drivers/hwtracing/stm/core.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * System Trace Module (STM) infrastructure
   4  * Copyright (c) 2014, Intel Corporation.
   5  *
   6  * STM class implements generic infrastructure for  System Trace Module devices
   7  * as defined in MIPI STPv2 specification.
   8  */
   9
  10 #include <linux/pm_runtime.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/device.h>
  15 #include <linux/compat.h>
  16 #include <linux/kdev_t.h>
  17 #include <linux/srcu.h>
  18 #include <linux/slab.h>
  19 #include <linux/stm.h>
  20 #include <linux/fs.h>
  21 #include <linux/mm.h>
  22 #include <linux/vmalloc.h>
  23 #include "stm.h"
  24
  25 #include <uapi/linux/stm.h>
  26
  27 static unsigned int stm_core_up;
  28
  29 /*
  30  * The SRCU here makes sure that STM device doesn't disappear from under a
  31  * stm_source_write() caller, which may want to have as little overhead as
  32  * possible.
  33  */
  34 static struct srcu_struct stm_source_srcu;
  35
  36 static ssize_t masters_show(struct device *dev,
  37                             struct device_attribute *attr,
  38                             char *buf)
  39 {
  40         struct stm_device *stm = to_stm_device(dev);
  41         int ret;
  42
  43         ret = sprintf(buf, "%u %u\n", stm->data->sw_start, stm->data->sw_end);
  44
  45         return ret;
  46 }
  47
  48 static DEVICE_ATTR_RO(masters);
  49
  50 static ssize_t channels_show(struct device *dev,
  51                              struct device_attribute *attr,
  52                              char *buf)
  53 {
  54         struct stm_device *stm = to_stm_device(dev);
  55         int ret;
  56
  57         ret = sprintf(buf, "%u\n", stm->data->sw_nchannels);
  58
  59         return ret;
  60 }
  61
  62 static DEVICE_ATTR_RO(channels);
  63
  64 static ssize_t hw_override_show(struct device *dev,
  65                                 struct device_attribute *attr,
  66                                 char *buf)
  67 {
  68         struct stm_device *stm = to_stm_device(dev);
  69         int ret;
  70
  71         ret = sprintf(buf, "%u\n", stm->data->hw_override);
  72
  73         return ret;
  74 }
  75
  76 static DEVICE_ATTR_RO(hw_override);
  77
  78 static struct attribute *stm_attrs[] = {
  79         &dev_attr_masters.attr,
  80         &dev_attr_channels.attr,
  81         &dev_attr_hw_override.attr,
  82         NULL,
  83 };
  84
  85 ATTRIBUTE_GROUPS(stm);
  86
  87 static struct class stm_class = {
  88         .name           = "stm",
  89         .dev_groups     = stm_groups,
  90 };
  91
  92 /**
  93  * stm_find_device() - find stm device by name
  94  * @buf:        character buffer containing the name
  95  *
  96  * This is called when either policy gets assigned to an stm device or an
  97  * stm_source device gets linked to an stm device.
  98  *
  99  * This grabs device's reference (get_device()) and module reference, both
 100  * of which the calling path needs to make sure to drop with stm_put_device().
 101  *
 102  * Return:      stm device pointer or null if lookup failed.
 103  */
 104 struct stm_device *stm_find_device(const char *buf)
 105 {
 106         struct stm_device *stm;
 107         struct device *dev;
 108
 109         if (!stm_core_up)
 110                 return NULL;
 111
 112         dev = class_find_device_by_name(&stm_class, buf);
 113         if (!dev)
 114                 return NULL;
 115
 116         stm = to_stm_device(dev);
 117         if (!try_module_get(stm->owner)) {
 118                 /* matches class_find_device() above */
 119                 put_device(dev);
 120                 return NULL;
 121         }
 122
 123         return stm;
 124 }
 125
 126 /**
 127  * stm_put_device() - drop references on the stm device
 128  * @stm:        stm device, previously acquired by stm_find_device()
 129  *
 130  * This drops the module reference and device reference taken by
 131  * stm_find_device() or stm_char_open().
 132  */
 133 void stm_put_device(struct stm_device *stm)
 134 {
 135         module_put(stm->owner);
 136         put_device(&stm->dev);
 137 }
 138
 139 /*
 140  * Internally we only care about software-writable masters here, that is the
 141  * ones in the range [stm_data->sw_start..stm_data..sw_end], however we need
 142  * original master numbers to be visible externally, since they are the ones
 143  * that will appear in the STP stream. Thus, the internal bookkeeping uses
 144  * $master - stm_data->sw_start to reference master descriptors and such.
 145  */
 146
 147 #define __stm_master(_s, _m)                            \
 148         ((_s)->masters[(_m) - (_s)->data->sw_start])
 149
 150 static inline struct stp_master *
 151 stm_master(struct stm_device *stm, unsigned int idx)
 152 {
 153         if (idx < stm->data->sw_start || idx > stm->data->sw_end)
 154                 return NULL;
 155
 156         return __stm_master(stm, idx);
 157 }
 158
 159 static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
 160 {
 161         struct stp_master *master;
 162
 163         master = kzalloc(struct_size(master, chan_map,
 164                                      BITS_TO_LONGS(stm->data->sw_nchannels)),
 165                          GFP_ATOMIC);
 166         if (!master)
 167                 return -ENOMEM;
 168
 169         master->nr_free = stm->data->sw_nchannels;
 170         __stm_master(stm, idx) = master;
 171
 172         return 0;
 173 }
 174
 175 static void stp_master_free(struct stm_device *stm, unsigned int idx)
 176 {
 177         struct stp_master *master = stm_master(stm, idx);
 178
 179         if (!master)
 180                 return;
 181
 182         __stm_master(stm, idx) = NULL;
 183         kfree(master);
 184 }
 185
 186 static void stm_output_claim(struct stm_device *stm, struct stm_output *output)
 187 {
 188         struct stp_master *master = stm_master(stm, output->master);
 189
 190         lockdep_assert_held(&stm->mc_lock);
 191         lockdep_assert_held(&output->lock);
 192
 193         if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
 194                 return;
 195
 196         bitmap_allocate_region(&master->chan_map[0], output->channel,
 197                                ilog2(output->nr_chans));
 198
 199         master->nr_free -= output->nr_chans;
 200 }
 201
 202 static void
 203 stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
 204 {
 205         struct stp_master *master = stm_master(stm, output->master);
 206
 207         lockdep_assert_held(&stm->mc_lock);
 208         lockdep_assert_held(&output->lock);
 209
 210         bitmap_release_region(&master->chan_map[0], output->channel,
 211                               ilog2(output->nr_chans));
 212
 213         master->nr_free += output->nr_chans;
 214         output->nr_chans = 0;
 215 }
 216
 217 /*
 218  * This is like bitmap_find_free_region(), except it can ignore @start bits
 219  * at the beginning.
 220  */
 221 static int find_free_channels(unsigned long *bitmap, unsigned int start,
 222                               unsigned int end, unsigned int width)
 223 {
 224         unsigned int pos;
 225         int i;
 226
 227         for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) {
 228                 pos = find_next_zero_bit(bitmap, end + 1, pos);
 229                 if (pos + width > end + 1)
 230                         break;
 231
 232                 if (pos & (width - 1))
 233                         continue;
 234
 235                 for (i = 1; i < width && !test_bit(pos + i, bitmap); i++)
 236                         ;
 237                 if (i == width)
 238                         return pos;
 239
 240                 /* step over [pos..pos+i) to continue search */
 241                 pos += i;
 242         }
 243
 244         return -1;
 245 }
 246
 247 static int
 248 stm_find_master_chan(struct stm_device *stm, unsigned int width,
 249                      unsigned int *mstart, unsigned int mend,
 250                      unsigned int *cstart, unsigned int cend)
 251 {
 252         struct stp_master *master;
 253         unsigned int midx;
 254         int pos, err;
 255
 256         for (midx = *mstart; midx <= mend; midx++) {
 257                 if (!stm_master(stm, midx)) {
 258                         err = stp_master_alloc(stm, midx);
 259                         if (err)
 260                                 return err;
 261                 }
 262
 263                 master = stm_master(stm, midx);
 264
 265                 if (!master->nr_free)
 266                         continue;
 267
 268                 pos = find_free_channels(master->chan_map, *cstart, cend,
 269                                          width);
 270                 if (pos < 0)
 271                         continue;
 272
 273                 *mstart = midx;
 274                 *cstart = pos;
 275                 return 0;
 276         }
 277
 278         return -ENOSPC;
 279 }
 280
 281 static int stm_output_assign(struct stm_device *stm, unsigned int width,
 282                              struct stp_policy_node *policy_node,
 283                              struct stm_output *output)
 284 {
 285         unsigned int midx, cidx, mend, cend;
 286         int ret = -EINVAL;
 287
 288         if (width > stm->data->sw_nchannels)
 289                 return -EINVAL;
 290
 291         /* We no longer accept policy_node==NULL here */
 292         if (WARN_ON_ONCE(!policy_node))
 293                 return -EINVAL;
 294
 295         /*
 296          * Also, the caller holds reference to policy_node, so it won't
 297          * disappear on us.
 298          */
 299         stp_policy_node_get_ranges(policy_node, &midx, &mend, &cidx, &cend);
 300
 301         spin_lock(&stm->mc_lock);
 302         spin_lock(&output->lock);
 303         /* output is already assigned -- shouldn't happen */
 304         if (WARN_ON_ONCE(output->nr_chans))
 305                 goto unlock;
 306
 307         ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
 308         if (ret < 0)
 309                 goto unlock;
 310
 311         output->master = midx;
 312         output->channel = cidx;
 313         output->nr_chans = width;
 314         if (stm->pdrv->output_open) {
 315                 void *priv = stp_policy_node_priv(policy_node);
 316
 317                 if (WARN_ON_ONCE(!priv))
 318                         goto unlock;
 319
 320                 /* configfs subsys mutex is held by the caller */
 321                 ret = stm->pdrv->output_open(priv, output);
 322                 if (ret)
 323                         goto unlock;
 324         }
 325
 326         stm_output_claim(stm, output);
 327         dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width);
 328
 329         ret = 0;
 330 unlock:
 331         if (ret)
 332                 output->nr_chans = 0;
 333
 334         spin_unlock(&output->lock);
 335         spin_unlock(&stm->mc_lock);
 336
 337         return ret;
 338 }
 339
 340 static void stm_output_free(struct stm_device *stm, struct stm_output *output)
 341 {
 342         spin_lock(&stm->mc_lock);
 343         spin_lock(&output->lock);
 344         if (output->nr_chans)
 345                 stm_output_disclaim(stm, output);
 346         if (stm->pdrv && stm->pdrv->output_close)
 347                 stm->pdrv->output_close(output);
 348         spin_unlock(&output->lock);
 349         spin_unlock(&stm->mc_lock);
 350 }
 351
 352 static void stm_output_init(struct stm_output *output)
 353 {
 354         spin_lock_init(&output->lock);
 355 }
 356
 357 static int major_match(struct device *dev, const void *data)
 358 {
 359         unsigned int major = *(unsigned int *)data;
 360
 361         return MAJOR(dev->devt) == major;
 362 }
 363
 364 /*
 365  * Framing protocol management
 366  * Modules can implement STM protocol drivers and (un-)register them
 367  * with the STM class framework.
 368  */
 369 static struct list_head stm_pdrv_head;
 370 static struct mutex stm_pdrv_mutex;
 371
 372 struct stm_pdrv_entry {
 373         struct list_head                        entry;
 374         const struct stm_protocol_driver        *pdrv;
 375         const struct config_item_type           *node_type;
 376 };
 377
 378 static const struct stm_pdrv_entry *
 379 __stm_lookup_protocol(const char *name)
 380 {
 381         struct stm_pdrv_entry *pe;
 382
 383         /*
 384          * If no name is given (NULL or ""), fall back to "p_basic".
 385          */
 386         if (!name || !*name)
 387                 name = "p_basic";
 388
 389         list_for_each_entry(pe, &stm_pdrv_head, entry) {
 390                 if (!strcmp(name, pe->pdrv->name))
 391                         return pe;
 392         }
 393
 394         return NULL;
 395 }
 396
 397 int stm_register_protocol(const struct stm_protocol_driver *pdrv)
 398 {
 399         struct stm_pdrv_entry *pe = NULL;
 400         int ret = -ENOMEM;
 401
 402         mutex_lock(&stm_pdrv_mutex);
 403
 404         if (__stm_lookup_protocol(pdrv->name)) {
 405                 ret = -EEXIST;
 406                 goto unlock;
 407         }
 408
 409         pe = kzalloc(sizeof(*pe), GFP_KERNEL);
 410         if (!pe)
 411                 goto unlock;
 412
 413         if (pdrv->policy_attr) {
 414                 pe->node_type = get_policy_node_type(pdrv->policy_attr);
 415                 if (!pe->node_type)
 416                         goto unlock;
 417         }
 418
 419         list_add_tail(&pe->entry, &stm_pdrv_head);
 420         pe->pdrv = pdrv;
 421
 422         ret = 0;
 423 unlock:
 424         mutex_unlock(&stm_pdrv_mutex);
 425
 426         if (ret)
 427                 kfree(pe);
 428
 429         return ret;
 430 }
 431 EXPORT_SYMBOL_GPL(stm_register_protocol);
 432
 433 void stm_unregister_protocol(const struct stm_protocol_driver *pdrv)
 434 {
 435         struct stm_pdrv_entry *pe, *iter;
 436
 437         mutex_lock(&stm_pdrv_mutex);
 438
 439         list_for_each_entry_safe(pe, iter, &stm_pdrv_head, entry) {
 440                 if (pe->pdrv == pdrv) {
 441                         list_del(&pe->entry);
 442
 443                         if (pe->node_type) {
 444                                 kfree(pe->node_type->ct_attrs);
 445                                 kfree(pe->node_type);
 446                         }
 447                         kfree(pe);
 448                         break;
 449                 }
 450         }
 451
 452         mutex_unlock(&stm_pdrv_mutex);
 453 }
 454 EXPORT_SYMBOL_GPL(stm_unregister_protocol);
 455
 456 static bool stm_get_protocol(const struct stm_protocol_driver *pdrv)
 457 {
 458         return try_module_get(pdrv->owner);
 459 }
 460
 461 void stm_put_protocol(const struct stm_protocol_driver *pdrv)
 462 {
 463         module_put(pdrv->owner);
 464 }
 465
 466 int stm_lookup_protocol(const char *name,
 467                         const struct stm_protocol_driver **pdrv,
 468                         const struct config_item_type **node_type)
 469 {
 470         const struct stm_pdrv_entry *pe;
 471
 472         mutex_lock(&stm_pdrv_mutex);
 473
 474         pe = __stm_lookup_protocol(name);
 475         if (pe && pe->pdrv && stm_get_protocol(pe->pdrv)) {
 476                 *pdrv = pe->pdrv;
 477                 *node_type = pe->node_type;
 478         }
 479
 480         mutex_unlock(&stm_pdrv_mutex);
 481
 482         return pe ? 0 : -ENOENT;
 483 }
 484
 485 static int stm_char_open(struct inode *inode, struct file *file)
 486 {
 487         struct stm_file *stmf;
 488         struct device *dev;
 489         unsigned int major = imajor(inode);
 490         int err = -ENOMEM;
 491
 492         dev = class_find_device(&stm_class, NULL, &major, major_match);
 493         if (!dev)
 494                 return -ENODEV;
 495
 496         stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
 497         if (!stmf)
 498                 goto err_put_device;
 499
 500         err = -ENODEV;
 501         stm_output_init(&stmf->output);
 502         stmf->stm = to_stm_device(dev);
 503
 504         if (!try_module_get(stmf->stm->owner))
 505                 goto err_free;
 506
 507         file->private_data = stmf;
 508
 509         return nonseekable_open(inode, file);
 510
 511 err_free:
 512         kfree(stmf);
 513 err_put_device:
 514         /* matches class_find_device() above */
 515         put_device(dev);
 516
 517         return err;
 518 }
 519
 520 static int stm_char_release(struct inode *inode, struct file *file)
 521 {
 522         struct stm_file *stmf = file->private_data;
 523         struct stm_device *stm = stmf->stm;
 524
 525         if (stm->data->unlink)
 526                 stm->data->unlink(stm->data, stmf->output.master,
 527                                   stmf->output.channel);
 528
 529         stm_output_free(stm, &stmf->output);
 530
 531         /*
 532          * matches the stm_char_open()'s
 533          * class_find_device() + try_module_get()
 534          */
 535         stm_put_device(stm);
 536         kfree(stmf);
 537
 538         return 0;
 539 }
 540
 541 static int
 542 stm_assign_first_policy(struct stm_device *stm, struct stm_output *output,
 543                         char **ids, unsigned int width)
 544 {
 545         struct stp_policy_node *pn;
 546         int err, n;
 547
 548         /*
 549          * On success, stp_policy_node_lookup() will return holding the
 550          * configfs subsystem mutex, which is then released in
 551          * stp_policy_node_put(). This allows the pdrv->output_open() in
 552          * stm_output_assign() to serialize against the attribute accessors.
 553          */
 554         for (n = 0, pn = NULL; ids[n] && !pn; n++)
 555                 pn = stp_policy_node_lookup(stm, ids[n]);
 556
 557         if (!pn)
 558                 return -EINVAL;
 559
 560         err = stm_output_assign(stm, width, pn, output);
 561
 562         stp_policy_node_put(pn);
 563
 564         return err;
 565 }
 566
 567 /**
 568  * stm_data_write() - send the given payload as data packets
 569  * @data:       stm driver's data
 570  * @m:          STP master
 571  * @c:          STP channel
 572  * @ts_first:   timestamp the first packet
 573  * @buf:        data payload buffer
 574  * @count:      data payload size
 575  */
 576 ssize_t notrace stm_data_write(struct stm_data *data, unsigned int m,
 577                                unsigned int c, bool ts_first, const void *buf,
 578                                size_t count)
 579 {
 580         unsigned int flags = ts_first ? STP_PACKET_TIMESTAMPED : 0;
 581         ssize_t sz;
 582         size_t pos;
 583
 584         for (pos = 0, sz = 0; pos < count; pos += sz) {
 585                 sz = min_t(unsigned int, count - pos, 8);
 586                 sz = data->packet(data, m, c, STP_PACKET_DATA, flags, sz,
 587                                   &((u8 *)buf)[pos]);
 588                 if (sz <= 0)
 589                         break;
 590
 591                 if (ts_first) {
 592                         flags = 0;
 593                         ts_first = false;
 594                 }
 595         }
 596
 597         return sz < 0 ? sz : pos;
 598 }
 599 EXPORT_SYMBOL_GPL(stm_data_write);
 600
 601 static ssize_t notrace
 602 stm_write(struct stm_device *stm, struct stm_output *output,
 603           unsigned int chan, const char *buf, size_t count)
 604 {
 605         int err;
 606
 607         /* stm->pdrv is serialized against policy_mutex */
 608         if (!stm->pdrv)
 609                 return -ENODEV;
 610
 611         err = stm->pdrv->write(stm->data, output, chan, buf, count);
 612         if (err < 0)
 613                 return err;
 614
 615         return err;
 616 }
 617
 618 static ssize_t stm_char_write(struct file *file, const char __user *buf,
 619                               size_t count, loff_t *ppos)
 620 {
 621         struct stm_file *stmf = file->private_data;
 622         struct stm_device *stm = stmf->stm;
 623         char *kbuf;
 624         int err;
 625
 626         if (count + 1 > PAGE_SIZE)
 627                 count = PAGE_SIZE - 1;
 628
 629         /*
 630          * If no m/c have been assigned to this writer up to this
 631          * point, try to use the task name and "default" policy entries.
 632          */
 633         if (!stmf->output.nr_chans) {
 634                 char comm[sizeof(current->comm)];
 635                 char *ids[] = { comm, "default", NULL };
 636
 637                 get_task_comm(comm, current);
 638
 639                 err = stm_assign_first_policy(stmf->stm, &stmf->output, ids, 1);
 640                 /*
 641                  * EBUSY means that somebody else just assigned this
 642                  * output, which is just fine for write()
 643                  */
 644                 if (err)
 645                         return err;
 646         }
 647
 648         kbuf = kmalloc(count + 1, GFP_KERNEL);
 649         if (!kbuf)
 650                 return -ENOMEM;
 651
 652         err = copy_from_user(kbuf, buf, count);
 653         if (err) {
 654                 kfree(kbuf);
 655                 return -EFAULT;
 656         }
 657
 658         pm_runtime_get_sync(&stm->dev);
 659
 660         count = stm_write(stm, &stmf->output, 0, kbuf, count);
 661
 662         pm_runtime_mark_last_busy(&stm->dev);
 663         pm_runtime_put_autosuspend(&stm->dev);
 664         kfree(kbuf);
 665
 666         return count;
 667 }
 668
 669 static void stm_mmap_open(struct vm_area_struct *vma)
 670 {
 671         struct stm_file *stmf = vma->vm_file->private_data;
 672         struct stm_device *stm = stmf->stm;
 673
 674         pm_runtime_get(&stm->dev);
 675 }
 676
 677 static void stm_mmap_close(struct vm_area_struct *vma)
 678 {
 679         struct stm_file *stmf = vma->vm_file->private_data;
 680         struct stm_device *stm = stmf->stm;
 681
 682         pm_runtime_mark_last_busy(&stm->dev);
 683         pm_runtime_put_autosuspend(&stm->dev);
 684 }
 685
 686 static const struct vm_operations_struct stm_mmap_vmops = {
 687         .open   = stm_mmap_open,
 688         .close  = stm_mmap_close,
 689 };
 690
 691 static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
 692 {
 693         struct stm_file *stmf = file->private_data;
 694         struct stm_device *stm = stmf->stm;
 695         unsigned long size, phys;
 696
 697         if (!stm->data->mmio_addr)
 698                 return -EOPNOTSUPP;
 699
 700         if (vma->vm_pgoff)
 701                 return -EINVAL;
 702
 703         size = vma->vm_end - vma->vm_start;
 704
 705         if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
 706                 return -EINVAL;
 707
 708         phys = stm->data->mmio_addr(stm->data, stmf->output.master,
 709                                     stmf->output.channel,
 710                                     stmf->output.nr_chans);
 711
 712         if (!phys)
 713                 return -EINVAL;
 714
 715         pm_runtime_get_sync(&stm->dev);
 716
 717         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 718         vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
 719         vma->vm_ops = &stm_mmap_vmops;
 720         vm_iomap_memory(vma, phys, size);
 721
 722         return 0;
 723 }
 724
 725 static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
 726 {
 727         struct stm_device *stm = stmf->stm;
 728         struct stp_policy_id *id;
 729         char *ids[] = { NULL, NULL };
 730         int ret = -EINVAL, wlimit = 1;
 731         u32 size;
 732
 733         if (stmf->output.nr_chans)
 734                 return -EBUSY;
 735
 736         if (copy_from_user(&size, arg, sizeof(size)))
 737                 return -EFAULT;
 738
 739         if (size < sizeof(*id) || size >= PATH_MAX + sizeof(*id))
 740                 return -EINVAL;
 741
 742         /*
 743          * size + 1 to make sure the .id string at the bottom is terminated,
 744          * which is also why memdup_user() is not useful here
 745          */
 746         id = kzalloc(size + 1, GFP_KERNEL);
 747         if (!id)
 748                 return -ENOMEM;
 749
 750         if (copy_from_user(id, arg, size)) {
 751                 ret = -EFAULT;
 752                 goto err_free;
 753         }
 754
 755         if (id->__reserved_0 || id->__reserved_1)
 756                 goto err_free;
 757
 758         if (stm->data->sw_mmiosz)
 759                 wlimit = PAGE_SIZE / stm->data->sw_mmiosz;
 760
 761         if (id->width < 1 || id->width > wlimit)
 762                 goto err_free;
 763
 764         ids[0] = id->id;
 765         ret = stm_assign_first_policy(stmf->stm, &stmf->output, ids,
 766                                       id->width);
 767         if (ret)
 768                 goto err_free;
 769
 770         if (stm->data->link)
 771                 ret = stm->data->link(stm->data, stmf->output.master,
 772                                       stmf->output.channel);
 773
 774         if (ret)
 775                 stm_output_free(stmf->stm, &stmf->output);
 776
 777 err_free:
 778         kfree(id);
 779
 780         return ret;
 781 }
 782
 783 static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
 784 {
 785         struct stp_policy_id id = {
 786                 .size           = sizeof(id),
 787                 .master         = stmf->output.master,
 788                 .channel        = stmf->output.channel,
 789                 .width          = stmf->output.nr_chans,
 790                 .__reserved_0   = 0,
 791                 .__reserved_1   = 0,
 792         };
 793
 794         return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
 795 }
 796
 797 static long
 798 stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 799 {
 800         struct stm_file *stmf = file->private_data;
 801         struct stm_data *stm_data = stmf->stm->data;
 802         int err = -ENOTTY;
 803         u64 options;
 804
 805         switch (cmd) {
 806         case STP_POLICY_ID_SET:
 807                 err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
 808                 if (err)
 809                         return err;
 810
 811                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
 812
 813         case STP_POLICY_ID_GET:
 814                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
 815
 816         case STP_SET_OPTIONS:
 817                 if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
 818                         return -EFAULT;
 819
 820                 if (stm_data->set_options)
 821                         err = stm_data->set_options(stm_data,
 822                                                     stmf->output.master,
 823                                                     stmf->output.channel,
 824                                                     stmf->output.nr_chans,
 825                                                     options);
 826
 827                 break;
 828         default:
 829                 break;
 830         }
 831
 832         return err;
 833 }
 834
 835 #ifdef CONFIG_COMPAT
 836 static long
 837 stm_char_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 838 {
 839         return stm_char_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
 840 }
 841 #else
 842 #define stm_char_compat_ioctl   NULL
 843 #endif
 844
 845 static const struct file_operations stm_fops = {
 846         .open           = stm_char_open,
 847         .release        = stm_char_release,
 848         .write          = stm_char_write,
 849         .mmap           = stm_char_mmap,
 850         .unlocked_ioctl = stm_char_ioctl,
 851         .compat_ioctl   = stm_char_compat_ioctl,
 852         .llseek         = no_llseek,
 853 };
 854
 855 static void stm_device_release(struct device *dev)
 856 {
 857         struct stm_device *stm = to_stm_device(dev);
 858
 859         vfree(stm);
 860 }
 861
 862 int stm_register_device(struct device *parent, struct stm_data *stm_data,
 863                         struct module *owner)
 864 {
 865         struct stm_device *stm;
 866         unsigned int nmasters;
 867         int err = -ENOMEM;
 868
 869         if (!stm_core_up)
 870                 return -EPROBE_DEFER;
 871
 872         if (!stm_data->packet || !stm_data->sw_nchannels)
 873                 return -EINVAL;
 874
 875         nmasters = stm_data->sw_end - stm_data->sw_start + 1;
 876         stm = vzalloc(sizeof(*stm) + nmasters * sizeof(void *));
 877         if (!stm)
 878                 return -ENOMEM;
 879
 880         stm->major = register_chrdev(0, stm_data->name, &stm_fops);
 881         if (stm->major < 0)
 882                 goto err_free;
 883
 884         device_initialize(&stm->dev);
 885         stm->dev.devt = MKDEV(stm->major, 0);
 886         stm->dev.class = &stm_class;
 887         stm->dev.parent = parent;
 888         stm->dev.release = stm_device_release;
 889
 890         mutex_init(&stm->link_mutex);
 891         spin_lock_init(&stm->link_lock);
 892         INIT_LIST_HEAD(&stm->link_list);
 893
 894         /* initialize the object before it is accessible via sysfs */
 895         spin_lock_init(&stm->mc_lock);
 896         mutex_init(&stm->policy_mutex);
 897         stm->sw_nmasters = nmasters;
 898         stm->owner = owner;
 899         stm->data = stm_data;
 900         stm_data->stm = stm;
 901
 902         err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
 903         if (err)
 904                 goto err_device;
 905
 906         err = device_add(&stm->dev);
 907         if (err)
 908                 goto err_device;
 909
 910         /*
 911          * Use delayed autosuspend to avoid bouncing back and forth
 912          * on recurring character device writes, with the initial
 913          * delay time of 2 seconds.
 914          */
 915         pm_runtime_no_callbacks(&stm->dev);
 916         pm_runtime_use_autosuspend(&stm->dev);
 917         pm_runtime_set_autosuspend_delay(&stm->dev, 2000);
 918         pm_runtime_set_suspended(&stm->dev);
 919         pm_runtime_enable(&stm->dev);
 920
 921         return 0;
 922
 923 err_device:
 924         unregister_chrdev(stm->major, stm_data->name);
 925
 926         /* matches device_initialize() above */
 927         put_device(&stm->dev);
 928 err_free:
 929         vfree(stm);
 930
 931         return err;
 932 }
 933 EXPORT_SYMBOL_GPL(stm_register_device);
 934
 935 static int __stm_source_link_drop(struct stm_source_device *src,
 936                                   struct stm_device *stm);
 937
 938 void stm_unregister_device(struct stm_data *stm_data)
 939 {
 940         struct stm_device *stm = stm_data->stm;
 941         struct stm_source_device *src, *iter;
 942         int i, ret;
 943
 944         pm_runtime_dont_use_autosuspend(&stm->dev);
 945         pm_runtime_disable(&stm->dev);
 946
 947         mutex_lock(&stm->link_mutex);
 948         list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
 949                 ret = __stm_source_link_drop(src, stm);
 950                 /*
 951                  * src <-> stm link must not change under the same
 952                  * stm::link_mutex, so complain loudly if it has;
 953                  * also in this situation ret!=0 means this src is
 954                  * not connected to this stm and it should be otherwise
 955                  * safe to proceed with the tear-down of stm.
 956                  */
 957                 WARN_ON_ONCE(ret);
 958         }
 959         mutex_unlock(&stm->link_mutex);
 960
 961         synchronize_srcu(&stm_source_srcu);
 962
 963         unregister_chrdev(stm->major, stm_data->name);
 964
 965         mutex_lock(&stm->policy_mutex);
 966         if (stm->policy)
 967                 stp_policy_unbind(stm->policy);
 968         mutex_unlock(&stm->policy_mutex);
 969
 970         for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
 971                 stp_master_free(stm, i);
 972
 973         device_unregister(&stm->dev);
 974         stm_data->stm = NULL;
 975 }
 976 EXPORT_SYMBOL_GPL(stm_unregister_device);
 977
 978 /*
 979  * stm::link_list access serialization uses a spinlock and a mutex; holding
 980  * either of them guarantees that the list is stable; modification requires
 981  * holding both of them.
 982  *
 983  * Lock ordering is as follows:
 984  *   stm::link_mutex
 985  *     stm::link_lock
 986  *       src::link_lock
 987  */
 988
 989 /**
 990  * stm_source_link_add() - connect an stm_source device to an stm device
 991  * @src:        stm_source device
 992  * @stm:        stm device
 993  *
 994  * This function establishes a link from stm_source to an stm device so that
 995  * the former can send out trace data to the latter.
 996  *
 997  * Return:      0 on success, -errno otherwise.
 998  */
 999 static int stm_source_link_add(struct stm_source_device *src,
1000                                struct stm_device *stm)
1001 {
1002         char *ids[] = { NULL, "default", NULL };
1003         int err = -ENOMEM;
1004
1005         mutex_lock(&stm->link_mutex);
1006         spin_lock(&stm->link_lock);
1007         spin_lock(&src->link_lock);
1008
1009         /* src->link is dereferenced under stm_source_srcu but not the list */
1010         rcu_assign_pointer(src->link, stm);
1011         list_add_tail(&src->link_entry, &stm->link_list);
1012
1013         spin_unlock(&src->link_lock);
1014         spin_unlock(&stm->link_lock);
1015         mutex_unlock(&stm->link_mutex);
1016
1017         ids[0] = kstrdup(src->data->name, GFP_KERNEL);
1018         if (!ids[0])
1019                 goto fail_detach;
1020
1021         err = stm_assign_first_policy(stm, &src->output, ids,
1022                                       src->data->nr_chans);
1023         kfree(ids[0]);
1024
1025         if (err)
1026                 goto fail_detach;
1027
1028         /* this is to notify the STM device that a new link has been made */
1029         if (stm->data->link)
1030                 err = stm->data->link(stm->data, src->output.master,
1031                                       src->output.channel);
1032
1033         if (err)
1034                 goto fail_free_output;
1035
1036         /* this is to let the source carry out all necessary preparations */
1037         if (src->data->link)
1038                 src->data->link(src->data);
1039
1040         return 0;
1041
1042 fail_free_output:
1043         stm_output_free(stm, &src->output);
1044
1045 fail_detach:
1046         mutex_lock(&stm->link_mutex);
1047         spin_lock(&stm->link_lock);
1048         spin_lock(&src->link_lock);
1049
1050         rcu_assign_pointer(src->link, NULL);
1051         list_del_init(&src->link_entry);
1052
1053         spin_unlock(&src->link_lock);
1054         spin_unlock(&stm->link_lock);
1055         mutex_unlock(&stm->link_mutex);
1056
1057         return err;
1058 }
1059
1060 /**
1061  * __stm_source_link_drop() - detach stm_source from an stm device
1062  * @src:        stm_source device
1063  * @stm:        stm device
1064  *
1065  * If @stm is @src::link, disconnect them from one another and put the
1066  * reference on the @stm device.
1067  *
1068  * Caller must hold stm::link_mutex.
1069  */
1070 static int __stm_source_link_drop(struct stm_source_device *src,
1071                                   struct stm_device *stm)
1072 {
1073         struct stm_device *link;
1074         int ret = 0;
1075
1076         lockdep_assert_held(&stm->link_mutex);
1077
1078         /* for stm::link_list modification, we hold both mutex and spinlock */
1079         spin_lock(&stm->link_lock);
1080         spin_lock(&src->link_lock);
1081         link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
1082
1083         /*
1084          * The linked device may have changed since we last looked, because
1085          * we weren't holding the src::link_lock back then; if this is the
1086          * case, tell the caller to retry.
1087          */
1088         if (link != stm) {
1089                 ret = -EAGAIN;
1090                 goto unlock;
1091         }
1092
1093         stm_output_free(link, &src->output);
1094         list_del_init(&src->link_entry);
1095         pm_runtime_mark_last_busy(&link->dev);
1096         pm_runtime_put_autosuspend(&link->dev);
1097         /* matches stm_find_device() from stm_source_link_store() */
1098         stm_put_device(link);
1099         rcu_assign_pointer(src->link, NULL);
1100
1101 unlock:
1102         spin_unlock(&src->link_lock);
1103         spin_unlock(&stm->link_lock);
1104
1105         /*
1106          * Call the unlink callbacks for both source and stm, when we know
1107          * that we have actually performed the unlinking.
1108          */
1109         if (!ret) {
1110                 if (src->data->unlink)
1111                         src->data->unlink(src->data);
1112
1113                 if (stm->data->unlink)
1114                         stm->data->unlink(stm->data, src->output.master,
1115                                           src->output.channel);
1116         }
1117
1118         return ret;
1119 }
1120
1121 /**
1122  * stm_source_link_drop() - detach stm_source from its stm device
1123  * @src:        stm_source device
1124  *
1125  * Unlinking means disconnecting from source's STM device; after this
1126  * writes will be unsuccessful until it is linked to a new STM device.
1127  *
1128  * This will happen on "stm_source_link" sysfs attribute write to undo
1129  * the existing link (if any), or on linked STM device's de-registration.
1130  */
1131 static void stm_source_link_drop(struct stm_source_device *src)
1132 {
1133         struct stm_device *stm;
1134         int idx, ret;
1135
1136 retry:
1137         idx = srcu_read_lock(&stm_source_srcu);
1138         /*
1139          * The stm device will be valid for the duration of this
1140          * read section, but the link may change before we grab
1141          * the src::link_lock in __stm_source_link_drop().
1142          */
1143         stm = srcu_dereference(src->link, &stm_source_srcu);
1144
1145         ret = 0;
1146         if (stm) {
1147                 mutex_lock(&stm->link_mutex);
1148                 ret = __stm_source_link_drop(src, stm);
1149                 mutex_unlock(&stm->link_mutex);
1150         }
1151
1152         srcu_read_unlock(&stm_source_srcu, idx);
1153
1154         /* if it did change, retry */
1155         if (ret == -EAGAIN)
1156                 goto retry;
1157 }
1158
1159 static ssize_t stm_source_link_show(struct device *dev,
1160                                     struct device_attribute *attr,
1161                                     char *buf)
1162 {
1163         struct stm_source_device *src = to_stm_source_device(dev);
1164         struct stm_device *stm;
1165         int idx, ret;
1166
1167         idx = srcu_read_lock(&stm_source_srcu);
1168         stm = srcu_dereference(src->link, &stm_source_srcu);
1169         ret = sprintf(buf, "%s\n",
1170                       stm ? dev_name(&stm->dev) : "<none>");
1171         srcu_read_unlock(&stm_source_srcu, idx);
1172
1173         return ret;
1174 }
1175
1176 static ssize_t stm_source_link_store(struct device *dev,
1177                                      struct device_attribute *attr,
1178                                      const char *buf, size_t count)
1179 {
1180         struct stm_source_device *src = to_stm_source_device(dev);
1181         struct stm_device *link;
1182         int err;
1183
1184         stm_source_link_drop(src);
1185
1186         link = stm_find_device(buf);
1187         if (!link)
1188                 return -EINVAL;
1189
1190         pm_runtime_get(&link->dev);
1191
1192         err = stm_source_link_add(src, link);
1193         if (err) {
1194                 pm_runtime_put_autosuspend(&link->dev);
1195                 /* matches the stm_find_device() above */
1196                 stm_put_device(link);
1197         }
1198
1199         return err ? : count;
1200 }
1201
1202 static DEVICE_ATTR_RW(stm_source_link);
1203
1204 static struct attribute *stm_source_attrs[] = {
1205         &dev_attr_stm_source_link.attr,
1206         NULL,
1207 };
1208
1209 ATTRIBUTE_GROUPS(stm_source);
1210
1211 static struct class stm_source_class = {
1212         .name           = "stm_source",
1213         .dev_groups     = stm_source_groups,
1214 };
1215
1216 static void stm_source_device_release(struct device *dev)
1217 {
1218         struct stm_source_device *src = to_stm_source_device(dev);
1219
1220         kfree(src);
1221 }
1222
1223 /**
1224  * stm_source_register_device() - register an stm_source device
1225  * @parent:     parent device
1226  * @data:       device description structure
1227  *
1228  * This will create a device of stm_source class that can write
1229  * data to an stm device once linked.
1230  *
1231  * Return:      0 on success, -errno otherwise.
1232  */
1233 int stm_source_register_device(struct device *parent,
1234                                struct stm_source_data *data)
1235 {
1236         struct stm_source_device *src;
1237         int err;
1238
1239         if (!stm_core_up)
1240                 return -EPROBE_DEFER;
1241
1242         src = kzalloc(sizeof(*src), GFP_KERNEL);
1243         if (!src)
1244                 return -ENOMEM;
1245
1246         device_initialize(&src->dev);
1247         src->dev.class = &stm_source_class;
1248         src->dev.parent = parent;
1249         src->dev.release = stm_source_device_release;
1250
1251         err = kobject_set_name(&src->dev.kobj, "%s", data->name);
1252         if (err)
1253                 goto err;
1254
1255         pm_runtime_no_callbacks(&src->dev);
1256         pm_runtime_forbid(&src->dev);
1257
1258         err = device_add(&src->dev);
1259         if (err)
1260                 goto err;
1261
1262         stm_output_init(&src->output);
1263         spin_lock_init(&src->link_lock);
1264         INIT_LIST_HEAD(&src->link_entry);
1265         src->data = data;
1266         data->src = src;
1267
1268         return 0;
1269
1270 err:
1271         put_device(&src->dev);
1272
1273         return err;
1274 }
1275 EXPORT_SYMBOL_GPL(stm_source_register_device);
1276
1277 /**
1278  * stm_source_unregister_device() - unregister an stm_source device
1279  * @data:       device description that was used to register the device
1280  *
1281  * This will remove a previously created stm_source device from the system.
1282  */
1283 void stm_source_unregister_device(struct stm_source_data *data)
1284 {
1285         struct stm_source_device *src = data->src;
1286
1287         stm_source_link_drop(src);
1288
1289         device_unregister(&src->dev);
1290 }
1291 EXPORT_SYMBOL_GPL(stm_source_unregister_device);
1292
1293 int notrace stm_source_write(struct stm_source_data *data,
1294                              unsigned int chan,
1295                              const char *buf, size_t count)
1296 {
1297         struct stm_source_device *src = data->src;
1298         struct stm_device *stm;
1299         int idx;
1300
1301         if (!src->output.nr_chans)
1302                 return -ENODEV;
1303
1304         if (chan >= src->output.nr_chans)
1305                 return -EINVAL;
1306
1307         idx = srcu_read_lock(&stm_source_srcu);
1308
1309         stm = srcu_dereference(src->link, &stm_source_srcu);
1310         if (stm)
1311                 count = stm_write(stm, &src->output, chan, buf, count);
1312         else
1313                 count = -ENODEV;
1314
1315         srcu_read_unlock(&stm_source_srcu, idx);
1316
1317         return count;
1318 }
1319 EXPORT_SYMBOL_GPL(stm_source_write);
1320
1321 static int __init stm_core_init(void)
1322 {
1323         int err;
1324
1325         err = class_register(&stm_class);
1326         if (err)
1327                 return err;
1328
1329         err = class_register(&stm_source_class);
1330         if (err)
1331                 goto err_stm;
1332
1333         err = stp_configfs_init();
1334         if (err)
1335                 goto err_src;
1336
1337         init_srcu_struct(&stm_source_srcu);
1338         INIT_LIST_HEAD(&stm_pdrv_head);
1339         mutex_init(&stm_pdrv_mutex);
1340
1341         /*
1342          * So as to not confuse existing users with a requirement
1343          * to load yet another module, do it here.
1344          */
1345         if (IS_ENABLED(CONFIG_STM_PROTO_BASIC))
1346                 (void)request_module_nowait("stm_p_basic");
1347         stm_core_up++;
1348
1349         return 0;
1350
1351 err_src:
1352         class_unregister(&stm_source_class);
1353 err_stm:
1354         class_unregister(&stm_class);
1355
1356         return err;
1357 }
1358
1359 module_init(stm_core_init);
1360
1361 static void __exit stm_core_exit(void)
1362 {
1363         cleanup_srcu_struct(&stm_source_srcu);
1364         class_unregister(&stm_source_class);
1365         class_unregister(&stm_class);
1366         stp_configfs_exit();
1367 }
1368
1369 module_exit(stm_core_exit);
1370
1371 MODULE_LICENSE("GPL v2");
1372 MODULE_DESCRIPTION("System Trace Module device class");
1373 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");