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/rpmsg/byteorder.h>
23 #include <linux/rpmsg/ns.h>
24 #include <linux/scatterlist.h>
25 #include <linux/slab.h>
26 #include <linux/sched.h>
27 #include <linux/virtio.h>
28 #include <linux/virtio_ids.h>
29 #include <linux/virtio_config.h>
30 #include <linux/wait.h>
31 
32 #include "rpmsg_internal.h"
33 
34 /**
35  * struct virtproc_info - virtual remote processor state
36  * @vdev:	the virtio device
37  * @rvq:	rx virtqueue
38  * @svq:	tx virtqueue
39  * @rbufs:	kernel address of rx buffers
40  * @sbufs:	kernel address of tx buffers
41  * @num_bufs:	total number of buffers for rx and tx
42  * @buf_size:   size of one rx or tx buffer
43  * @last_sbuf:	index of last tx buffer used
44  * @bufs_dma:	dma base addr of the buffers
45  * @tx_lock:	protects svq, sbufs and sleepers, to allow concurrent senders.
46  *		sending a message might require waking up a dozing remote
47  *		processor, which involves sleeping, hence the mutex.
48  * @endpoints:	idr of local endpoints, allows fast retrieval
49  * @endpoints_lock: lock of the endpoints set
50  * @sendq:	wait queue of sending contexts waiting for a tx buffers
51  * @sleepers:	number of senders that are waiting for a tx buffer
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 };
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 	__rpmsg32 src;
88 	__rpmsg32 dst;
89 	__rpmsg32 reserved;
90 	__rpmsg16 len;
91 	__rpmsg16 flags;
92 	u8 data[];
93 } __packed;
94 
95 
96 /**
97  * struct virtio_rpmsg_channel - rpmsg channel descriptor
98  * @rpdev: the rpmsg channel device
99  * @vrp: the virtio remote processor device this channel belongs to
100  *
101  * This structure stores the channel that links the rpmsg device to the virtio
102  * remote processor device.
103  */
104 struct virtio_rpmsg_channel {
105 	struct rpmsg_device rpdev;
106 
107 	struct virtproc_info *vrp;
108 };
109 
110 #define to_virtio_rpmsg_channel(_rpdev) \
111 	container_of(_rpdev, struct virtio_rpmsg_channel, rpdev)
112 
113 /*
114  * We're allocating buffers of 512 bytes each for communications. The
115  * number of buffers will be computed from the number of buffers supported
116  * by the vring, upto a maximum of 512 buffers (256 in each direction).
117  *
118  * Each buffer will have 16 bytes for the msg header and 496 bytes for
119  * the payload.
120  *
121  * This will utilize a maximum total space of 256KB for the buffers.
122  *
123  * We might also want to add support for user-provided buffers in time.
124  * This will allow bigger buffer size flexibility, and can also be used
125  * to achieve zero-copy messaging.
126  *
127  * Note that these numbers are purely a decision of this driver - we
128  * can change this without changing anything in the firmware of the remote
129  * processor.
130  */
131 #define MAX_RPMSG_NUM_BUFS	(512)
132 #define MAX_RPMSG_BUF_SIZE	(512)
133 
134 /*
135  * Local addresses are dynamically allocated on-demand.
136  * We do not dynamically assign addresses from the low 1024 range,
137  * in order to reserve that address range for predefined services.
138  */
139 #define RPMSG_RESERVED_ADDRESSES	(1024)
140 
141 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
142 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len);
143 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
144 			       u32 dst);
145 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
146 					u32 dst, void *data, int len);
147 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len);
148 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
149 				  int len, u32 dst);
150 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
151 					   u32 dst, void *data, int len);
152 static struct rpmsg_device *__rpmsg_create_channel(struct virtproc_info *vrp,
153 						   struct rpmsg_channel_info *chinfo);
154 
155 static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
156 	.destroy_ept = virtio_rpmsg_destroy_ept,
157 	.send = virtio_rpmsg_send,
158 	.sendto = virtio_rpmsg_sendto,
159 	.send_offchannel = virtio_rpmsg_send_offchannel,
160 	.trysend = virtio_rpmsg_trysend,
161 	.trysendto = virtio_rpmsg_trysendto,
162 	.trysend_offchannel = virtio_rpmsg_trysend_offchannel,
163 };
164 
165 /**
166  * rpmsg_sg_init - initialize scatterlist according to cpu address location
167  * @sg: scatterlist to fill
168  * @cpu_addr: virtual address of the buffer
169  * @len: buffer length
170  *
171  * An internal function filling scatterlist according to virtual address
172  * location (in vmalloc or in kernel).
173  */
174 static void
175 rpmsg_sg_init(struct scatterlist *sg, void *cpu_addr, unsigned int len)
176 {
177 	if (is_vmalloc_addr(cpu_addr)) {
178 		sg_init_table(sg, 1);
179 		sg_set_page(sg, vmalloc_to_page(cpu_addr), len,
180 			    offset_in_page(cpu_addr));
181 	} else {
182 		WARN_ON(!virt_addr_valid(cpu_addr));
183 		sg_init_one(sg, cpu_addr, len);
184 	}
185 }
186 
187 /**
188  * __ept_release() - deallocate an rpmsg endpoint
189  * @kref: the ept's reference count
190  *
191  * This function deallocates an ept, and is invoked when its @kref refcount
192  * drops to zero.
193  *
194  * Never invoke this function directly!
195  */
196 static void __ept_release(struct kref *kref)
197 {
198 	struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
199 						  refcount);
200 	/*
201 	 * At this point no one holds a reference to ept anymore,
202 	 * so we can directly free it
203 	 */
204 	kfree(ept);
205 }
206 
207 /* for more info, see below documentation of rpmsg_create_ept() */
208 static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
209 						 struct rpmsg_device *rpdev,
210 						 rpmsg_rx_cb_t cb,
211 						 void *priv, u32 addr)
212 {
213 	int id_min, id_max, id;
214 	struct rpmsg_endpoint *ept;
215 	struct device *dev = rpdev ? &rpdev->dev : &vrp->vdev->dev;
216 
217 	ept = kzalloc(sizeof(*ept), GFP_KERNEL);
218 	if (!ept)
219 		return NULL;
220 
221 	kref_init(&ept->refcount);
222 	mutex_init(&ept->cb_lock);
223 
224 	ept->rpdev = rpdev;
225 	ept->cb = cb;
226 	ept->priv = priv;
227 	ept->ops = &virtio_endpoint_ops;
228 
229 	/* do we need to allocate a local address ? */
230 	if (addr == RPMSG_ADDR_ANY) {
231 		id_min = RPMSG_RESERVED_ADDRESSES;
232 		id_max = 0;
233 	} else {
234 		id_min = addr;
235 		id_max = addr + 1;
236 	}
237 
238 	mutex_lock(&vrp->endpoints_lock);
239 
240 	/* bind the endpoint to an rpmsg address (and allocate one if needed) */
241 	id = idr_alloc(&vrp->endpoints, ept, id_min, id_max, GFP_KERNEL);
242 	if (id < 0) {
243 		dev_err(dev, "idr_alloc failed: %d\n", id);
244 		goto free_ept;
245 	}
246 	ept->addr = id;
247 
248 	mutex_unlock(&vrp->endpoints_lock);
249 
250 	return ept;
251 
252 free_ept:
253 	mutex_unlock(&vrp->endpoints_lock);
254 	kref_put(&ept->refcount, __ept_release);
255 	return NULL;
256 }
257 
258 static struct rpmsg_device *virtio_rpmsg_create_channel(struct rpmsg_device *rpdev,
259 							struct rpmsg_channel_info *chinfo)
260 {
261 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
262 	struct virtproc_info *vrp = vch->vrp;
263 
264 	return __rpmsg_create_channel(vrp, chinfo);
265 }
266 
267 static int virtio_rpmsg_release_channel(struct rpmsg_device *rpdev,
268 					struct rpmsg_channel_info *chinfo)
269 {
270 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
271 	struct virtproc_info *vrp = vch->vrp;
272 
273 	return rpmsg_unregister_device(&vrp->vdev->dev, chinfo);
274 }
275 
276 static struct rpmsg_endpoint *virtio_rpmsg_create_ept(struct rpmsg_device *rpdev,
277 						      rpmsg_rx_cb_t cb,
278 						      void *priv,
279 						      struct rpmsg_channel_info chinfo)
280 {
281 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
282 
283 	return __rpmsg_create_ept(vch->vrp, rpdev, cb, priv, chinfo.src);
284 }
285 
286 /**
287  * __rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
288  * @vrp: virtproc which owns this ept
289  * @ept: endpoing to destroy
290  *
291  * An internal function which destroy an ept without assuming it is
292  * bound to an rpmsg channel. This is needed for handling the internal
293  * name service endpoint, which isn't bound to an rpmsg channel.
294  * See also __rpmsg_create_ept().
295  */
296 static void
297 __rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
298 {
299 	/* make sure new inbound messages can't find this ept anymore */
300 	mutex_lock(&vrp->endpoints_lock);
301 	idr_remove(&vrp->endpoints, ept->addr);
302 	mutex_unlock(&vrp->endpoints_lock);
303 
304 	/* make sure in-flight inbound messages won't invoke cb anymore */
305 	mutex_lock(&ept->cb_lock);
306 	ept->cb = NULL;
307 	mutex_unlock(&ept->cb_lock);
308 
309 	kref_put(&ept->refcount, __ept_release);
310 }
311 
312 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
313 {
314 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(ept->rpdev);
315 
316 	__rpmsg_destroy_ept(vch->vrp, ept);
317 }
318 
319 static int virtio_rpmsg_announce_create(struct rpmsg_device *rpdev)
320 {
321 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
322 	struct virtproc_info *vrp = vch->vrp;
323 	struct device *dev = &rpdev->dev;
324 	int err = 0;
325 
326 	/* need to tell remote processor's name service about this channel ? */
327 	if (rpdev->announce && rpdev->ept &&
328 	    virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
329 		struct rpmsg_ns_msg nsm;
330 
331 		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
332 		nsm.addr = cpu_to_rpmsg32(rpdev, rpdev->ept->addr);
333 		nsm.flags = cpu_to_rpmsg32(rpdev, RPMSG_NS_CREATE);
334 
335 		err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
336 		if (err)
337 			dev_err(dev, "failed to announce service %d\n", err);
338 	}
339 
340 	return err;
341 }
342 
343 static int virtio_rpmsg_announce_destroy(struct rpmsg_device *rpdev)
344 {
345 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
346 	struct virtproc_info *vrp = vch->vrp;
347 	struct device *dev = &rpdev->dev;
348 	int err = 0;
349 
350 	/* tell remote processor's name service we're removing this channel */
351 	if (rpdev->announce && rpdev->ept &&
352 	    virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
353 		struct rpmsg_ns_msg nsm;
354 
355 		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
356 		nsm.addr = cpu_to_rpmsg32(rpdev, rpdev->ept->addr);
357 		nsm.flags = cpu_to_rpmsg32(rpdev, RPMSG_NS_DESTROY);
358 
359 		err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
360 		if (err)
361 			dev_err(dev, "failed to announce service %d\n", err);
362 	}
363 
364 	return err;
365 }
366 
367 static const struct rpmsg_device_ops virtio_rpmsg_ops = {
368 	.create_channel = virtio_rpmsg_create_channel,
369 	.release_channel = virtio_rpmsg_release_channel,
370 	.create_ept = virtio_rpmsg_create_ept,
371 	.announce_create = virtio_rpmsg_announce_create,
372 	.announce_destroy = virtio_rpmsg_announce_destroy,
373 };
374 
375 static void virtio_rpmsg_release_device(struct device *dev)
376 {
377 	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
378 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
379 
380 	kfree(vch);
381 }
382 
383 /*
384  * create an rpmsg channel using its name and address info.
385  * this function will be used to create both static and dynamic
386  * channels.
387  */
388 static struct rpmsg_device *__rpmsg_create_channel(struct virtproc_info *vrp,
389 						   struct rpmsg_channel_info *chinfo)
390 {
391 	struct virtio_rpmsg_channel *vch;
392 	struct rpmsg_device *rpdev;
393 	struct device *tmp, *dev = &vrp->vdev->dev;
394 	int ret;
395 
396 	/* make sure a similar channel doesn't already exist */
397 	tmp = rpmsg_find_device(dev, chinfo);
398 	if (tmp) {
399 		/* decrement the matched device's refcount back */
400 		put_device(tmp);
401 		dev_err(dev, "channel %s:%x:%x already exist\n",
402 				chinfo->name, chinfo->src, chinfo->dst);
403 		return NULL;
404 	}
405 
406 	vch = kzalloc(sizeof(*vch), GFP_KERNEL);
407 	if (!vch)
408 		return NULL;
409 
410 	/* Link the channel to our vrp */
411 	vch->vrp = vrp;
412 
413 	/* Assign public information to the rpmsg_device */
414 	rpdev = &vch->rpdev;
415 	rpdev->src = chinfo->src;
416 	rpdev->dst = chinfo->dst;
417 	rpdev->ops = &virtio_rpmsg_ops;
418 	rpdev->little_endian = virtio_is_little_endian(vrp->vdev);
419 
420 	/*
421 	 * rpmsg server channels has predefined local address (for now),
422 	 * and their existence needs to be announced remotely
423 	 */
424 	rpdev->announce = rpdev->src != RPMSG_ADDR_ANY;
425 
426 	strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE);
427 
428 	rpdev->dev.parent = &vrp->vdev->dev;
429 	rpdev->dev.release = virtio_rpmsg_release_device;
430 	ret = rpmsg_register_device(rpdev);
431 	if (ret)
432 		return NULL;
433 
434 	return rpdev;
435 }
436 
437 /* super simple buffer "allocator" that is just enough for now */
438 static void *get_a_tx_buf(struct virtproc_info *vrp)
439 {
440 	unsigned int len;
441 	void *ret;
442 
443 	/* support multiple concurrent senders */
444 	mutex_lock(&vrp->tx_lock);
445 
446 	/*
447 	 * either pick the next unused tx buffer
448 	 * (half of our buffers are used for sending messages)
449 	 */
450 	if (vrp->last_sbuf < vrp->num_bufs / 2)
451 		ret = vrp->sbufs + vrp->buf_size * vrp->last_sbuf++;
452 	/* or recycle a used one */
453 	else
454 		ret = virtqueue_get_buf(vrp->svq, &len);
455 
456 	mutex_unlock(&vrp->tx_lock);
457 
458 	return ret;
459 }
460 
461 /**
462  * rpmsg_upref_sleepers() - enable "tx-complete" interrupts, if needed
463  * @vrp: virtual remote processor state
464  *
465  * This function is called before a sender is blocked, waiting for
466  * a tx buffer to become available.
467  *
468  * If we already have blocking senders, this function merely increases
469  * the "sleepers" reference count, and exits.
470  *
471  * Otherwise, if this is the first sender to block, we also enable
472  * virtio's tx callbacks, so we'd be immediately notified when a tx
473  * buffer is consumed (we rely on virtio's tx callback in order
474  * to wake up sleeping senders as soon as a tx buffer is used by the
475  * remote processor).
476  */
477 static void rpmsg_upref_sleepers(struct virtproc_info *vrp)
478 {
479 	/* support multiple concurrent senders */
480 	mutex_lock(&vrp->tx_lock);
481 
482 	/* are we the first sleeping context waiting for tx buffers ? */
483 	if (atomic_inc_return(&vrp->sleepers) == 1)
484 		/* enable "tx-complete" interrupts before dozing off */
485 		virtqueue_enable_cb(vrp->svq);
486 
487 	mutex_unlock(&vrp->tx_lock);
488 }
489 
490 /**
491  * rpmsg_downref_sleepers() - disable "tx-complete" interrupts, if needed
492  * @vrp: virtual remote processor state
493  *
494  * This function is called after a sender, that waited for a tx buffer
495  * to become available, is unblocked.
496  *
497  * If we still have blocking senders, this function merely decreases
498  * the "sleepers" reference count, and exits.
499  *
500  * Otherwise, if there are no more blocking senders, we also disable
501  * virtio's tx callbacks, to avoid the overhead incurred with handling
502  * those (now redundant) interrupts.
503  */
504 static void rpmsg_downref_sleepers(struct virtproc_info *vrp)
505 {
506 	/* support multiple concurrent senders */
507 	mutex_lock(&vrp->tx_lock);
508 
509 	/* are we the last sleeping context waiting for tx buffers ? */
510 	if (atomic_dec_and_test(&vrp->sleepers))
511 		/* disable "tx-complete" interrupts */
512 		virtqueue_disable_cb(vrp->svq);
513 
514 	mutex_unlock(&vrp->tx_lock);
515 }
516 
517 /**
518  * rpmsg_send_offchannel_raw() - send a message across to the remote processor
519  * @rpdev: the rpmsg channel
520  * @src: source address
521  * @dst: destination address
522  * @data: payload of message
523  * @len: length of payload
524  * @wait: indicates whether caller should block in case no TX buffers available
525  *
526  * This function is the base implementation for all of the rpmsg sending API.
527  *
528  * It will send @data of length @len to @dst, and say it's from @src. The
529  * message will be sent to the remote processor which the @rpdev channel
530  * belongs to.
531  *
532  * The message is sent using one of the TX buffers that are available for
533  * communication with this remote processor.
534  *
535  * If @wait is true, the caller will be blocked until either a TX buffer is
536  * available, or 15 seconds elapses (we don't want callers to
537  * sleep indefinitely due to misbehaving remote processors), and in that
538  * case -ERESTARTSYS is returned. The number '15' itself was picked
539  * arbitrarily; there's little point in asking drivers to provide a timeout
540  * value themselves.
541  *
542  * Otherwise, if @wait is false, and there are no TX buffers available,
543  * the function will immediately fail, and -ENOMEM will be returned.
544  *
545  * Normally drivers shouldn't use this function directly; instead, drivers
546  * should use the appropriate rpmsg_{try}send{to, _offchannel} API
547  * (see include/linux/rpmsg.h).
548  *
549  * Returns 0 on success and an appropriate error value on failure.
550  */
551 static int rpmsg_send_offchannel_raw(struct rpmsg_device *rpdev,
552 				     u32 src, u32 dst,
553 				     void *data, int len, bool wait)
554 {
555 	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
556 	struct virtproc_info *vrp = vch->vrp;
557 	struct device *dev = &rpdev->dev;
558 	struct scatterlist sg;
559 	struct rpmsg_hdr *msg;
560 	int err;
561 
562 	/* bcasting isn't allowed */
563 	if (src == RPMSG_ADDR_ANY || dst == RPMSG_ADDR_ANY) {
564 		dev_err(dev, "invalid addr (src 0x%x, dst 0x%x)\n", src, dst);
565 		return -EINVAL;
566 	}
567 
568 	/*
569 	 * We currently use fixed-sized buffers, and therefore the payload
570 	 * length is limited.
571 	 *
572 	 * One of the possible improvements here is either to support
573 	 * user-provided buffers (and then we can also support zero-copy
574 	 * messaging), or to improve the buffer allocator, to support
575 	 * variable-length buffer sizes.
576 	 */
577 	if (len > vrp->buf_size - sizeof(struct rpmsg_hdr)) {
578 		dev_err(dev, "message is too big (%d)\n", len);
579 		return -EMSGSIZE;
580 	}
581 
582 	/* grab a buffer */
583 	msg = get_a_tx_buf(vrp);
584 	if (!msg && !wait)
585 		return -ENOMEM;
586 
587 	/* no free buffer ? wait for one (but bail after 15 seconds) */
588 	while (!msg) {
589 		/* enable "tx-complete" interrupts, if not already enabled */
590 		rpmsg_upref_sleepers(vrp);
591 
592 		/*
593 		 * sleep until a free buffer is available or 15 secs elapse.
594 		 * the timeout period is not configurable because there's
595 		 * little point in asking drivers to specify that.
596 		 * if later this happens to be required, it'd be easy to add.
597 		 */
598 		err = wait_event_interruptible_timeout(vrp->sendq,
599 					(msg = get_a_tx_buf(vrp)),
600 					msecs_to_jiffies(15000));
601 
602 		/* disable "tx-complete" interrupts if we're the last sleeper */
603 		rpmsg_downref_sleepers(vrp);
604 
605 		/* timeout ? */
606 		if (!err) {
607 			dev_err(dev, "timeout waiting for a tx buffer\n");
608 			return -ERESTARTSYS;
609 		}
610 	}
611 
612 	msg->len = cpu_to_rpmsg16(rpdev, len);
613 	msg->flags = 0;
614 	msg->src = cpu_to_rpmsg32(rpdev, src);
615 	msg->dst = cpu_to_rpmsg32(rpdev, dst);
616 	msg->reserved = 0;
617 	memcpy(msg->data, data, len);
618 
619 	dev_dbg(dev, "TX From 0x%x, To 0x%x, Len %d, Flags %d, Reserved %d\n",
620 		src, dst, len, msg->flags, msg->reserved);
621 #if defined(CONFIG_DYNAMIC_DEBUG)
622 	dynamic_hex_dump("rpmsg_virtio TX: ", DUMP_PREFIX_NONE, 16, 1,
623 			 msg, sizeof(*msg) + len, true);
624 #endif
625 
626 	rpmsg_sg_init(&sg, msg, sizeof(*msg) + len);
627 
628 	mutex_lock(&vrp->tx_lock);
629 
630 	/* add message to the remote processor's virtqueue */
631 	err = virtqueue_add_outbuf(vrp->svq, &sg, 1, msg, GFP_KERNEL);
632 	if (err) {
633 		/*
634 		 * need to reclaim the buffer here, otherwise it's lost
635 		 * (memory won't leak, but rpmsg won't use it again for TX).
636 		 * this will wait for a buffer management overhaul.
637 		 */
638 		dev_err(dev, "virtqueue_add_outbuf failed: %d\n", err);
639 		goto out;
640 	}
641 
642 	/* tell the remote processor it has a pending message to read */
643 	virtqueue_kick(vrp->svq);
644 out:
645 	mutex_unlock(&vrp->tx_lock);
646 	return err;
647 }
648 
649 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
650 {
651 	struct rpmsg_device *rpdev = ept->rpdev;
652 	u32 src = ept->addr, dst = rpdev->dst;
653 
654 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
655 }
656 
657 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
658 			       u32 dst)
659 {
660 	struct rpmsg_device *rpdev = ept->rpdev;
661 	u32 src = ept->addr;
662 
663 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
664 }
665 
666 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
667 					u32 dst, void *data, int len)
668 {
669 	struct rpmsg_device *rpdev = ept->rpdev;
670 
671 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
672 }
673 
674 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
675 {
676 	struct rpmsg_device *rpdev = ept->rpdev;
677 	u32 src = ept->addr, dst = rpdev->dst;
678 
679 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
680 }
681 
682 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
683 				  int len, u32 dst)
684 {
685 	struct rpmsg_device *rpdev = ept->rpdev;
686 	u32 src = ept->addr;
687 
688 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
689 }
690 
691 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
692 					   u32 dst, void *data, int len)
693 {
694 	struct rpmsg_device *rpdev = ept->rpdev;
695 
696 	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
697 }
698 
699 static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
700 			     struct rpmsg_hdr *msg, unsigned int len)
701 {
702 	struct rpmsg_endpoint *ept;
703 	struct scatterlist sg;
704 	bool little_endian = virtio_is_little_endian(vrp->vdev);
705 	unsigned int msg_len = __rpmsg16_to_cpu(little_endian, msg->len);
706 	int err;
707 
708 	dev_dbg(dev, "From: 0x%x, To: 0x%x, Len: %d, Flags: %d, Reserved: %d\n",
709 		__rpmsg32_to_cpu(little_endian, msg->src),
710 		__rpmsg32_to_cpu(little_endian, msg->dst), msg_len,
711 		__rpmsg16_to_cpu(little_endian, msg->flags),
712 		__rpmsg32_to_cpu(little_endian, msg->reserved));
713 #if defined(CONFIG_DYNAMIC_DEBUG)
714 	dynamic_hex_dump("rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
715 			 msg, sizeof(*msg) + msg_len, true);
716 #endif
717 
718 	/*
719 	 * We currently use fixed-sized buffers, so trivially sanitize
720 	 * the reported payload length.
721 	 */
722 	if (len > vrp->buf_size ||
723 	    msg_len > (len - sizeof(struct rpmsg_hdr))) {
724 		dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg_len);
725 		return -EINVAL;
726 	}
727 
728 	/* use the dst addr to fetch the callback of the appropriate user */
729 	mutex_lock(&vrp->endpoints_lock);
730 
731 	ept = idr_find(&vrp->endpoints, __rpmsg32_to_cpu(little_endian, msg->dst));
732 
733 	/* let's make sure no one deallocates ept while we use it */
734 	if (ept)
735 		kref_get(&ept->refcount);
736 
737 	mutex_unlock(&vrp->endpoints_lock);
738 
739 	if (ept) {
740 		/* make sure ept->cb doesn't go away while we use it */
741 		mutex_lock(&ept->cb_lock);
742 
743 		if (ept->cb)
744 			ept->cb(ept->rpdev, msg->data, msg_len, ept->priv,
745 				__rpmsg32_to_cpu(little_endian, msg->src));
746 
747 		mutex_unlock(&ept->cb_lock);
748 
749 		/* farewell, ept, we don't need you anymore */
750 		kref_put(&ept->refcount, __ept_release);
751 	} else
752 		dev_warn(dev, "msg received with no recipient\n");
753 
754 	/* publish the real size of the buffer */
755 	rpmsg_sg_init(&sg, msg, vrp->buf_size);
756 
757 	/* add the buffer back to the remote processor's virtqueue */
758 	err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, msg, GFP_KERNEL);
759 	if (err < 0) {
760 		dev_err(dev, "failed to add a virtqueue buffer: %d\n", err);
761 		return err;
762 	}
763 
764 	return 0;
765 }
766 
767 /* called when an rx buffer is used, and it's time to digest a message */
768 static void rpmsg_recv_done(struct virtqueue *rvq)
769 {
770 	struct virtproc_info *vrp = rvq->vdev->priv;
771 	struct device *dev = &rvq->vdev->dev;
772 	struct rpmsg_hdr *msg;
773 	unsigned int len, msgs_received = 0;
774 	int err;
775 
776 	msg = virtqueue_get_buf(rvq, &len);
777 	if (!msg) {
778 		dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
779 		return;
780 	}
781 
782 	while (msg) {
783 		err = rpmsg_recv_single(vrp, dev, msg, len);
784 		if (err)
785 			break;
786 
787 		msgs_received++;
788 
789 		msg = virtqueue_get_buf(rvq, &len);
790 	}
791 
792 	dev_dbg(dev, "Received %u messages\n", msgs_received);
793 
794 	/* tell the remote processor we added another available rx buffer */
795 	if (msgs_received)
796 		virtqueue_kick(vrp->rvq);
797 }
798 
799 /*
800  * This is invoked whenever the remote processor completed processing
801  * a TX msg we just sent it, and the buffer is put back to the used ring.
802  *
803  * Normally, though, we suppress this "tx complete" interrupt in order to
804  * avoid the incurred overhead.
805  */
806 static void rpmsg_xmit_done(struct virtqueue *svq)
807 {
808 	struct virtproc_info *vrp = svq->vdev->priv;
809 
810 	dev_dbg(&svq->vdev->dev, "%s\n", __func__);
811 
812 	/* wake up potential senders that are waiting for a tx buffer */
813 	wake_up_interruptible(&vrp->sendq);
814 }
815 
816 /*
817  * Called to expose to user a /dev/rpmsg_ctrlX interface allowing to
818  * create endpoint-to-endpoint communication without associated RPMsg channel.
819  * The endpoints are rattached to the ctrldev RPMsg device.
820  */
821 static struct rpmsg_device *rpmsg_virtio_add_ctrl_dev(struct virtio_device *vdev)
822 {
823 	struct virtproc_info *vrp = vdev->priv;
824 	struct virtio_rpmsg_channel *vch;
825 	struct rpmsg_device *rpdev_ctrl;
826 	int err = 0;
827 
828 	vch = kzalloc(sizeof(*vch), GFP_KERNEL);
829 	if (!vch)
830 		return ERR_PTR(-ENOMEM);
831 
832 	/* Link the channel to the vrp */
833 	vch->vrp = vrp;
834 
835 	/* Assign public information to the rpmsg_device */
836 	rpdev_ctrl = &vch->rpdev;
837 	rpdev_ctrl->ops = &virtio_rpmsg_ops;
838 
839 	rpdev_ctrl->dev.parent = &vrp->vdev->dev;
840 	rpdev_ctrl->dev.release = virtio_rpmsg_release_device;
841 	rpdev_ctrl->little_endian = virtio_is_little_endian(vrp->vdev);
842 
843 	err = rpmsg_chrdev_register_device(rpdev_ctrl);
844 	if (err) {
845 		kfree(vch);
846 		return ERR_PTR(err);
847 	}
848 
849 	return rpdev_ctrl;
850 }
851 
852 static void rpmsg_virtio_del_ctrl_dev(struct rpmsg_device *rpdev_ctrl)
853 {
854 	if (!rpdev_ctrl)
855 		return;
856 	kfree(to_virtio_rpmsg_channel(rpdev_ctrl));
857 }
858 
859 static int rpmsg_probe(struct virtio_device *vdev)
860 {
861 	vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
862 	static const char * const names[] = { "input", "output" };
863 	struct virtqueue *vqs[2];
864 	struct virtproc_info *vrp;
865 	struct virtio_rpmsg_channel *vch = NULL;
866 	struct rpmsg_device *rpdev_ns, *rpdev_ctrl;
867 	void *bufs_va;
868 	int err = 0, i;
869 	size_t total_buf_space;
870 	bool notify;
871 
872 	vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
873 	if (!vrp)
874 		return -ENOMEM;
875 
876 	vrp->vdev = vdev;
877 
878 	idr_init(&vrp->endpoints);
879 	mutex_init(&vrp->endpoints_lock);
880 	mutex_init(&vrp->tx_lock);
881 	init_waitqueue_head(&vrp->sendq);
882 
883 	/* We expect two virtqueues, rx and tx (and in this order) */
884 	err = virtio_find_vqs(vdev, 2, vqs, vq_cbs, names, NULL);
885 	if (err)
886 		goto free_vrp;
887 
888 	vrp->rvq = vqs[0];
889 	vrp->svq = vqs[1];
890 
891 	/* we expect symmetric tx/rx vrings */
892 	WARN_ON(virtqueue_get_vring_size(vrp->rvq) !=
893 		virtqueue_get_vring_size(vrp->svq));
894 
895 	/* we need less buffers if vrings are small */
896 	if (virtqueue_get_vring_size(vrp->rvq) < MAX_RPMSG_NUM_BUFS / 2)
897 		vrp->num_bufs = virtqueue_get_vring_size(vrp->rvq) * 2;
898 	else
899 		vrp->num_bufs = MAX_RPMSG_NUM_BUFS;
900 
901 	vrp->buf_size = MAX_RPMSG_BUF_SIZE;
902 
903 	total_buf_space = vrp->num_bufs * vrp->buf_size;
904 
905 	/* allocate coherent memory for the buffers */
906 	bufs_va = dma_alloc_coherent(vdev->dev.parent,
907 				     total_buf_space, &vrp->bufs_dma,
908 				     GFP_KERNEL);
909 	if (!bufs_va) {
910 		err = -ENOMEM;
911 		goto vqs_del;
912 	}
913 
914 	dev_dbg(&vdev->dev, "buffers: va %pK, dma %pad\n",
915 		bufs_va, &vrp->bufs_dma);
916 
917 	/* half of the buffers is dedicated for RX */
918 	vrp->rbufs = bufs_va;
919 
920 	/* and half is dedicated for TX */
921 	vrp->sbufs = bufs_va + total_buf_space / 2;
922 
923 	/* set up the receive buffers */
924 	for (i = 0; i < vrp->num_bufs / 2; i++) {
925 		struct scatterlist sg;
926 		void *cpu_addr = vrp->rbufs + i * vrp->buf_size;
927 
928 		rpmsg_sg_init(&sg, cpu_addr, vrp->buf_size);
929 
930 		err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, cpu_addr,
931 					  GFP_KERNEL);
932 		WARN_ON(err); /* sanity check; this can't really happen */
933 	}
934 
935 	/* suppress "tx-complete" interrupts */
936 	virtqueue_disable_cb(vrp->svq);
937 
938 	vdev->priv = vrp;
939 
940 	rpdev_ctrl = rpmsg_virtio_add_ctrl_dev(vdev);
941 	if (IS_ERR(rpdev_ctrl)) {
942 		err = PTR_ERR(rpdev_ctrl);
943 		goto free_coherent;
944 	}
945 
946 	/* if supported by the remote processor, enable the name service */
947 	if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
948 		vch = kzalloc(sizeof(*vch), GFP_KERNEL);
949 		if (!vch) {
950 			err = -ENOMEM;
951 			goto free_ctrldev;
952 		}
953 
954 		/* Link the channel to our vrp */
955 		vch->vrp = vrp;
956 
957 		/* Assign public information to the rpmsg_device */
958 		rpdev_ns = &vch->rpdev;
959 		rpdev_ns->ops = &virtio_rpmsg_ops;
960 		rpdev_ns->little_endian = virtio_is_little_endian(vrp->vdev);
961 
962 		rpdev_ns->dev.parent = &vrp->vdev->dev;
963 		rpdev_ns->dev.release = virtio_rpmsg_release_device;
964 
965 		err = rpmsg_ns_register_device(rpdev_ns);
966 		if (err)
967 			goto free_vch;
968 	}
969 
970 	/*
971 	 * Prepare to kick but don't notify yet - we can't do this before
972 	 * device is ready.
973 	 */
974 	notify = virtqueue_kick_prepare(vrp->rvq);
975 
976 	/* From this point on, we can notify and get callbacks. */
977 	virtio_device_ready(vdev);
978 
979 	/* tell the remote processor it can start sending messages */
980 	/*
981 	 * this might be concurrent with callbacks, but we are only
982 	 * doing notify, not a full kick here, so that's ok.
983 	 */
984 	if (notify)
985 		virtqueue_notify(vrp->rvq);
986 
987 	dev_info(&vdev->dev, "rpmsg host is online\n");
988 
989 	return 0;
990 
991 free_vch:
992 	kfree(vch);
993 free_ctrldev:
994 	rpmsg_virtio_del_ctrl_dev(rpdev_ctrl);
995 free_coherent:
996 	dma_free_coherent(vdev->dev.parent, total_buf_space,
997 			  bufs_va, vrp->bufs_dma);
998 vqs_del:
999 	vdev->config->del_vqs(vrp->vdev);
1000 free_vrp:
1001 	kfree(vrp);
1002 	return err;
1003 }
1004 
1005 static int rpmsg_remove_device(struct device *dev, void *data)
1006 {
1007 	device_unregister(dev);
1008 
1009 	return 0;
1010 }
1011 
1012 static void rpmsg_remove(struct virtio_device *vdev)
1013 {
1014 	struct virtproc_info *vrp = vdev->priv;
1015 	size_t total_buf_space = vrp->num_bufs * vrp->buf_size;
1016 	int ret;
1017 
1018 	vdev->config->reset(vdev);
1019 
1020 	ret = device_for_each_child(&vdev->dev, NULL, rpmsg_remove_device);
1021 	if (ret)
1022 		dev_warn(&vdev->dev, "can't remove rpmsg device: %d\n", ret);
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