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 err, tmpaddr, request;
 217        struct rpmsg_endpoint *ept;
 218        struct device *dev = rpdev ? &rpdev->dev : &vrp->vdev->dev;
 219
 220        if (!idr_pre_get(&vrp->endpoints, GFP_KERNEL))
 221                return NULL;
 222
 223        ept = kzalloc(sizeof(*ept), GFP_KERNEL);
 224        if (!ept) {
 225                dev_err(dev, "failed to kzalloc a new ept\n");
 226                return NULL;
 227        }
 228
 229        kref_init(&ept->refcount);
 230        mutex_init(&ept->cb_lock);
 231
 232        ept->rpdev = rpdev;
 233        ept->cb = cb;
 234        ept->priv = priv;
 235
 236        /* do we need to allocate a local address ? */
 237        request = addr == RPMSG_ADDR_ANY ? RPMSG_RESERVED_ADDRESSES : addr;
 238
 239        mutex_lock(&vrp->endpoints_lock);
 240
 241        /* bind the endpoint to an rpmsg address (and allocate one if needed) */
 242        err = idr_get_new_above(&vrp->endpoints, ept, request, &tmpaddr);
 243        if (err) {
 244                dev_err(dev, "idr_get_new_above failed: %d\n", err);
 245                goto free_ept;
 246        }
 247
 248        /* make sure the user's address request is fulfilled, if relevant */
 249        if (addr != RPMSG_ADDR_ANY && tmpaddr != addr) {
 250                dev_err(dev, "address 0x%x already in use\n", addr);
 251                goto rem_idr;
 252        }
 253
 254        ept->addr = tmpaddr;
 255
 256        mutex_unlock(&vrp->endpoints_lock);
 257
 258        return ept;
 259
 260rem_idr:
 261        idr_remove(&vrp->endpoints, request);
 262free_ept:
 263        mutex_unlock(&vrp->endpoints_lock);
 264        kref_put(&ept->refcount, __ept_release);
 265        return NULL;
 266}
 267
 268/**
 269 * rpmsg_create_ept() - create a new rpmsg_endpoint
 270 * @rpdev: rpmsg channel device
 271 * @cb: rx callback handler
 272 * @priv: private data for the driver's use
 273 * @addr: local rpmsg address to bind with @cb
 274 *
 275 * Every rpmsg address in the system is bound to an rx callback (so when
 276 * inbound messages arrive, they are dispatched by the rpmsg bus using the
 277 * appropriate callback handler) by means of an rpmsg_endpoint struct.
 278 *
 279 * This function allows drivers to create such an endpoint, and by that,
 280 * bind a callback, and possibly some private data too, to an rpmsg address
 281 * (either one that is known in advance, or one that will be dynamically
 282 * assigned for them).
 283 *
 284 * Simple rpmsg drivers need not call rpmsg_create_ept, because an endpoint
 285 * is already created for them when they are probed by the rpmsg bus
 286 * (using the rx callback provided when they registered to the rpmsg bus).
 287 *
 288 * So things should just work for simple drivers: they already have an
 289 * endpoint, their rx callback is bound to their rpmsg address, and when
 290 * relevant inbound messages arrive (i.e. messages which their dst address
 291 * equals to the src address of their rpmsg channel), the driver's handler
 292 * is invoked to process it.
 293 *
 294 * That said, more complicated drivers might do need to allocate
 295 * additional rpmsg addresses, and bind them to different rx callbacks.
 296 * To accomplish that, those drivers need to call this function.
 297 *
 298 * Drivers should provide their @rpdev channel (so the new endpoint would belong
 299 * to the same remote processor their channel belongs to), an rx callback
 300 * function, an optional private data (which is provided back when the
 301 * rx callback is invoked), and an address they want to bind with the
 302 * callback. If @addr is RPMSG_ADDR_ANY, then rpmsg_create_ept will
 303 * dynamically assign them an available rpmsg address (drivers should have
 304 * a very good reason why not to always use RPMSG_ADDR_ANY here).
 305 *
 306 * Returns a pointer to the endpoint on success, or NULL on error.
 307 */
 308struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_channel *rpdev,
 309                                rpmsg_rx_cb_t cb, void *priv, u32 addr)
 310{
 311        return __rpmsg_create_ept(rpdev->vrp, rpdev, cb, priv, addr);
 312}
 313EXPORT_SYMBOL(rpmsg_create_ept);
 314
 315/**
 316 * __rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
 317 * @vrp: virtproc which owns this ept
 318 * @ept: endpoing to destroy
 319 *
 320 * An internal function which destroy an ept without assuming it is
 321 * bound to an rpmsg channel. This is needed for handling the internal
 322 * name service endpoint, which isn't bound to an rpmsg channel.
 323 * See also __rpmsg_create_ept().
 324 */
 325static void
 326__rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
 327{
 328        /* make sure new inbound messages can't find this ept anymore */
 329        mutex_lock(&vrp->endpoints_lock);
 330        idr_remove(&vrp->endpoints, ept->addr);
 331        mutex_unlock(&vrp->endpoints_lock);
 332
 333        /* make sure in-flight inbound messages won't invoke cb anymore */
 334        mutex_lock(&ept->cb_lock);
 335        ept->cb = NULL;
 336        mutex_unlock(&ept->cb_lock);
 337
 338        kref_put(&ept->refcount, __ept_release);
 339}
 340
 341/**
 342 * rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
 343 * @ept: endpoing to destroy
 344 *
 345 * Should be used by drivers to destroy an rpmsg endpoint previously
 346 * created with rpmsg_create_ept().
 347 */
 348void rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
 349{
 350        __rpmsg_destroy_ept(ept->rpdev->vrp, ept);
 351}
 352EXPORT_SYMBOL(rpmsg_destroy_ept);
 353
 354/*
 355 * when an rpmsg driver is probed with a channel, we seamlessly create
 356 * it an endpoint, binding its rx callback to a unique local rpmsg
 357 * address.
 358 *
 359 * if we need to, we also announce about this channel to the remote
 360 * processor (needed in case the driver is exposing an rpmsg service).
 361 */
 362static int rpmsg_dev_probe(struct device *dev)
 363{
 364        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 365        struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
 366        struct virtproc_info *vrp = rpdev->vrp;
 367        struct rpmsg_endpoint *ept;
 368        int err;
 369
 370        ept = rpmsg_create_ept(rpdev, rpdrv->callback, NULL, rpdev->src);
 371        if (!ept) {
 372                dev_err(dev, "failed to create endpoint\n");
 373                err = -ENOMEM;
 374                goto out;
 375        }
 376
 377        rpdev->ept = ept;
 378        rpdev->src = ept->addr;
 379
 380        err = rpdrv->probe(rpdev);
 381        if (err) {
 382                dev_err(dev, "%s: failed: %d\n", __func__, err);
 383                rpmsg_destroy_ept(ept);
 384                goto out;
 385        }
 386
 387        /* need to tell remote processor's name service about this channel ? */
 388        if (rpdev->announce &&
 389                        virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
 390                struct rpmsg_ns_msg nsm;
 391
 392                strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
 393                nsm.addr = rpdev->src;
 394                nsm.flags = RPMSG_NS_CREATE;
 395
 396                err = rpmsg_sendto(rpdev, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
 397                if (err)
 398                        dev_err(dev, "failed to announce service %d\n", err);
 399        }
 400
 401out:
 402        return err;
 403}
 404
 405static int rpmsg_dev_remove(struct device *dev)
 406{
 407        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 408        struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
 409        struct virtproc_info *vrp = rpdev->vrp;
 410        int err = 0;
 411
 412        /* tell remote processor's name service we're removing this channel */
 413        if (rpdev->announce &&
 414                        virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
 415                struct rpmsg_ns_msg nsm;
 416
 417                strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
 418                nsm.addr = rpdev->src;
 419                nsm.flags = RPMSG_NS_DESTROY;
 420
 421                err = rpmsg_sendto(rpdev, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
 422                if (err)
 423                        dev_err(dev, "failed to announce service %d\n", err);
 424        }
 425
 426        rpdrv->remove(rpdev);
 427
 428        rpmsg_destroy_ept(rpdev->ept);
 429
 430        return err;
 431}
 432
 433static struct bus_type rpmsg_bus = {
 434        .name           = "rpmsg",
 435        .match          = rpmsg_dev_match,
 436        .dev_attrs      = rpmsg_dev_attrs,
 437        .uevent         = rpmsg_uevent,
 438        .probe          = rpmsg_dev_probe,
 439        .remove         = rpmsg_dev_remove,
 440};
 441
 442/**
 443 * register_rpmsg_driver() - register an rpmsg driver with the rpmsg bus
 444 * @rpdrv: pointer to a struct rpmsg_driver
 445 *
 446 * Returns 0 on success, and an appropriate error value on failure.
 447 */
 448int register_rpmsg_driver(struct rpmsg_driver *rpdrv)
 449{
 450        rpdrv->drv.bus = &rpmsg_bus;
 451        return driver_register(&rpdrv->drv);
 452}
 453EXPORT_SYMBOL(register_rpmsg_driver);
 454
 455/**
 456 * unregister_rpmsg_driver() - unregister an rpmsg driver from the rpmsg bus
 457 * @rpdrv: pointer to a struct rpmsg_driver
 458 *
 459 * Returns 0 on success, and an appropriate error value on failure.
 460 */
 461void unregister_rpmsg_driver(struct rpmsg_driver *rpdrv)
 462{
 463        driver_unregister(&rpdrv->drv);
 464}
 465EXPORT_SYMBOL(unregister_rpmsg_driver);
 466
 467static void rpmsg_release_device(struct device *dev)
 468{
 469        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 470
 471        kfree(rpdev);
 472}
 473
 474/*
 475 * match an rpmsg channel with a channel info struct.
 476 * this is used to make sure we're not creating rpmsg devices for channels
 477 * that already exist.
 478 */
 479static int rpmsg_channel_match(struct device *dev, void *data)
 480{
 481        struct rpmsg_channel_info *chinfo = data;
 482        struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
 483
 484        if (chinfo->src != RPMSG_ADDR_ANY && chinfo->src != rpdev->src)
 485                return 0;
 486
 487        if (chinfo->dst != RPMSG_ADDR_ANY && chinfo->dst != rpdev->dst)
 488                return 0;
 489
 490        if (strncmp(chinfo->name, rpdev->id.name, RPMSG_NAME_SIZE))
 491                return 0;
 492
 493        /* found a match ! */
 494        return 1;
 495}
 496
 497/*
 498 * create an rpmsg channel using its name and address info.
 499 * this function will be used to create both static and dynamic
 500 * channels.
 501 */
 502static struct rpmsg_channel *rpmsg_create_channel(struct virtproc_info *vrp,
 503                                struct rpmsg_channel_info *chinfo)
 504{
 505        struct rpmsg_channel *rpdev;
 506        struct device *tmp, *dev = &vrp->vdev->dev;
 507        int ret;
 508
 509        /* make sure a similar channel doesn't already exist */
 510        tmp = device_find_child(dev, chinfo, rpmsg_channel_match);
 511        if (tmp) {
 512                /* decrement the matched device's refcount back */
 513                put_device(tmp);
 514                dev_err(dev, "channel %s:%x:%x already exist\n",
 515                                chinfo->name, chinfo->src, chinfo->dst);
 516                return NULL;
 517        }
 518
 519        rpdev = kzalloc(sizeof(struct rpmsg_channel), GFP_KERNEL);
 520        if (!rpdev) {
 521                pr_err("kzalloc failed\n");
 522                return NULL;
 523        }
 524
 525        rpdev->vrp = vrp;
 526        rpdev->src = chinfo->src;
 527        rpdev->dst = chinfo->dst;
 528
 529        /*
 530         * rpmsg server channels has predefined local address (for now),
 531         * and their existence needs to be announced remotely
 532         */
 533        rpdev->announce = rpdev->src != RPMSG_ADDR_ANY ? true : false;
 534
 535        strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE);
 536
 537        /* very simple device indexing plumbing which is enough for now */
 538        dev_set_name(&rpdev->dev, "rpmsg%d", rpmsg_dev_index++);
 539
 540        rpdev->dev.parent = &vrp->vdev->dev;
 541        rpdev->dev.bus = &rpmsg_bus;
 542        rpdev->dev.release = rpmsg_release_device;
 543
 544        ret = device_register(&rpdev->dev);
 545        if (ret) {
 546                dev_err(dev, "device_register failed: %d\n", ret);
 547                put_device(&rpdev->dev);
 548                return NULL;
 549        }
 550
 551        return rpdev;
 552}
 553
 554/*
 555 * find an existing channel using its name + address properties,
 556 * and destroy it
 557 */
 558static int rpmsg_destroy_channel(struct virtproc_info *vrp,
 559                                        struct rpmsg_channel_info *chinfo)
 560{
 561        struct virtio_device *vdev = vrp->vdev;
 562        struct device *dev;
 563
 564        dev = device_find_child(&vdev->dev, chinfo, rpmsg_channel_match);
 565        if (!dev)
 566                return -EINVAL;
 567
 568        device_unregister(dev);
 569
 570        put_device(dev);
 571
 572        return 0;
 573}
 574
 575/* super simple buffer "allocator" that is just enough for now */
 576static void *get_a_tx_buf(struct virtproc_info *vrp)
 577{
 578        unsigned int len;
 579        void *ret;
 580
 581        /* support multiple concurrent senders */
 582        mutex_lock(&vrp->tx_lock);
 583
 584        /*
 585         * either pick the next unused tx buffer
 586         * (half of our buffers are used for sending messages)
 587         */
 588        if (vrp->last_sbuf < RPMSG_NUM_BUFS / 2)
 589                ret = vrp->sbufs + RPMSG_BUF_SIZE * vrp->last_sbuf++;
 590        /* or recycle a used one */
 591        else
 592                ret = virtqueue_get_buf(vrp->svq, &len);
 593
 594        mutex_unlock(&vrp->tx_lock);
 595
 596        return ret;
 597}
 598
 599/**
 600 * rpmsg_upref_sleepers() - enable "tx-complete" interrupts, if needed
 601 * @vrp: virtual remote processor state
 602 *
 603 * This function is called before a sender is blocked, waiting for
 604 * a tx buffer to become available.
 605 *
 606 * If we already have blocking senders, this function merely increases
 607 * the "sleepers" reference count, and exits.
 608 *
 609 * Otherwise, if this is the first sender to block, we also enable
 610 * virtio's tx callbacks, so we'd be immediately notified when a tx
 611 * buffer is consumed (we rely on virtio's tx callback in order
 612 * to wake up sleeping senders as soon as a tx buffer is used by the
 613 * remote processor).
 614 */
 615static void rpmsg_upref_sleepers(struct virtproc_info *vrp)
 616{
 617        /* support multiple concurrent senders */
 618        mutex_lock(&vrp->tx_lock);
 619
 620        /* are we the first sleeping context waiting for tx buffers ? */
 621        if (atomic_inc_return(&vrp->sleepers) == 1)
 622                /* enable "tx-complete" interrupts before dozing off */
 623                virtqueue_enable_cb(vrp->svq);
 624
 625        mutex_unlock(&vrp->tx_lock);
 626}
 627
 628/**
 629 * rpmsg_downref_sleepers() - disable "tx-complete" interrupts, if needed
 630 * @vrp: virtual remote processor state
 631 *
 632 * This function is called after a sender, that waited for a tx buffer
 633 * to become available, is unblocked.
 634 *
 635 * If we still have blocking senders, this function merely decreases
 636 * the "sleepers" reference count, and exits.
 637 *
 638 * Otherwise, if there are no more blocking senders, we also disable
 639 * virtio's tx callbacks, to avoid the overhead incurred with handling
 640 * those (now redundant) interrupts.
 641 */
 642static void rpmsg_downref_sleepers(struct virtproc_info *vrp)
 643{
 644        /* support multiple concurrent senders */
 645        mutex_lock(&vrp->tx_lock);
 646
 647        /* are we the last sleeping context waiting for tx buffers ? */
 648        if (atomic_dec_and_test(&vrp->sleepers))
 649                /* disable "tx-complete" interrupts */
 650                virtqueue_disable_cb(vrp->svq);
 651
 652        mutex_unlock(&vrp->tx_lock);
 653}
 654
 655/**
 656 * rpmsg_send_offchannel_raw() - send a message across to the remote processor
 657 * @rpdev: the rpmsg channel
 658 * @src: source address
 659 * @dst: destination address
 660 * @data: payload of message
 661 * @len: length of payload
 662 * @wait: indicates whether caller should block in case no TX buffers available
 663 *
 664 * This function is the base implementation for all of the rpmsg sending API.
 665 *
 666 * It will send @data of length @len to @dst, and say it's from @src. The
 667 * message will be sent to the remote processor which the @rpdev channel
 668 * belongs to.
 669 *
 670 * The message is sent using one of the TX buffers that are available for
 671 * communication with this remote processor.
 672 *
 673 * If @wait is true, the caller will be blocked until either a TX buffer is
 674 * available, or 15 seconds elapses (we don't want callers to
 675 * sleep indefinitely due to misbehaving remote processors), and in that
 676 * case -ERESTARTSYS is returned. The number '15' itself was picked
 677 * arbitrarily; there's little point in asking drivers to provide a timeout
 678 * value themselves.
 679 *
 680 * Otherwise, if @wait is false, and there are no TX buffers available,
 681 * the function will immediately fail, and -ENOMEM will be returned.
 682 *
 683 * Normally drivers shouldn't use this function directly; instead, drivers
 684 * should use the appropriate rpmsg_{try}send{to, _offchannel} API
 685 * (see include/linux/rpmsg.h).
 686 *
 687 * Returns 0 on success and an appropriate error value on failure.
 688 */
 689int rpmsg_send_offchannel_raw(struct rpmsg_channel *rpdev, u32 src, u32 dst,
 690                                        void *data, int len, bool wait)
 691{
 692        struct virtproc_info *vrp = rpdev->vrp;
 693        struct device *dev = &rpdev->dev;
 694        struct scatterlist sg;
 695        struct rpmsg_hdr *msg;
 696        int err;
 697
 698        /* bcasting isn't allowed */
 699        if (src == RPMSG_ADDR_ANY || dst == RPMSG_ADDR_ANY) {
 700                dev_err(dev, "invalid addr (src 0x%x, dst 0x%x)\n", src, dst);
 701                return -EINVAL;
 702        }
 703
 704        /*
 705         * We currently use fixed-sized buffers, and therefore the payload
 706         * length is limited.
 707         *
 708         * One of the possible improvements here is either to support
 709         * user-provided buffers (and then we can also support zero-copy
 710         * messaging), or to improve the buffer allocator, to support
 711         * variable-length buffer sizes.
 712         */
 713        if (len > RPMSG_BUF_SIZE - sizeof(struct rpmsg_hdr)) {
 714                dev_err(dev, "message is too big (%d)\n", len);
 715                return -EMSGSIZE;
 716        }
 717
 718        /* grab a buffer */
 719        msg = get_a_tx_buf(vrp);
 720        if (!msg && !wait)
 721                return -ENOMEM;
 722
 723        /* no free buffer ? wait for one (but bail after 15 seconds) */
 724        while (!msg) {
 725                /* enable "tx-complete" interrupts, if not already enabled */
 726                rpmsg_upref_sleepers(vrp);
 727
 728                /*
 729                 * sleep until a free buffer is available or 15 secs elapse.
 730                 * the timeout period is not configurable because there's
 731                 * little point in asking drivers to specify that.
 732                 * if later this happens to be required, it'd be easy to add.
 733                 */
 734                err = wait_event_interruptible_timeout(vrp->sendq,
 735                                        (msg = get_a_tx_buf(vrp)),
 736                                        msecs_to_jiffies(15000));
 737
 738                /* disable "tx-complete" interrupts if we're the last sleeper */
 739                rpmsg_downref_sleepers(vrp);
 740
 741                /* timeout ? */
 742                if (!err) {
 743                        dev_err(dev, "timeout waiting for a tx buffer\n");
 744                        return -ERESTARTSYS;
 745                }
 746        }
 747
 748        msg->len = len;
 749        msg->flags = 0;
 750        msg->src = src;
 751        msg->dst = dst;
 752        msg->reserved = 0;
 753        memcpy(msg->data, data, len);
 754
 755        dev_dbg(dev, "TX From 0x%x, To 0x%x, Len %d, Flags %d, Reserved %d\n",
 756                                        msg->src, msg->dst, msg->len,
 757                                        msg->flags, msg->reserved);
 758        print_hex_dump(KERN_DEBUG, "rpmsg_virtio TX: ", DUMP_PREFIX_NONE, 16, 1,
 759                                        msg, sizeof(*msg) + msg->len, true);
 760
 761        sg_init_one(&sg, msg, sizeof(*msg) + len);
 762
 763        mutex_lock(&vrp->tx_lock);
 764
 765        /* add message to the remote processor's virtqueue */
 766        err = virtqueue_add_buf(vrp->svq, &sg, 1, 0, msg, GFP_KERNEL);
 767        if (err < 0) {
 768                /*
 769                 * need to reclaim the buffer here, otherwise it's lost
 770                 * (memory won't leak, but rpmsg won't use it again for TX).
 771                 * this will wait for a buffer management overhaul.
 772                 */
 773                dev_err(dev, "virtqueue_add_buf failed: %d\n", err);
 774                goto out;
 775        }
 776
 777        /* tell the remote processor it has a pending message to read */
 778        virtqueue_kick(vrp->svq);
 779
 780        err = 0;
 781out:
 782        mutex_unlock(&vrp->tx_lock);
 783        return err;
 784}
 785EXPORT_SYMBOL(rpmsg_send_offchannel_raw);
 786
 787/* called when an rx buffer is used, and it's time to digest a message */
 788static void rpmsg_recv_done(struct virtqueue *rvq)
 789{
 790        struct rpmsg_hdr *msg;
 791        unsigned int len;
 792        struct rpmsg_endpoint *ept;
 793        struct scatterlist sg;
 794        struct virtproc_info *vrp = rvq->vdev->priv;
 795        struct device *dev = &rvq->vdev->dev;
 796        int err;
 797
 798        msg = virtqueue_get_buf(rvq, &len);
 799        if (!msg) {
 800                dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
 801                return;
 802        }
 803
 804        dev_dbg(dev, "From: 0x%x, To: 0x%x, Len: %d, Flags: %d, Reserved: %d\n",
 805                                        msg->src, msg->dst, msg->len,
 806                                        msg->flags, msg->reserved);
 807        print_hex_dump(KERN_DEBUG, "rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
 808                                        msg, sizeof(*msg) + msg->len, true);
 809
 810        /*
 811         * We currently use fixed-sized buffers, so trivially sanitize
 812         * the reported payload length.
 813         */
 814        if (len > RPMSG_BUF_SIZE ||
 815                msg->len > (len - sizeof(struct rpmsg_hdr))) {
 816                dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg->len);
 817                return;
 818        }
 819
 820        /* use the dst addr to fetch the callback of the appropriate user */
 821        mutex_lock(&vrp->endpoints_lock);
 822
 823        ept = idr_find(&vrp->endpoints, msg->dst);
 824
 825        /* let's make sure no one deallocates ept while we use it */
 826        if (ept)
 827                kref_get(&ept->refcount);
 828
 829        mutex_unlock(&vrp->endpoints_lock);
 830
 831        if (ept) {
 832                /* make sure ept->cb doesn't go away while we use it */
 833                mutex_lock(&ept->cb_lock);
 834
 835                if (ept->cb)
 836                        ept->cb(ept->rpdev, msg->data, msg->len, ept->priv,
 837                                msg->src);
 838
 839                mutex_unlock(&ept->cb_lock);
 840
 841                /* farewell, ept, we don't need you anymore */
 842                kref_put(&ept->refcount, __ept_release);
 843        } else
 844                dev_warn(dev, "msg received with no recepient\n");
 845
 846        /* publish the real size of the buffer */
 847        sg_init_one(&sg, msg, RPMSG_BUF_SIZE);
 848
 849        /* add the buffer back to the remote processor's virtqueue */
 850        err = virtqueue_add_buf(vrp->rvq, &sg, 0, 1, msg, GFP_KERNEL);
 851        if (err < 0) {
 852                dev_err(dev, "failed to add a virtqueue buffer: %d\n", err);
 853                return;
 854        }
 855
 856        /* tell the remote processor we added another available rx buffer */
 857        virtqueue_kick(vrp->rvq);
 858}
 859
 860/*
 861 * This is invoked whenever the remote processor completed processing
 862 * a TX msg we just sent it, and the buffer is put back to the used ring.
 863 *
 864 * Normally, though, we suppress this "tx complete" interrupt in order to
 865 * avoid the incurred overhead.
 866 */
 867static void rpmsg_xmit_done(struct virtqueue *svq)
 868{
 869        struct virtproc_info *vrp = svq->vdev->priv;
 870
 871        dev_dbg(&svq->vdev->dev, "%s\n", __func__);
 872
 873        /* wake up potential senders that are waiting for a tx buffer */
 874        wake_up_interruptible(&vrp->sendq);
 875}
 876
 877/* invoked when a name service announcement arrives */
 878static void rpmsg_ns_cb(struct rpmsg_channel *rpdev, void *data, int len,
 879                                                        void *priv, u32 src)
 880{
 881        struct rpmsg_ns_msg *msg = data;
 882        struct rpmsg_channel *newch;
 883        struct rpmsg_channel_info chinfo;
 884        struct virtproc_info *vrp = priv;
 885        struct device *dev = &vrp->vdev->dev;
 886        int ret;
 887
 888        print_hex_dump(KERN_DEBUG, "NS announcement: ",
 889                        DUMP_PREFIX_NONE, 16, 1,
 890                        data, len, true);
 891
 892        if (len != sizeof(*msg)) {
 893                dev_err(dev, "malformed ns msg (%d)\n", len);
 894                return;
 895        }
 896
 897        /*
 898         * the name service ept does _not_ belong to a real rpmsg channel,
 899         * and is handled by the rpmsg bus itself.
 900         * for sanity reasons, make sure a valid rpdev has _not_ sneaked
 901         * in somehow.
 902         */
 903        if (rpdev) {
 904                dev_err(dev, "anomaly: ns ept has an rpdev handle\n");
 905                return;
 906        }
 907
 908        /* don't trust the remote processor for null terminating the name */
 909        msg->name[RPMSG_NAME_SIZE - 1] = '\0';
 910
 911        dev_info(dev, "%sing channel %s addr 0x%x\n",
 912                        msg->flags & RPMSG_NS_DESTROY ? "destroy" : "creat",
 913                        msg->name, msg->addr);
 914
 915        strncpy(chinfo.name, msg->name, sizeof(chinfo.name));
 916        chinfo.src = RPMSG_ADDR_ANY;
 917        chinfo.dst = msg->addr;
 918
 919        if (msg->flags & RPMSG_NS_DESTROY) {
 920                ret = rpmsg_destroy_channel(vrp, &chinfo);
 921                if (ret)
 922                        dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret);
 923        } else {
 924                newch = rpmsg_create_channel(vrp, &chinfo);
 925                if (!newch)
 926                        dev_err(dev, "rpmsg_create_channel failed\n");
 927        }
 928}
 929
 930static int rpmsg_probe(struct virtio_device *vdev)
 931{
 932        vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
 933        const char *names[] = { "input", "output" };
 934        struct virtqueue *vqs[2];
 935        struct virtproc_info *vrp;
 936        void *bufs_va;
 937        int err = 0, i;
 938
 939        vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
 940        if (!vrp)
 941                return -ENOMEM;
 942
 943        vrp->vdev = vdev;
 944
 945        idr_init(&vrp->endpoints);
 946        mutex_init(&vrp->endpoints_lock);
 947        mutex_init(&vrp->tx_lock);
 948        init_waitqueue_head(&vrp->sendq);
 949
 950        /* We expect two virtqueues, rx and tx (and in this order) */
 951        err = vdev->config->find_vqs(vdev, 2, vqs, vq_cbs, names);
 952        if (err)
 953                goto free_vrp;
 954
 955        vrp->rvq = vqs[0];
 956        vrp->svq = vqs[1];
 957
 958        /* allocate coherent memory for the buffers */
 959        bufs_va = dma_alloc_coherent(vdev->dev.parent->parent,
 960                                RPMSG_TOTAL_BUF_SPACE,
 961                                &vrp->bufs_dma, GFP_KERNEL);
 962        if (!bufs_va)
 963                goto vqs_del;
 964
 965        dev_dbg(&vdev->dev, "buffers: va %p, dma 0x%llx\n", bufs_va,
 966                                        (unsigned long long)vrp->bufs_dma);
 967
 968        /* half of the buffers is dedicated for RX */
 969        vrp->rbufs = bufs_va;
 970
 971        /* and half is dedicated for TX */
 972        vrp->sbufs = bufs_va + RPMSG_TOTAL_BUF_SPACE / 2;
 973
 974        /* set up the receive buffers */
 975        for (i = 0; i < RPMSG_NUM_BUFS / 2; i++) {
 976                struct scatterlist sg;
 977                void *cpu_addr = vrp->rbufs + i * RPMSG_BUF_SIZE;
 978
 979                sg_init_one(&sg, cpu_addr, RPMSG_BUF_SIZE);
 980
 981                err = virtqueue_add_buf(vrp->rvq, &sg, 0, 1, cpu_addr,
 982                                                                GFP_KERNEL);
 983                WARN_ON(err < 0); /* sanity check; this can't really happen */
 984        }
 985
 986        /* suppress "tx-complete" interrupts */
 987        virtqueue_disable_cb(vrp->svq);
 988
 989        vdev->priv = vrp;
 990
 991        /* if supported by the remote processor, enable the name service */
 992        if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
 993                /* a dedicated endpoint handles the name service msgs */
 994                vrp->ns_ept = __rpmsg_create_ept(vrp, NULL, rpmsg_ns_cb,
 995                                                vrp, RPMSG_NS_ADDR);
 996                if (!vrp->ns_ept) {
 997                        dev_err(&vdev->dev, "failed to create the ns ept\n");
 998                        err = -ENOMEM;
 999                        goto free_coherent;
1000                }
1001        }
1002
1003        /* tell the remote processor it can start sending messages */
1004        virtqueue_kick(vrp->rvq);
1005
1006        dev_info(&vdev->dev, "rpmsg host is online\n");
1007
1008        return 0;
1009
1010free_coherent:
1011        dma_free_coherent(vdev->dev.parent->parent, RPMSG_TOTAL_BUF_SPACE,
1012                                        bufs_va, vrp->bufs_dma);
1013vqs_del:
1014        vdev->config->del_vqs(vrp->vdev);
1015free_vrp:
1016        kfree(vrp);
1017        return err;
1018}
1019
1020static int rpmsg_remove_device(struct device *dev, void *data)
1021{
1022        device_unregister(dev);
1023
1024        return 0;
1025}
1026
1027static void __devexit rpmsg_remove(struct virtio_device *vdev)
1028{
1029        struct virtproc_info *vrp = vdev->priv;
1030        int ret;
1031
1032        vdev->config->reset(vdev);
1033
1034        ret = device_for_each_child(&vdev->dev, NULL, rpmsg_remove_device);
1035        if (ret)
1036                dev_warn(&vdev->dev, "can't remove rpmsg device: %d\n", ret);
1037
1038        if (vrp->ns_ept)
1039                __rpmsg_destroy_ept(vrp, vrp->ns_ept);
1040
1041        idr_remove_all(&vrp->endpoints);
1042        idr_destroy(&vrp->endpoints);
1043
1044        vdev->config->del_vqs(vrp->vdev);
1045
1046        dma_free_coherent(vdev->dev.parent->parent, RPMSG_TOTAL_BUF_SPACE,
1047                                        vrp->rbufs, vrp->bufs_dma);
1048
1049        kfree(vrp);
1050}
1051
1052static struct virtio_device_id id_table[] = {
1053        { VIRTIO_ID_RPMSG, VIRTIO_DEV_ANY_ID },
1054        { 0 },
1055};
1056
1057static unsigned int features[] = {
1058        VIRTIO_RPMSG_F_NS,
1059};
1060
1061static struct virtio_driver virtio_ipc_driver = {
1062        .feature_table  = features,
1063        .feature_table_size = ARRAY_SIZE(features),
1064        .driver.name    = KBUILD_MODNAME,
1065        .driver.owner   = THIS_MODULE,
1066        .id_table       = id_table,
1067        .probe          = rpmsg_probe,
1068        .remove         = __devexit_p(rpmsg_remove),
1069};
1070
1071static int __init rpmsg_init(void)
1072{
1073        int ret;
1074
1075        ret = bus_register(&rpmsg_bus);
1076        if (ret) {
1077                pr_err("failed to register rpmsg bus: %d\n", ret);
1078                return ret;
1079        }
1080
1081        ret = register_virtio_driver(&virtio_ipc_driver);
1082        if (ret) {
1083                pr_err("failed to register virtio driver: %d\n", ret);
1084                bus_unregister(&rpmsg_bus);
1085        }
1086
1087        return ret;
1088}
1089subsys_initcall(rpmsg_init);
1090
1091static void __exit rpmsg_fini(void)
1092{
1093        unregister_virtio_driver(&virtio_ipc_driver);
1094        bus_unregister(&rpmsg_bus);
1095}
1096module_exit(rpmsg_fini);
1097
1098MODULE_DEVICE_TABLE(virtio, id_table);
1099MODULE_DESCRIPTION("Virtio-based remote processor messaging bus");
1100MODULE_LICENSE("GPL v2");
1101
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