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 static int stm_dev_match(struct device *dev, const void *data)
  93 {
  94         const char *name = data;
  95
  96         return sysfs_streq(name, dev_name(dev));
  97 }
  98
  99 /**
 100  * stm_find_device() - find stm device by name
 101  * @buf:        character buffer containing the name
 102  *
 103  * This is called when either policy gets assigned to an stm device or an
 104  * stm_source device gets linked to an stm device.
 105  *
 106  * This grabs device's reference (get_device()) and module reference, both
 107  * of which the calling path needs to make sure to drop with stm_put_device().
 108  *
 109  * Return:      stm device pointer or null if lookup failed.
 110  */
 111 struct stm_device *stm_find_device(const char *buf)
 112 {
 113         struct stm_device *stm;
 114         struct device *dev;
 115
 116         if (!stm_core_up)
 117                 return NULL;
 118
 119         dev = class_find_device(&stm_class, NULL, buf, stm_dev_match);
 120         if (!dev)
 121                 return NULL;
 122
 123         stm = to_stm_device(dev);
 124         if (!try_module_get(stm->owner)) {
 125                 /* matches class_find_device() above */
 126                 put_device(dev);
 127                 return NULL;
 128         }
 129
 130         return stm;
 131 }
 132
 133 /**
 134  * stm_put_device() - drop references on the stm device
 135  * @stm:        stm device, previously acquired by stm_find_device()
 136  *
 137  * This drops the module reference and device reference taken by
 138  * stm_find_device() or stm_char_open().
 139  */
 140 void stm_put_device(struct stm_device *stm)
 141 {
 142         module_put(stm->owner);
 143         put_device(&stm->dev);
 144 }
 145
 146 /*
 147  * Internally we only care about software-writable masters here, that is the
 148  * ones in the range [stm_data->sw_start..stm_data..sw_end], however we need
 149  * original master numbers to be visible externally, since they are the ones
 150  * that will appear in the STP stream. Thus, the internal bookkeeping uses
 151  * $master - stm_data->sw_start to reference master descriptors and such.
 152  */
 153
 154 #define __stm_master(_s, _m)                            \
 155         ((_s)->masters[(_m) - (_s)->data->sw_start])
 156
 157 static inline struct stp_master *
 158 stm_master(struct stm_device *stm, unsigned int idx)
 159 {
 160         if (idx < stm->data->sw_start || idx > stm->data->sw_end)
 161                 return NULL;
 162
 163         return __stm_master(stm, idx);
 164 }
 165
 166 static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
 167 {
 168         struct stp_master *master;
 169
 170         master = kzalloc(struct_size(master, chan_map,
 171                                      BITS_TO_LONGS(stm->data->sw_nchannels)),
 172                          GFP_ATOMIC);
 173         if (!master)
 174                 return -ENOMEM;
 175
 176         master->nr_free = stm->data->sw_nchannels;
 177         __stm_master(stm, idx) = master;
 178
 179         return 0;
 180 }
 181
 182 static void stp_master_free(struct stm_device *stm, unsigned int idx)
 183 {
 184         struct stp_master *master = stm_master(stm, idx);
 185
 186         if (!master)
 187                 return;
 188
 189         __stm_master(stm, idx) = NULL;
 190         kfree(master);
 191 }
 192
 193 static void stm_output_claim(struct stm_device *stm, struct stm_output *output)
 194 {
 195         struct stp_master *master = stm_master(stm, output->master);
 196
 197         lockdep_assert_held(&stm->mc_lock);
 198         lockdep_assert_held(&output->lock);
 199
 200         if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
 201                 return;
 202
 203         bitmap_allocate_region(&master->chan_map[0], output->channel,
 204                                ilog2(output->nr_chans));
 205
 206         master->nr_free -= output->nr_chans;
 207 }
 208
 209 static void
 210 stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
 211 {
 212         struct stp_master *master = stm_master(stm, output->master);
 213
 214         lockdep_assert_held(&stm->mc_lock);
 215         lockdep_assert_held(&output->lock);
 216
 217         bitmap_release_region(&master->chan_map[0], output->channel,
 218                               ilog2(output->nr_chans));
 219
 220         master->nr_free += output->nr_chans;
 221         output->nr_chans = 0;
 222 }
 223
 224 /*
 225  * This is like bitmap_find_free_region(), except it can ignore @start bits
 226  * at the beginning.
 227  */
 228 static int find_free_channels(unsigned long *bitmap, unsigned int start,
 229                               unsigned int end, unsigned int width)
 230 {
 231         unsigned int pos;
 232         int i;
 233
 234         for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) {
 235                 pos = find_next_zero_bit(bitmap, end + 1, pos);
 236                 if (pos + width > end + 1)
 237                         break;
 238
 239                 if (pos & (width - 1))
 240                         continue;
 241
 242                 for (i = 1; i < width && !test_bit(pos + i, bitmap); i++)
 243                         ;
 244                 if (i == width)
 245                         return pos;
 246
 247                 /* step over [pos..pos+i) to continue search */
 248                 pos += i;
 249         }
 250
 251         return -1;
 252 }
 253
 254 static int
 255 stm_find_master_chan(struct stm_device *stm, unsigned int width,
 256                      unsigned int *mstart, unsigned int mend,
 257                      unsigned int *cstart, unsigned int cend)
 258 {
 259         struct stp_master *master;
 260         unsigned int midx;
 261         int pos, err;
 262
 263         for (midx = *mstart; midx <= mend; midx++) {
 264                 if (!stm_master(stm, midx)) {
 265                         err = stp_master_alloc(stm, midx);
 266                         if (err)
 267                                 return err;
 268                 }
 269
 270                 master = stm_master(stm, midx);
 271
 272                 if (!master->nr_free)
 273                         continue;
 274
 275                 pos = find_free_channels(master->chan_map, *cstart, cend,
 276                                          width);
 277                 if (pos < 0)
 278                         continue;
 279
 280                 *mstart = midx;
 281                 *cstart = pos;
 282                 return 0;
 283         }
 284
 285         return -ENOSPC;
 286 }
 287
 288 static int stm_output_assign(struct stm_device *stm, unsigned int width,
 289                              struct stp_policy_node *policy_node,
 290                              struct stm_output *output)
 291 {
 292         unsigned int midx, cidx, mend, cend;
 293         int ret = -EINVAL;
 294
 295         if (width > stm->data->sw_nchannels)
 296                 return -EINVAL;
 297
 298         /* We no longer accept policy_node==NULL here */
 299         if (WARN_ON_ONCE(!policy_node))
 300                 return -EINVAL;
 301
 302         /*
 303          * Also, the caller holds reference to policy_node, so it won't
 304          * disappear on us.
 305          */
 306         stp_policy_node_get_ranges(policy_node, &midx, &mend, &cidx, &cend);
 307
 308         spin_lock(&stm->mc_lock);
 309         spin_lock(&output->lock);
 310         /* output is already assigned -- shouldn't happen */
 311         if (WARN_ON_ONCE(output->nr_chans))
 312                 goto unlock;
 313
 314         ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
 315         if (ret < 0)
 316                 goto unlock;
 317
 318         output->master = midx;
 319         output->channel = cidx;
 320         output->nr_chans = width;
 321         if (stm->pdrv->output_open) {
 322                 void *priv = stp_policy_node_priv(policy_node);
 323
 324                 if (WARN_ON_ONCE(!priv))
 325                         goto unlock;
 326
 327                 /* configfs subsys mutex is held by the caller */
 328                 ret = stm->pdrv->output_open(priv, output);
 329                 if (ret)
 330                         goto unlock;
 331         }
 332
 333         stm_output_claim(stm, output);
 334         dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width);
 335
 336         ret = 0;
 337 unlock:
 338         if (ret)
 339                 output->nr_chans = 0;
 340
 341         spin_unlock(&output->lock);
 342         spin_unlock(&stm->mc_lock);
 343
 344         return ret;
 345 }
 346
 347 static void stm_output_free(struct stm_device *stm, struct stm_output *output)
 348 {
 349         spin_lock(&stm->mc_lock);
 350         spin_lock(&output->lock);
 351         if (output->nr_chans)
 352                 stm_output_disclaim(stm, output);
 353         if (stm->pdrv && stm->pdrv->output_close)
 354                 stm->pdrv->output_close(output);
 355         spin_unlock(&output->lock);
 356         spin_unlock(&stm->mc_lock);
 357 }
 358
 359 static void stm_output_init(struct stm_output *output)
 360 {
 361         spin_lock_init(&output->lock);
 362 }
 363
 364 static int major_match(struct device *dev, const void *data)
 365 {
 366         unsigned int major = *(unsigned int *)data;
 367
 368         return MAJOR(dev->devt) == major;
 369 }
 370
 371 /*
 372  * Framing protocol management
 373  * Modules can implement STM protocol drivers and (un-)register them
 374  * with the STM class framework.
 375  */
 376 static struct list_head stm_pdrv_head;
 377 static struct mutex stm_pdrv_mutex;
 378
 379 struct stm_pdrv_entry {
 380         struct list_head                        entry;
 381         const struct stm_protocol_driver        *pdrv;
 382         const struct config_item_type           *node_type;
 383 };
 384
 385 static const struct stm_pdrv_entry *
 386 __stm_lookup_protocol(const char *name)
 387 {
 388         struct stm_pdrv_entry *pe;
 389
 390         /*
 391          * If no name is given (NULL or ""), fall back to "p_basic".
 392          */
 393         if (!name || !*name)
 394                 name = "p_basic";
 395
 396         list_for_each_entry(pe, &stm_pdrv_head, entry) {
 397                 if (!strcmp(name, pe->pdrv->name))
 398                         return pe;
 399         }
 400
 401         return NULL;
 402 }
 403
 404 int stm_register_protocol(const struct stm_protocol_driver *pdrv)
 405 {
 406         struct stm_pdrv_entry *pe = NULL;
 407         int ret = -ENOMEM;
 408
 409         mutex_lock(&stm_pdrv_mutex);
 410
 411         if (__stm_lookup_protocol(pdrv->name)) {
 412                 ret = -EEXIST;
 413                 goto unlock;
 414         }
 415
 416         pe = kzalloc(sizeof(*pe), GFP_KERNEL);
 417         if (!pe)
 418                 goto unlock;
 419
 420         if (pdrv->policy_attr) {
 421                 pe->node_type = get_policy_node_type(pdrv->policy_attr);
 422                 if (!pe->node_type)
 423                         goto unlock;
 424         }
 425
 426         list_add_tail(&pe->entry, &stm_pdrv_head);
 427         pe->pdrv = pdrv;
 428
 429         ret = 0;
 430 unlock:
 431         mutex_unlock(&stm_pdrv_mutex);
 432
 433         if (ret)
 434                 kfree(pe);
 435
 436         return ret;
 437 }
 438 EXPORT_SYMBOL_GPL(stm_register_protocol);
 439
 440 void stm_unregister_protocol(const struct stm_protocol_driver *pdrv)
 441 {
 442         struct stm_pdrv_entry *pe, *iter;
 443
 444         mutex_lock(&stm_pdrv_mutex);
 445
 446         list_for_each_entry_safe(pe, iter, &stm_pdrv_head, entry) {
 447                 if (pe->pdrv == pdrv) {
 448                         list_del(&pe->entry);
 449
 450                         if (pe->node_type) {
 451                                 kfree(pe->node_type->ct_attrs);
 452                                 kfree(pe->node_type);
 453                         }
 454                         kfree(pe);
 455                         break;
 456                 }
 457         }
 458
 459         mutex_unlock(&stm_pdrv_mutex);
 460 }
 461 EXPORT_SYMBOL_GPL(stm_unregister_protocol);
 462
 463 static bool stm_get_protocol(const struct stm_protocol_driver *pdrv)
 464 {
 465         return try_module_get(pdrv->owner);
 466 }
 467
 468 void stm_put_protocol(const struct stm_protocol_driver *pdrv)
 469 {
 470         module_put(pdrv->owner);
 471 }
 472
 473 int stm_lookup_protocol(const char *name,
 474                         const struct stm_protocol_driver **pdrv,
 475                         const struct config_item_type **node_type)
 476 {
 477         const struct stm_pdrv_entry *pe;
 478
 479         mutex_lock(&stm_pdrv_mutex);
 480
 481         pe = __stm_lookup_protocol(name);
 482         if (pe && pe->pdrv && stm_get_protocol(pe->pdrv)) {
 483                 *pdrv = pe->pdrv;
 484                 *node_type = pe->node_type;
 485         }
 486
 487         mutex_unlock(&stm_pdrv_mutex);
 488
 489         return pe ? 0 : -ENOENT;
 490 }
 491
 492 static int stm_char_open(struct inode *inode, struct file *file)
 493 {
 494         struct stm_file *stmf;
 495         struct device *dev;
 496         unsigned int major = imajor(inode);
 497         int err = -ENOMEM;
 498
 499         dev = class_find_device(&stm_class, NULL, &major, major_match);
 500         if (!dev)
 501                 return -ENODEV;
 502
 503         stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
 504         if (!stmf)
 505                 goto err_put_device;
 506
 507         err = -ENODEV;
 508         stm_output_init(&stmf->output);
 509         stmf->stm = to_stm_device(dev);
 510
 511         if (!try_module_get(stmf->stm->owner))
 512                 goto err_free;
 513
 514         file->private_data = stmf;
 515
 516         return nonseekable_open(inode, file);
 517
 518 err_free:
 519         kfree(stmf);
 520 err_put_device:
 521         /* matches class_find_device() above */
 522         put_device(dev);
 523
 524         return err;
 525 }
 526
 527 static int stm_char_release(struct inode *inode, struct file *file)
 528 {
 529         struct stm_file *stmf = file->private_data;
 530         struct stm_device *stm = stmf->stm;
 531
 532         if (stm->data->unlink)
 533                 stm->data->unlink(stm->data, stmf->output.master,
 534                                   stmf->output.channel);
 535
 536         stm_output_free(stm, &stmf->output);
 537
 538         /*
 539          * matches the stm_char_open()'s
 540          * class_find_device() + try_module_get()
 541          */
 542         stm_put_device(stm);
 543         kfree(stmf);
 544
 545         return 0;
 546 }
 547
 548 static int
 549 stm_assign_first_policy(struct stm_device *stm, struct stm_output *output,
 550                         char **ids, unsigned int width)
 551 {
 552         struct stp_policy_node *pn;
 553         int err, n;
 554
 555         /*
 556          * On success, stp_policy_node_lookup() will return holding the
 557          * configfs subsystem mutex, which is then released in
 558          * stp_policy_node_put(). This allows the pdrv->output_open() in
 559          * stm_output_assign() to serialize against the attribute accessors.
 560          */
 561         for (n = 0, pn = NULL; ids[n] && !pn; n++)
 562                 pn = stp_policy_node_lookup(stm, ids[n]);
 563
 564         if (!pn)
 565                 return -EINVAL;
 566
 567         err = stm_output_assign(stm, width, pn, output);
 568
 569         stp_policy_node_put(pn);
 570
 571         return err;
 572 }
 573
 574 /**
 575  * stm_data_write() - send the given payload as data packets
 576  * @data:       stm driver's data
 577  * @m:          STP master
 578  * @c:          STP channel
 579  * @ts_first:   timestamp the first packet
 580  * @buf:        data payload buffer
 581  * @count:      data payload size
 582  */
 583 ssize_t notrace stm_data_write(struct stm_data *data, unsigned int m,
 584                                unsigned int c, bool ts_first, const void *buf,
 585                                size_t count)
 586 {
 587         unsigned int flags = ts_first ? STP_PACKET_TIMESTAMPED : 0;
 588         ssize_t sz;
 589         size_t pos;
 590
 591         for (pos = 0, sz = 0; pos < count; pos += sz) {
 592                 sz = min_t(unsigned int, count - pos, 8);
 593                 sz = data->packet(data, m, c, STP_PACKET_DATA, flags, sz,
 594                                   &((u8 *)buf)[pos]);
 595                 if (sz <= 0)
 596                         break;
 597
 598                 if (ts_first) {
 599                         flags = 0;
 600                         ts_first = false;
 601                 }
 602         }
 603
 604         return sz < 0 ? sz : pos;
 605 }
 606 EXPORT_SYMBOL_GPL(stm_data_write);
 607
 608 static ssize_t notrace
 609 stm_write(struct stm_device *stm, struct stm_output *output,
 610           unsigned int chan, const char *buf, size_t count)
 611 {
 612         int err;
 613
 614         /* stm->pdrv is serialized against policy_mutex */
 615         if (!stm->pdrv)
 616                 return -ENODEV;
 617
 618         err = stm->pdrv->write(stm->data, output, chan, buf, count);
 619         if (err < 0)
 620                 return err;
 621
 622         return err;
 623 }
 624
 625 static ssize_t stm_char_write(struct file *file, const char __user *buf,
 626                               size_t count, loff_t *ppos)
 627 {
 628         struct stm_file *stmf = file->private_data;
 629         struct stm_device *stm = stmf->stm;
 630         char *kbuf;
 631         int err;
 632
 633         if (count + 1 > PAGE_SIZE)
 634                 count = PAGE_SIZE - 1;
 635
 636         /*
 637          * If no m/c have been assigned to this writer up to this
 638          * point, try to use the task name and "default" policy entries.
 639          */
 640         if (!stmf->output.nr_chans) {
 641                 char comm[sizeof(current->comm)];
 642                 char *ids[] = { comm, "default", NULL };
 643
 644                 get_task_comm(comm, current);
 645
 646                 err = stm_assign_first_policy(stmf->stm, &stmf->output, ids, 1);
 647                 /*
 648                  * EBUSY means that somebody else just assigned this
 649                  * output, which is just fine for write()
 650                  */
 651                 if (err)
 652                         return err;
 653         }
 654
 655         kbuf = kmalloc(count + 1, GFP_KERNEL);
 656         if (!kbuf)
 657                 return -ENOMEM;
 658
 659         err = copy_from_user(kbuf, buf, count);
 660         if (err) {
 661                 kfree(kbuf);
 662                 return -EFAULT;
 663         }
 664
 665         pm_runtime_get_sync(&stm->dev);
 666
 667         count = stm_write(stm, &stmf->output, 0, kbuf, count);
 668
 669         pm_runtime_mark_last_busy(&stm->dev);
 670         pm_runtime_put_autosuspend(&stm->dev);
 671         kfree(kbuf);
 672
 673         return count;
 674 }
 675
 676 static void stm_mmap_open(struct vm_area_struct *vma)
 677 {
 678         struct stm_file *stmf = vma->vm_file->private_data;
 679         struct stm_device *stm = stmf->stm;
 680
 681         pm_runtime_get(&stm->dev);
 682 }
 683
 684 static void stm_mmap_close(struct vm_area_struct *vma)
 685 {
 686         struct stm_file *stmf = vma->vm_file->private_data;
 687         struct stm_device *stm = stmf->stm;
 688
 689         pm_runtime_mark_last_busy(&stm->dev);
 690         pm_runtime_put_autosuspend(&stm->dev);
 691 }
 692
 693 static const struct vm_operations_struct stm_mmap_vmops = {
 694         .open   = stm_mmap_open,
 695         .close  = stm_mmap_close,
 696 };
 697
 698 static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
 699 {
 700         struct stm_file *stmf = file->private_data;
 701         struct stm_device *stm = stmf->stm;
 702         unsigned long size, phys;
 703
 704         if (!stm->data->mmio_addr)
 705                 return -EOPNOTSUPP;
 706
 707         if (vma->vm_pgoff)
 708                 return -EINVAL;
 709
 710         size = vma->vm_end - vma->vm_start;
 711
 712         if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
 713                 return -EINVAL;
 714
 715         phys = stm->data->mmio_addr(stm->data, stmf->output.master,
 716                                     stmf->output.channel,
 717                                     stmf->output.nr_chans);
 718
 719         if (!phys)
 720                 return -EINVAL;
 721
 722         pm_runtime_get_sync(&stm->dev);
 723
 724         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 725         vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
 726         vma->vm_ops = &stm_mmap_vmops;
 727         vm_iomap_memory(vma, phys, size);
 728
 729         return 0;
 730 }
 731
 732 static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
 733 {
 734         struct stm_device *stm = stmf->stm;
 735         struct stp_policy_id *id;
 736         char *ids[] = { NULL, NULL };
 737         int ret = -EINVAL, wlimit = 1;
 738         u32 size;
 739
 740         if (stmf->output.nr_chans)
 741                 return -EBUSY;
 742
 743         if (copy_from_user(&size, arg, sizeof(size)))
 744                 return -EFAULT;
 745
 746         if (size < sizeof(*id) || size >= PATH_MAX + sizeof(*id))
 747                 return -EINVAL;
 748
 749         /*
 750          * size + 1 to make sure the .id string at the bottom is terminated,
 751          * which is also why memdup_user() is not useful here
 752          */
 753         id = kzalloc(size + 1, GFP_KERNEL);
 754         if (!id)
 755                 return -ENOMEM;
 756
 757         if (copy_from_user(id, arg, size)) {
 758                 ret = -EFAULT;
 759                 goto err_free;
 760         }
 761
 762         if (id->__reserved_0 || id->__reserved_1)
 763                 goto err_free;
 764
 765         if (stm->data->sw_mmiosz)
 766                 wlimit = PAGE_SIZE / stm->data->sw_mmiosz;
 767
 768         if (id->width < 1 || id->width > wlimit)
 769                 goto err_free;
 770
 771         ids[0] = id->id;
 772         ret = stm_assign_first_policy(stmf->stm, &stmf->output, ids,
 773                                       id->width);
 774         if (ret)
 775                 goto err_free;
 776
 777         if (stm->data->link)
 778                 ret = stm->data->link(stm->data, stmf->output.master,
 779                                       stmf->output.channel);
 780
 781         if (ret)
 782                 stm_output_free(stmf->stm, &stmf->output);
 783
 784 err_free:
 785         kfree(id);
 786
 787         return ret;
 788 }
 789
 790 static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
 791 {
 792         struct stp_policy_id id = {
 793                 .size           = sizeof(id),
 794                 .master         = stmf->output.master,
 795                 .channel        = stmf->output.channel,
 796                 .width          = stmf->output.nr_chans,
 797                 .__reserved_0   = 0,
 798                 .__reserved_1   = 0,
 799         };
 800
 801         return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
 802 }
 803
 804 static long
 805 stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 806 {
 807         struct stm_file *stmf = file->private_data;
 808         struct stm_data *stm_data = stmf->stm->data;
 809         int err = -ENOTTY;
 810         u64 options;
 811
 812         switch (cmd) {
 813         case STP_POLICY_ID_SET:
 814                 err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
 815                 if (err)
 816                         return err;
 817
 818                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
 819
 820         case STP_POLICY_ID_GET:
 821                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
 822
 823         case STP_SET_OPTIONS:
 824                 if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
 825                         return -EFAULT;
 826
 827                 if (stm_data->set_options)
 828                         err = stm_data->set_options(stm_data,
 829                                                     stmf->output.master,
 830                                                     stmf->output.channel,
 831                                                     stmf->output.nr_chans,
 832                                                     options);
 833
 834                 break;
 835         default:
 836                 break;
 837         }
 838
 839         return err;
 840 }
 841
 842 #ifdef CONFIG_COMPAT
 843 static long
 844 stm_char_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 845 {
 846         return stm_char_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
 847 }
 848 #else
 849 #define stm_char_compat_ioctl   NULL
 850 #endif
 851
 852 static const struct file_operations stm_fops = {
 853         .open           = stm_char_open,
 854         .release        = stm_char_release,
 855         .write          = stm_char_write,
 856         .mmap           = stm_char_mmap,
 857         .unlocked_ioctl = stm_char_ioctl,
 858         .compat_ioctl   = stm_char_compat_ioctl,
 859         .llseek         = no_llseek,
 860 };
 861
 862 static void stm_device_release(struct device *dev)
 863 {
 864         struct stm_device *stm = to_stm_device(dev);
 865
 866         vfree(stm);
 867 }
 868
 869 int stm_register_device(struct device *parent, struct stm_data *stm_data,
 870                         struct module *owner)
 871 {
 872         struct stm_device *stm;
 873         unsigned int nmasters;
 874         int err = -ENOMEM;
 875
 876         if (!stm_core_up)
 877                 return -EPROBE_DEFER;
 878
 879         if (!stm_data->packet || !stm_data->sw_nchannels)
 880                 return -EINVAL;
 881
 882         nmasters = stm_data->sw_end - stm_data->sw_start + 1;
 883         stm = vzalloc(sizeof(*stm) + nmasters * sizeof(void *));
 884         if (!stm)
 885                 return -ENOMEM;
 886
 887         stm->major = register_chrdev(0, stm_data->name, &stm_fops);
 888         if (stm->major < 0)
 889                 goto err_free;
 890
 891         device_initialize(&stm->dev);
 892         stm->dev.devt = MKDEV(stm->major, 0);
 893         stm->dev.class = &stm_class;
 894         stm->dev.parent = parent;
 895         stm->dev.release = stm_device_release;
 896
 897         mutex_init(&stm->link_mutex);
 898         spin_lock_init(&stm->link_lock);
 899         INIT_LIST_HEAD(&stm->link_list);
 900
 901         /* initialize the object before it is accessible via sysfs */
 902         spin_lock_init(&stm->mc_lock);
 903         mutex_init(&stm->policy_mutex);
 904         stm->sw_nmasters = nmasters;
 905         stm->owner = owner;
 906         stm->data = stm_data;
 907         stm_data->stm = stm;
 908
 909         err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
 910         if (err)
 911                 goto err_device;
 912
 913         err = device_add(&stm->dev);
 914         if (err)
 915                 goto err_device;
 916
 917         /*
 918          * Use delayed autosuspend to avoid bouncing back and forth
 919          * on recurring character device writes, with the initial
 920          * delay time of 2 seconds.
 921          */
 922         pm_runtime_no_callbacks(&stm->dev);
 923         pm_runtime_use_autosuspend(&stm->dev);
 924         pm_runtime_set_autosuspend_delay(&stm->dev, 2000);
 925         pm_runtime_set_suspended(&stm->dev);
 926         pm_runtime_enable(&stm->dev);
 927
 928         return 0;
 929
 930 err_device:
 931         unregister_chrdev(stm->major, stm_data->name);
 932
 933         /* matches device_initialize() above */
 934         put_device(&stm->dev);
 935 err_free:
 936         vfree(stm);
 937
 938         return err;
 939 }
 940 EXPORT_SYMBOL_GPL(stm_register_device);
 941
 942 static int __stm_source_link_drop(struct stm_source_device *src,
 943                                   struct stm_device *stm);
 944
 945 void stm_unregister_device(struct stm_data *stm_data)
 946 {
 947         struct stm_device *stm = stm_data->stm;
 948         struct stm_source_device *src, *iter;
 949         int i, ret;
 950
 951         pm_runtime_dont_use_autosuspend(&stm->dev);
 952         pm_runtime_disable(&stm->dev);
 953
 954         mutex_lock(&stm->link_mutex);
 955         list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
 956                 ret = __stm_source_link_drop(src, stm);
 957                 /*
 958                  * src <-> stm link must not change under the same
 959                  * stm::link_mutex, so complain loudly if it has;
 960                  * also in this situation ret!=0 means this src is
 961                  * not connected to this stm and it should be otherwise
 962                  * safe to proceed with the tear-down of stm.
 963                  */
 964                 WARN_ON_ONCE(ret);
 965         }
 966         mutex_unlock(&stm->link_mutex);
 967
 968         synchronize_srcu(&stm_source_srcu);
 969
 970         unregister_chrdev(stm->major, stm_data->name);
 971
 972         mutex_lock(&stm->policy_mutex);
 973         if (stm->policy)
 974                 stp_policy_unbind(stm->policy);
 975         mutex_unlock(&stm->policy_mutex);
 976
 977         for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
 978                 stp_master_free(stm, i);
 979
 980         device_unregister(&stm->dev);
 981         stm_data->stm = NULL;
 982 }
 983 EXPORT_SYMBOL_GPL(stm_unregister_device);
 984
 985 /*
 986  * stm::link_list access serialization uses a spinlock and a mutex; holding
 987  * either of them guarantees that the list is stable; modification requires
 988  * holding both of them.
 989  *
 990  * Lock ordering is as follows:
 991  *   stm::link_mutex
 992  *     stm::link_lock
 993  *       src::link_lock
 994  */
 995
 996 /**
 997  * stm_source_link_add() - connect an stm_source device to an stm device
 998  * @src:        stm_source device
 999  * @stm:        stm device
1000  *
1001  * This function establishes a link from stm_source to an stm device so that
1002  * the former can send out trace data to the latter.
1003  *
1004  * Return:      0 on success, -errno otherwise.
1005  */
1006 static int stm_source_link_add(struct stm_source_device *src,
1007                                struct stm_device *stm)
1008 {
1009         char *ids[] = { NULL, "default", NULL };
1010         int err = -ENOMEM;
1011
1012         mutex_lock(&stm->link_mutex);
1013         spin_lock(&stm->link_lock);
1014         spin_lock(&src->link_lock);
1015
1016         /* src->link is dereferenced under stm_source_srcu but not the list */
1017         rcu_assign_pointer(src->link, stm);
1018         list_add_tail(&src->link_entry, &stm->link_list);
1019
1020         spin_unlock(&src->link_lock);
1021         spin_unlock(&stm->link_lock);
1022         mutex_unlock(&stm->link_mutex);
1023
1024         ids[0] = kstrdup(src->data->name, GFP_KERNEL);
1025         if (!ids[0])
1026                 goto fail_detach;
1027
1028         err = stm_assign_first_policy(stm, &src->output, ids,
1029                                       src->data->nr_chans);
1030         kfree(ids[0]);
1031
1032         if (err)
1033                 goto fail_detach;
1034
1035         /* this is to notify the STM device that a new link has been made */
1036         if (stm->data->link)
1037                 err = stm->data->link(stm->data, src->output.master,
1038                                       src->output.channel);
1039
1040         if (err)
1041                 goto fail_free_output;
1042
1043         /* this is to let the source carry out all necessary preparations */
1044         if (src->data->link)
1045                 src->data->link(src->data);
1046
1047         return 0;
1048
1049 fail_free_output:
1050         stm_output_free(stm, &src->output);
1051
1052 fail_detach:
1053         mutex_lock(&stm->link_mutex);
1054         spin_lock(&stm->link_lock);
1055         spin_lock(&src->link_lock);
1056
1057         rcu_assign_pointer(src->link, NULL);
1058         list_del_init(&src->link_entry);
1059
1060         spin_unlock(&src->link_lock);
1061         spin_unlock(&stm->link_lock);
1062         mutex_unlock(&stm->link_mutex);
1063
1064         return err;
1065 }
1066
1067 /**
1068  * __stm_source_link_drop() - detach stm_source from an stm device
1069  * @src:        stm_source device
1070  * @stm:        stm device
1071  *
1072  * If @stm is @src::link, disconnect them from one another and put the
1073  * reference on the @stm device.
1074  *
1075  * Caller must hold stm::link_mutex.
1076  */
1077 static int __stm_source_link_drop(struct stm_source_device *src,
1078                                   struct stm_device *stm)
1079 {
1080         struct stm_device *link;
1081         int ret = 0;
1082
1083         lockdep_assert_held(&stm->link_mutex);
1084
1085         /* for stm::link_list modification, we hold both mutex and spinlock */
1086         spin_lock(&stm->link_lock);
1087         spin_lock(&src->link_lock);
1088         link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
1089
1090         /*
1091          * The linked device may have changed since we last looked, because
1092          * we weren't holding the src::link_lock back then; if this is the
1093          * case, tell the caller to retry.
1094          */
1095         if (link != stm) {
1096                 ret = -EAGAIN;
1097                 goto unlock;
1098         }
1099
1100         stm_output_free(link, &src->output);
1101         list_del_init(&src->link_entry);
1102         pm_runtime_mark_last_busy(&link->dev);
1103         pm_runtime_put_autosuspend(&link->dev);
1104         /* matches stm_find_device() from stm_source_link_store() */
1105         stm_put_device(link);
1106         rcu_assign_pointer(src->link, NULL);
1107
1108 unlock:
1109         spin_unlock(&src->link_lock);
1110         spin_unlock(&stm->link_lock);
1111
1112         /*
1113          * Call the unlink callbacks for both source and stm, when we know
1114          * that we have actually performed the unlinking.
1115          */
1116         if (!ret) {
1117                 if (src->data->unlink)
1118                         src->data->unlink(src->data);
1119
1120                 if (stm->data->unlink)
1121                         stm->data->unlink(stm->data, src->output.master,
1122                                           src->output.channel);
1123         }
1124
1125         return ret;
1126 }
1127
1128 /**
1129  * stm_source_link_drop() - detach stm_source from its stm device
1130  * @src:        stm_source device
1131  *
1132  * Unlinking means disconnecting from source's STM device; after this
1133  * writes will be unsuccessful until it is linked to a new STM device.
1134  *
1135  * This will happen on "stm_source_link" sysfs attribute write to undo
1136  * the existing link (if any), or on linked STM device's de-registration.
1137  */
1138 static void stm_source_link_drop(struct stm_source_device *src)
1139 {
1140         struct stm_device *stm;
1141         int idx, ret;
1142
1143 retry:
1144         idx = srcu_read_lock(&stm_source_srcu);
1145         /*
1146          * The stm device will be valid for the duration of this
1147          * read section, but the link may change before we grab
1148          * the src::link_lock in __stm_source_link_drop().
1149          */
1150         stm = srcu_dereference(src->link, &stm_source_srcu);
1151
1152         ret = 0;
1153         if (stm) {
1154                 mutex_lock(&stm->link_mutex);
1155                 ret = __stm_source_link_drop(src, stm);
1156                 mutex_unlock(&stm->link_mutex);
1157         }
1158
1159         srcu_read_unlock(&stm_source_srcu, idx);
1160
1161         /* if it did change, retry */
1162         if (ret == -EAGAIN)
1163                 goto retry;
1164 }
1165
1166 static ssize_t stm_source_link_show(struct device *dev,
1167                                     struct device_attribute *attr,
1168                                     char *buf)
1169 {
1170         struct stm_source_device *src = to_stm_source_device(dev);
1171         struct stm_device *stm;
1172         int idx, ret;
1173
1174         idx = srcu_read_lock(&stm_source_srcu);
1175         stm = srcu_dereference(src->link, &stm_source_srcu);
1176         ret = sprintf(buf, "%s\n",
1177                       stm ? dev_name(&stm->dev) : "<none>");
1178         srcu_read_unlock(&stm_source_srcu, idx);
1179
1180         return ret;
1181 }
1182
1183 static ssize_t stm_source_link_store(struct device *dev,
1184                                      struct device_attribute *attr,
1185                                      const char *buf, size_t count)
1186 {
1187         struct stm_source_device *src = to_stm_source_device(dev);
1188         struct stm_device *link;
1189         int err;
1190
1191         stm_source_link_drop(src);
1192
1193         link = stm_find_device(buf);
1194         if (!link)
1195                 return -EINVAL;
1196
1197         pm_runtime_get(&link->dev);
1198
1199         err = stm_source_link_add(src, link);
1200         if (err) {
1201                 pm_runtime_put_autosuspend(&link->dev);
1202                 /* matches the stm_find_device() above */
1203                 stm_put_device(link);
1204         }
1205
1206         return err ? : count;
1207 }
1208
1209 static DEVICE_ATTR_RW(stm_source_link);
1210
1211 static struct attribute *stm_source_attrs[] = {
1212         &dev_attr_stm_source_link.attr,
1213         NULL,
1214 };
1215
1216 ATTRIBUTE_GROUPS(stm_source);
1217
1218 static struct class stm_source_class = {
1219         .name           = "stm_source",
1220         .dev_groups     = stm_source_groups,
1221 };
1222
1223 static void stm_source_device_release(struct device *dev)
1224 {
1225         struct stm_source_device *src = to_stm_source_device(dev);
1226
1227         kfree(src);
1228 }
1229
1230 /**
1231  * stm_source_register_device() - register an stm_source device
1232  * @parent:     parent device
1233  * @data:       device description structure
1234  *
1235  * This will create a device of stm_source class that can write
1236  * data to an stm device once linked.
1237  *
1238  * Return:      0 on success, -errno otherwise.
1239  */
1240 int stm_source_register_device(struct device *parent,
1241                                struct stm_source_data *data)
1242 {
1243         struct stm_source_device *src;
1244         int err;
1245
1246         if (!stm_core_up)
1247                 return -EPROBE_DEFER;
1248
1249         src = kzalloc(sizeof(*src), GFP_KERNEL);
1250         if (!src)
1251                 return -ENOMEM;
1252
1253         device_initialize(&src->dev);
1254         src->dev.class = &stm_source_class;
1255         src->dev.parent = parent;
1256         src->dev.release = stm_source_device_release;
1257
1258         err = kobject_set_name(&src->dev.kobj, "%s", data->name);
1259         if (err)
1260                 goto err;
1261
1262         pm_runtime_no_callbacks(&src->dev);
1263         pm_runtime_forbid(&src->dev);
1264
1265         err = device_add(&src->dev);
1266         if (err)
1267                 goto err;
1268
1269         stm_output_init(&src->output);
1270         spin_lock_init(&src->link_lock);
1271         INIT_LIST_HEAD(&src->link_entry);
1272         src->data = data;
1273         data->src = src;
1274
1275         return 0;
1276
1277 err:
1278         put_device(&src->dev);
1279         kfree(src);
1280
1281         return err;
1282 }
1283 EXPORT_SYMBOL_GPL(stm_source_register_device);
1284
1285 /**
1286  * stm_source_unregister_device() - unregister an stm_source device
1287  * @data:       device description that was used to register the device
1288  *
1289  * This will remove a previously created stm_source device from the system.
1290  */
1291 void stm_source_unregister_device(struct stm_source_data *data)
1292 {
1293         struct stm_source_device *src = data->src;
1294
1295         stm_source_link_drop(src);
1296
1297         device_unregister(&src->dev);
1298 }
1299 EXPORT_SYMBOL_GPL(stm_source_unregister_device);
1300
1301 int notrace stm_source_write(struct stm_source_data *data,
1302                              unsigned int chan,
1303                              const char *buf, size_t count)
1304 {
1305         struct stm_source_device *src = data->src;
1306         struct stm_device *stm;
1307         int idx;
1308
1309         if (!src->output.nr_chans)
1310                 return -ENODEV;
1311
1312         if (chan >= src->output.nr_chans)
1313                 return -EINVAL;
1314
1315         idx = srcu_read_lock(&stm_source_srcu);
1316
1317         stm = srcu_dereference(src->link, &stm_source_srcu);
1318         if (stm)
1319                 count = stm_write(stm, &src->output, chan, buf, count);
1320         else
1321                 count = -ENODEV;
1322
1323         srcu_read_unlock(&stm_source_srcu, idx);
1324
1325         return count;
1326 }
1327 EXPORT_SYMBOL_GPL(stm_source_write);
1328
1329 static int __init stm_core_init(void)
1330 {
1331         int err;
1332
1333         err = class_register(&stm_class);
1334         if (err)
1335                 return err;
1336
1337         err = class_register(&stm_source_class);
1338         if (err)
1339                 goto err_stm;
1340
1341         err = stp_configfs_init();
1342         if (err)
1343                 goto err_src;
1344
1345         init_srcu_struct(&stm_source_srcu);
1346         INIT_LIST_HEAD(&stm_pdrv_head);
1347         mutex_init(&stm_pdrv_mutex);
1348
1349         /*
1350          * So as to not confuse existing users with a requirement
1351          * to load yet another module, do it here.
1352          */
1353         if (IS_ENABLED(CONFIG_STM_PROTO_BASIC))
1354                 (void)request_module_nowait("stm_p_basic");
1355         stm_core_up++;
1356
1357         return 0;
1358
1359 err_src:
1360         class_unregister(&stm_source_class);
1361 err_stm:
1362         class_unregister(&stm_class);
1363
1364         return err;
1365 }
1366
1367 module_init(stm_core_init);
1368
1369 static void __exit stm_core_exit(void)
1370 {
1371         cleanup_srcu_struct(&stm_source_srcu);
1372         class_unregister(&stm_source_class);
1373         class_unregister(&stm_class);
1374         stp_configfs_exit();
1375 }
1376
1377 module_exit(stm_core_exit);
1378
1379 MODULE_LICENSE("GPL v2");
1380 MODULE_DESCRIPTION("System Trace Module device class");
1381 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");