drivers/hwtracing/stm/core.c

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