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 = -ENODEV;
 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                 return -ENOMEM;
 373
 374         stm_output_init(&stmf->output);
 375         stmf->stm = to_stm_device(dev);
 376
 377         if (!try_module_get(stmf->stm->owner))
 378                 goto err_free;
 379
 380         file->private_data = stmf;
 381
 382         return nonseekable_open(inode, file);
 383
 384 err_free:
 385         /* matches class_find_device() above */
 386         put_device(dev);
 387         kfree(stmf);
 388
 389         return err;
 390 }
 391
 392 static int stm_char_release(struct inode *inode, struct file *file)
 393 {
 394         struct stm_file *stmf = file->private_data;
 395         struct stm_device *stm = stmf->stm;
 396
 397         if (stm->data->unlink)
 398                 stm->data->unlink(stm->data, stmf->output.master,
 399                                   stmf->output.channel);
 400
 401         stm_output_free(stm, &stmf->output);
 402
 403         /*
 404          * matches the stm_char_open()'s
 405          * class_find_device() + try_module_get()
 406          */
 407         stm_put_device(stm);
 408         kfree(stmf);
 409
 410         return 0;
 411 }
 412
 413 static int stm_file_assign(struct stm_file *stmf, char *id, unsigned int width)
 414 {
 415         struct stm_device *stm = stmf->stm;
 416         int ret;
 417
 418         stmf->policy_node = stp_policy_node_lookup(stm, id);
 419
 420         ret = stm_output_assign(stm, width, stmf->policy_node, &stmf->output);
 421
 422         if (stmf->policy_node)
 423                 stp_policy_node_put(stmf->policy_node);
 424
 425         return ret;
 426 }
 427
 428 static ssize_t stm_write(struct stm_data *data, unsigned int master,
 429                           unsigned int channel, const char *buf, size_t count)
 430 {
 431         unsigned int flags = STP_PACKET_TIMESTAMPED;
 432         const unsigned char *p = buf, nil = 0;
 433         size_t pos;
 434         ssize_t sz;
 435
 436         for (pos = 0, p = buf; count > pos; pos += sz, p += sz) {
 437                 sz = min_t(unsigned int, count - pos, 8);
 438                 sz = data->packet(data, master, channel, STP_PACKET_DATA, flags,
 439                                   sz, p);
 440                 flags = 0;
 441
 442                 if (sz < 0)
 443                         break;
 444         }
 445
 446         data->packet(data, master, channel, STP_PACKET_FLAG, 0, 0, &nil);
 447
 448         return pos;
 449 }
 450
 451 static ssize_t stm_char_write(struct file *file, const char __user *buf,
 452                               size_t count, loff_t *ppos)
 453 {
 454         struct stm_file *stmf = file->private_data;
 455         struct stm_device *stm = stmf->stm;
 456         char *kbuf;
 457         int err;
 458
 459         if (count + 1 > PAGE_SIZE)
 460                 count = PAGE_SIZE - 1;
 461
 462         /*
 463          * if no m/c have been assigned to this writer up to this
 464          * point, use "default" policy entry
 465          */
 466         if (!stmf->output.nr_chans) {
 467                 err = stm_file_assign(stmf, "default", 1);
 468                 /*
 469                  * EBUSY means that somebody else just assigned this
 470                  * output, which is just fine for write()
 471                  */
 472                 if (err && err != -EBUSY)
 473                         return err;
 474         }
 475
 476         kbuf = kmalloc(count + 1, GFP_KERNEL);
 477         if (!kbuf)
 478                 return -ENOMEM;
 479
 480         err = copy_from_user(kbuf, buf, count);
 481         if (err) {
 482                 kfree(kbuf);
 483                 return -EFAULT;
 484         }
 485
 486         pm_runtime_get_sync(&stm->dev);
 487
 488         count = stm_write(stm->data, stmf->output.master, stmf->output.channel,
 489                           kbuf, count);
 490
 491         pm_runtime_mark_last_busy(&stm->dev);
 492         pm_runtime_put_autosuspend(&stm->dev);
 493         kfree(kbuf);
 494
 495         return count;
 496 }
 497
 498 static void stm_mmap_open(struct vm_area_struct *vma)
 499 {
 500         struct stm_file *stmf = vma->vm_file->private_data;
 501         struct stm_device *stm = stmf->stm;
 502
 503         pm_runtime_get(&stm->dev);
 504 }
 505
 506 static void stm_mmap_close(struct vm_area_struct *vma)
 507 {
 508         struct stm_file *stmf = vma->vm_file->private_data;
 509         struct stm_device *stm = stmf->stm;
 510
 511         pm_runtime_mark_last_busy(&stm->dev);
 512         pm_runtime_put_autosuspend(&stm->dev);
 513 }
 514
 515 static const struct vm_operations_struct stm_mmap_vmops = {
 516         .open   = stm_mmap_open,
 517         .close  = stm_mmap_close,
 518 };
 519
 520 static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
 521 {
 522         struct stm_file *stmf = file->private_data;
 523         struct stm_device *stm = stmf->stm;
 524         unsigned long size, phys;
 525
 526         if (!stm->data->mmio_addr)
 527                 return -EOPNOTSUPP;
 528
 529         if (vma->vm_pgoff)
 530                 return -EINVAL;
 531
 532         size = vma->vm_end - vma->vm_start;
 533
 534         if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
 535                 return -EINVAL;
 536
 537         phys = stm->data->mmio_addr(stm->data, stmf->output.master,
 538                                     stmf->output.channel,
 539                                     stmf->output.nr_chans);
 540
 541         if (!phys)
 542                 return -EINVAL;
 543
 544         pm_runtime_get_sync(&stm->dev);
 545
 546         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 547         vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
 548         vma->vm_ops = &stm_mmap_vmops;
 549         vm_iomap_memory(vma, phys, size);
 550
 551         return 0;
 552 }
 553
 554 static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
 555 {
 556         struct stm_device *stm = stmf->stm;
 557         struct stp_policy_id *id;
 558         int ret = -EINVAL;
 559         u32 size;
 560
 561         if (stmf->output.nr_chans)
 562                 return -EBUSY;
 563
 564         if (copy_from_user(&size, arg, sizeof(size)))
 565                 return -EFAULT;
 566
 567         if (size >= PATH_MAX + sizeof(*id))
 568                 return -EINVAL;
 569
 570         /*
 571          * size + 1 to make sure the .id string at the bottom is terminated,
 572          * which is also why memdup_user() is not useful here
 573          */
 574         id = kzalloc(size + 1, GFP_KERNEL);
 575         if (!id)
 576                 return -ENOMEM;
 577
 578         if (copy_from_user(id, arg, size)) {
 579                 ret = -EFAULT;
 580                 goto err_free;
 581         }
 582
 583         if (id->__reserved_0 || id->__reserved_1)
 584                 goto err_free;
 585
 586         if (id->width < 1 ||
 587             id->width > PAGE_SIZE / stm->data->sw_mmiosz)
 588                 goto err_free;
 589
 590         ret = stm_file_assign(stmf, id->id, id->width);
 591         if (ret)
 592                 goto err_free;
 593
 594         if (stm->data->link)
 595                 ret = stm->data->link(stm->data, stmf->output.master,
 596                                       stmf->output.channel);
 597
 598         if (ret)
 599                 stm_output_free(stmf->stm, &stmf->output);
 600
 601 err_free:
 602         kfree(id);
 603
 604         return ret;
 605 }
 606
 607 static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
 608 {
 609         struct stp_policy_id id = {
 610                 .size           = sizeof(id),
 611                 .master         = stmf->output.master,
 612                 .channel        = stmf->output.channel,
 613                 .width          = stmf->output.nr_chans,
 614                 .__reserved_0   = 0,
 615                 .__reserved_1   = 0,
 616         };
 617
 618         return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
 619 }
 620
 621 static long
 622 stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 623 {
 624         struct stm_file *stmf = file->private_data;
 625         struct stm_data *stm_data = stmf->stm->data;
 626         int err = -ENOTTY;
 627         u64 options;
 628
 629         switch (cmd) {
 630         case STP_POLICY_ID_SET:
 631                 err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
 632                 if (err)
 633                         return err;
 634
 635                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
 636
 637         case STP_POLICY_ID_GET:
 638                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
 639
 640         case STP_SET_OPTIONS:
 641                 if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
 642                         return -EFAULT;
 643
 644                 if (stm_data->set_options)
 645                         err = stm_data->set_options(stm_data,
 646                                                     stmf->output.master,
 647                                                     stmf->output.channel,
 648                                                     stmf->output.nr_chans,
 649                                                     options);
 650
 651                 break;
 652         default:
 653                 break;
 654         }
 655
 656         return err;
 657 }
 658
 659 #ifdef CONFIG_COMPAT
 660 static long
 661 stm_char_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 662 {
 663         return stm_char_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
 664 }
 665 #else
 666 #define stm_char_compat_ioctl   NULL
 667 #endif
 668
 669 static const struct file_operations stm_fops = {
 670         .open           = stm_char_open,
 671         .release        = stm_char_release,
 672         .write          = stm_char_write,
 673         .mmap           = stm_char_mmap,
 674         .unlocked_ioctl = stm_char_ioctl,
 675         .compat_ioctl   = stm_char_compat_ioctl,
 676         .llseek         = no_llseek,
 677 };
 678
 679 static void stm_device_release(struct device *dev)
 680 {
 681         struct stm_device *stm = to_stm_device(dev);
 682
 683         kfree(stm);
 684 }
 685
 686 int stm_register_device(struct device *parent, struct stm_data *stm_data,
 687                         struct module *owner)
 688 {
 689         struct stm_device *stm;
 690         unsigned int nmasters;
 691         int err = -ENOMEM;
 692
 693         if (!stm_core_up)
 694                 return -EPROBE_DEFER;
 695
 696         if (!stm_data->packet || !stm_data->sw_nchannels)
 697                 return -EINVAL;
 698
 699         nmasters = stm_data->sw_end - stm_data->sw_start + 1;
 700         stm = kzalloc(sizeof(*stm) + nmasters * sizeof(void *), GFP_KERNEL);
 701         if (!stm)
 702                 return -ENOMEM;
 703
 704         stm->major = register_chrdev(0, stm_data->name, &stm_fops);
 705         if (stm->major < 0)
 706                 goto err_free;
 707
 708         device_initialize(&stm->dev);
 709         stm->dev.devt = MKDEV(stm->major, 0);
 710         stm->dev.class = &stm_class;
 711         stm->dev.parent = parent;
 712         stm->dev.release = stm_device_release;
 713
 714         mutex_init(&stm->link_mutex);
 715         spin_lock_init(&stm->link_lock);
 716         INIT_LIST_HEAD(&stm->link_list);
 717
 718         /* initialize the object before it is accessible via sysfs */
 719         spin_lock_init(&stm->mc_lock);
 720         mutex_init(&stm->policy_mutex);
 721         stm->sw_nmasters = nmasters;
 722         stm->owner = owner;
 723         stm->data = stm_data;
 724         stm_data->stm = stm;
 725
 726         err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
 727         if (err)
 728                 goto err_device;
 729
 730         err = device_add(&stm->dev);
 731         if (err)
 732                 goto err_device;
 733
 734         /*
 735          * Use delayed autosuspend to avoid bouncing back and forth
 736          * on recurring character device writes, with the initial
 737          * delay time of 2 seconds.
 738          */
 739         pm_runtime_no_callbacks(&stm->dev);
 740         pm_runtime_use_autosuspend(&stm->dev);
 741         pm_runtime_set_autosuspend_delay(&stm->dev, 2000);
 742         pm_runtime_set_suspended(&stm->dev);
 743         pm_runtime_enable(&stm->dev);
 744
 745         return 0;
 746
 747 err_device:
 748         unregister_chrdev(stm->major, stm_data->name);
 749
 750         /* matches device_initialize() above */
 751         put_device(&stm->dev);
 752 err_free:
 753         kfree(stm);
 754
 755         return err;
 756 }
 757 EXPORT_SYMBOL_GPL(stm_register_device);
 758
 759 static int __stm_source_link_drop(struct stm_source_device *src,
 760                                   struct stm_device *stm);
 761
 762 void stm_unregister_device(struct stm_data *stm_data)
 763 {
 764         struct stm_device *stm = stm_data->stm;
 765         struct stm_source_device *src, *iter;
 766         int i, ret;
 767
 768         pm_runtime_dont_use_autosuspend(&stm->dev);
 769         pm_runtime_disable(&stm->dev);
 770
 771         mutex_lock(&stm->link_mutex);
 772         list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
 773                 ret = __stm_source_link_drop(src, stm);
 774                 /*
 775                  * src <-> stm link must not change under the same
 776                  * stm::link_mutex, so complain loudly if it has;
 777                  * also in this situation ret!=0 means this src is
 778                  * not connected to this stm and it should be otherwise
 779                  * safe to proceed with the tear-down of stm.
 780                  */
 781                 WARN_ON_ONCE(ret);
 782         }
 783         mutex_unlock(&stm->link_mutex);
 784
 785         synchronize_srcu(&stm_source_srcu);
 786
 787         unregister_chrdev(stm->major, stm_data->name);
 788
 789         mutex_lock(&stm->policy_mutex);
 790         if (stm->policy)
 791                 stp_policy_unbind(stm->policy);
 792         mutex_unlock(&stm->policy_mutex);
 793
 794         for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
 795                 stp_master_free(stm, i);
 796
 797         device_unregister(&stm->dev);
 798         stm_data->stm = NULL;
 799 }
 800 EXPORT_SYMBOL_GPL(stm_unregister_device);
 801
 802 /*
 803  * stm::link_list access serialization uses a spinlock and a mutex; holding
 804  * either of them guarantees that the list is stable; modification requires
 805  * holding both of them.
 806  *
 807  * Lock ordering is as follows:
 808  *   stm::link_mutex
 809  *     stm::link_lock
 810  *       src::link_lock
 811  */
 812
 813 /**
 814  * stm_source_link_add() - connect an stm_source device to an stm device
 815  * @src:        stm_source device
 816  * @stm:        stm device
 817  *
 818  * This function establishes a link from stm_source to an stm device so that
 819  * the former can send out trace data to the latter.
 820  *
 821  * Return:      0 on success, -errno otherwise.
 822  */
 823 static int stm_source_link_add(struct stm_source_device *src,
 824                                struct stm_device *stm)
 825 {
 826         char *id;
 827         int err;
 828
 829         mutex_lock(&stm->link_mutex);
 830         spin_lock(&stm->link_lock);
 831         spin_lock(&src->link_lock);
 832
 833         /* src->link is dereferenced under stm_source_srcu but not the list */
 834         rcu_assign_pointer(src->link, stm);
 835         list_add_tail(&src->link_entry, &stm->link_list);
 836
 837         spin_unlock(&src->link_lock);
 838         spin_unlock(&stm->link_lock);
 839         mutex_unlock(&stm->link_mutex);
 840
 841         id = kstrdup(src->data->name, GFP_KERNEL);
 842         if (id) {
 843                 src->policy_node =
 844                         stp_policy_node_lookup(stm, id);
 845
 846                 kfree(id);
 847         }
 848
 849         err = stm_output_assign(stm, src->data->nr_chans,
 850                                 src->policy_node, &src->output);
 851
 852         if (src->policy_node)
 853                 stp_policy_node_put(src->policy_node);
 854
 855         if (err)
 856                 goto fail_detach;
 857
 858         /* this is to notify the STM device that a new link has been made */
 859         if (stm->data->link)
 860                 err = stm->data->link(stm->data, src->output.master,
 861                                       src->output.channel);
 862
 863         if (err)
 864                 goto fail_free_output;
 865
 866         /* this is to let the source carry out all necessary preparations */
 867         if (src->data->link)
 868                 src->data->link(src->data);
 869
 870         return 0;
 871
 872 fail_free_output:
 873         stm_output_free(stm, &src->output);
 874
 875 fail_detach:
 876         mutex_lock(&stm->link_mutex);
 877         spin_lock(&stm->link_lock);
 878         spin_lock(&src->link_lock);
 879
 880         rcu_assign_pointer(src->link, NULL);
 881         list_del_init(&src->link_entry);
 882
 883         spin_unlock(&src->link_lock);
 884         spin_unlock(&stm->link_lock);
 885         mutex_unlock(&stm->link_mutex);
 886
 887         return err;
 888 }
 889
 890 /**
 891  * __stm_source_link_drop() - detach stm_source from an stm device
 892  * @src:        stm_source device
 893  * @stm:        stm device
 894  *
 895  * If @stm is @src::link, disconnect them from one another and put the
 896  * reference on the @stm device.
 897  *
 898  * Caller must hold stm::link_mutex.
 899  */
 900 static int __stm_source_link_drop(struct stm_source_device *src,
 901                                   struct stm_device *stm)
 902 {
 903         struct stm_device *link;
 904         int ret = 0;
 905
 906         lockdep_assert_held(&stm->link_mutex);
 907
 908         /* for stm::link_list modification, we hold both mutex and spinlock */
 909         spin_lock(&stm->link_lock);
 910         spin_lock(&src->link_lock);
 911         link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
 912
 913         /*
 914          * The linked device may have changed since we last looked, because
 915          * we weren't holding the src::link_lock back then; if this is the
 916          * case, tell the caller to retry.
 917          */
 918         if (link != stm) {
 919                 ret = -EAGAIN;
 920                 goto unlock;
 921         }
 922
 923         stm_output_free(link, &src->output);
 924         list_del_init(&src->link_entry);
 925         pm_runtime_mark_last_busy(&link->dev);
 926         pm_runtime_put_autosuspend(&link->dev);
 927         /* matches stm_find_device() from stm_source_link_store() */
 928         stm_put_device(link);
 929         rcu_assign_pointer(src->link, NULL);
 930
 931 unlock:
 932         spin_unlock(&src->link_lock);
 933         spin_unlock(&stm->link_lock);
 934
 935         /*
 936          * Call the unlink callbacks for both source and stm, when we know
 937          * that we have actually performed the unlinking.
 938          */
 939         if (!ret) {
 940                 if (src->data->unlink)
 941                         src->data->unlink(src->data);
 942
 943                 if (stm->data->unlink)
 944                         stm->data->unlink(stm->data, src->output.master,
 945                                           src->output.channel);
 946         }
 947
 948         return ret;
 949 }
 950
 951 /**
 952  * stm_source_link_drop() - detach stm_source from its stm device
 953  * @src:        stm_source device
 954  *
 955  * Unlinking means disconnecting from source's STM device; after this
 956  * writes will be unsuccessful until it is linked to a new STM device.
 957  *
 958  * This will happen on "stm_source_link" sysfs attribute write to undo
 959  * the existing link (if any), or on linked STM device's de-registration.
 960  */
 961 static void stm_source_link_drop(struct stm_source_device *src)
 962 {
 963         struct stm_device *stm;
 964         int idx, ret;
 965
 966 retry:
 967         idx = srcu_read_lock(&stm_source_srcu);
 968         /*
 969          * The stm device will be valid for the duration of this
 970          * read section, but the link may change before we grab
 971          * the src::link_lock in __stm_source_link_drop().
 972          */
 973         stm = srcu_dereference(src->link, &stm_source_srcu);
 974
 975         ret = 0;
 976         if (stm) {
 977                 mutex_lock(&stm->link_mutex);
 978                 ret = __stm_source_link_drop(src, stm);
 979                 mutex_unlock(&stm->link_mutex);
 980         }
 981
 982         srcu_read_unlock(&stm_source_srcu, idx);
 983
 984         /* if it did change, retry */
 985         if (ret == -EAGAIN)
 986                 goto retry;
 987 }
 988
 989 static ssize_t stm_source_link_show(struct device *dev,
 990                                     struct device_attribute *attr,
 991                                     char *buf)
 992 {
 993         struct stm_source_device *src = to_stm_source_device(dev);
 994         struct stm_device *stm;
 995         int idx, ret;
 996
 997         idx = srcu_read_lock(&stm_source_srcu);
 998         stm = srcu_dereference(src->link, &stm_source_srcu);
 999         ret = sprintf(buf, "%s\n",
1000                       stm ? dev_name(&stm->dev) : "<none>");
1001         srcu_read_unlock(&stm_source_srcu, idx);
1002
1003         return ret;
1004 }
1005
1006 static ssize_t stm_source_link_store(struct device *dev,
1007                                      struct device_attribute *attr,
1008                                      const char *buf, size_t count)
1009 {
1010         struct stm_source_device *src = to_stm_source_device(dev);
1011         struct stm_device *link;
1012         int err;
1013
1014         stm_source_link_drop(src);
1015
1016         link = stm_find_device(buf);
1017         if (!link)
1018                 return -EINVAL;
1019
1020         pm_runtime_get(&link->dev);
1021
1022         err = stm_source_link_add(src, link);
1023         if (err) {
1024                 pm_runtime_put_autosuspend(&link->dev);
1025                 /* matches the stm_find_device() above */
1026                 stm_put_device(link);
1027         }
1028
1029         return err ? : count;
1030 }
1031
1032 static DEVICE_ATTR_RW(stm_source_link);
1033
1034 static struct attribute *stm_source_attrs[] = {
1035         &dev_attr_stm_source_link.attr,
1036         NULL,
1037 };
1038
1039 ATTRIBUTE_GROUPS(stm_source);
1040
1041 static struct class stm_source_class = {
1042         .name           = "stm_source",
1043         .dev_groups     = stm_source_groups,
1044 };
1045
1046 static void stm_source_device_release(struct device *dev)
1047 {
1048         struct stm_source_device *src = to_stm_source_device(dev);
1049
1050         kfree(src);
1051 }
1052
1053 /**
1054  * stm_source_register_device() - register an stm_source device
1055  * @parent:     parent device
1056  * @data:       device description structure
1057  *
1058  * This will create a device of stm_source class that can write
1059  * data to an stm device once linked.
1060  *
1061  * Return:      0 on success, -errno otherwise.
1062  */
1063 int stm_source_register_device(struct device *parent,
1064                                struct stm_source_data *data)
1065 {
1066         struct stm_source_device *src;
1067         int err;
1068
1069         if (!stm_core_up)
1070                 return -EPROBE_DEFER;
1071
1072         src = kzalloc(sizeof(*src), GFP_KERNEL);
1073         if (!src)
1074                 return -ENOMEM;
1075
1076         device_initialize(&src->dev);
1077         src->dev.class = &stm_source_class;
1078         src->dev.parent = parent;
1079         src->dev.release = stm_source_device_release;
1080
1081         err = kobject_set_name(&src->dev.kobj, "%s", data->name);
1082         if (err)
1083                 goto err;
1084
1085         pm_runtime_no_callbacks(&src->dev);
1086         pm_runtime_forbid(&src->dev);
1087
1088         err = device_add(&src->dev);
1089         if (err)
1090                 goto err;
1091
1092         stm_output_init(&src->output);
1093         spin_lock_init(&src->link_lock);
1094         INIT_LIST_HEAD(&src->link_entry);
1095         src->data = data;
1096         data->src = src;
1097
1098         return 0;
1099
1100 err:
1101         put_device(&src->dev);
1102         kfree(src);
1103
1104         return err;
1105 }
1106 EXPORT_SYMBOL_GPL(stm_source_register_device);
1107
1108 /**
1109  * stm_source_unregister_device() - unregister an stm_source device
1110  * @data:       device description that was used to register the device
1111  *
1112  * This will remove a previously created stm_source device from the system.
1113  */
1114 void stm_source_unregister_device(struct stm_source_data *data)
1115 {
1116         struct stm_source_device *src = data->src;
1117
1118         stm_source_link_drop(src);
1119
1120         device_destroy(&stm_source_class, src->dev.devt);
1121 }
1122 EXPORT_SYMBOL_GPL(stm_source_unregister_device);
1123
1124 int stm_source_write(struct stm_source_data *data, unsigned int chan,
1125                      const char *buf, size_t count)
1126 {
1127         struct stm_source_device *src = data->src;
1128         struct stm_device *stm;
1129         int idx;
1130
1131         if (!src->output.nr_chans)
1132                 return -ENODEV;
1133
1134         if (chan >= src->output.nr_chans)
1135                 return -EINVAL;
1136
1137         idx = srcu_read_lock(&stm_source_srcu);
1138
1139         stm = srcu_dereference(src->link, &stm_source_srcu);
1140         if (stm)
1141                 count = stm_write(stm->data, src->output.master,
1142                                   src->output.channel + chan,
1143                                   buf, count);
1144         else
1145                 count = -ENODEV;
1146
1147         srcu_read_unlock(&stm_source_srcu, idx);
1148
1149         return count;
1150 }
1151 EXPORT_SYMBOL_GPL(stm_source_write);
1152
1153 static int __init stm_core_init(void)
1154 {
1155         int err;
1156
1157         err = class_register(&stm_class);
1158         if (err)
1159                 return err;
1160
1161         err = class_register(&stm_source_class);
1162         if (err)
1163                 goto err_stm;
1164
1165         err = stp_configfs_init();
1166         if (err)
1167                 goto err_src;
1168
1169         init_srcu_struct(&stm_source_srcu);
1170
1171         stm_core_up++;
1172
1173         return 0;
1174
1175 err_src:
1176         class_unregister(&stm_source_class);
1177 err_stm:
1178         class_unregister(&stm_class);
1179
1180         return err;
1181 }
1182
1183 module_init(stm_core_init);
1184
1185 static void __exit stm_core_exit(void)
1186 {
1187         cleanup_srcu_struct(&stm_source_srcu);
1188         class_unregister(&stm_source_class);
1189         class_unregister(&stm_class);
1190         stp_configfs_exit();
1191 }
1192
1193 module_exit(stm_core_exit);
1194
1195 MODULE_LICENSE("GPL v2");
1196 MODULE_DESCRIPTION("System Trace Module device class");
1197 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");