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