xref: /linux/drivers/rpmsg/virtio_rpmsg_bus.c (revision ba2290b1b7505b28912092a0976e071a447ee18c)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Virtio-based remote processor messaging bus
4  *
5  * Copyright (C) 2011 Texas Instruments, Inc.
6  * Copyright (C) 2011 Google, Inc.
7  *
8  * Ohad Ben-Cohen <ohad@wizery.com>
9  * Brian Swetland <swetland@google.com>
10  */
11 
12 #define pr_fmt(fmt) "%s: " fmt, __func__
13 
14 #include <linux/dma-mapping.h>
15 #include <linux/idr.h>
16 #include <linux/jiffies.h>
17 #include <linux/kernel.h>
18 #include <linux/module.h>
19 #include <linux/mutex.h>
20 #include <linux/of_device.h>
21 #include <linux/rpmsg.h>
22 #include <linux/scatterlist.h>
23 #include <linux/slab.h>
24 #include <linux/sched.h>
25 #include <linux/virtio.h>
26 #include <linux/virtio_byteorder.h>
27 #include <linux/virtio_ids.h>
28 #include <linux/virtio_config.h>
29 #include <linux/wait.h>
30 
31 #include "rpmsg_internal.h"
32 
33 /**
34  * struct virtproc_info - virtual remote processor state
35  * @vdev:	the virtio device
36  * @rvq:	rx virtqueue
37  * @svq:	tx virtqueue
38  * @rbufs:	kernel address of rx buffers
39  * @sbufs:	kernel address of tx buffers
40  * @num_bufs:	total number of buffers for rx and tx
41  * @buf_size:   size of one rx or tx buffer
42  * @last_sbuf:	index of last tx buffer used
43  * @bufs_dma:	dma base addr of the buffers
44  * @tx_lock:	protects svq, sbufs and sleepers, to allow concurrent senders.
45  *		sending a message might require waking up a dozing remote
46  *		processor, which involves sleeping, hence the mutex.
47  * @endpoints:	idr of local endpoints, allows fast retrieval
48  * @endpoints_lock: lock of the endpoints set
49  * @sendq:	wait queue of sending contexts waiting for a tx buffers
50  * @sleepers:	number of senders that are waiting for a tx buffer
51  * @ns_ept:	the bus's name service endpoint
52  *
53  * This structure stores the rpmsg state of a given virtio remote processor
54  * device (there might be several virtio proc devices for each physical
55  * remote processor).
56  */
57 struct virtproc_info {
58 	struct virtio_device *vdev;
59 	struct virtqueue *rvq, *svq;
60 	void *rbufs, *sbufs;
61 	unsigned int num_bufs;
62 	unsigned int buf_size;
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 /* The feature bitmap for virtio rpmsg */
74 #define VIRTIO_RPMSG_F_NS	0 /* RP supports name service notifications */
75 
76 /**
77  * struct rpmsg_hdr - common header for all rpmsg messages
78  * @src: source address
79  * @dst: destination address
80  * @reserved: reserved for future use
81  * @len: length of payload (in bytes)
82  * @flags: message flags
83  * @data: @len bytes of message payload data
84  *
85  * Every message sent(/received) on the rpmsg bus begins with this header.
86  */
87 struct rpmsg_hdr {
88 	__virtio32 src;
89 	__virtio32 dst;
90 	__virtio32 reserved;
91 	__virtio16 len;
92 	__virtio16 flags;
93 	u8 data[];
94 } __packed;
95 
96 /**
97  * struct rpmsg_ns_msg - dynamic name service announcement message
98  * @name: name of remote service that is published
99  * @addr: address of remote service that is published
100  * @flags: indicates whether service is created or destroyed
101  *
102  * This message is sent across to publish a new service, or announce
103  * about its removal. When we receive these messages, an appropriate
104  * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
105  * or ->remove() handler of the appropriate rpmsg driver will be invoked
106  * (if/as-soon-as one is registered).
107  */
108 struct rpmsg_ns_msg {
109 	char name[RPMSG_NAME_SIZE];
110 	__virtio32 addr;
111 	__virtio32 flags;
112 } __packed;
113 
114 /**
115  * enum rpmsg_ns_flags - dynamic name service announcement flags
116  *
117  * @RPMSG_NS_CREATE: a new remote service was just created
118  * @RPMSG_NS_DESTROY: a known remote service was just destroyed
119  */
120 enum rpmsg_ns_flags {
121 	RPMSG_NS_CREATE		= 0,
122 	RPMSG_NS_DESTROY	= 1,
123 };
124 
125 /**
126  * struct virtio_rpmsg_channel - rpmsg channel descriptor
127  * @rpdev: the rpmsg channel device
128  * @vrp: the virtio remote processor device this channel belongs to
129  *
130  * This structure stores the channel that links the rpmsg device to the virtio
131  * remote processor device.
132  */
133 struct virtio_rpmsg_channel {
134 	struct rpmsg_device rpdev;
135 
136 	struct virtproc_info *vrp;
137 };
138 
139 #define to_virtio_rpmsg_channel(_rpdev) \
140 	container_of(_rpdev, struct virtio_rpmsg_channel, rpdev)
141 
142 /*
143  * We're allocating buffers of 512 bytes each for communications. The
144  * number of buffers will be computed from the number of buffers supported
145  * by the vring, upto a maximum of 512 buffers (256 in each direction).
146  *
147  * Each buffer will have 16 bytes for the msg header and 496 bytes for
148  * the payload.
149  *
150  * This will utilize a maximum total space of 256KB for the buffers.
151  *
152  * We might also want to add support for user-provided buffers in time.
153  * This will allow bigger buffer size flexibility, and can also be used
154  * to achieve zero-copy messaging.
155  *
156  * Note that these numbers are purely a decision of this driver - we
157  * can change this without changing anything in the firmware of the remote
158  * processor.
159  */
160 #define MAX_RPMSG_NUM_BUFS	(512)
161 #define MAX_RPMSG_BUF_SIZE	(512)
162 
163 /*
164  * Local addresses are dynamically allocated on-demand.
165  * We do not dynamically assign addresses from the low 1024 range,
166  * in order to reserve that address range for predefined services.
167  */
168 #define RPMSG_RESERVED_ADDRESSES	(1024)
169 
170 /* Address 53 is reserved for advertising remote services */
171 #define RPMSG_NS_ADDR			(53)
172 
173 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
174 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len);
175 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
176 			       u32 dst);
177 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
178 					u32 dst, void *data, int len);
179 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len);
180 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
181 				  int len, u32 dst);
182 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
183 					   u32 dst, void *data, int len);
184 
185 static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
186 	.destroy_ept = virtio_rpmsg_destroy_ept,
187 	.send = virtio_rpmsg_send,
188 	.sendto = virtio_rpmsg_sendto,
189 	.send_offchannel = virtio_rpmsg_send_offchannel,
190 	.trysend = virtio_rpmsg_trysend,
191 	.trysendto = virtio_rpmsg_trysendto,
192 	.trysend_offchannel = virtio_rpmsg_trysend_offchannel,
193 };
194 
195 /**
196  * rpmsg_sg_init - initialize scatterlist according to cpu address location
197  * @sg: scatterlist to fill
198  * @cpu_addr: virtual address of the buffer
199  * @len: buffer length
200  *
201  * An internal function filling scatterlist according to virtual address
202  * location (in vmalloc or in kernel).
203  */
204 static void
205 rpmsg_sg_init(struct scatterlist *sg, void *cpu_addr, unsigned int len)
206 {
207 	if (is_vmalloc_addr(cpu_addr)) {
208 		sg_init_table(sg, 1);
209 		sg_set_page(sg, vmalloc_to_page(cpu_addr), len,
210 			    offset_in_page(cpu_addr));
211 	} else {
212 		WARN_ON(!virt_addr_valid(cpu_addr));
213 		sg_init_one(sg, cpu_addr, len);
214 	}
215 }
216 
217 /**
218  * __ept_release() - deallocate an rpmsg endpoint
219  * @kref: the ept's reference count
220  *
221  * This function deallocates an ept, and is invoked when its @kref refcount
222  * drops to zero.
223  *
224  * Never invoke this function directly!
225  */
226 static void __ept_release(struct kref *kref)
227 {
228 	struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
229 						  refcount);
230 	/*
231 	 * At this point no one holds a reference to ept anymore,
232 	 * so we can directly free it
233 	 */
234 	kfree(ept);
235 }
236 
237 /* for more info, see below documentation of rpmsg_create_ept() */
238 static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
239 						 struct rpmsg_device *rpdev,
240 						 rpmsg_rx_cb_t cb,
241 						 void *priv, u32 addr)
242 {
243 	int id_min, id_max, id;
244 	struct rpmsg_endpoint *ept;
245 	struct device *dev = rpdev ? &rpdev->dev : &vrp->vdev->dev;
246 
247 	ept = kzalloc(sizeof(*ept), GFP_KERNEL);
248 	if (!ept)
249 		return NULL;
250 
251 	kref_init(&ept->refcount);
252 	mutex_init(&ept->cb_lock);
253 
254 	ept->rpdev = rpdev;
255 	ept->cb = cb;
256 	ept->priv = priv;
257 	ept->ops = &virtio_endpoint_ops;
258 
259 	/* do we need to allocate a local address ? */
260 	if (addr == RPMSG_ADDR_ANY) {
261 		id_min = RPMSG_RESERVED_ADDRESSES;
262 		id_max = 0;
263 	} else {
264 		id_min = addr;
265 		id_max = addr + 1;
266 	}
267 
268 	mutex_lock(&vrp->endpoints_lock);
269 
270 	/* bind the endpoint to an rpmsg address (and allocate one if needed) */
271 	id = idr_alloc(&vrp->endpoints, ept, id_min, id_max, GFP_KERNEL);
272 	if (id < 0) {
273 		dev_err(dev, "idr_alloc failed: %d\n", id);
274 		goto free_ept;
275 	}
276 	ept->addr = id;
277 
278 	mutex_unlock(&vrp->endpoints_lock);
279 
280 	return ept;
281 
282 free_ept:
283 	mutex_unlock(&vrp->endpoints_lock);
284 	kref_put(&ept->refcount, __ept_release);
285 	return NULL;
286 }
287 
288 static struct rpmsg_endpoint *virtio_rpmsg_create_ept(struct rpmsg_device *rpdev,
289 						      rpmsg_rx_cb_t cb,
290 						      void *priv,
291 						      struct rpmsg_channel_info chinfo)
292 {
293 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
294 
295 	return __rpmsg_create_ept(vch->vrp, rpdev, cb, priv, chinfo.src);
296 }
297 
298 /**
299  * __rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
300  * @vrp: virtproc which owns this ept
301  * @ept: endpoing to destroy
302  *
303  * An internal function which destroy an ept without assuming it is
304  * bound to an rpmsg channel. This is needed for handling the internal
305  * name service endpoint, which isn't bound to an rpmsg channel.
306  * See also __rpmsg_create_ept().
307  */
308 static void
309 __rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
310 {
311 	/* make sure new inbound messages can't find this ept anymore */
312 	mutex_lock(&vrp->endpoints_lock);
313 	idr_remove(&vrp->endpoints, ept->addr);
314 	mutex_unlock(&vrp->endpoints_lock);
315 
316 	/* make sure in-flight inbound messages won't invoke cb anymore */
317 	mutex_lock(&ept->cb_lock);
318 	ept->cb = NULL;
319 	mutex_unlock(&ept->cb_lock);
320 
321 	kref_put(&ept->refcount, __ept_release);
322 }
323 
324 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
325 {
326 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(ept->rpdev);
327 
328 	__rpmsg_destroy_ept(vch->vrp, ept);
329 }
330 
331 static int virtio_rpmsg_announce_create(struct rpmsg_device *rpdev)
332 {
333 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
334 	struct virtproc_info *vrp = vch->vrp;
335 	struct device *dev = &rpdev->dev;
336 	int err = 0;
337 
338 	/* need to tell remote processor's name service about this channel ? */
339 	if (rpdev->announce && rpdev->ept &&
340 	    virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
341 		struct rpmsg_ns_msg nsm;
342 
343 		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
344 		nsm.addr = cpu_to_virtio32(vrp->vdev, rpdev->ept->addr);
345 		nsm.flags = cpu_to_virtio32(vrp->vdev, RPMSG_NS_CREATE);
346 
347 		err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
348 		if (err)
349 			dev_err(dev, "failed to announce service %d\n", err);
350 	}
351 
352 	return err;
353 }
354 
355 static int virtio_rpmsg_announce_destroy(struct rpmsg_device *rpdev)
356 {
357 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
358 	struct virtproc_info *vrp = vch->vrp;
359 	struct device *dev = &rpdev->dev;
360 	int err = 0;
361 
362 	/* tell remote processor's name service we're removing this channel */
363 	if (rpdev->announce && rpdev->ept &&
364 	    virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
365 		struct rpmsg_ns_msg nsm;
366 
367 		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
368 		nsm.addr = cpu_to_virtio32(vrp->vdev, rpdev->ept->addr);
369 		nsm.flags = cpu_to_virtio32(vrp->vdev, RPMSG_NS_DESTROY);
370 
371 		err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
372 		if (err)
373 			dev_err(dev, "failed to announce service %d\n", err);
374 	}
375 
376 	return err;
377 }
378 
379 static const struct rpmsg_device_ops virtio_rpmsg_ops = {
380 	.create_ept = virtio_rpmsg_create_ept,
381 	.announce_create = virtio_rpmsg_announce_create,
382 	.announce_destroy = virtio_rpmsg_announce_destroy,
383 };
384 
385 static void virtio_rpmsg_release_device(struct device *dev)
386 {
387 	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
388 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
389 
390 	kfree(vch);
391 }
392 
393 /*
394  * create an rpmsg channel using its name and address info.
395  * this function will be used to create both static and dynamic
396  * channels.
397  */
398 static struct rpmsg_device *rpmsg_create_channel(struct virtproc_info *vrp,
399 						 struct rpmsg_channel_info *chinfo)
400 {
401 	struct virtio_rpmsg_channel *vch;
402 	struct rpmsg_device *rpdev;
403 	struct device *tmp, *dev = &vrp->vdev->dev;
404 	int ret;
405 
406 	/* make sure a similar channel doesn't already exist */
407 	tmp = rpmsg_find_device(dev, chinfo);
408 	if (tmp) {
409 		/* decrement the matched device's refcount back */
410 		put_device(tmp);
411 		dev_err(dev, "channel %s:%x:%x already exist\n",
412 				chinfo->name, chinfo->src, chinfo->dst);
413 		return NULL;
414 	}
415 
416 	vch = kzalloc(sizeof(*vch), GFP_KERNEL);
417 	if (!vch)
418 		return NULL;
419 
420 	/* Link the channel to our vrp */
421 	vch->vrp = vrp;
422 
423 	/* Assign public information to the rpmsg_device */
424 	rpdev = &vch->rpdev;
425 	rpdev->src = chinfo->src;
426 	rpdev->dst = chinfo->dst;
427 	rpdev->ops = &virtio_rpmsg_ops;
428 
429 	/*
430 	 * rpmsg server channels has predefined local address (for now),
431 	 * and their existence needs to be announced remotely
432 	 */
433 	rpdev->announce = rpdev->src != RPMSG_ADDR_ANY;
434 
435 	strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE);
436 
437 	rpdev->dev.parent = &vrp->vdev->dev;
438 	rpdev->dev.release = virtio_rpmsg_release_device;
439 	ret = rpmsg_register_device(rpdev);
440 	if (ret)
441 		return NULL;
442 
443 	return rpdev;
444 }
445 
446 /* super simple buffer "allocator" that is just enough for now */
447 static void *get_a_tx_buf(struct virtproc_info *vrp)
448 {
449 	unsigned int len;
450 	void *ret;
451 
452 	/* support multiple concurrent senders */
453 	mutex_lock(&vrp->tx_lock);
454 
455 	/*
456 	 * either pick the next unused tx buffer
457 	 * (half of our buffers are used for sending messages)
458 	 */
459 	if (vrp->last_sbuf < vrp->num_bufs / 2)
460 		ret = vrp->sbufs + vrp->buf_size * vrp->last_sbuf++;
461 	/* or recycle a used one */
462 	else
463 		ret = virtqueue_get_buf(vrp->svq, &len);
464 
465 	mutex_unlock(&vrp->tx_lock);
466 
467 	return ret;
468 }
469 
470 /**
471  * rpmsg_upref_sleepers() - enable "tx-complete" interrupts, if needed
472  * @vrp: virtual remote processor state
473  *
474  * This function is called before a sender is blocked, waiting for
475  * a tx buffer to become available.
476  *
477  * If we already have blocking senders, this function merely increases
478  * the "sleepers" reference count, and exits.
479  *
480  * Otherwise, if this is the first sender to block, we also enable
481  * virtio's tx callbacks, so we'd be immediately notified when a tx
482  * buffer is consumed (we rely on virtio's tx callback in order
483  * to wake up sleeping senders as soon as a tx buffer is used by the
484  * remote processor).
485  */
486 static void rpmsg_upref_sleepers(struct virtproc_info *vrp)
487 {
488 	/* support multiple concurrent senders */
489 	mutex_lock(&vrp->tx_lock);
490 
491 	/* are we the first sleeping context waiting for tx buffers ? */
492 	if (atomic_inc_return(&vrp->sleepers) == 1)
493 		/* enable "tx-complete" interrupts before dozing off */
494 		virtqueue_enable_cb(vrp->svq);
495 
496 	mutex_unlock(&vrp->tx_lock);
497 }
498 
499 /**
500  * rpmsg_downref_sleepers() - disable "tx-complete" interrupts, if needed
501  * @vrp: virtual remote processor state
502  *
503  * This function is called after a sender, that waited for a tx buffer
504  * to become available, is unblocked.
505  *
506  * If we still have blocking senders, this function merely decreases
507  * the "sleepers" reference count, and exits.
508  *
509  * Otherwise, if there are no more blocking senders, we also disable
510  * virtio's tx callbacks, to avoid the overhead incurred with handling
511  * those (now redundant) interrupts.
512  */
513 static void rpmsg_downref_sleepers(struct virtproc_info *vrp)
514 {
515 	/* support multiple concurrent senders */
516 	mutex_lock(&vrp->tx_lock);
517 
518 	/* are we the last sleeping context waiting for tx buffers ? */
519 	if (atomic_dec_and_test(&vrp->sleepers))
520 		/* disable "tx-complete" interrupts */
521 		virtqueue_disable_cb(vrp->svq);
522 
523 	mutex_unlock(&vrp->tx_lock);
524 }
525 
526 /**
527  * rpmsg_send_offchannel_raw() - send a message across to the remote processor
528  * @rpdev: the rpmsg channel
529  * @src: source address
530  * @dst: destination address
531  * @data: payload of message
532  * @len: length of payload
533  * @wait: indicates whether caller should block in case no TX buffers available
534  *
535  * This function is the base implementation for all of the rpmsg sending API.
536  *
537  * It will send @data of length @len to @dst, and say it's from @src. The
538  * message will be sent to the remote processor which the @rpdev channel
539  * belongs to.
540  *
541  * The message is sent using one of the TX buffers that are available for
542  * communication with this remote processor.
543  *
544  * If @wait is true, the caller will be blocked until either a TX buffer is
545  * available, or 15 seconds elapses (we don't want callers to
546  * sleep indefinitely due to misbehaving remote processors), and in that
547  * case -ERESTARTSYS is returned. The number '15' itself was picked
548  * arbitrarily; there's little point in asking drivers to provide a timeout
549  * value themselves.
550  *
551  * Otherwise, if @wait is false, and there are no TX buffers available,
552  * the function will immediately fail, and -ENOMEM will be returned.
553  *
554  * Normally drivers shouldn't use this function directly; instead, drivers
555  * should use the appropriate rpmsg_{try}send{to, _offchannel} API
556  * (see include/linux/rpmsg.h).
557  *
558  * Returns 0 on success and an appropriate error value on failure.
559  */
560 static int rpmsg_send_offchannel_raw(struct rpmsg_device *rpdev,
561 				     u32 src, u32 dst,
562 				     void *data, int len, bool wait)
563 {
564 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
565 	struct virtproc_info *vrp = vch->vrp;
566 	struct device *dev = &rpdev->dev;
567 	struct scatterlist sg;
568 	struct rpmsg_hdr *msg;
569 	int err;
570 
571 	/* bcasting isn't allowed */
572 	if (src == RPMSG_ADDR_ANY || dst == RPMSG_ADDR_ANY) {
573 		dev_err(dev, "invalid addr (src 0x%x, dst 0x%x)\n", src, dst);
574 		return -EINVAL;
575 	}
576 
577 	/*
578 	 * We currently use fixed-sized buffers, and therefore the payload
579 	 * length is limited.
580 	 *
581 	 * One of the possible improvements here is either to support
582 	 * user-provided buffers (and then we can also support zero-copy
583 	 * messaging), or to improve the buffer allocator, to support
584 	 * variable-length buffer sizes.
585 	 */
586 	if (len > vrp->buf_size - sizeof(struct rpmsg_hdr)) {
587 		dev_err(dev, "message is too big (%d)\n", len);
588 		return -EMSGSIZE;
589 	}
590 
591 	/* grab a buffer */
592 	msg = get_a_tx_buf(vrp);
593 	if (!msg && !wait)
594 		return -ENOMEM;
595 
596 	/* no free buffer ? wait for one (but bail after 15 seconds) */
597 	while (!msg) {
598 		/* enable "tx-complete" interrupts, if not already enabled */
599 		rpmsg_upref_sleepers(vrp);
600 
601 		/*
602 		 * sleep until a free buffer is available or 15 secs elapse.
603 		 * the timeout period is not configurable because there's
604 		 * little point in asking drivers to specify that.
605 		 * if later this happens to be required, it'd be easy to add.
606 		 */
607 		err = wait_event_interruptible_timeout(vrp->sendq,
608 					(msg = get_a_tx_buf(vrp)),
609 					msecs_to_jiffies(15000));
610 
611 		/* disable "tx-complete" interrupts if we're the last sleeper */
612 		rpmsg_downref_sleepers(vrp);
613 
614 		/* timeout ? */
615 		if (!err) {
616 			dev_err(dev, "timeout waiting for a tx buffer\n");
617 			return -ERESTARTSYS;
618 		}
619 	}
620 
621 	msg->len = cpu_to_virtio16(vrp->vdev, len);
622 	msg->flags = 0;
623 	msg->src = cpu_to_virtio32(vrp->vdev, src);
624 	msg->dst = cpu_to_virtio32(vrp->vdev, dst);
625 	msg->reserved = 0;
626 	memcpy(msg->data, data, len);
627 
628 	dev_dbg(dev, "TX From 0x%x, To 0x%x, Len %d, Flags %d, Reserved %d\n",
629 		src, dst, len, msg->flags, msg->reserved);
630 #if defined(CONFIG_DYNAMIC_DEBUG)
631 	dynamic_hex_dump("rpmsg_virtio TX: ", DUMP_PREFIX_NONE, 16, 1,
632 			 msg, sizeof(*msg) + len, true);
633 #endif
634 
635 	rpmsg_sg_init(&sg, msg, sizeof(*msg) + len);
636 
637 	mutex_lock(&vrp->tx_lock);
638 
639 	/* add message to the remote processor's virtqueue */
640 	err = virtqueue_add_outbuf(vrp->svq, &sg, 1, msg, GFP_KERNEL);
641 	if (err) {
642 		/*
643 		 * need to reclaim the buffer here, otherwise it's lost
644 		 * (memory won't leak, but rpmsg won't use it again for TX).
645 		 * this will wait for a buffer management overhaul.
646 		 */
647 		dev_err(dev, "virtqueue_add_outbuf failed: %d\n", err);
648 		goto out;
649 	}
650 
651 	/* tell the remote processor it has a pending message to read */
652 	virtqueue_kick(vrp->svq);
653 out:
654 	mutex_unlock(&vrp->tx_lock);
655 	return err;
656 }
657 
658 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
659 {
660 	struct rpmsg_device *rpdev = ept->rpdev;
661 	u32 src = ept->addr, dst = rpdev->dst;
662 
663 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
664 }
665 
666 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
667 			       u32 dst)
668 {
669 	struct rpmsg_device *rpdev = ept->rpdev;
670 	u32 src = ept->addr;
671 
672 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
673 }
674 
675 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
676 					u32 dst, void *data, int len)
677 {
678 	struct rpmsg_device *rpdev = ept->rpdev;
679 
680 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
681 }
682 
683 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
684 {
685 	struct rpmsg_device *rpdev = ept->rpdev;
686 	u32 src = ept->addr, dst = rpdev->dst;
687 
688 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
689 }
690 
691 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
692 				  int len, u32 dst)
693 {
694 	struct rpmsg_device *rpdev = ept->rpdev;
695 	u32 src = ept->addr;
696 
697 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
698 }
699 
700 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
701 					   u32 dst, void *data, int len)
702 {
703 	struct rpmsg_device *rpdev = ept->rpdev;
704 
705 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
706 }
707 
708 static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
709 			     struct rpmsg_hdr *msg, unsigned int len)
710 {
711 	struct rpmsg_endpoint *ept;
712 	struct scatterlist sg;
713 	unsigned int msg_len = virtio16_to_cpu(vrp->vdev, msg->len);
714 	int err;
715 
716 	dev_dbg(dev, "From: 0x%x, To: 0x%x, Len: %d, Flags: %d, Reserved: %d\n",
717 		virtio32_to_cpu(vrp->vdev, msg->src),
718 		virtio32_to_cpu(vrp->vdev, msg->dst), msg_len,
719 		virtio16_to_cpu(vrp->vdev, msg->flags),
720 		virtio32_to_cpu(vrp->vdev, msg->reserved));
721 #if defined(CONFIG_DYNAMIC_DEBUG)
722 	dynamic_hex_dump("rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
723 			 msg, sizeof(*msg) + msg_len, true);
724 #endif
725 
726 	/*
727 	 * We currently use fixed-sized buffers, so trivially sanitize
728 	 * the reported payload length.
729 	 */
730 	if (len > vrp->buf_size ||
731 	    msg_len > (len - sizeof(struct rpmsg_hdr))) {
732 		dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg_len);
733 		return -EINVAL;
734 	}
735 
736 	/* use the dst addr to fetch the callback of the appropriate user */
737 	mutex_lock(&vrp->endpoints_lock);
738 
739 	ept = idr_find(&vrp->endpoints, virtio32_to_cpu(vrp->vdev, msg->dst));
740 
741 	/* let's make sure no one deallocates ept while we use it */
742 	if (ept)
743 		kref_get(&ept->refcount);
744 
745 	mutex_unlock(&vrp->endpoints_lock);
746 
747 	if (ept) {
748 		/* make sure ept->cb doesn't go away while we use it */
749 		mutex_lock(&ept->cb_lock);
750 
751 		if (ept->cb)
752 			ept->cb(ept->rpdev, msg->data, msg_len, ept->priv,
753 				virtio32_to_cpu(vrp->vdev, msg->src));
754 
755 		mutex_unlock(&ept->cb_lock);
756 
757 		/* farewell, ept, we don't need you anymore */
758 		kref_put(&ept->refcount, __ept_release);
759 	} else
760 		dev_warn(dev, "msg received with no recipient\n");
761 
762 	/* publish the real size of the buffer */
763 	rpmsg_sg_init(&sg, msg, vrp->buf_size);
764 
765 	/* add the buffer back to the remote processor's virtqueue */
766 	err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, msg, GFP_KERNEL);
767 	if (err < 0) {
768 		dev_err(dev, "failed to add a virtqueue buffer: %d\n", err);
769 		return err;
770 	}
771 
772 	return 0;
773 }
774 
775 /* called when an rx buffer is used, and it's time to digest a message */
776 static void rpmsg_recv_done(struct virtqueue *rvq)
777 {
778 	struct virtproc_info *vrp = rvq->vdev->priv;
779 	struct device *dev = &rvq->vdev->dev;
780 	struct rpmsg_hdr *msg;
781 	unsigned int len, msgs_received = 0;
782 	int err;
783 
784 	msg = virtqueue_get_buf(rvq, &len);
785 	if (!msg) {
786 		dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
787 		return;
788 	}
789 
790 	while (msg) {
791 		err = rpmsg_recv_single(vrp, dev, msg, len);
792 		if (err)
793 			break;
794 
795 		msgs_received++;
796 
797 		msg = virtqueue_get_buf(rvq, &len);
798 	}
799 
800 	dev_dbg(dev, "Received %u messages\n", msgs_received);
801 
802 	/* tell the remote processor we added another available rx buffer */
803 	if (msgs_received)
804 		virtqueue_kick(vrp->rvq);
805 }
806 
807 /*
808  * This is invoked whenever the remote processor completed processing
809  * a TX msg we just sent it, and the buffer is put back to the used ring.
810  *
811  * Normally, though, we suppress this "tx complete" interrupt in order to
812  * avoid the incurred overhead.
813  */
814 static void rpmsg_xmit_done(struct virtqueue *svq)
815 {
816 	struct virtproc_info *vrp = svq->vdev->priv;
817 
818 	dev_dbg(&svq->vdev->dev, "%s\n", __func__);
819 
820 	/* wake up potential senders that are waiting for a tx buffer */
821 	wake_up_interruptible(&vrp->sendq);
822 }
823 
824 /* invoked when a name service announcement arrives */
825 static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len,
826 		       void *priv, u32 src)
827 {
828 	struct rpmsg_ns_msg *msg = data;
829 	struct rpmsg_device *newch;
830 	struct rpmsg_channel_info chinfo;
831 	struct virtproc_info *vrp = priv;
832 	struct device *dev = &vrp->vdev->dev;
833 	int ret;
834 
835 #if defined(CONFIG_DYNAMIC_DEBUG)
836 	dynamic_hex_dump("NS announcement: ", DUMP_PREFIX_NONE, 16, 1,
837 			 data, len, true);
838 #endif
839 
840 	if (len != sizeof(*msg)) {
841 		dev_err(dev, "malformed ns msg (%d)\n", len);
842 		return -EINVAL;
843 	}
844 
845 	/*
846 	 * the name service ept does _not_ belong to a real rpmsg channel,
847 	 * and is handled by the rpmsg bus itself.
848 	 * for sanity reasons, make sure a valid rpdev has _not_ sneaked
849 	 * in somehow.
850 	 */
851 	if (rpdev) {
852 		dev_err(dev, "anomaly: ns ept has an rpdev handle\n");
853 		return -EINVAL;
854 	}
855 
856 	/* don't trust the remote processor for null terminating the name */
857 	msg->name[RPMSG_NAME_SIZE - 1] = '\0';
858 
859 	strncpy(chinfo.name, msg->name, sizeof(chinfo.name));
860 	chinfo.src = RPMSG_ADDR_ANY;
861 	chinfo.dst = virtio32_to_cpu(vrp->vdev, msg->addr);
862 
863 	dev_info(dev, "%sing channel %s addr 0x%x\n",
864 		 virtio32_to_cpu(vrp->vdev, msg->flags) & RPMSG_NS_DESTROY ?
865 		 "destroy" : "creat", msg->name, chinfo.dst);
866 
867 	if (virtio32_to_cpu(vrp->vdev, msg->flags) & RPMSG_NS_DESTROY) {
868 		ret = rpmsg_unregister_device(&vrp->vdev->dev, &chinfo);
869 		if (ret)
870 			dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret);
871 	} else {
872 		newch = rpmsg_create_channel(vrp, &chinfo);
873 		if (!newch)
874 			dev_err(dev, "rpmsg_create_channel failed\n");
875 	}
876 
877 	return 0;
878 }
879 
880 static int rpmsg_probe(struct virtio_device *vdev)
881 {
882 	vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
883 	static const char * const names[] = { "input", "output" };
884 	struct virtqueue *vqs[2];
885 	struct virtproc_info *vrp;
886 	void *bufs_va;
887 	int err = 0, i;
888 	size_t total_buf_space;
889 	bool notify;
890 
891 	vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
892 	if (!vrp)
893 		return -ENOMEM;
894 
895 	vrp->vdev = vdev;
896 
897 	idr_init(&vrp->endpoints);
898 	mutex_init(&vrp->endpoints_lock);
899 	mutex_init(&vrp->tx_lock);
900 	init_waitqueue_head(&vrp->sendq);
901 
902 	/* We expect two virtqueues, rx and tx (and in this order) */
903 	err = virtio_find_vqs(vdev, 2, vqs, vq_cbs, names, NULL);
904 	if (err)
905 		goto free_vrp;
906 
907 	vrp->rvq = vqs[0];
908 	vrp->svq = vqs[1];
909 
910 	/* we expect symmetric tx/rx vrings */
911 	WARN_ON(virtqueue_get_vring_size(vrp->rvq) !=
912 		virtqueue_get_vring_size(vrp->svq));
913 
914 	/* we need less buffers if vrings are small */
915 	if (virtqueue_get_vring_size(vrp->rvq) < MAX_RPMSG_NUM_BUFS / 2)
916 		vrp->num_bufs = virtqueue_get_vring_size(vrp->rvq) * 2;
917 	else
918 		vrp->num_bufs = MAX_RPMSG_NUM_BUFS;
919 
920 	vrp->buf_size = MAX_RPMSG_BUF_SIZE;
921 
922 	total_buf_space = vrp->num_bufs * vrp->buf_size;
923 
924 	/* allocate coherent memory for the buffers */
925 	bufs_va = dma_alloc_coherent(vdev->dev.parent,
926 				     total_buf_space, &vrp->bufs_dma,
927 				     GFP_KERNEL);
928 	if (!bufs_va) {
929 		err = -ENOMEM;
930 		goto vqs_del;
931 	}
932 
933 	dev_dbg(&vdev->dev, "buffers: va %pK, dma %pad\n",
934 		bufs_va, &vrp->bufs_dma);
935 
936 	/* half of the buffers is dedicated for RX */
937 	vrp->rbufs = bufs_va;
938 
939 	/* and half is dedicated for TX */
940 	vrp->sbufs = bufs_va + total_buf_space / 2;
941 
942 	/* set up the receive buffers */
943 	for (i = 0; i < vrp->num_bufs / 2; i++) {
944 		struct scatterlist sg;
945 		void *cpu_addr = vrp->rbufs + i * vrp->buf_size;
946 
947 		rpmsg_sg_init(&sg, cpu_addr, vrp->buf_size);
948 
949 		err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, cpu_addr,
950 					  GFP_KERNEL);
951 		WARN_ON(err); /* sanity check; this can't really happen */
952 	}
953 
954 	/* suppress "tx-complete" interrupts */
955 	virtqueue_disable_cb(vrp->svq);
956 
957 	vdev->priv = vrp;
958 
959 	/* if supported by the remote processor, enable the name service */
960 	if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
961 		/* a dedicated endpoint handles the name service msgs */
962 		vrp->ns_ept = __rpmsg_create_ept(vrp, NULL, rpmsg_ns_cb,
963 						vrp, RPMSG_NS_ADDR);
964 		if (!vrp->ns_ept) {
965 			dev_err(&vdev->dev, "failed to create the ns ept\n");
966 			err = -ENOMEM;
967 			goto free_coherent;
968 		}
969 	}
970 
971 	/*
972 	 * Prepare to kick but don't notify yet - we can't do this before
973 	 * device is ready.
974 	 */
975 	notify = virtqueue_kick_prepare(vrp->rvq);
976 
977 	/* From this point on, we can notify and get callbacks. */
978 	virtio_device_ready(vdev);
979 
980 	/* tell the remote processor it can start sending messages */
981 	/*
982 	 * this might be concurrent with callbacks, but we are only
983 	 * doing notify, not a full kick here, so that's ok.
984 	 */
985 	if (notify)
986 		virtqueue_notify(vrp->rvq);
987 
988 	dev_info(&vdev->dev, "rpmsg host is online\n");
989 
990 	return 0;
991 
992 free_coherent:
993 	dma_free_coherent(vdev->dev.parent, total_buf_space,
994 			  bufs_va, vrp->bufs_dma);
995 vqs_del:
996 	vdev->config->del_vqs(vrp->vdev);
997 free_vrp:
998 	kfree(vrp);
999 	return err;
1000 }
1001 
1002 static int rpmsg_remove_device(struct device *dev, void *data)
1003 {
1004 	device_unregister(dev);
1005 
1006 	return 0;
1007 }
1008 
1009 static void rpmsg_remove(struct virtio_device *vdev)
1010 {
1011 	struct virtproc_info *vrp = vdev->priv;
1012 	size_t total_buf_space = vrp->num_bufs * vrp->buf_size;
1013 	int ret;
1014 
1015 	vdev->config->reset(vdev);
1016 
1017 	ret = device_for_each_child(&vdev->dev, NULL, rpmsg_remove_device);
1018 	if (ret)
1019 		dev_warn(&vdev->dev, "can't remove rpmsg device: %d\n", ret);
1020 
1021 	if (vrp->ns_ept)
1022 		__rpmsg_destroy_ept(vrp, vrp->ns_ept);
1023 
1024 	idr_destroy(&vrp->endpoints);
1025 
1026 	vdev->config->del_vqs(vrp->vdev);
1027 
1028 	dma_free_coherent(vdev->dev.parent, total_buf_space,
1029 			  vrp->rbufs, vrp->bufs_dma);
1030 
1031 	kfree(vrp);
1032 }
1033 
1034 static struct virtio_device_id id_table[] = {
1035 	{ VIRTIO_ID_RPMSG, VIRTIO_DEV_ANY_ID },
1036 	{ 0 },
1037 };
1038 
1039 static unsigned int features[] = {
1040 	VIRTIO_RPMSG_F_NS,
1041 };
1042 
1043 static struct virtio_driver virtio_ipc_driver = {
1044 	.feature_table	= features,
1045 	.feature_table_size = ARRAY_SIZE(features),
1046 	.driver.name	= KBUILD_MODNAME,
1047 	.driver.owner	= THIS_MODULE,
1048 	.id_table	= id_table,
1049 	.probe		= rpmsg_probe,
1050 	.remove		= rpmsg_remove,
1051 };
1052 
1053 static int __init rpmsg_init(void)
1054 {
1055 	int ret;
1056 
1057 	ret = register_virtio_driver(&virtio_ipc_driver);
1058 	if (ret)
1059 		pr_err("failed to register virtio driver: %d\n", ret);
1060 
1061 	return ret;
1062 }
1063 subsys_initcall(rpmsg_init);
1064 
1065 static void __exit rpmsg_fini(void)
1066 {
1067 	unregister_virtio_driver(&virtio_ipc_driver);
1068 }
1069 module_exit(rpmsg_fini);
1070 
1071 MODULE_DEVICE_TABLE(virtio, id_table);
1072 MODULE_DESCRIPTION("Virtio-based remote processor messaging bus");
1073 MODULE_LICENSE("GPL v2");
1074