) {
546 		dev_err(dev, "device_register failed: %d\n", ret);
547 		put_device(&rpdev->dev);
548 		return NULL;
549 	}
550 
551 	return rpdev;
552 }
553 
554 /*
555  * find an existing channel using its name + address properties,
556  * and destroy it
557  */
rpmsg_destroy_channel(struct virtproc_info * vrp,struct rpmsg_channel_info * chinfo)558 static int rpmsg_destroy_channel(struct virtproc_info *vrp,
559 					struct rpmsg_channel_info *chinfo)
560 {
561 	struct virtio_device *vdev = vrp->vdev;
562 	struct device *dev;
563 
564 	dev = device_find_child(&vdev->dev, chinfo, rpmsg_channel_match);
565 	if (!dev)
566 		return -EINVAL;
567 
568 	device_unregister(dev);
569 
570 	put_device(dev);
571 
572 	return 0;
573 }
574 
575 /* super simple buffer "allocator" that is just enough for now */
get_a_tx_buf(struct virtproc_info * vrp)576 static void *get_a_tx_buf(struct virtproc_info *vrp)
577 {
578 	unsigned int len;
579 	void *ret;
580 
581 	/* support multiple concurrent senders */
582 	mutex_lock(&vrp->tx_lock);
583 
584 	/*
585 	 * either pick the next unused tx buffer
586 	 * (half of our buffers are used for sending messages)
587 	 */
588 	if (vrp->last_sbuf < RPMSG_NUM_BUFS / 2)
589 		ret = vrp->sbufs + RPMSG_BUF_SIZE * vrp->last_sbuf++;
590 	/* or recycle a used one */
591 	else
592 		ret = virtqueue_get_buf(vrp->svq, &len);
593 
594 	mutex_unlock(&vrp->tx_lock);
595 
596 	return ret;
597 }
598 
599 /**
600  * rpmsg_upref_sleepers() - enable "tx-complete" interrupts, if needed
601  * @vrp: virtual remote processor state
602  *
603  * This function is called before a sender is blocked, waiting for
604  * a tx buffer to become available.
605  *
606  * If we already have blocking senders, this function merely increases
607  * the "sleepers" reference count, and exits.
608  *
609  * Otherwise, if this is the first sender to block, we also enable
610  * virtio's tx callbacks, so we'd be immediately notified when a tx
611  * buffer is consumed (we rely on virtio's tx callback in order
612  * to wake up sleeping senders as soon as a tx buffer is used by the
613  * remote processor).
614  */
rpmsg_upref_sleepers(struct virtproc_info * vrp)615 static void rpmsg_upref_sleepers(struct virtproc_info *vrp)
616 {
617 	/* support multiple concurrent senders */
618 	mutex_lock(&vrp->tx_lock);
619 
620 	/* are we the first sleeping context waiting for tx buffers ? */
621 	if (atomic_inc_return(&vrp->sleepers) == 1)
622 		/* enable "tx-complete" interrupts before dozing off */
623 		virtqueue_enable_cb(vrp->svq);
624 
625 	mutex_unlock(&vrp->tx_lock);
626 }
627 
628 /**
629  * rpmsg_downref_sleepers() - disable "tx-complete" interrupts, if needed
630  * @vrp: virtual remote processor state
631  *
632  * This function is called after a sender, that waited for a tx buffer
633  * to become available, is unblocked.
634  *
635  * If we still have blocking senders, this function merely decreases
636  * the "sleepers" reference count, and exits.
637  *
638  * Otherwise, if there are no more blocking senders, we also disable
639  * virtio's tx callbacks, to avoid the overhead incurred with handling
640  * those (now redundant) interrupts.
641  */
rpmsg_downref_sleepers(struct virtproc_info * vrp)642 static void rpmsg_downref_sleepers(struct virtproc_info *vrp)
643 {
644 	/* support multiple concurrent senders */
645 	mutex_lock(&vrp->tx_lock);
646 
647 	/* are we the last sleeping context waiting for tx buffers ? */
648 	if (atomic_dec_and_test(&vrp->sleepers))
649 		/* disable "tx-complete" interrupts */
650 		virtqueue_disable_cb(vrp->svq);
651 
652 	mutex_unlock(&vrp->tx_lock);
653 }
654 
655 /**
656  * rpmsg_send_offchannel_raw() - send a message across to the remote processor
657  * @rpdev: the rpmsg channel
658  * @src: source address
659  * @dst: destination address
660  * @data: payload of message
661  * @len: length of payload
662  * @wait: indicates whether caller should block in case no TX buffers available
663  *
664  * This function is the base implementation for all of the rpmsg sending API.
665  *
666  * It will send @data of length @len to @dst, and say it's from @src. The
667  * message will be sent to the remote processor which the @rpdev channel
668  * belongs to.
669  *
670  * The message is sent using one of the TX buffers that are available for
671  * communication with this remote processor.
672  *
673  * If @wait is true, the caller will be blocked until either a TX buffer is
674  * available, or 15 seconds elapses (we don't want callers to
675  * sleep indefinitely due to misbehaving remote processors), and in that
676  * case -ERESTARTSYS is returned. The number '15' itself was picked
677  * arbitrarily; there's little point in asking drivers to provide a timeout
678  * value themselves.
679  *
680  * Otherwise, if @wait is false, and there are no TX buffers available,
681  * the function will immediately fail, and -ENOMEM will be returned.
682  *
683  * Normally drivers shouldn't use this function directly; instead, drivers
684  * should use the appropriate rpmsg_{try}send{to, _offchannel} API
685  * (see include/linux/rpmsg.h).
686  *
687  * Returns 0 on success and an appropriate error value on failure.
688  */
rpmsg_send_offchannel_raw(struct rpmsg_channel * rpdev,u32 src,u32 dst,void * data,int len,bool wait)689 int rpmsg_send_offchannel_raw(struct rpmsg_channel *rpdev, u32 src, u32 dst,
690 					void *data, int len, bool wait)
691 {
692 	struct virtproc_info *vrp = rpdev->vrp;
693 	struct device *dev = &rpdev->dev;
694 	struct scatterlist sg;
695 	struct rpmsg_hdr *msg;
696 	int err;
697 
698 	/* bcasting isn't allowed */
699 	if (src == RPMSG_ADDR_ANY || dst == RPMSG_ADDR_ANY) {
700 		dev_err(dev, "invalid addr (src 0x%x, dst 0x%x)\n", src, dst);
701 		return -EINVAL;
702 	}
703 
704 	/*
705 	 * We currently use fixed-sized buffers, and therefore the payload
706 	 * length is limited.
707 	 *
708 	 * One of the possible improvements here is either to support
709 	 * user-provided buffers (and then we can also support zero-copy
710 	 * messaging), or to improve the buffer allocator, to support
711 	 * variable-length buffer sizes.
712 	 */
713 	if (len > RPMSG_BUF_SIZE - sizeof(struct rpmsg_hdr)) {
714 		dev_err(dev, "message is too big (%d)\n", len);
715 		return -EMSGSIZE;
716 	}
717 
718 	/* grab a buffer */
719 	msg = get_a_tx_buf(vrp);
720 	if (!msg && !wait)
721 		return -ENOMEM;
722 
723 	/* no free buffer ? wait for one (but bail after 15 seconds) */
724 	while (!msg) {
725 		/* enable "tx-complete" interrupts, if not already enabled */
726 		rpmsg_upref_sleepers(vrp);
727 
728 		/*
729 		 * sleep until a free buffer is available or 15 secs elapse.
730 		 * the timeout period is not configurable because there's
731 		 * little point in asking drivers to specify that.
732 		 * if later this happens to be required, it'd be easy to add.
733 		 */
734 		err = wait_event_interruptible_timeout(vrp->sendq,
735 					(msg = get_a_tx_buf(vrp)),
736 					msecs_to_jiffies(15000));
737 
738 		/* disable "tx-complete" interrupts if we're the last sleeper */
739 		rpmsg_downref_sleepers(vrp);
740 
741 		/* timeout ? */
742 		if (!err) {
743 			dev_err(dev, "timeout waiting for a tx buffer\n");
744 			return -ERESTARTSYS;
745 		}
746 	}
747 
748 	msg->len = len;
749 	msg->flags = 0;
750 	msg->src = src;
751 	msg->dst = dst;
752 	msg->reserved = 0;
753 	memcpy(msg->data, data, len);
754 
755 	dev_dbg(dev, "TX From 0x%x, To 0x%x, Len %d, Flags %d, Reserved %d\n",
756 					msg->src, msg->dst, msg->len,
757 					msg->flags, msg->reserved);
758 	print_hex_dump(KERN_DEBUG, "rpmsg_virtio TX: ", DUMP_PREFIX_NONE, 16, 1,
759 					msg, sizeof(*msg) + msg->len, true);
760 
761 	sg_init_one(&sg, msg, sizeof(*msg) + len);
762 
763 	mutex_lock(&vrp->tx_lock);
764 
765 	/* add message to the remote processor's virtqueue */
766 	err = virtqueue_add_buf(vrp->svq, &sg, 1, 0, msg, GFP_KERNEL);
767 	if (err < 0) {
768 		/*
769 		 * need to reclaim the buffer here, otherwise it's lost
770 		 * (memory won't leak, but rpmsg won't use it again for TX).
771 		 * this will wait for a buffer management overhaul.
772 		 */
773 		dev_err(dev, "virtqueue_add_buf failed: %d\n", err);
774 		goto out;
775 	}
776 
777 	/* tell the remote processor it has a pending message to read */
778 	virtqueue_kick(vrp->svq);
779 
780 	err = 0;
781 out:
782 	mutex_unlock(&vrp->tx_lock);
783 	return err;
784 }
785 EXPORT_SYMBOL(rpmsg_send_offchannel_raw);
786 
787 /* called when an rx buffer is used, and it's time to digest a message */
rpmsg_recv_done(struct virtqueue * rvq)788 static void rpmsg_recv_done(struct virtqueue *rvq)
789 {
790 	struct rpmsg_hdr *msg;
791 	unsigned int len;
792 	struct rpmsg_endpoint *ept;
793 	struct scatterlist sg;
794 	struct virtproc_info *vrp = rvq->vdev->priv;
795 	struct device *dev = &rvq->vdev->dev;
796 	int err;
797 
798 	msg = virtqueue_get_buf(rvq, &len);
799 	if (!msg) {
800 		dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
801 		return;
802 	}
803 
804 	dev_dbg(dev, "From: 0x%x, To: 0x%x, Len: %d, Flags: %d, Reserved: %d\n",
805 					msg->src, msg->dst, msg->len,
806 					msg->flags, msg->reserved);
807 	print_hex_dump(KERN_DEBUG, "rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
808 					msg, sizeof(*msg) + msg->len, true);
809 
810 	/*
811 	 * We currently use fixed-sized buffers, so trivially sanitize
812 	 * the reported payload length.
813 	 */
814 	if (len > RPMSG_BUF_SIZE ||
815 		msg->len > (len - sizeof(struct rpmsg_hdr))) {
816 		dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg->len);
817 		return;
818 	}
819 
820 	/* use the dst addr to fetch the callback of the appropriate user */
821 	mutex_lock(&vrp->endpoints_lock);
822 
823 	ept = idr_find(&vrp->endpoints, msg->dst);
824 
825 	/* let's make sure no one deallocates ept while we use it */
826 	if (ept)
827 		kref_get(&ept->refcount);
828 
829 	mutex_unlock(&vrp->endpoints_lock);
830 
831 	if (ept) {
832 		/* make sure ept->cb doesn't go away while we use it */
833 		mutex_lock(&ept->cb_lock);
834 
835 		if (ept->cb)
836 			ept->cb(ept->rpdev, msg->data, msg->len, ept->priv,
837 				msg->src);
838 
839 		mutex_unlock(&ept->cb_lock);
840 
841 		/* farewell, ept, we don't need you anymore */
842 		kref_put(&ept->refcount, __ept_release);
843 	} else
844 		dev_warn(dev, "msg received with no recepient\n");
845 
846 	/* publish the real size of the buffer */
847 	sg_init_one(&sg, msg, RPMSG_BUF_SIZE);
848 
849 	/* add the buffer back to the remote processor's virtqueue */
850 	err = virtqueue_add_buf(vrp->rvq, &sg, 0, 1, msg, GFP_KERNEL);
851 	if (err < 0) {
852 		dev_err(dev, "failed to add a virtqueue buffer: %d\n", err);
853 		return;
854 	}
855 
856 	/* tell the remote processor we added another available rx buffer */
857 	virtqueue_kick(vrp->rvq);
858 }
859 
860 /*
861  * This is invoked whenever the remote processor completed processing
862  * a TX msg we just sent it, and the buffer is put back to the used ring.
863  *
864  * Normally, though, we suppress this "tx complete" interrupt in order to
865  * avoid the incurred overhead.
866  */
rpmsg_xmit_done(struct virtqueue * svq)867 static void rpmsg_xmit_done(struct virtqueue *svq)
868 {
869 	struct virtproc_info *vrp = svq->vdev->priv;
870 
871 	dev_dbg(&svq->vdev->dev, "%s\n", __func__);
872 
873 	/* wake up potential senders that are waiting for a tx buffer */
874 	wake_up_interruptible(&vrp->sendq);
875 }
876 
877 /* invoked when a name service announcement arrives */
rpmsg_ns_cb(struct rpmsg_channel * rpdev,void * data,int len,void * priv,u32 src)878 static void rpmsg_ns_cb(struct rpmsg_channel *rpdev, void *data, int len,
879 							void *priv, u32 src)
880 {
881 	struct rpmsg_ns_msg *msg = data;
882 	struct rpmsg_channel *newch;
883 	struct rpmsg_channel_info chinfo;
884 	struct virtproc_info *vrp = priv;
885 	struct device *dev = &vrp->vdev->dev;
886 	int ret;
887 
888 	print_hex_dump(KERN_DEBUG, "NS announcement: ",
889 			DUMP_PREFIX_NONE, 16, 1,
890 			data, len, true);
891 
892 	if (len != sizeof(*msg)) {
893 		dev_err(dev, "malformed ns msg (%d)\n", len);
894 		return;
895 	}
896 
897 	/*
898 	 * the name service ept does _not_ belong to a real rpmsg channel,
899 	 * and is handled by the rpmsg bus itself.
900 	 * for sanity reasons, make sure a valid rpdev has _not_ sneaked
901 	 * in somehow.
902 	 */
903 	if (rpdev) {
904 		dev_err(dev, "anomaly: ns ept has an rpdev handle\n");
905 		return;
906 	}
907 
908 	/* don't trust the remote processor for null terminating the name */
909 	msg->name[RPMSG_NAME_SIZE - 1] = '\0';
910 
911 	dev_info(dev, "%sing channel %s addr 0x%x\n",
912 			msg->flags & RPMSG_NS_DESTROY ? "destroy" : "creat",
913 			msg->name, msg->addr);
914 
915 	strncpy(chinfo.name, msg->name, sizeof(chinfo.name));
916 	chinfo.src = RPMSG_ADDR_ANY;
917 	chinfo.dst = msg->addr;
918 
919 	if (msg->flags & RPMSG_NS_DESTROY) {
920 		ret = rpmsg_destroy_channel(vrp, &chinfo);
921 		if (ret)
922 			dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret);
923 	} else {
924 		newch = rpmsg_create_channel(vrp, &chinfo);
925 		if (!newch)
926 			dev_err(dev, "rpmsg_create_channel failed\n");
927 	}
928 }
929 
rpmsg_probe(struct virtio_device * vdev)930 static int rpmsg_probe(struct virtio_device *vdev)
931 {
932 	vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
933 	const char *names[] = { "input", "output" };
934 	struct virtqueue *vqs[2];
935 	struct virtproc_info *vrp;
936 	void *bufs_va;
937 	int err = 0, i;
938 
939 	vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
940 	if (!vrp)
941 		return -ENOMEM;
942 
943 	vrp->vdev = vdev;
944 
945 	idr_init(&vrp->endpoints);
946 	mutex_init(&vrp->endpoints_lock);
947 	mutex_init(&vrp->tx_lock);
948 	init_waitqueue_head(&vrp->sendq);
949 
950 	/* We expect two virtqueues, rx and tx (and in this order) */
951 	err = vdev->config->find_vqs(vdev, 2, vqs, vq_cbs, names);
952 	if (err)
953 		goto free_vrp;
954 
955 	vrp->rvq = vqs[0];
956 	vrp->svq = vqs[1];
957 
958 	/* allocate coherent memory for the buffers */
959 	bufs_va = dma_alloc_coherent(vdev->dev.parent, RPMSG_TOTAL_BUF_SPACE,
960 				&vrp->bufs_dma, GFP_KERNEL);
961 	if (!bufs_va)
962 		goto vqs_del;
963 
964 	dev_dbg(&vdev->dev, "buffers: va %p, dma 0x%llx\n", bufs_va,
965 					(unsigned long long)vrp->bufs_dma);
966 
967 	/* half of the buffers is dedicated for RX */
968 	vrp->rbufs = bufs_va;
969 
970 	/* and half is dedicated for TX */
971 	vrp->sbufs = bufs_va + RPMSG_TOTAL_BUF_SPACE / 2;
972 
973 	/* set up the receive buffers */
974 	for (i = 0; i < RPMSG_NUM_BUFS / 2; i++) {
975 		struct scatterlist sg;
976 		void *cpu_addr = vrp->rbufs + i * RPMSG_BUF_SIZE;
977 
978 		sg_init_one(&sg, cpu_addr, RPMSG_BUF_SIZE);
979 
980 		err = virtqueue_add_buf(vrp->rvq, &sg, 0, 1, cpu_addr,
981 								GFP_KERNEL);
982 		WARN_ON(err < 0); /* sanity check; this can't really happen */
983 	}
984 
985 	/* suppress "tx-complete" interrupts */
986 	virtqueue_disable_cb(vrp->svq);
987 
988 	vdev->priv = vrp;
989 
990 	/* if supported by the remote processor, enable the name service */
991 	if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
992 		/* a dedicated endpoint handles the name service msgs */
993 		vrp->ns_ept = __rpmsg_create_ept(vrp, NULL, rpmsg_ns_cb,
994 						vrp, RPMSG_NS_ADDR);
995 		if (!vrp->ns_ept) {
996 			dev_err(&vdev->dev, "failed to create the ns ept\n");
997 			err = -ENOMEM;
998 			goto free_coherent;
999 		}
1000 	}
1001 
1002 	/* tell the remote processor it can start sending messages */
1003 	virtqueue_kick(vrp->rvq);
1004 
1005 	dev_info(&vdev->dev, "rpmsg host is online\n");
1006 
1007 	return 0;
1008 
1009 free_coherent:
1010 	dma_free_coherent(vdev->dev.parent, RPMSG_TOTAL_BUF_SPACE, bufs_va,
1011 					vrp->bufs_dma);
1012 vqs_del:
1013 	vdev->config->del_vqs(vrp->vdev);
1014 free_vrp:
1015 	kfree(vrp);
1016 	return err;
1017 }
1018 
rpmsg_remove_device(struct device * dev,void * data)1019 static int rpmsg_remove_device(struct device *dev, void *data)
1020 {
1021 	device_unregister(dev);
1022 
1023 	return 0;
1024 }
1025 
rpmsg_remove(struct virtio_device * vdev)1026 static void __devexit rpmsg_remove(struct virtio_device *vdev)
1027 {
1028 	struct virtproc_info *vrp = vdev->priv;
1029 	int ret;
1030 
1031 	vdev->config->reset(vdev);
1032 
1033 	ret = device_for_each_child(&vdev->dev, NULL, rpmsg_remove_device);
1034 	if (ret)
1035 		dev_warn(&vdev->dev, "can't remove rpmsg device: %d\n", ret);
1036 
1037 	if (vrp->ns_ept)
1038 		__rpmsg_destroy_ept(vrp, vrp->ns_ept);
1039 
1040 	idr_remove_all(&vrp->endpoints);
1041 	idr_destroy(&vrp->endpoints);
1042 
1043 	vdev->config->del_vqs(vrp->vdev);
1044 
1045 	dma_free_coherent(vdev->dev.parent, RPMSG_TOTAL_BUF_SPACE,
1046 					vrp->rbufs, vrp->bufs_dma);
1047 
1048 	kfree(vrp);
1049 }
1050 
1051 static struct virtio_device_id id_table[] = {
1052 	{ VIRTIO_ID_RPMSG, VIRTIO_DEV_ANY_ID },
1053 	{ 0 },
1054 };
1055 
1056 static unsigned int features[] = {
1057 	VIRTIO_RPMSG_F_NS,
1058 };
1059 
1060 static struct virtio_driver virtio_ipc_driver = {
1061 	.feature_table	= features,
1062 	.feature_table_size = ARRAY_SIZE(features),
1063 	.driver.name	= KBUILD_MODNAME,
1064 	.driver.owner	= THIS_MODULE,
1065 	.id_table	= id_table,
1066 	.probe		= rpmsg_probe,
1067 	.remove		= __devexit_p(rpmsg_remove),
1068 };
1069 
rpmsg_init(void)1070 static int __init rpmsg_init(void)
1071 {
1072 	int ret;
1073 
1074 	ret = bus_register(&rpmsg_bus);
1075 	if (ret) {
1076 		pr_err("failed to register rpmsg bus: %d\n", ret);
1077 		return ret;
1078 	}
1079 
1080 	ret = register_virtio_driver(&virtio_ipc_driver);
1081 	if (ret) {
1082 		pr_err("failed to register virtio driver: %d\n", ret);
1083 		bus_unregister(&rpmsg_bus);
1084 	}
1085 
1086 	return ret;
1087 }
1088 subsys_initcall(rpmsg_init);
1089 
rpmsg_fini(void)1090 static void __exit rpmsg_fini(void)
1091 {
1092 	unregister_virtio_driver(&virtio_ipc_driver);
1093 	bus_unregister(&rpmsg_bus);
1094 }
1095 module_exit(rpmsg_fini);
1096 
1097 MODULE_DEVICE_TABLE(virtio, id_table);
1098 MODULE_DESCRIPTION("Virtio-based remote processor messaging bus");
1099 MODULE_LICENSE("GPL v2");
1100