linux/drivers/rpmsg/virtio_rpmsg_bus.c
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   1/*
   2 * Virtio-based remote processor messaging bus
   3 *
   4 * Copyright (C) 2011 Texas Instruments, Inc.
   5 * Copyright (C) 2011 Google, Inc.
   6 *
   7 * Ohad Ben-Cohen <ohad@wizery.com>
   8 * Brian Swetland <swetland@google.com>
   9 *
  10 * This software is licensed under the terms of the GNU General Public
  11 * License version 2, as published by the Free Software Foundation, and
  12 * may be copied, distributed, and modified under those terms.
  13 *
  14 * This program is distributed in the hope that it will be useful,
  15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 * GNU General Public License for more details.
  18 */
  19
  20#define pr_fmt(fmt) "%s: " fmt, __func__
  21
  22#include <linux/kernel.h>
  23#include <linux/module.h>
  24#include <linux/virtio.h>
  25#include <linux/virtio_ids.h>
  26#include <linux/virtio_config.h>
  27#include <linux/scatterlist.h>
  28#include <linux/dma-mapping.h>
  29#include <linux/slab.h>
  30#include <linux/idr.h>
  31#include <linux/jiffies.h>
  32#include <linux/sched.h>
  33#include <linux/wait.h>
  34#include <linux/rpmsg.h>
  35#include <linux/mutex.h>
  36
  37/**
  38 * struct virtproc_info - virtual remote processor state
  39 * @vdev:       the virtio device
  40 * @rvq:        rx virtqueue
  41 * @svq:        tx virtqueue
  42 * @rbufs:      kernel address of rx buffers
  43 * @sbufs:      kernel address of tx buffers
  44 * @last_sbuf:  index of last tx buffer used
  45 * @bufs_dma:   dma base addr of the buffers
  46 * @tx_lock:    protects svq, sbufs and sleepers, to allow concurrent senders.
  47 *              sending a message might require waking up a dozing remote
  48 *              processor, which involves sleeping, hence the mutex.
  49 * @endpoints:  idr of local endpoints, allows fast retrieval
  50 * @endpoints_lock: lock of the endpoints set
  51 * @sendq:      wait queue of sending contexts waiting for a tx buffers
  52 * @sleepers:   number of senders that are waiting for a tx buffer
  53 * @ns_ept:     the bus's name service endpoint
  54 *
  55 * This structure stores the rpmsg state of a given virtio remote processor
  56 * device (there might be several virtio proc devices for each physical
  57 * remote processor).
  58 */
  59struct virtproc_info {
  60        struct virtio_device *vdev;
  61        struct virtqueue *rvq, *svq;
  62        void *rbufs, *sbufs;
  63        int last_sbuf;
  64        dma_addr_t bufs_dma;
  65        struct mutex tx_lock;
  66        struct idr endpoints;
  67        struct mutex endpoints_lock;
  68        wait_queue_head_t sendq;
  69        atomic_t sleepers;
  70        struct rpmsg_endpoint *ns_ept;
  71};
  72
  73/**
  74 * struct rpmsg_channel_info - internal channel info representation
  75 * @name: name of service
  76 * @src: local address
  77 * @dst: destination address
  78 */
  79struct rpmsg_channel_info {
  80        char name[RPMSG_NAME_SIZE];
  81        u32 src;
  82        u32 dst;
  83};
  84
  85#define to_rpmsg_channel(d) container_of(d, struct rpmsg_channel, dev)
  86#define to_rpmsg_driver(d) container_of(d, struct rpmsg_driver, drv)
  87
  88/*
  89 * We're allocating 512 buffers of 512 bytes for communications, and then
  90 * using the first 256 buffers for RX, and the last 256 buffers for TX.
  91 *
  92 * Each buffer will have 16 bytes for the msg header and 496 bytes for
  93 * the payload.
  94 *
  95 * This will require a total space of 256KB for the buffers.
  96 *
  97 * We might also want to add support for user-provided buffers in time.
  98 * This will allow bigger buffer size flexibility, and can also be used
  99 * to achieve zero-copy messaging.
 100 *
 101 * Note that these numbers are purely a decision of this driver - we
 102 * can change this without changing anything in the firmware of the remote
 103 * processor.
 104 */
 105#define RPMSG_NUM_BUFS          (512)
 106#define RPMSG_BUF_SIZE          (512)
 107#define RPMSG_TOTAL_BUF_SPACE   (RPMSG_NUM_BUFS * RPMSG_BUF_SIZE)
 108
 109/*
 110 * Local addresses are dynamically allocated on-demand.
 111 * We do not dynamically assign addresses from the low 1024 range,
 112 * in order to reserve that address range for predefined services.
 113 */
 114#define RPMSG_RESERVED_ADDRESSES        (1024)
 115
 116/* Address 53 is reserved for advertising remote services */
 117#define RPMSG_NS_ADDR                   (53)
 118
 119/* sysfs show configuration fields */
 120#define rpmsg_show_attr(field, path, format_string)                     \
 121static ssize_t                                                          \
 122field##_show(struct device *dev,                                        \
 123                        struct device_attribute *attr, char *buf)       \
 124{                                                                       \
 125        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);            \
 126                                                                        \
 127        return sprintf(buf, format_string, rpdev->path);                \
 128}
 129
 130/* for more info, see Documentation/ABI/testing/sysfs-bus-rpmsg */
 131rpmsg_show_attr(name, id.name, "%s\n");
 132rpmsg_show_attr(src, src, "0x%x\n");
 133rpmsg_show_attr(dst, dst, "0x%x\n");
 134rpmsg_show_attr(announce, announce ? "true" : "false", "%s\n");
 135
 136/*
 137 * Unique (and free running) index for rpmsg devices.
 138 *
 139 * Yeah, we're not recycling those numbers (yet?). will be easy
 140 * to change if/when we want to.
 141 */
 142static unsigned int rpmsg_dev_index;
 143
 144static ssize_t modalias_show(struct device *dev,
 145                             struct device_attribute *attr, char *buf)
 146{
 147        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 148
 149        return sprintf(buf, RPMSG_DEVICE_MODALIAS_FMT "\n", rpdev->id.name);
 150}
 151
 152static struct device_attribute rpmsg_dev_attrs[] = {
 153        __ATTR_RO(name),
 154        __ATTR_RO(modalias),
 155        __ATTR_RO(dst),
 156        __ATTR_RO(src),
 157        __ATTR_RO(announce),
 158        __ATTR_NULL
 159};
 160
 161/* rpmsg devices and drivers are matched using the service name */
 162static inline int rpmsg_id_match(const struct rpmsg_channel *rpdev,
 163                                  const struct rpmsg_device_id *id)
 164{
 165        return strncmp(id->name, rpdev->id.name, RPMSG_NAME_SIZE) == 0;
 166}
 167
 168/* match rpmsg channel and rpmsg driver */
 169static int rpmsg_dev_match(struct device *dev, struct device_driver *drv)
 170{
 171        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 172        struct rpmsg_driver *rpdrv = to_rpmsg_driver(drv);
 173        const struct rpmsg_device_id *ids = rpdrv->id_table;
 174        unsigned int i;
 175
 176        for (i = 0; ids[i].name[0]; i++)
 177                if (rpmsg_id_match(rpdev, &ids[i]))
 178                        return 1;
 179
 180        return 0;
 181}
 182
 183static int rpmsg_uevent(struct device *dev, struct kobj_uevent_env *env)
 184{
 185        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 186
 187        return add_uevent_var(env, "MODALIAS=" RPMSG_DEVICE_MODALIAS_FMT,
 188                                        rpdev->id.name);
 189}
 190
 191/**
 192 * __ept_release() - deallocate an rpmsg endpoint
 193 * @kref: the ept's reference count
 194 *
 195 * This function deallocates an ept, and is invoked when its @kref refcount
 196 * drops to zero.
 197 *
 198 * Never invoke this function directly!
 199 */
 200static void __ept_release(struct kref *kref)
 201{
 202        struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
 203                                                  refcount);
 204        /*
 205         * At this point no one holds a reference to ept anymore,
 206         * so we can directly free it
 207         */
 208        kfree(ept);
 209}
 210
 211/* for more info, see below documentation of rpmsg_create_ept() */
 212static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
 213                struct rpmsg_channel *rpdev, rpmsg_rx_cb_t cb,
 214                void *priv, u32 addr)
 215{
 216        int id_min, id_max, id;
 217        struct rpmsg_endpoint *ept;
 218        struct device *dev = rpdev ? &rpdev->dev : &vrp->vdev->dev;
 219
 220        ept = kzalloc(sizeof(*ept), GFP_KERNEL);
 221        if (!ept) {
 222                dev_err(dev, "failed to kzalloc a new ept\n");
 223                return NULL;
 224        }
 225
 226        kref_init(&ept->refcount);
 227        mutex_init(&ept->cb_lock);
 228
 229        ept->rpdev = rpdev;
 230        ept->cb = cb;
 231        ept->priv = priv;
 232
 233        /* do we need to allocate a local address ? */
 234        if (addr == RPMSG_ADDR_ANY) {
 235                id_min = RPMSG_RESERVED_ADDRESSES;
 236                id_max = 0;
 237        } else {
 238                id_min = addr;
 239                id_max = addr + 1;
 240        }
 241
 242        mutex_lock(&vrp->endpoints_lock);
 243
 244        /* bind the endpoint to an rpmsg address (and allocate one if needed) */
 245        id = idr_alloc(&vrp->endpoints, ept, id_min, id_max, GFP_KERNEL);
 246        if (id < 0) {
 247                dev_err(dev, "idr_alloc failed: %d\n", id);
 248                goto free_ept;
 249        }
 250        ept->addr = id;
 251
 252        mutex_unlock(&vrp->endpoints_lock);
 253
 254        return ept;
 255
 256free_ept:
 257        mutex_unlock(&vrp->endpoints_lock);
 258        kref_put(&ept->refcount, __ept_release);
 259        return NULL;
 260}
 261
 262/**
 263 * rpmsg_create_ept() - create a new rpmsg_endpoint
 264 * @rpdev: rpmsg channel device
 265 * @cb: rx callback handler
 266 * @priv: private data for the driver's use
 267 * @addr: local rpmsg address to bind with @cb
 268 *
 269 * Every rpmsg address in the system is bound to an rx callback (so when
 270 * inbound messages arrive, they are dispatched by the rpmsg bus using the
 271 * appropriate callback handler) by means of an rpmsg_endpoint struct.
 272 *
 273 * This function allows drivers to create such an endpoint, and by that,
 274 * bind a callback, and possibly some private data too, to an rpmsg address
 275 * (either one that is known in advance, or one that will be dynamically
 276 * assigned for them).
 277 *
 278 * Simple rpmsg drivers need not call rpmsg_create_ept, because an endpoint
 279 * is already created for them when they are probed by the rpmsg bus
 280 * (using the rx callback provided when they registered to the rpmsg bus).
 281 *
 282 * So things should just work for simple drivers: they already have an
 283 * endpoint, their rx callback is bound to their rpmsg address, and when
 284 * relevant inbound messages arrive (i.e. messages which their dst address
 285 * equals to the src address of their rpmsg channel), the driver's handler
 286 * is invoked to process it.
 287 *
 288 * That said, more complicated drivers might do need to allocate
 289 * additional rpmsg addresses, and bind them to different rx callbacks.
 290 * To accomplish that, those drivers need to call this function.
 291 *
 292 * Drivers should provide their @rpdev channel (so the new endpoint would belong
 293 * to the same remote processor their channel belongs to), an rx callback
 294 * function, an optional private data (which is provided back when the
 295 * rx callback is invoked), and an address they want to bind with the
 296 * callback. If @addr is RPMSG_ADDR_ANY, then rpmsg_create_ept will
 297 * dynamically assign them an available rpmsg address (drivers should have
 298 * a very good reason why not to always use RPMSG_ADDR_ANY here).
 299 *
 300 * Returns a pointer to the endpoint on success, or NULL on error.
 301 */
 302struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_channel *rpdev,
 303                                rpmsg_rx_cb_t cb, void *priv, u32 addr)
 304{
 305        return __rpmsg_create_ept(rpdev->vrp, rpdev, cb, priv, addr);
 306}
 307EXPORT_SYMBOL(rpmsg_create_ept);
 308
 309/**
 310 * __rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
 311 * @vrp: virtproc which owns this ept
 312 * @ept: endpoing to destroy
 313 *
 314 * An internal function which destroy an ept without assuming it is
 315 * bound to an rpmsg channel. This is needed for handling the internal
 316 * name service endpoint, which isn't bound to an rpmsg channel.
 317 * See also __rpmsg_create_ept().
 318 */
 319static void
 320__rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
 321{
 322        /* make sure new inbound messages can't find this ept anymore */
 323        mutex_lock(&vrp->endpoints_lock);
 324        idr_remove(&vrp->endpoints, ept->addr);
 325        mutex_unlock(&vrp->endpoints_lock);
 326
 327        /* make sure in-flight inbound messages won't invoke cb anymore */
 328        mutex_lock(&ept->cb_lock);
 329        ept->cb = NULL;
 330        mutex_unlock(&ept->cb_lock);
 331
 332        kref_put(&ept->refcount, __ept_release);
 333}
 334
 335/**
 336 * rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
 337 * @ept: endpoing to destroy
 338 *
 339 * Should be used by drivers to destroy an rpmsg endpoint previously
 340 * created with rpmsg_create_ept().
 341 */
 342void rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
 343{
 344        __rpmsg_destroy_ept(ept->rpdev->vrp, ept);
 345}
 346EXPORT_SYMBOL(rpmsg_destroy_ept);
 347
 348/*
 349 * when an rpmsg driver is probed with a channel, we seamlessly create
 350 * it an endpoint, binding its rx callback to a unique local rpmsg
 351 * address.
 352 *
 353 * if we need to, we also announce about this channel to the remote
 354 * processor (needed in case the driver is exposing an rpmsg service).
 355 */
 356static int rpmsg_dev_probe(struct device *dev)
 357{
 358        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 359        struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
 360        struct virtproc_info *vrp = rpdev->vrp;
 361        struct rpmsg_endpoint *ept;
 362        int err;
 363
 364        ept = rpmsg_create_ept(rpdev, rpdrv->callback, NULL, rpdev->src);
 365        if (!ept) {
 366                dev_err(dev, "failed to create endpoint\n");
 367                err = -ENOMEM;
 368                goto out;
 369        }
 370
 371        rpdev->ept = ept;
 372        rpdev->src = ept->addr;
 373
 374        err = rpdrv->probe(rpdev);
 375        if (err) {
 376                dev_err(dev, "%s: failed: %d\n", __func__, err);
 377                rpmsg_destroy_ept(ept);
 378                goto out;
 379        }
 380
 381        /* need to tell remote processor's name service about this channel ? */
 382        if (rpdev->announce &&
 383                        virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
 384                struct rpmsg_ns_msg nsm;
 385
 386                strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
 387                nsm.addr = rpdev->src;
 388                nsm.flags = RPMSG_NS_CREATE;
 389
 390                err = rpmsg_sendto(rpdev, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
 391                if (err)
 392                        dev_err(dev, "failed to announce service %d\n", err);
 393        }
 394
 395out:
 396        return err;
 397}
 398
 399static int rpmsg_dev_remove(struct device *dev)
 400{
 401        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 402        struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
 403        struct virtproc_info *vrp = rpdev->vrp;
 404        int err = 0;
 405
 406        /* tell remote processor's name service we're removing this channel */
 407        if (rpdev->announce &&
 408                        virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
 409                struct rpmsg_ns_msg nsm;
 410
 411                strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
 412                nsm.addr = rpdev->src;
 413                nsm.flags = RPMSG_NS_DESTROY;
 414
 415                err = rpmsg_sendto(rpdev, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
 416                if (err)
 417                        dev_err(dev, "failed to announce service %d\n", err);
 418        }
 419
 420        rpdrv->remove(rpdev);
 421
 422        rpmsg_destroy_ept(rpdev->ept);
 423
 424        return err;
 425}
 426
 427static struct bus_type rpmsg_bus = {
 428        .name           = "rpmsg",
 429        .match          = rpmsg_dev_match,
 430        .dev_attrs      = rpmsg_dev_attrs,
 431        .uevent         = rpmsg_uevent,
 432        .probe          = rpmsg_dev_probe,
 433        .remove         = rpmsg_dev_remove,
 434};
 435
 436/**
 437 * register_rpmsg_driver() - register an rpmsg driver with the rpmsg bus
 438 * @rpdrv: pointer to a struct rpmsg_driver
 439 *
 440 * Returns 0 on success, and an appropriate error value on failure.
 441 */
 442int register_rpmsg_driver(struct rpmsg_driver *rpdrv)
 443{
 444        rpdrv->drv.bus = &rpmsg_bus;
 445        return driver_register(&rpdrv->drv);
 446}
 447EXPORT_SYMBOL(register_rpmsg_driver);
 448
 449/**
 450 * unregister_rpmsg_driver() - unregister an rpmsg driver from the rpmsg bus
 451 * @rpdrv: pointer to a struct rpmsg_driver
 452 *
 453 * Returns 0 on success, and an appropriate error value on failure.
 454 */
 455void unregister_rpmsg_driver(struct rpmsg_driver *rpdrv)
 456{
 457        driver_unregister(&rpdrv->drv);
 458}
 459EXPORT_SYMBOL(unregister_rpmsg_driver);
 460
 461static void rpmsg_release_device(struct device *dev)
 462{
 463        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 464
 465        kfree(rpdev);
 466}
 467
 468/*
 469 * match an rpmsg channel with a channel info struct.
 470 * this is used to make sure we're not creating rpmsg devices for channels
 471 * that already exist.
 472 */
 473static int rpmsg_channel_match(struct device *dev, void *data)
 474{
 475        struct rpmsg_channel_info *chinfo = data;
 476        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 477
 478        if (chinfo->src != RPMSG_ADDR_ANY && chinfo->src != rpdev->src)
 479                return 0;
 480
 481        if (chinfo->dst != RPMSG_ADDR_ANY && chinfo->dst != rpdev->dst)
 482                return 0;
 483
 484        if (strncmp(chinfo->name, rpdev->id.name, RPMSG_NAME_SIZE))
 485                return 0;
 486
 487        /* found a match ! */
 488        return 1;
 489}
 490
 491/*
 492 * create an rpmsg channel using its name and address info.
 493 * this function will be used to create both static and dynamic
 494 * channels.
 495 */
 496static struct rpmsg_channel *rpmsg_create_channel(struct virtproc_info *vrp,
 497                                struct rpmsg_channel_info *chinfo)
 498{
 499        struct rpmsg_channel *rpdev;
 500        struct device *tmp, *dev = &vrp->vdev->dev;
 501        int ret;
 502
 503        /* make sure a similar channel doesn't already exist */
 504        tmp = device_find_child(dev, chinfo, rpmsg_channel_match);
 505        if (tmp) {
 506                /* decrement the matched device's refcount back */
 507                put_device(tmp);
 508                dev_err(dev, "channel %s:%x:%x already exist\n",
 509                                chinfo->name, chinfo->src, chinfo->dst);
 510                return NULL;
 511        }
 512
 513        rpdev = kzalloc(sizeof(struct rpmsg_channel), GFP_KERNEL);
 514        if (!rpdev) {
 515                pr_err("kzalloc failed\n");
 516                return NULL;
 517        }
 518
 519        rpdev->vrp = vrp;
 520        rpdev->src = chinfo->src;
 521        rpdev->dst = chinfo->dst;
 522
 523        /*
 524         * rpmsg server channels has predefined local address (for now),
 525         * and their existence needs to be announced remotely
 526         */
 527        rpdev->announce = rpdev->src != RPMSG_ADDR_ANY ? true : false;
 528
 529        strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE);
 530
 531        /* very simple device indexing plumbing which is enough for now */
 532        dev_set_name(&rpdev->dev, "rpmsg%d", rpmsg_dev_index++);
 533
 534        rpdev->dev.parent = &vrp->vdev->dev;
 535        rpdev->dev.bus = &rpmsg_bus;
 536        rpdev->dev.release = rpmsg_release_device;
 537
 538        ret = device_register(&rpdev->dev);
 539        if (ret) {
 540                dev_err(dev, "device_register failed: %d\n", ret);
 541                put_device(&rpdev->dev);
 542                return NULL;
 543        }
 544
 545        return rpdev;
 546}
 547
 548/*
 549 * find an existing channel using its name + address properties,
 550 * and destroy it
 551 */
 552static int rpmsg_destroy_channel(struct virtproc_info *vrp,
 553                                        struct rpmsg_channel_info *chinfo)
 554{
 555        struct virtio_device *vdev = vrp->vdev;
 556        struct device *dev;
 557
 558        dev = device_find_child(&vdev->dev, chinfo, rpmsg_channel_match);
 559        if (!dev)
 560                return -EINVAL;
 561
 562        device_unregister(dev);
 563
 564        put_device(dev);
 565
 566        return 0;
 567}
 568
 569/* super simple buffer "allocator" that is just enough for now */
 570static void *get_a_tx_buf(struct virtproc_info *vrp)
 571{
 572        unsigned int len;
 573        void *ret;
 574
 575        /* support multiple concurrent senders */
 576        mutex_lock(&vrp->tx_lock);
 577
 578        /*
 579         * either pick the next unused tx buffer
 580         * (half of our buffers are used for sending messages)
 581         */
 582        if (vrp->last_sbuf < RPMSG_NUM_BUFS / 2)
 583                ret = vrp->sbufs + RPMSG_BUF_SIZE * vrp->last_sbuf++;
 584        /* or recycle a used one */
 585        else
 586                ret = virtqueue_get_buf(vrp->svq, &len);
 587
 588        mutex_unlock(&vrp->tx_lock);
 589
 590        return ret;
 591}
 592
 593/**
 594 * rpmsg_upref_sleepers() - enable "tx-complete" interrupts, if needed
 595 * @vrp: virtual remote processor state
 596 *
 597 * This function is called before a sender is blocked, waiting for
 598 * a tx buffer to become available.
 599 *
 600 * If we already have blocking senders, this function merely increases
 601 * the "sleepers" reference count, and exits.
 602 *
 603 * Otherwise, if this is the first sender to block, we also enable
 604 * virtio's tx callbacks, so we'd be immediately notified when a tx
 605 * buffer is consumed (we rely on virtio's tx callback in order
 606 * to wake up sleeping senders as soon as a tx buffer is used by the
 607 * remote processor).
 608 */
 609static void rpmsg_upref_sleepers(struct virtproc_info *vrp)
 610{
 611        /* support multiple concurrent senders */
 612        mutex_lock(&vrp->tx_lock);
 613
 614        /* are we the first sleeping context waiting for tx buffers ? */
 615        if (atomic_inc_return(&vrp->sleepers) == 1)
 616                /* enable "tx-complete" interrupts before dozing off */
 617                virtqueue_enable_cb(vrp->svq);
 618
 619        mutex_unlock(&vrp->tx_lock);
 620}
 621
 622/**
 623 * rpmsg_downref_sleepers() - disable "tx-complete" interrupts, if needed
 624 * @vrp: virtual remote processor state
 625 *
 626 * This function is called after a sender, that waited for a tx buffer
 627 * to become available, is unblocked.
 628 *
 629 * If we still have blocking senders, this function merely decreases
 630 * the "sleepers" reference count, and exits.
 631 *
 632 * Otherwise, if there are no more blocking senders, we also disable
 633 * virtio's tx callbacks, to avoid the overhead incurred with handling
 634 * those (now redundant) interrupts.
 635 */
 636static void rpmsg_downref_sleepers(struct virtproc_info *vrp)
 637{
 638        /* support multiple concurrent senders */
 639        mutex_lock(&vrp->tx_lock);
 640
 641        /* are we the last sleeping context waiting for tx buffers ? */
 642        if (atomic_dec_and_test(&vrp->sleepers))
 643                /* disable "tx-complete" interrupts */
 644                virtqueue_disable_cb(vrp->svq);
 645
 646        mutex_unlock(&vrp->tx_lock);
 647}
 648
 649/**
 650 * rpmsg_send_offchannel_raw() - send a message across to the remote processor
 651 * @rpdev: the rpmsg channel
 652 * @src: source address
 653 * @dst: destination address
 654 * @data: payload of message
 655 * @len: length of payload
 656 * @wait: indicates whether caller should block in case no TX buffers available
 657 *
 658 * This function is the base implementation for all of the rpmsg sending API.
 659 *
 660 * It will send @data of length @len to @dst, and say it's from @src. The
 661 * message will be sent to the remote processor which the @rpdev channel
 662 * belongs to.
 663 *
 664 * The message is sent using one of the TX buffers that are available for
 665 * communication with this remote processor.
 666 *
 667 * If @wait is true, the caller will be blocked until either a TX buffer is
 668 * available, or 15 seconds elapses (we don't want callers to
 669 * sleep indefinitely due to misbehaving remote processors), and in that
 670 * case -ERESTARTSYS is returned. The number '15' itself was picked
 671 * arbitrarily; there's little point in asking drivers to provide a timeout
 672 * value themselves.
 673 *
 674 * Otherwise, if @wait is false, and there are no TX buffers available,
 675 * the function will immediately fail, and -ENOMEM will be returned.
 676 *
 677 * Normally drivers shouldn't use this function directly; instead, drivers
 678 * should use the appropriate rpmsg_{try}send{to, _offchannel} API
 679 * (see include/linux/rpmsg.h).
 680 *
 681 * Returns 0 on success and an appropriate error value on failure.
 682 */
 683int rpmsg_send_offchannel_raw(struct rpmsg_channel *rpdev, u32 src, u32 dst,
 684                                        void *data, int len, bool wait)
 685{
 686        struct virtproc_info *vrp = rpdev->vrp;
 687        struct device *dev = &rpdev->dev;
 688        struct scatterlist sg;
 689        struct rpmsg_hdr *msg;
 690        int err;
 691
 692        /* bcasting isn't allowed */
 693        if (src == RPMSG_ADDR_ANY || dst == RPMSG_ADDR_ANY) {
 694                dev_err(dev, "invalid addr (src 0x%x, dst 0x%x)\n", src, dst);
 695                return -EINVAL;
 696        }
 697
 698        /*
 699         * We currently use fixed-sized buffers, and therefore the payload
 700         * length is limited.
 701         *
 702         * One of the possible improvements here is either to support
 703         * user-provided buffers (and then we can also support zero-copy
 704         * messaging), or to improve the buffer allocator, to support
 705         * variable-length buffer sizes.
 706         */
 707        if (len > RPMSG_BUF_SIZE - sizeof(struct rpmsg_hdr)) {
 708                dev_err(dev, "message is too big (%d)\n", len);
 709                return -EMSGSIZE;
 710        }
 711
 712        /* grab a buffer */
 713        msg = get_a_tx_buf(vrp);
 714        if (!msg && !wait)
 715                return -ENOMEM;
 716
 717        /* no free buffer ? wait for one (but bail after 15 seconds) */
 718        while (!msg) {
 719                /* enable "tx-complete" interrupts, if not already enabled */
 720                rpmsg_upref_sleepers(vrp);
 721
 722                /*
 723                 * sleep until a free buffer is available or 15 secs elapse.
 724                 * the timeout period is not configurable because there's
 725                 * little point in asking drivers to specify that.
 726                 * if later this happens to be required, it'd be easy to add.
 727                 */
 728                err = wait_event_interruptible_timeout(vrp->sendq,
 729                                        (msg = get_a_tx_buf(vrp)),
 730                                        msecs_to_jiffies(15000));
 731
 732                /* disable "tx-complete" interrupts if we're the last sleeper */
 733                rpmsg_downref_sleepers(vrp);
 734
 735                /* timeout ? */
 736                if (!err) {
 737                        dev_err(dev, "timeout waiting for a tx buffer\n");
 738                        return -ERESTARTSYS;
 739                }
 740        }
 741
 742        msg->len = len;
 743        msg->flags = 0;
 744        msg->src = src;
 745        msg->dst = dst;
 746        msg->reserved = 0;
 747        memcpy(msg->data, data, len);
 748
 749        dev_dbg(dev, "TX From 0x%x, To 0x%x, Len %d, Flags %d, Reserved %d\n",
 750                                        msg->src, msg->dst, msg->len,
 751                                        msg->flags, msg->reserved);
 752        print_hex_dump(KERN_DEBUG, "rpmsg_virtio TX: ", DUMP_PREFIX_NONE, 16, 1,
 753                                        msg, sizeof(*msg) + msg->len, true);
 754
 755        sg_init_one(&sg, msg, sizeof(*msg) + len);
 756
 757        mutex_lock(&vrp->tx_lock);
 758
 759        /* add message to the remote processor's virtqueue */
 760        err = virtqueue_add_outbuf(vrp->svq, &sg, 1, msg, GFP_KERNEL);
 761        if (err) {
 762                /*
 763                 * need to reclaim the buffer here, otherwise it's lost
 764                 * (memory won't leak, but rpmsg won't use it again for TX).
 765                 * this will wait for a buffer management overhaul.
 766                 */
 767                dev_err(dev, "virtqueue_add_outbuf failed: %d\n", err);
 768                goto out;
 769        }
 770
 771        /* tell the remote processor it has a pending message to read */
 772        virtqueue_kick(vrp->svq);
 773out:
 774        mutex_unlock(&vrp->tx_lock);
 775        return err;
 776}
 777EXPORT_SYMBOL(rpmsg_send_offchannel_raw);
 778
 779static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
 780                             struct rpmsg_hdr *msg, unsigned int len)
 781{
 782        struct rpmsg_endpoint *ept;
 783        struct scatterlist sg;
 784        int err;
 785
 786        dev_dbg(dev, "From: 0x%x, To: 0x%x, Len: %d, Flags: %d, Reserved: %d\n",
 787                                        msg->src, msg->dst, msg->len,
 788                                        msg->flags, msg->reserved);
 789        print_hex_dump(KERN_DEBUG, "rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
 790                                        msg, sizeof(*msg) + msg->len, true);
 791
 792        /*
 793         * We currently use fixed-sized buffers, so trivially sanitize
 794         * the reported payload length.
 795         */
 796        if (len > RPMSG_BUF_SIZE ||
 797                msg->len > (len - sizeof(struct rpmsg_hdr))) {
 798                dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg->len);
 799                return -EINVAL;
 800        }
 801
 802        /* use the dst addr to fetch the callback of the appropriate user */
 803        mutex_lock(&vrp->endpoints_lock);
 804
 805        ept = idr_find(&vrp->endpoints, msg->dst);
 806
 807        /* let's make sure no one deallocates ept while we use it */
 808        if (ept)
 809                kref_get(&ept->refcount);
 810
 811        mutex_unlock(&vrp->endpoints_lock);
 812
 813        if (ept) {
 814                /* make sure ept->cb doesn't go away while we use it */
 815                mutex_lock(&ept->cb_lock);
 816
 817                if (ept->cb)
 818                        ept->cb(ept->rpdev, msg->data, msg->len, ept->priv,
 819                                msg->src);
 820
 821                mutex_unlock(&ept->cb_lock);
 822
 823                /* farewell, ept, we don't need you anymore */
 824                kref_put(&ept->refcount, __ept_release);
 825        } else
 826                dev_warn(dev, "msg received with no recipient\n");
 827
 828        /* publish the real size of the buffer */
 829        sg_init_one(&sg, msg, RPMSG_BUF_SIZE);
 830
 831        /* add the buffer back to the remote processor's virtqueue */
 832        err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, msg, GFP_KERNEL);
 833        if (err < 0) {
 834                dev_err(dev, "failed to add a virtqueue buffer: %d\n", err);
 835                return err;
 836        }
 837
 838        return 0;
 839}
 840
 841/* called when an rx buffer is used, and it's time to digest a message */
 842static void rpmsg_recv_done(struct virtqueue *rvq)
 843{
 844        struct virtproc_info *vrp = rvq->vdev->priv;
 845        struct device *dev = &rvq->vdev->dev;
 846        struct rpmsg_hdr *msg;
 847        unsigned int len, msgs_received = 0;
 848        int err;
 849
 850        msg = virtqueue_get_buf(rvq, &len);
 851        if (!msg) {
 852                dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
 853                return;
 854        }
 855
 856        while (msg) {
 857                err = rpmsg_recv_single(vrp, dev, msg, len);
 858                if (err)
 859                        break;
 860
 861                msgs_received++;
 862
 863                msg = virtqueue_get_buf(rvq, &len);
 864        };
 865
 866        dev_dbg(dev, "Received %u messages\n", msgs_received);
 867
 868        /* tell the remote processor we added another available rx buffer */
 869        if (msgs_received)
 870                virtqueue_kick(vrp->rvq);
 871}
 872
 873/*
 874 * This is invoked whenever the remote processor completed processing
 875 * a TX msg we just sent it, and the buffer is put back to the used ring.
 876 *
 877 * Normally, though, we suppress this "tx complete" interrupt in order to
 878 * avoid the incurred overhead.
 879 */
 880static void rpmsg_xmit_done(struct virtqueue *svq)
 881{
 882        struct virtproc_info *vrp = svq->vdev->priv;
 883
 884        dev_dbg(&svq->vdev->dev, "%s\n", __func__);
 885
 886        /* wake up potential senders that are waiting for a tx buffer */
 887        wake_up_interruptible(&vrp->sendq);
 888}
 889
 890/* invoked when a name service announcement arrives */
 891static void rpmsg_ns_cb(struct rpmsg_channel *rpdev, void *data, int len,
 892                                                        void *priv, u32 src)
 893{
 894        struct rpmsg_ns_msg *msg = data;
 895        struct rpmsg_channel *newch;
 896        struct rpmsg_channel_info chinfo;
 897        struct virtproc_info *vrp = priv;
 898        struct device *dev = &vrp->vdev->dev;
 899        int ret;
 900
 901        print_hex_dump(KERN_DEBUG, "NS announcement: ",
 902                        DUMP_PREFIX_NONE, 16, 1,
 903                        data, len, true);
 904
 905        if (len != sizeof(*msg)) {
 906                dev_err(dev, "malformed ns msg (%d)\n", len);
 907                return;
 908        }
 909
 910        /*
 911         * the name service ept does _not_ belong to a real rpmsg channel,
 912         * and is handled by the rpmsg bus itself.
 913         * for sanity reasons, make sure a valid rpdev has _not_ sneaked
 914         * in somehow.
 915         */
 916        if (rpdev) {
 917                dev_err(dev, "anomaly: ns ept has an rpdev handle\n");
 918                return;
 919        }
 920
 921        /* don't trust the remote processor for null terminating the name */
 922        msg->name[RPMSG_NAME_SIZE - 1] = '\0';
 923
 924        dev_info(dev, "%sing channel %s addr 0x%x\n",
 925                        msg->flags & RPMSG_NS_DESTROY ? "destroy" : "creat",
 926                        msg->name, msg->addr);
 927
 928        strncpy(chinfo.name, msg->name, sizeof(chinfo.name));
 929        chinfo.src = RPMSG_ADDR_ANY;
 930        chinfo.dst = msg->addr;
 931
 932        if (msg->flags & RPMSG_NS_DESTROY) {
 933                ret = rpmsg_destroy_channel(vrp, &chinfo);
 934                if (ret)
 935                        dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret);
 936        } else {
 937                newch = rpmsg_create_channel(vrp, &chinfo);
 938                if (!newch)
 939                        dev_err(dev, "rpmsg_create_channel failed\n");
 940        }
 941}
 942
 943static int rpmsg_probe(struct virtio_device *vdev)
 944{
 945        vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
 946        const char *names[] = { "input", "output" };
 947        struct virtqueue *vqs[2];
 948        struct virtproc_info *vrp;
 949        void *bufs_va;
 950        int err = 0, i;
 951
 952        vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
 953        if (!vrp)
 954                return -ENOMEM;
 955
 956        vrp->vdev = vdev;
 957
 958        idr_init(&vrp->endpoints);
 959        mutex_init(&vrp->endpoints_lock);
 960        mutex_init(&vrp->tx_lock);
 961        init_waitqueue_head(&vrp->sendq);
 962
 963        /* We expect two virtqueues, rx and tx (and in this order) */
 964        err = vdev->config->find_vqs(vdev, 2, vqs, vq_cbs, names);
 965        if (err)
 966                goto free_vrp;
 967
 968        vrp->rvq = vqs[0];
 969        vrp->svq = vqs[1];
 970
 971        /* allocate coherent memory for the buffers */
 972        bufs_va = dma_alloc_coherent(vdev->dev.parent->parent,
 973                                RPMSG_TOTAL_BUF_SPACE,
 974                                &vrp->bufs_dma, GFP_KERNEL);
 975        if (!bufs_va) {
 976                err = -ENOMEM;
 977                goto vqs_del;
 978        }
 979
 980        dev_dbg(&vdev->dev, "buffers: va %p, dma 0x%llx\n", bufs_va,
 981                                        (unsigned long long)vrp->bufs_dma);
 982
 983        /* half of the buffers is dedicated for RX */
 984        vrp->rbufs = bufs_va;
 985
 986        /* and half is dedicated for TX */
 987        vrp->sbufs = bufs_va + RPMSG_TOTAL_BUF_SPACE / 2;
 988
 989        /* set up the receive buffers */
 990        for (i = 0; i < RPMSG_NUM_BUFS / 2; i++) {
 991                struct scatterlist sg;
 992                void *cpu_addr = vrp->rbufs + i * RPMSG_BUF_SIZE;
 993
 994                sg_init_one(&sg, cpu_addr, RPMSG_BUF_SIZE);
 995
 996                err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, cpu_addr,
 997                                                                GFP_KERNEL);
 998                WARN_ON(err); /* sanity check; this can't really happen */
 999        }
1000
1001        /* suppress "tx-complete" interrupts */
1002        virtqueue_disable_cb(vrp->svq);
1003
1004        vdev->priv = vrp;
1005
1006        /* if supported by the remote processor, enable the name service */
1007        if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
1008                /* a dedicated endpoint handles the name service msgs */
1009                vrp->ns_ept = __rpmsg_create_ept(vrp, NULL, rpmsg_ns_cb,
1010                                                vrp, RPMSG_NS_ADDR);
1011                if (!vrp->ns_ept) {
1012                        dev_err(&vdev->dev, "failed to create the ns ept\n");
1013                        err = -ENOMEM;
1014                        goto free_coherent;
1015                }
1016        }
1017
1018        /* tell the remote processor it can start sending messages */
1019        virtqueue_kick(vrp->rvq);
1020
1021        dev_info(&vdev->dev, "rpmsg host is online\n");
1022
1023        return 0;
1024
1025free_coherent:
1026        dma_free_coherent(vdev->dev.parent->parent, RPMSG_TOTAL_BUF_SPACE,
1027                                        bufs_va, vrp->bufs_dma);
1028vqs_del:
1029        vdev->config->del_vqs(vrp->vdev);
1030free_vrp:
1031        kfree(vrp);
1032        return err;
1033}
1034
1035static int rpmsg_remove_device(struct device *dev, void *data)
1036{
1037        device_unregister(dev);
1038
1039        return 0;
1040}
1041
1042static void rpmsg_remove(struct virtio_device *vdev)
1043{
1044        struct virtproc_info *vrp = vdev->priv;
1045        int ret;
1046
1047        vdev->config->reset(vdev);
1048
1049        ret = device_for_each_child(&vdev->dev, NULL, rpmsg_remove_device);
1050        if (ret)
1051                dev_warn(&vdev->dev, "can't remove rpmsg device: %d\n", ret);
1052
1053        if (vrp->ns_ept)
1054                __rpmsg_destroy_ept(vrp, vrp->ns_ept);
1055
1056        idr_destroy(&vrp->endpoints);
1057
1058        vdev->config->del_vqs(vrp->vdev);
1059
1060        dma_free_coherent(vdev->dev.parent->parent, RPMSG_TOTAL_BUF_SPACE,
1061                                        vrp->rbufs, vrp->bufs_dma);
1062
1063        kfree(vrp);
1064}
1065
1066static struct virtio_device_id id_table[] = {
1067        { VIRTIO_ID_RPMSG, VIRTIO_DEV_ANY_ID },
1068        { 0 },
1069};
1070
1071static unsigned int features[] = {
1072        VIRTIO_RPMSG_F_NS,
1073};
1074
1075static struct virtio_driver virtio_ipc_driver = {
1076        .feature_table  = features,
1077        .feature_table_size = ARRAY_SIZE(features),
1078        .driver.name    = KBUILD_MODNAME,
1079        .driver.owner   = THIS_MODULE,
1080        .id_table       = id_table,
1081        .probe          = rpmsg_probe,
1082        .remove         = rpmsg_remove,
1083};
1084
1085static int __init rpmsg_init(void)
1086{
1087        int ret;
1088
1089        ret = bus_register(&rpmsg_bus);
1090        if (ret) {
1091                pr_err("failed to register rpmsg bus: %d\n", ret);
1092                return ret;
1093        }
1094
1095        ret = register_virtio_driver(&virtio_ipc_driver);
1096        if (ret) {
1097                pr_err("failed to register virtio driver: %d\n", ret);
1098                bus_unregister(&rpmsg_bus);
1099        }
1100
1101        return ret;
1102}
1103subsys_initcall(rpmsg_init);
1104
1105static void __exit rpmsg_fini(void)
1106{
1107        unregister_virtio_driver(&virtio_ipc_driver);
1108        bus_unregister(&rpmsg_bus);
1109}
1110module_exit(rpmsg_fini);
1111
1112MODULE_DEVICE_TABLE(virtio, id_table);
1113MODULE_DESCRIPTION("Virtio-based remote processor messaging bus");
1114MODULE_LICENSE("GPL v2");
1115
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