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/kernel.h>
15 #include <linux/module.h>
16 #include <linux/virtio.h>
17 #include <linux/virtio_ids.h>
18 #include <linux/virtio_config.h>
19 #include <linux/scatterlist.h>
20 #include <linux/dma-mapping.h>
21 #include <linux/slab.h>
22 #include <linux/idr.h>
23 #include <linux/jiffies.h>
24 #include <linux/sched.h>
25 #include <linux/wait.h>
26 #include <linux/rpmsg.h>
27 #include <linux/mutex.h>
28 #include <linux/of_device.h>
29 
30 #include "rpmsg_internal.h"
31 
32 /**
33  * struct virtproc_info - virtual remote processor state
34  * @vdev:	the virtio device
35  * @rvq:	rx virtqueue
36  * @svq:	tx virtqueue
37  * @rbufs:	kernel address of rx buffers
38  * @sbufs:	kernel address of tx buffers
39  * @num_bufs:	total number of buffers for rx and tx
40  * @buf_size:   size of one rx or tx buffer
41  * @last_sbuf:	index of last tx buffer used
42  * @bufs_dma:	dma base addr of the buffers
43  * @tx_lock:	protects svq, sbufs and sleepers, to allow concurrent senders.
44  *		sending a message might require waking up a dozing remote
45  *		processor, which involves sleeping, hence the mutex.
46  * @endpoints:	idr of local endpoints, allows fast retrieval
47  * @endpoints_lock: lock of the endpoints set
48  * @sendq:	wait queue of sending contexts waiting for a tx buffers
49  * @sleepers:	number of senders that are waiting for a tx buffer
50  * @ns_ept:	the bus's name service endpoint
51  *
52  * This structure stores the rpmsg state of a given virtio remote processor
53  * device (there might be several virtio proc devices for each physical
54  * remote processor).
55  */
56 struct virtproc_info {
57 	struct virtio_device *vdev;
58 	struct virtqueue *rvq, *svq;
59 	void *rbufs, *sbufs;
60 	unsigned int num_bufs;
61 	unsigned int buf_size;
62 	int last_sbuf;
63 	dma_addr_t bufs_dma;
64 	struct mutex tx_lock;
65 	struct idr endpoints;
66 	struct mutex endpoints_lock;
67 	wait_queue_head_t sendq;
68 	atomic_t sleepers;
69 	struct rpmsg_endpoint *ns_ept;
70 };
71 
72 /* The feature bitmap for virtio rpmsg */
73 #define VIRTIO_RPMSG_F_NS	0 /* RP supports name service notifications */
74 
75 /**
76  * struct rpmsg_hdr - common header for all rpmsg messages
77  * @src: source address
78  * @dst: destination address
79  * @reserved: reserved for future use
80  * @len: length of payload (in bytes)
81  * @flags: message flags
82  * @data: @len bytes of message payload data
83  *
84  * Every message sent(/received) on the rpmsg bus begins with this header.
85  */
86 struct rpmsg_hdr {
87 	u32 src;
88 	u32 dst;
89 	u32 reserved;
90 	u16 len;
91 	u16 flags;
92 	u8 data[0];
93 } __packed;
94 
95 /**
96  * struct rpmsg_ns_msg - dynamic name service announcement message
97  * @name: name of remote service that is published
98  * @addr: address of remote service that is published
99  * @flags: indicates whether service is created or destroyed
100  *
101  * This message is sent across to publish a new service, or announce
102  * about its removal. When we receive these messages, an appropriate
103  * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
104  * or ->remove() handler of the appropriate rpmsg driver will be invoked
105  * (if/as-soon-as one is registered).
106  */
107 struct rpmsg_ns_msg {
108 	char name[RPMSG_NAME_SIZE];
109 	u32 addr;
110 	u32 flags;
111 } __packed;
112 
113 /**
114  * enum rpmsg_ns_flags - dynamic name service announcement flags
115  *
116  * @RPMSG_NS_CREATE: a new remote service was just created
117  * @RPMSG_NS_DESTROY: a known remote service was just destroyed
118  */
119 enum rpmsg_ns_flags {
120 	RPMSG_NS_CREATE		= 0,
121 	RPMSG_NS_DESTROY	= 1,
122 };
123 
124 /**
125  * @vrp: the remote processor this channel belongs to
126  */
127 struct virtio_rpmsg_channel {
128 	struct rpmsg_device rpdev;
129 
130 	struct virtproc_info *vrp;
131 };
132 
133 #define to_virtio_rpmsg_channel(_rpdev) \
134 	container_of(_rpdev, struct virtio_rpmsg_channel, rpdev)
135 
136 /*
137  * We're allocating buffers of 512 bytes each for communications. The
138  * number of buffers will be computed from the number of buffers supported
139  * by the vring, upto a maximum of 512 buffers (256 in each direction).
140  *
141  * Each buffer will have 16 bytes for the msg header and 496 bytes for
142  * the payload.
143  *
144  * This will utilize a maximum total space of 256KB for the buffers.
145  *
146  * We might also want to add support for user-provided buffers in time.
147  * This will allow bigger buffer size flexibility, and can also be used
148  * to achieve zero-copy messaging.
149  *
150  * Note that these numbers are purely a decision of this driver - we
151  * can change this without changing anything in the firmware of the remote
152  * processor.
153  */
154 #define MAX_RPMSG_NUM_BUFS	(512)
155 #define MAX_RPMSG_BUF_SIZE	(512)
156 
157 /*
158  * Local addresses are dynamically allocated on-demand.
159  * We do not dynamically assign addresses from the low 1024 range,
160  * in order to reserve that address range for predefined services.
161  */
162 #define RPMSG_RESERVED_ADDRESSES	(1024)
163 
164 /* Address 53 is reserved for advertising remote services */
165 #define RPMSG_NS_ADDR			(53)
166 
167 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
168 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len);
169 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
170 			       u32 dst);
171 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
172 					u32 dst, void *data, int len);
173 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len);
174 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
175 				  int len, u32 dst);
176 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
177 					   u32 dst, void *data, int len);
178 
179 static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
180 	.destroy_ept = virtio_rpmsg_destroy_ept,
181 	.send = virtio_rpmsg_send,
182 	.sendto = virtio_rpmsg_sendto,
183 	.send_offchannel = virtio_rpmsg_send_offchannel,
184 	.trysend = virtio_rpmsg_trysend,
185 	.trysendto = virtio_rpmsg_trysendto,
186 	.trysend_offchannel = virtio_rpmsg_trysend_offchannel,
187 };
188 
189 /**
190  * rpmsg_sg_init - initialize scatterlist according to cpu address location
191  * @sg: scatterlist to fill
192  * @cpu_addr: virtual address of the buffer
193  * @len: buffer length
194  *
195  * An internal function filling scatterlist according to virtual address
196  * location (in vmalloc or in kernel).
197  */
198 static void
199 rpmsg_sg_init(struct scatterlist *sg, void *cpu_addr, unsigned int len)
200 {
201 	if (is_vmalloc_addr(cpu_addr)) {
202 		sg_init_table(sg, 1);
203 		sg_set_page(sg, vmalloc_to_page(cpu_addr), len,
204 			    offset_in_page(cpu_addr));
205 	} else {
206 		WARN_ON(!virt_addr_valid(cpu_addr));
207 		sg_init_one(sg, cpu_addr, len);
208 	}
209 }
210 
211 /**
212  * __ept_release() - deallocate an rpmsg endpoint
213  * @kref: the ept's reference count
214  *
215  * This function deallocates an ept, and is invoked when its @kref refcount
216  * drops to zero.
217  *
218  * Never invoke this function directly!
219  */
220 static void __ept_release(struct kref *kref)
221 {
222 	struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
223 						  refcount);
224 	/*
225 	 * At this point no one holds a reference to ept anymore,
226 	 * so we can directly free it
227 	 */
228 	kfree(ept);
229 }
230 
231 /* for more info, see below documentation of rpmsg_create_ept() */
232 static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
233 						 struct rpmsg_device *rpdev,
234 						 rpmsg_rx_cb_t cb,
235 						 void *priv, u32 addr)
236 {
237 	int id_min, id_max, id;
238 	struct rpmsg_endpoint *ept;
239 	struct device *dev = rpdev ? &rpdev->dev : &vrp->vdev->dev;
240 
241 	ept = kzalloc(sizeof(*ept), GFP_KERNEL);
242 	if (!ept)
243 		return NULL;
244 
245 	kref_init(&ept->refcount);
246 	mutex_init(&ept->cb_lock);
247 
248 	ept->rpdev = rpdev;
249 	ept->cb = cb;
250 	ept->priv = priv;
251 	ept->ops = &virtio_endpoint_ops;
252 
253 	/* do we need to allocate a local address ? */
254 	if (addr == RPMSG_ADDR_ANY) {
255 		id_min = RPMSG_RESERVED_ADDRESSES;
256 		id_max = 0;
257 	} else {
258 		id_min = addr;
259 		id_max = addr + 1;
260 	}
261 
262 	mutex_lock(&vrp->endpoints_lock);
263 
264 	/* bind the endpoint to an rpmsg address (and allocate one if needed) */
265 	id = idr_alloc(&vrp->endpoints, ept, id_min, id_max, GFP_KERNEL);
266 	if (id < 0) {
267 		dev_err(dev, "idr_alloc failed: %d\n", id);
268 		goto free_ept;
269 	}
270 	ept->addr = id;
271 
272 	mutex_unlock(&vrp->endpoints_lock);
273 
274 	return ept;
275 
276 free_ept:
277 	mutex_unlock(&vrp->endpoints_lock);
278 	kref_put(&ept->refcount, __ept_release);
279 	return NULL;
280 }
281 
282 static struct rpmsg_endpoint *virtio_rpmsg_create_ept(struct rpmsg_device *rpdev,
283 						      rpmsg_rx_cb_t cb,
284 						      void *priv,
285 						      struct rpmsg_channel_info chinfo)
286 {
287 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
288 
289 	return __rpmsg_create_ept(vch->vrp, rpdev, cb, priv, chinfo.src);
290 }
291 
292 /**
293  * __rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
294  * @vrp: virtproc which owns this ept
295  * @ept: endpoing to destroy
296  *
297  * An internal function which destroy an ept without assuming it is
298  * bound to an rpmsg channel. This is needed for handling the internal
299  * name service endpoint, which isn't bound to an rpmsg channel.
300  * See also __rpmsg_create_ept().
301  */
302 static void
303 __rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
304 {
305 	/* make sure new inbound messages can't find this ept anymore */
306 	mutex_lock(&vrp->endpoints_lock);
307 	idr_remove(&vrp->endpoints, ept->addr);
308 	mutex_unlock(&vrp->endpoints_lock);
309 
310 	/* make sure in-flight inbound messages won't invoke cb anymore */
311 	mutex_lock(&ept->cb_lock);
312 	ept->cb = NULL;
313 	mutex_unlock(&ept->cb_lock);
314 
315 	kref_put(&ept->refcount, __ept_release);
316 }
317 
318 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
319 {
320 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(ept->rpdev);
321 
322 	__rpmsg_destroy_ept(vch->vrp, ept);
323 }
324 
325 static int virtio_rpmsg_announce_create(struct rpmsg_device *rpdev)
326 {
327 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
328 	struct virtproc_info *vrp = vch->vrp;
329 	struct device *dev = &rpdev->dev;
330 	int err = 0;
331 
332 	/* need to tell remote processor's name service about this channel ? */
333 	if (rpdev->announce && rpdev->ept &&
334 	    virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
335 		struct rpmsg_ns_msg nsm;
336 
337 		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
338 		nsm.addr = rpdev->ept->addr;
339 		nsm.flags = RPMSG_NS_CREATE;
340 
341 		err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
342 		if (err)
343 			dev_err(dev, "failed to announce service %d\n", err);
344 	}
345 
346 	return err;
347 }
348 
349 static int virtio_rpmsg_announce_destroy(struct rpmsg_device *rpdev)
350 {
351 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
352 	struct virtproc_info *vrp = vch->vrp;
353 	struct device *dev = &rpdev->dev;
354 	int err = 0;
355 
356 	/* tell remote processor's name service we're removing this channel */
357 	if (rpdev->announce && rpdev->ept &&
358 	    virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
359 		struct rpmsg_ns_msg nsm;
360 
361 		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
362 		nsm.addr = rpdev->ept->addr;
363 		nsm.flags = RPMSG_NS_DESTROY;
364 
365 		err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
366 		if (err)
367 			dev_err(dev, "failed to announce service %d\n", err);
368 	}
369 
370 	return err;
371 }
372 
373 static const struct rpmsg_device_ops virtio_rpmsg_ops = {
374 	.create_ept = virtio_rpmsg_create_ept,
375 	.announce_create = virtio_rpmsg_announce_create,
376 	.announce_destroy = virtio_rpmsg_announce_destroy,
377 };
378 
379 static void virtio_rpmsg_release_device(struct device *dev)
380 {
381 	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
382 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
383 
384 	kfree(vch);
385 }
386 
387 /*
388  * create an rpmsg channel using its name and address info.
389  * this function will be used to create both static and dynamic
390  * channels.
391  */
392 static struct rpmsg_device *rpmsg_create_channel(struct virtproc_info *vrp,
393 						 struct rpmsg_channel_info *chinfo)
394 {
395 	struct virtio_rpmsg_channel *vch;
396 	struct rpmsg_device *rpdev;
397 	struct device *tmp, *dev = &vrp->vdev->dev;
398 	int ret;
399 
400 	/* make sure a similar channel doesn't already exist */
401 	tmp = rpmsg_find_device(dev, chinfo);
402 	if (tmp) {
403 		/* decrement the matched device's refcount back */
404 		put_device(tmp);
405 		dev_err(dev, "channel %s:%x:%x already exist\n",
406 				chinfo->name, chinfo->src, chinfo->dst);
407 		return NULL;
408 	}
409 
410 	vch = kzalloc(sizeof(*vch), GFP_KERNEL);
411 	if (!vch)
412 		return NULL;
413 
414 	/* Link the channel to our vrp */
415 	vch->vrp = vrp;
416 
417 	/* Assign public information to the rpmsg_device */
418 	rpdev = &vch->rpdev;
419 	rpdev->src = chinfo->src;
420 	rpdev->dst = chinfo->dst;
421 	rpdev->ops = &virtio_rpmsg_ops;
422 
423 	/*
424 	 * rpmsg server channels has predefined local address (for now),
425 	 * and their existence needs to be announced remotely
426 	 */
427 	rpdev->announce = rpdev->src != RPMSG_ADDR_ANY;
428 
429 	strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE);
430 
431 	rpdev->dev.parent = &vrp->vdev->dev;
432 	rpdev->dev.release = virtio_rpmsg_release_device;
433 	ret = rpmsg_register_device(rpdev);
434 	if (ret)
435 		return NULL;
436 
437 	return rpdev;
438 }
439 
440 /* super simple buffer "allocator" that is just enough for now */
441 static void *get_a_tx_buf(struct virtproc_info *vrp)
442 {
443 	unsigned int len;
444 	void *ret;
445 
446 	/* support multiple concurrent senders */
447 	mutex_lock(&vrp->tx_lock);
448 
449 	/*
450 	 * either pick the next unused tx buffer
451 	 * (half of our buffers are used for sending messages)
452 	 */
453 	if (vrp->last_sbuf < vrp->num_bufs / 2)
454 		ret = vrp->sbufs + vrp->buf_size * vrp->last_sbuf++;
455 	/* or recycle a used one */
456 	else
457 		ret = virtqueue_get_buf(vrp->svq, &len);
458 
459 	mutex_unlock(&vrp->tx_lock);
460 
461 	return ret;
462 }
463 
464 /**
465  * rpmsg_upref_sleepers() - enable "tx-complete" interrupts, if needed
466  * @vrp: virtual remote processor state
467  *
468  * This function is called before a sender is blocked, waiting for
469  * a tx buffer to become available.
470  *
471  * If we already have blocking senders, this function merely increases
472  * the "sleepers" reference count, and exits.
473  *
474  * Otherwise, if this is the first sender to block, we also enable
475  * virtio's tx callbacks, so we'd be immediately notified when a tx
476  * buffer is consumed (we rely on virtio's tx callback in order
477  * to wake up sleeping senders as soon as a tx buffer is used by the
478  * remote processor).
479  */
480 static void rpmsg_upref_sleepers(struct virtproc_info *vrp)
481 {
482 	/* support multiple concurrent senders */
483 	mutex_lock(&vrp->tx_lock);
484 
485 	/* are we the first sleeping context waiting for tx buffers ? */
486 	if (atomic_inc_return(&vrp->sleepers) == 1)
487 		/* enable "tx-complete" interrupts before dozing off */
488 		virtqueue_enable_cb(vrp->svq);
489 
490 	mutex_unlock(&vrp->tx_lock);
491 }
492 
493 /**
494  * rpmsg_downref_sleepers() - disable "tx-complete" interrupts, if needed
495  * @vrp: virtual remote processor state
496  *
497  * This function is called after a sender, that waited for a tx buffer
498  * to become available, is unblocked.
499  *
500  * If we still have blocking senders, this function merely decreases
501  * the "sleepers" reference count, and exits.
502  *
503  * Otherwise, if there are no more blocking senders, we also disable
504  * virtio's tx callbacks, to avoid the overhead incurred with handling
505  * those (now redundant) interrupts.
506  */
507 static void rpmsg_downref_sleepers(struct virtproc_info *vrp)
508 {
509 	/* support multiple concurrent senders */
510 	mutex_lock(&vrp->tx_lock);
511 
512 	/* are we the last sleeping context waiting for tx buffers ? */
513 	if (atomic_dec_and_test(&vrp->sleepers))
514 		/* disable "tx-complete" interrupts */
515 		virtqueue_disable_cb(vrp->svq);
516 
517 	mutex_unlock(&vrp->tx_lock);
518 }
519 
520 /**
521  * rpmsg_send_offchannel_raw() - send a message across to the remote processor
522  * @rpdev: the rpmsg channel
523  * @src: source address
524  * @dst: destination address
525  * @data: payload of message
526  * @len: length of payload
527  * @wait: indicates whether caller should block in case no TX buffers available
528  *
529  * This function is the base implementation for all of the rpmsg sending API.
530  *
531  * It will send @data of length @len to @dst, and say it's from @src. The
532  * message will be sent to the remote processor which the @rpdev channel
533  * belongs to.
534  *
535  * The message is sent using one of the TX buffers that are available for
536  * communication with this remote processor.
537  *
538  * If @wait is true, the caller will be blocked until either a TX buffer is
539  * available, or 15 seconds elapses (we don't want callers to
540  * sleep indefinitely due to misbehaving remote processors), and in that
541  * case -ERESTARTSYS is returned. The number '15' itself was picked
542  * arbitrarily; there's little point in asking drivers to provide a timeout
543  * value themselves.
544  *
545  * Otherwise, if @wait is false, and there are no TX buffers available,
546  * the function will immediately fail, and -ENOMEM will be returned.
547  *
548  * Normally drivers shouldn't use this function directly; instead, drivers
549  * should use the appropriate rpmsg_{try}send{to, _offchannel} API
550  * (see include/linux/rpmsg.h).
551  *
552  * Returns 0 on success and an appropriate error value on failure.
553  */
554 static int rpmsg_send_offchannel_raw(struct rpmsg_device *rpdev,
555 				     u32 src, u32 dst,
556 				     void *data, int len, bool wait)
557 {
558 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
559 	struct virtproc_info *vrp = vch->vrp;
560 	struct device *dev = &rpdev->dev;
561 	struct scatterlist sg;
562 	struct rpmsg_hdr *msg;
563 	int err;
564 
565 	/* bcasting isn't allowed */
566 	if (src == RPMSG_ADDR_ANY || dst == RPMSG_ADDR_ANY) {
567 		dev_err(dev, "invalid addr (src 0x%x, dst 0x%x)\n", src, dst);
568 		return -EINVAL;
569 	}
570 
571 	/*
572 	 * We currently use fixed-sized buffers, and therefore the payload
573 	 * length is limited.
574 	 *
575 	 * One of the possible improvements here is either to support
576 	 * user-provided buffers (and then we can also support zero-copy
577 	 * messaging), or to improve the buffer allocator, to support
578 	 * variable-length buffer sizes.
579 	 */
580 	if (len > vrp->buf_size - sizeof(struct rpmsg_hdr)) {
581 		dev_err(dev, "message is too big (%d)\n", len);
582 		return -EMSGSIZE;
583 	}
584 
585 	/* grab a buffer */
586 	msg = get_a_tx_buf(vrp);
587 	if (!msg && !wait)
588 		return -ENOMEM;
589 
590 	/* no free buffer ? wait for one (but bail after 15 seconds) */
591 	while (!msg) {
592 		/* enable "tx-complete" interrupts, if not already enabled */
593 		rpmsg_upref_sleepers(vrp);
594 
595 		/*
596 		 * sleep until a free buffer is available or 15 secs elapse.
597 		 * the timeout period is not configurable because there's
598 		 * little point in asking drivers to specify that.
599 		 * if later this happens to be required, it'd be easy to add.
600 		 */
601 		err = wait_event_interruptible_timeout(vrp->sendq,
602 					(msg = get_a_tx_buf(vrp)),
603 					msecs_to_jiffies(15000));
604 
605 		/* disable "tx-complete" interrupts if we're the last sleeper */
606 		rpmsg_downref_sleepers(vrp);
607 
608 		/* timeout ? */
609 		if (!err) {
610 			dev_err(dev, "timeout waiting for a tx buffer\n");
611 			return -ERESTARTSYS;
612 		}
613 	}
614 
615 	msg->len = len;
616 	msg->flags = 0;
617 	msg->src = src;
618 	msg->dst = dst;
619 	msg->reserved = 0;
620 	memcpy(msg->data, data, len);
621 
622 	dev_dbg(dev, "TX From 0x%x, To 0x%x, Len %d, Flags %d, Reserved %d\n",
623 		msg->src, msg->dst, msg->len, msg->flags, msg->reserved);
624 #if defined(CONFIG_DYNAMIC_DEBUG)
625 	dynamic_hex_dump("rpmsg_virtio TX: ", DUMP_PREFIX_NONE, 16, 1,
626 			 msg, sizeof(*msg) + msg->len, true);
627 #endif
628 
629 	rpmsg_sg_init(&sg, msg, sizeof(*msg) + len);
630 
631 	mutex_lock(&vrp->tx_lock);
632 
633 	/* add message to the remote processor's virtqueue */
634 	err = virtqueue_add_outbuf(vrp->svq, &sg, 1, msg, GFP_KERNEL);
635 	if (err) {
636 		/*
637 		 * need to reclaim the buffer here, otherwise it's lost
638 		 * (memory won't leak, but rpmsg won't use it again for TX).
639 		 * this will wait for a buffer management overhaul.
640 		 */
641 		dev_err(dev, "virtqueue_add_outbuf failed: %d\n", err);
642 		goto out;
643 	}
644 
645 	/* tell the remote processor it has a pending message to read */
646 	virtqueue_kick(vrp->svq);
647 out:
648 	mutex_unlock(&vrp->tx_lock);
649 	return err;
650 }
651 
652 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
653 {
654 	struct rpmsg_device *rpdev = ept->rpdev;
655 	u32 src = ept->addr, dst = rpdev->dst;
656 
657 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
658 }
659 
660 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
661 			       u32 dst)
662 {
663 	struct rpmsg_device *rpdev = ept->rpdev;
664 	u32 src = ept->addr;
665 
666 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
667 }
668 
669 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
670 					u32 dst, void *data, int len)
671 {
672 	struct rpmsg_device *rpdev = ept->rpdev;
673 
674 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
675 }
676 
677 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
678 {
679 	struct rpmsg_device *rpdev = ept->rpdev;
680 	u32 src = ept->addr, dst = rpdev->dst;
681 
682 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
683 }
684 
685 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
686 				  int len, u32 dst)
687 {
688 	struct rpmsg_device *rpdev = ept->rpdev;
689 	u32 src = ept->addr;
690 
691 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
692 }
693 
694 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
695 					   u32 dst, void *data, int len)
696 {
697 	struct rpmsg_device *rpdev = ept->rpdev;
698 
699 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
700 }
701 
702 static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
703 			     struct rpmsg_hdr *msg, unsigned int len)
704 {
705 	struct rpmsg_endpoint *ept;
706 	struct scatterlist sg;
707 	int err;
708 
709 	dev_dbg(dev, "From: 0x%x, To: 0x%x, Len: %d, Flags: %d, Reserved: %d\n",
710 		msg->src, msg->dst, msg->len, msg->flags, msg->reserved);
711 #if defined(CONFIG_DYNAMIC_DEBUG)
712 	dynamic_hex_dump("rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
713 			 msg, sizeof(*msg) + msg->len, true);
714 #endif
715 
716 	/*
717 	 * We currently use fixed-sized buffers, so trivially sanitize
718 	 * the reported payload length.
719 	 */
720 	if (len > vrp->buf_size ||
721 	    msg->len > (len - sizeof(struct rpmsg_hdr))) {
722 		dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg->len);
723 		return -EINVAL;
724 	}
725 
726 	/* use the dst addr to fetch the callback of the appropriate user */
727 	mutex_lock(&vrp->endpoints_lock);
728 
729 	ept = idr_find(&vrp->endpoints, msg->dst);
730 
731 	/* let's make sure no one deallocates ept while we use it */
732 	if (ept)
733 		kref_get(&ept->refcount);
734 
735 	mutex_unlock(&vrp->endpoints_lock);
736 
737 	if (ept) {
738 		/* make sure ept->cb doesn't go away while we use it */
739 		mutex_lock(&ept->cb_lock);
740 
741 		if (ept->cb)
742 			ept->cb(ept->rpdev, msg->data, msg->len, ept->priv,
743 				msg->src);
744 
745 		mutex_unlock(&ept->cb_lock);
746 
747 		/* farewell, ept, we don't need you anymore */
748 		kref_put(&ept->refcount, __ept_release);
749 	} else
750 		dev_warn(dev, "msg received with no recipient\n");
751 
752 	/* publish the real size of the buffer */
753 	rpmsg_sg_init(&sg, msg, vrp->buf_size);
754 
755 	/* add the buffer back to the remote processor's virtqueue */
756 	err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, msg, GFP_KERNEL);
757 	if (err < 0) {
758 		dev_err(dev, "failed to add a virtqueue buffer: %d\n", err);
759 		return err;
760 	}
761 
762 	return 0;
763 }
764 
765 /* called when an rx buffer is used, and it's time to digest a message */
766 static void rpmsg_recv_done(struct virtqueue *rvq)
767 {
768 	struct virtproc_info *vrp = rvq->vdev->priv;
769 	struct device *dev = &rvq->vdev->dev;
770 	struct rpmsg_hdr *msg;
771 	unsigned int len, msgs_received = 0;
772 	int err;
773 
774 	msg = virtqueue_get_buf(rvq, &len);
775 	if (!msg) {
776 		dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
777 		return;
778 	}
779 
780 	while (msg) {
781 		err = rpmsg_recv_single(vrp, dev, msg, len);
782 		if (err)
783 			break;
784 
785 		msgs_received++;
786 
787 		msg = virtqueue_get_buf(rvq, &len);
788 	}
789 
790 	dev_dbg(dev, "Received %u messages\n", msgs_received);
791 
792 	/* tell the remote processor we added another available rx buffer */
793 	if (msgs_received)
794 		virtqueue_kick(vrp->rvq);
795 }
796 
797 /*
798  * This is invoked whenever the remote processor completed processing
799  * a TX msg we just sent it, and the buffer is put back to the used ring.
800  *
801  * Normally, though, we suppress this "tx complete" interrupt in order to
802  * avoid the incurred overhead.
803  */
804 static void rpmsg_xmit_done(struct virtqueue *svq)
805 {
806 	struct virtproc_info *vrp = svq->vdev->priv;
807 
808 	dev_dbg(&svq->vdev->dev, "%s\n", __func__);
809 
810 	/* wake up potential senders that are waiting for a tx buffer */
811 	wake_up_interruptible(&vrp->sendq);
812 }
813 
814 /* invoked when a name service announcement arrives */
815 static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len,
816 		       void *priv, u32 src)
817 {
818 	struct rpmsg_ns_msg *msg = data;
819 	struct rpmsg_device *newch;
820 	struct rpmsg_channel_info chinfo;
821 	struct virtproc_info *vrp = priv;
822 	struct device *dev = &vrp->vdev->dev;
823 	int ret;
824 
825 #if defined(CONFIG_DYNAMIC_DEBUG)
826 	dynamic_hex_dump("NS announcement: ", DUMP_PREFIX_NONE, 16, 1,
827 			 data, len, true);
828 #endif
829 
830 	if (len != sizeof(*msg)) {
831 		dev_err(dev, "malformed ns msg (%d)\n", len);
832 		return -EINVAL;
833 	}
834 
835 	/*
836 	 * the name service ept does _not_ belong to a real rpmsg channel,
837 	 * and is handled by the rpmsg bus itself.
838 	 * for sanity reasons, make sure a valid rpdev has _not_ sneaked
839 	 * in somehow.
840 	 */
841 	if (rpdev) {
842 		dev_err(dev, "anomaly: ns ept has an rpdev handle\n");
843 		return -EINVAL;
844 	}
845 
846 	/* don't trust the remote processor for null terminating the name */
847 	msg->name[RPMSG_NAME_SIZE - 1] = '\0';
848 
849 	dev_info(dev, "%sing channel %s addr 0x%x\n",
850 		 msg->flags & RPMSG_NS_DESTROY ? "destroy" : "creat",
851 		 msg->name, msg->addr);
852 
853 	strncpy(chinfo.name, msg->name, sizeof(chinfo.name));
854 	chinfo.src = RPMSG_ADDR_ANY;
855 	chinfo.dst = msg->addr;
856 
857 	if (msg->flags & RPMSG_NS_DESTROY) {
858 		ret = rpmsg_unregister_device(&vrp->vdev->dev, &chinfo);
859 		if (ret)
860 			dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret);
861 	} else {
862 		newch = rpmsg_create_channel(vrp, &chinfo);
863 		if (!newch)
864 			dev_err(dev, "rpmsg_create_channel failed\n");
865 	}
866 
867 	return 0;
868 }
869 
870 static int rpmsg_probe(struct virtio_device *vdev)
871 {
872 	vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
873 	static const char * const names[] = { "input", "output" };
874 	struct virtqueue *vqs[2];
875 	struct virtproc_info *vrp;
876 	void *bufs_va;
877 	int err = 0, i;
878 	size_t total_buf_space;
879 	bool notify;
880 
881 	vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
882 	if (!vrp)
883 		return -ENOMEM;
884 
885 	vrp->vdev = vdev;
886 
887 	idr_init(&vrp->endpoints);
888 	mutex_init(&vrp->endpoints_lock);
889 	mutex_init(&vrp->tx_lock);
890 	init_waitqueue_head(&vrp->sendq);
891 
892 	/* We expect two virtqueues, rx and tx (and in this order) */
893 	err = virtio_find_vqs(vdev, 2, vqs, vq_cbs, names, NULL);
894 	if (err)
895 		goto free_vrp;
896 
897 	vrp->rvq = vqs[0];
898 	vrp->svq = vqs[1];
899 
900 	/* we expect symmetric tx/rx vrings */
901 	WARN_ON(virtqueue_get_vring_size(vrp->rvq) !=
902 		virtqueue_get_vring_size(vrp->svq));
903 
904 	/* we need less buffers if vrings are small */
905 	if (virtqueue_get_vring_size(vrp->rvq) < MAX_RPMSG_NUM_BUFS / 2)
906 		vrp->num_bufs = virtqueue_get_vring_size(vrp->rvq) * 2;
907 	else
908 		vrp->num_bufs = MAX_RPMSG_NUM_BUFS;
909 
910 	vrp->buf_size = MAX_RPMSG_BUF_SIZE;
911 
912 	total_buf_space = vrp->num_bufs * vrp->buf_size;
913 
914 	/* allocate coherent memory for the buffers */
915 	bufs_va = dma_alloc_coherent(vdev->dev.parent->parent,
916 				     total_buf_space, &vrp->bufs_dma,
917 				     GFP_KERNEL);
918 	if (!bufs_va) {
919 		err = -ENOMEM;
920 		goto vqs_del;
921 	}
922 
923 	dev_dbg(&vdev->dev, "buffers: va %p, dma %pad\n",
924 		bufs_va, &vrp->bufs_dma);
925 
926 	/* half of the buffers is dedicated for RX */
927 	vrp->rbufs = bufs_va;
928 
929 	/* and half is dedicated for TX */
930 	vrp->sbufs = bufs_va + total_buf_space / 2;
931 
932 	/* set up the receive buffers */
933 	for (i = 0; i < vrp->num_bufs / 2; i++) {
934 		struct scatterlist sg;
935 		void *cpu_addr = vrp->rbufs + i * vrp->buf_size;
936 
937 		rpmsg_sg_init(&sg, cpu_addr, vrp->buf_size);
938 
939 		err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, cpu_addr,
940 					  GFP_KERNEL);
941 		WARN_ON(err); /* sanity check; this can't really happen */
942 	}
943 
944 	/* suppress "tx-complete" interrupts */
945 	virtqueue_disable_cb(vrp->svq);
946 
947 	vdev->priv = vrp;
948 
949 	/* if supported by the remote processor, enable the name service */
950 	if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
951 		/* a dedicated endpoint handles the name service msgs */
952 		vrp->ns_ept = __rpmsg_create_ept(vrp, NULL, rpmsg_ns_cb,
953 						vrp, RPMSG_NS_ADDR);
954 		if (!vrp->ns_ept) {
955 			dev_err(&vdev->dev, "failed to create the ns ept\n");
956 			err = -ENOMEM;
957 			goto free_coherent;
958 		}
959 	}
960 
961 	/*
962 	 * Prepare to kick but don't notify yet - we can't do this before
963 	 * device is ready.
964 	 */
965 	notify = virtqueue_kick_prepare(vrp->rvq);
966 
967 	/* From this point on, we can notify and get callbacks. */
968 	virtio_device_ready(vdev);
969 
970 	/* tell the remote processor it can start sending messages */
971 	/*
972 	 * this might be concurrent with callbacks, but we are only
973 	 * doing notify, not a full kick here, so that's ok.
974 	 */
975 	if (notify)
976 		virtqueue_notify(vrp->rvq);
977 
978 	dev_info(&vdev->dev, "rpmsg host is online\n");
979 
980 	return 0;
981 
982 free_coherent:
983 	dma_free_coherent(vdev->dev.parent->parent, total_buf_space,
984 			  bufs_va, vrp->bufs_dma);
985 vqs_del:
986 	vdev->config->del_vqs(vrp->vdev);
987 free_vrp:
988 	kfree(vrp);
989 	return err;
990 }
991 
992 static int rpmsg_remove_device(struct device *dev, void *data)
993 {
994 	device_unregister(dev);
995 
996 	return 0;
997 }
998 
999 static void rpmsg_remove(struct virtio_device *vdev)
1000 {
1001 	struct virtproc_info *vrp = vdev->priv;
1002 	size_t total_buf_space = vrp->num_bufs * vrp->buf_size;
1003 	int ret;
1004 
1005 	vdev->config->reset(vdev);
1006 
1007 	ret = device_for_each_child(&vdev->dev, NULL, rpmsg_remove_device);
1008 	if (ret)
1009 		dev_warn(&vdev->dev, "can't remove rpmsg device: %d\n", ret);
1010 
1011 	if (vrp->ns_ept)
1012 		__rpmsg_destroy_ept(vrp, vrp->ns_ept);
1013 
1014 	idr_destroy(&vrp->endpoints);
1015 
1016 	vdev->config->del_vqs(vrp->vdev);
1017 
1018 	dma_free_coherent(vdev->dev.parent->parent, total_buf_space,
1019 			  vrp->rbufs, vrp->bufs_dma);
1020 
1021 	kfree(vrp);
1022 }
1023 
1024 static struct virtio_device_id id_table[] = {
1025 	{ VIRTIO_ID_RPMSG, VIRTIO_DEV_ANY_ID },
1026 	{ 0 },
1027 };
1028 
1029 static unsigned int features[] = {
1030 	VIRTIO_RPMSG_F_NS,
1031 };
1032 
1033 static struct virtio_driver virtio_ipc_driver = {
1034 	.feature_table	= features,
1035 	.feature_table_size = ARRAY_SIZE(features),
1036 	.driver.name	= KBUILD_MODNAME,
1037 	.driver.owner	= THIS_MODULE,
1038 	.id_table	= id_table,
1039 	.probe		= rpmsg_probe,
1040 	.remove		= rpmsg_remove,
1041 };
1042 
1043 static int __init rpmsg_init(void)
1044 {
1045 	int ret;
1046 
1047 	ret = register_virtio_driver(&virtio_ipc_driver);
1048 	if (ret)
1049 		pr_err("failed to register virtio driver: %d\n", ret);
1050 
1051 	return ret;
1052 }
1053 subsys_initcall(rpmsg_init);
1054 
1055 static void __exit rpmsg_fini(void)
1056 {
1057 	unregister_virtio_driver(&virtio_ipc_driver);
1058 }
1059 module_exit(rpmsg_fini);
1060 
1061 MODULE_DEVICE_TABLE(virtio, id_table);
1062 MODULE_DESCRIPTION("Virtio-based remote processor messaging bus");
1063 MODULE_LICENSE("GPL v2");
1064