drivers/gpu/drm/amd/amdkfd/kfd_device.c

   1 /*
   2  * Copyright 2014 Advanced Micro Devices, Inc.
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included in
  12  * all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  17  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
  18  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  19  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  20  * OTHER DEALINGS IN THE SOFTWARE.
  21  */
  22
  23 #include <linux/amd-iommu.h>
  24 #include <linux/bsearch.h>
  25 #include <linux/pci.h>
  26 #include <linux/slab.h>
  27 #include "kfd_priv.h"
  28 #include "kfd_device_queue_manager.h"
  29 #include "kfd_pm4_headers.h"
  30
  31 #define MQD_SIZE_ALIGNED 768
  32
  33 static const struct kfd_device_info kaveri_device_info = {
  34         .asic_family = CHIP_KAVERI,
  35         .max_pasid_bits = 16,
  36         /* max num of queues for KV.TODO should be a dynamic value */
  37         .max_no_of_hqd  = 24,
  38         .ih_ring_entry_size = 4 * sizeof(uint32_t),
  39         .event_interrupt_class = &event_interrupt_class_cik,
  40         .num_of_watch_points = 4,
  41         .mqd_size_aligned = MQD_SIZE_ALIGNED
  42 };
  43
  44 static const struct kfd_device_info carrizo_device_info = {
  45         .asic_family = CHIP_CARRIZO,
  46         .max_pasid_bits = 16,
  47         /* max num of queues for CZ.TODO should be a dynamic value */
  48         .max_no_of_hqd  = 24,
  49         .ih_ring_entry_size = 4 * sizeof(uint32_t),
  50         .event_interrupt_class = &event_interrupt_class_cik,
  51         .num_of_watch_points = 4,
  52         .mqd_size_aligned = MQD_SIZE_ALIGNED
  53 };
  54
  55 struct kfd_deviceid {
  56         unsigned short did;
  57         const struct kfd_device_info *device_info;
  58 };
  59
  60 /* Please keep this sorted by increasing device id. */
  61 static const struct kfd_deviceid supported_devices[] = {
  62         { 0x1304, &kaveri_device_info },        /* Kaveri */
  63         { 0x1305, &kaveri_device_info },        /* Kaveri */
  64         { 0x1306, &kaveri_device_info },        /* Kaveri */
  65         { 0x1307, &kaveri_device_info },        /* Kaveri */
  66         { 0x1309, &kaveri_device_info },        /* Kaveri */
  67         { 0x130A, &kaveri_device_info },        /* Kaveri */
  68         { 0x130B, &kaveri_device_info },        /* Kaveri */
  69         { 0x130C, &kaveri_device_info },        /* Kaveri */
  70         { 0x130D, &kaveri_device_info },        /* Kaveri */
  71         { 0x130E, &kaveri_device_info },        /* Kaveri */
  72         { 0x130F, &kaveri_device_info },        /* Kaveri */
  73         { 0x1310, &kaveri_device_info },        /* Kaveri */
  74         { 0x1311, &kaveri_device_info },        /* Kaveri */
  75         { 0x1312, &kaveri_device_info },        /* Kaveri */
  76         { 0x1313, &kaveri_device_info },        /* Kaveri */
  77         { 0x1315, &kaveri_device_info },        /* Kaveri */
  78         { 0x1316, &kaveri_device_info },        /* Kaveri */
  79         { 0x1317, &kaveri_device_info },        /* Kaveri */
  80         { 0x1318, &kaveri_device_info },        /* Kaveri */
  81         { 0x131B, &kaveri_device_info },        /* Kaveri */
  82         { 0x131C, &kaveri_device_info },        /* Kaveri */
  83         { 0x131D, &kaveri_device_info },        /* Kaveri */
  84         { 0x9870, &carrizo_device_info },       /* Carrizo */
  85         { 0x9874, &carrizo_device_info },       /* Carrizo */
  86         { 0x9875, &carrizo_device_info },       /* Carrizo */
  87         { 0x9876, &carrizo_device_info },       /* Carrizo */
  88         { 0x9877, &carrizo_device_info }        /* Carrizo */
  89 };
  90
  91 static int kfd_gtt_sa_init(struct kfd_dev *kfd, unsigned int buf_size,
  92                                 unsigned int chunk_size);
  93 static void kfd_gtt_sa_fini(struct kfd_dev *kfd);
  94
  95 static const struct kfd_device_info *lookup_device_info(unsigned short did)
  96 {
  97         size_t i;
  98
  99         for (i = 0; i < ARRAY_SIZE(supported_devices); i++) {
 100                 if (supported_devices[i].did == did) {
 101                         BUG_ON(supported_devices[i].device_info == NULL);
 102                         return supported_devices[i].device_info;
 103                 }
 104         }
 105
 106         return NULL;
 107 }
 108
 109 struct kfd_dev *kgd2kfd_probe(struct kgd_dev *kgd,
 110         struct pci_dev *pdev, const struct kfd2kgd_calls *f2g)
 111 {
 112         struct kfd_dev *kfd;
 113
 114         const struct kfd_device_info *device_info =
 115                                         lookup_device_info(pdev->device);
 116
 117         if (!device_info)
 118                 return NULL;
 119
 120         kfd = kzalloc(sizeof(*kfd), GFP_KERNEL);
 121         if (!kfd)
 122                 return NULL;
 123
 124         kfd->kgd = kgd;
 125         kfd->device_info = device_info;
 126         kfd->pdev = pdev;
 127         kfd->init_complete = false;
 128         kfd->kfd2kgd = f2g;
 129
 130         mutex_init(&kfd->doorbell_mutex);
 131         memset(&kfd->doorbell_available_index, 0,
 132                 sizeof(kfd->doorbell_available_index));
 133
 134         return kfd;
 135 }
 136
 137 static bool device_iommu_pasid_init(struct kfd_dev *kfd)
 138 {
 139         const u32 required_iommu_flags = AMD_IOMMU_DEVICE_FLAG_ATS_SUP |
 140                                         AMD_IOMMU_DEVICE_FLAG_PRI_SUP |
 141                                         AMD_IOMMU_DEVICE_FLAG_PASID_SUP;
 142
 143         struct amd_iommu_device_info iommu_info;
 144         unsigned int pasid_limit;
 145         int err;
 146
 147         err = amd_iommu_device_info(kfd->pdev, &iommu_info);
 148         if (err < 0) {
 149                 dev_err(kfd_device,
 150                         "error getting iommu info. is the iommu enabled?\n");
 151                 return false;
 152         }
 153
 154         if ((iommu_info.flags & required_iommu_flags) != required_iommu_flags) {
 155                 dev_err(kfd_device, "error required iommu flags ats(%i), pri(%i), pasid(%i)\n",
 156                        (iommu_info.flags & AMD_IOMMU_DEVICE_FLAG_ATS_SUP) != 0,
 157                        (iommu_info.flags & AMD_IOMMU_DEVICE_FLAG_PRI_SUP) != 0,
 158                        (iommu_info.flags & AMD_IOMMU_DEVICE_FLAG_PASID_SUP) != 0);
 159                 return false;
 160         }
 161
 162         pasid_limit = min_t(unsigned int,
 163                         (unsigned int)1 << kfd->device_info->max_pasid_bits,
 164                         iommu_info.max_pasids);
 165         /*
 166          * last pasid is used for kernel queues doorbells
 167          * in the future the last pasid might be used for a kernel thread.
 168          */
 169         pasid_limit = min_t(unsigned int,
 170                                 pasid_limit,
 171                                 kfd->doorbell_process_limit - 1);
 172
 173         err = amd_iommu_init_device(kfd->pdev, pasid_limit);
 174         if (err < 0) {
 175                 dev_err(kfd_device, "error initializing iommu device\n");
 176                 return false;
 177         }
 178
 179         if (!kfd_set_pasid_limit(pasid_limit)) {
 180                 dev_err(kfd_device, "error setting pasid limit\n");
 181                 amd_iommu_free_device(kfd->pdev);
 182                 return false;
 183         }
 184
 185         return true;
 186 }
 187
 188 static void iommu_pasid_shutdown_callback(struct pci_dev *pdev, int pasid)
 189 {
 190         struct kfd_dev *dev = kfd_device_by_pci_dev(pdev);
 191
 192         if (dev)
 193                 kfd_unbind_process_from_device(dev, pasid);
 194 }
 195
 196 /*
 197  * This function called by IOMMU driver on PPR failure
 198  */
 199 static int iommu_invalid_ppr_cb(struct pci_dev *pdev, int pasid,
 200                 unsigned long address, u16 flags)
 201 {
 202         struct kfd_dev *dev;
 203
 204         dev_warn(kfd_device,
 205                         "Invalid PPR device %x:%x.%x pasid %d address 0x%lX flags 0x%X",
 206                         PCI_BUS_NUM(pdev->devfn),
 207                         PCI_SLOT(pdev->devfn),
 208                         PCI_FUNC(pdev->devfn),
 209                         pasid,
 210                         address,
 211                         flags);
 212
 213         dev = kfd_device_by_pci_dev(pdev);
 214         BUG_ON(dev == NULL);
 215
 216         kfd_signal_iommu_event(dev, pasid, address,
 217                         flags & PPR_FAULT_WRITE, flags & PPR_FAULT_EXEC);
 218
 219         return AMD_IOMMU_INV_PRI_RSP_INVALID;
 220 }
 221
 222 bool kgd2kfd_device_init(struct kfd_dev *kfd,
 223                          const struct kgd2kfd_shared_resources *gpu_resources)
 224 {
 225         unsigned int size;
 226
 227         kfd->shared_resources = *gpu_resources;
 228
 229         /* calculate max size of mqds needed for queues */
 230         size = max_num_of_queues_per_device *
 231                         kfd->device_info->mqd_size_aligned;
 232
 233         /*
 234          * calculate max size of runlist packet.
 235          * There can be only 2 packets at once
 236          */
 237         size += (KFD_MAX_NUM_OF_PROCESSES * sizeof(struct pm4_map_process) +
 238                 max_num_of_queues_per_device *
 239                 sizeof(struct pm4_map_queues) + sizeof(struct pm4_runlist)) * 2;
 240
 241         /* Add size of HIQ & DIQ */
 242         size += KFD_KERNEL_QUEUE_SIZE * 2;
 243
 244         /* add another 512KB for all other allocations on gart (HPD, fences) */
 245         size += 512 * 1024;
 246
 247         if (kfd->kfd2kgd->init_gtt_mem_allocation(
 248                         kfd->kgd, size, &kfd->gtt_mem,
 249                         &kfd->gtt_start_gpu_addr, &kfd->gtt_start_cpu_ptr)){
 250                 dev_err(kfd_device,
 251                         "Could not allocate %d bytes for device (%x:%x)\n",
 252                         size, kfd->pdev->vendor, kfd->pdev->device);
 253                 goto out;
 254         }
 255
 256         dev_info(kfd_device,
 257                 "Allocated %d bytes on gart for device(%x:%x)\n",
 258                 size, kfd->pdev->vendor, kfd->pdev->device);
 259
 260         /* Initialize GTT sa with 512 byte chunk size */
 261         if (kfd_gtt_sa_init(kfd, size, 512) != 0) {
 262                 dev_err(kfd_device,
 263                         "Error initializing gtt sub-allocator\n");
 264                 goto kfd_gtt_sa_init_error;
 265         }
 266
 267         kfd_doorbell_init(kfd);
 268
 269         if (kfd_topology_add_device(kfd) != 0) {
 270                 dev_err(kfd_device,
 271                         "Error adding device (%x:%x) to topology\n",
 272                         kfd->pdev->vendor, kfd->pdev->device);
 273                 goto kfd_topology_add_device_error;
 274         }
 275
 276         if (kfd_interrupt_init(kfd)) {
 277                 dev_err(kfd_device,
 278                         "Error initializing interrupts for device (%x:%x)\n",
 279                         kfd->pdev->vendor, kfd->pdev->device);
 280                 goto kfd_interrupt_error;
 281         }
 282
 283         if (!device_iommu_pasid_init(kfd)) {
 284                 dev_err(kfd_device,
 285                         "Error initializing iommuv2 for device (%x:%x)\n",
 286                         kfd->pdev->vendor, kfd->pdev->device);
 287                 goto device_iommu_pasid_error;
 288         }
 289         amd_iommu_set_invalidate_ctx_cb(kfd->pdev,
 290                                                 iommu_pasid_shutdown_callback);
 291         amd_iommu_set_invalid_ppr_cb(kfd->pdev, iommu_invalid_ppr_cb);
 292
 293         kfd->dqm = device_queue_manager_init(kfd);
 294         if (!kfd->dqm) {
 295                 dev_err(kfd_device,
 296                         "Error initializing queue manager for device (%x:%x)\n",
 297                         kfd->pdev->vendor, kfd->pdev->device);
 298                 goto device_queue_manager_error;
 299         }
 300
 301         if (kfd->dqm->ops.start(kfd->dqm) != 0) {
 302                 dev_err(kfd_device,
 303                         "Error starting queuen manager for device (%x:%x)\n",
 304                         kfd->pdev->vendor, kfd->pdev->device);
 305                 goto dqm_start_error;
 306         }
 307
 308         kfd->dbgmgr = NULL;
 309
 310         kfd->init_complete = true;
 311         dev_info(kfd_device, "added device (%x:%x)\n", kfd->pdev->vendor,
 312                  kfd->pdev->device);
 313
 314         pr_debug("kfd: Starting kfd with the following scheduling policy %d\n",
 315                 sched_policy);
 316
 317         goto out;
 318
 319 dqm_start_error:
 320         device_queue_manager_uninit(kfd->dqm);
 321 device_queue_manager_error:
 322         amd_iommu_free_device(kfd->pdev);
 323 device_iommu_pasid_error:
 324         kfd_interrupt_exit(kfd);
 325 kfd_interrupt_error:
 326         kfd_topology_remove_device(kfd);
 327 kfd_topology_add_device_error:
 328         kfd_gtt_sa_fini(kfd);
 329 kfd_gtt_sa_init_error:
 330         kfd->kfd2kgd->free_gtt_mem(kfd->kgd, kfd->gtt_mem);
 331         dev_err(kfd_device,
 332                 "device (%x:%x) NOT added due to errors\n",
 333                 kfd->pdev->vendor, kfd->pdev->device);
 334 out:
 335         return kfd->init_complete;
 336 }
 337
 338 void kgd2kfd_device_exit(struct kfd_dev *kfd)
 339 {
 340         if (kfd->init_complete) {
 341                 device_queue_manager_uninit(kfd->dqm);
 342                 amd_iommu_free_device(kfd->pdev);
 343                 kfd_interrupt_exit(kfd);
 344                 kfd_topology_remove_device(kfd);
 345                 kfd_gtt_sa_fini(kfd);
 346                 kfd->kfd2kgd->free_gtt_mem(kfd->kgd, kfd->gtt_mem);
 347         }
 348
 349         kfree(kfd);
 350 }
 351
 352 void kgd2kfd_suspend(struct kfd_dev *kfd)
 353 {
 354         BUG_ON(kfd == NULL);
 355
 356         if (kfd->init_complete) {
 357                 kfd->dqm->ops.stop(kfd->dqm);
 358                 amd_iommu_set_invalidate_ctx_cb(kfd->pdev, NULL);
 359                 amd_iommu_set_invalid_ppr_cb(kfd->pdev, NULL);
 360                 amd_iommu_free_device(kfd->pdev);
 361         }
 362 }
 363
 364 int kgd2kfd_resume(struct kfd_dev *kfd)
 365 {
 366         unsigned int pasid_limit;
 367         int err;
 368
 369         BUG_ON(kfd == NULL);
 370
 371         pasid_limit = kfd_get_pasid_limit();
 372
 373         if (kfd->init_complete) {
 374                 err = amd_iommu_init_device(kfd->pdev, pasid_limit);
 375                 if (err < 0)
 376                         return -ENXIO;
 377                 amd_iommu_set_invalidate_ctx_cb(kfd->pdev,
 378                                                 iommu_pasid_shutdown_callback);
 379                 amd_iommu_set_invalid_ppr_cb(kfd->pdev, iommu_invalid_ppr_cb);
 380                 kfd->dqm->ops.start(kfd->dqm);
 381         }
 382
 383         return 0;
 384 }
 385
 386 /* This is called directly from KGD at ISR. */
 387 void kgd2kfd_interrupt(struct kfd_dev *kfd, const void *ih_ring_entry)
 388 {
 389         if (!kfd->init_complete)
 390                 return;
 391
 392         spin_lock(&kfd->interrupt_lock);
 393
 394         if (kfd->interrupts_active
 395             && interrupt_is_wanted(kfd, ih_ring_entry)
 396             && enqueue_ih_ring_entry(kfd, ih_ring_entry))
 397                 schedule_work(&kfd->interrupt_work);
 398
 399         spin_unlock(&kfd->interrupt_lock);
 400 }
 401
 402 static int kfd_gtt_sa_init(struct kfd_dev *kfd, unsigned int buf_size,
 403                                 unsigned int chunk_size)
 404 {
 405         unsigned int num_of_bits;
 406
 407         BUG_ON(!kfd);
 408         BUG_ON(!kfd->gtt_mem);
 409         BUG_ON(buf_size < chunk_size);
 410         BUG_ON(buf_size == 0);
 411         BUG_ON(chunk_size == 0);
 412
 413         kfd->gtt_sa_chunk_size = chunk_size;
 414         kfd->gtt_sa_num_of_chunks = buf_size / chunk_size;
 415
 416         num_of_bits = kfd->gtt_sa_num_of_chunks / BITS_PER_BYTE;
 417         BUG_ON(num_of_bits == 0);
 418
 419         kfd->gtt_sa_bitmap = kzalloc(num_of_bits, GFP_KERNEL);
 420
 421         if (!kfd->gtt_sa_bitmap)
 422                 return -ENOMEM;
 423
 424         pr_debug("kfd: gtt_sa_num_of_chunks = %d, gtt_sa_bitmap = %p\n",
 425                         kfd->gtt_sa_num_of_chunks, kfd->gtt_sa_bitmap);
 426
 427         mutex_init(&kfd->gtt_sa_lock);
 428
 429         return 0;
 430
 431 }
 432
 433 static void kfd_gtt_sa_fini(struct kfd_dev *kfd)
 434 {
 435         mutex_destroy(&kfd->gtt_sa_lock);
 436         kfree(kfd->gtt_sa_bitmap);
 437 }
 438
 439 static inline uint64_t kfd_gtt_sa_calc_gpu_addr(uint64_t start_addr,
 440                                                 unsigned int bit_num,
 441                                                 unsigned int chunk_size)
 442 {
 443         return start_addr + bit_num * chunk_size;
 444 }
 445
 446 static inline uint32_t *kfd_gtt_sa_calc_cpu_addr(void *start_addr,
 447                                                 unsigned int bit_num,
 448                                                 unsigned int chunk_size)
 449 {
 450         return (uint32_t *) ((uint64_t) start_addr + bit_num * chunk_size);
 451 }
 452
 453 int kfd_gtt_sa_allocate(struct kfd_dev *kfd, unsigned int size,
 454                         struct kfd_mem_obj **mem_obj)
 455 {
 456         unsigned int found, start_search, cur_size;
 457
 458         BUG_ON(!kfd);
 459
 460         if (size == 0)
 461                 return -EINVAL;
 462
 463         if (size > kfd->gtt_sa_num_of_chunks * kfd->gtt_sa_chunk_size)
 464                 return -ENOMEM;
 465
 466         *mem_obj = kmalloc(sizeof(struct kfd_mem_obj), GFP_KERNEL);
 467         if ((*mem_obj) == NULL)
 468                 return -ENOMEM;
 469
 470         pr_debug("kfd: allocated mem_obj = %p for size = %d\n", *mem_obj, size);
 471
 472         start_search = 0;
 473
 474         mutex_lock(&kfd->gtt_sa_lock);
 475
 476 kfd_gtt_restart_search:
 477         /* Find the first chunk that is free */
 478         found = find_next_zero_bit(kfd->gtt_sa_bitmap,
 479                                         kfd->gtt_sa_num_of_chunks,
 480                                         start_search);
 481
 482         pr_debug("kfd: found = %d\n", found);
 483
 484         /* If there wasn't any free chunk, bail out */
 485         if (found == kfd->gtt_sa_num_of_chunks)
 486                 goto kfd_gtt_no_free_chunk;
 487
 488         /* Update fields of mem_obj */
 489         (*mem_obj)->range_start = found;
 490         (*mem_obj)->range_end = found;
 491         (*mem_obj)->gpu_addr = kfd_gtt_sa_calc_gpu_addr(
 492                                         kfd->gtt_start_gpu_addr,
 493                                         found,
 494                                         kfd->gtt_sa_chunk_size);
 495         (*mem_obj)->cpu_ptr = kfd_gtt_sa_calc_cpu_addr(
 496                                         kfd->gtt_start_cpu_ptr,
 497                                         found,
 498                                         kfd->gtt_sa_chunk_size);
 499
 500         pr_debug("kfd: gpu_addr = %p, cpu_addr = %p\n",
 501                         (uint64_t *) (*mem_obj)->gpu_addr, (*mem_obj)->cpu_ptr);
 502
 503         /* If we need only one chunk, mark it as allocated and get out */
 504         if (size <= kfd->gtt_sa_chunk_size) {
 505                 pr_debug("kfd: single bit\n");
 506                 set_bit(found, kfd->gtt_sa_bitmap);
 507                 goto kfd_gtt_out;
 508         }
 509
 510         /* Otherwise, try to see if we have enough contiguous chunks */
 511         cur_size = size - kfd->gtt_sa_chunk_size;
 512         do {
 513                 (*mem_obj)->range_end =
 514                         find_next_zero_bit(kfd->gtt_sa_bitmap,
 515                                         kfd->gtt_sa_num_of_chunks, ++found);
 516                 /*
 517                  * If next free chunk is not contiguous than we need to
 518                  * restart our search from the last free chunk we found (which
 519                  * wasn't contiguous to the previous ones
 520                  */
 521                 if ((*mem_obj)->range_end != found) {
 522                         start_search = found;
 523                         goto kfd_gtt_restart_search;
 524                 }
 525
 526                 /*
 527                  * If we reached end of buffer, bail out with error
 528                  */
 529                 if (found == kfd->gtt_sa_num_of_chunks)
 530                         goto kfd_gtt_no_free_chunk;
 531
 532                 /* Check if we don't need another chunk */
 533                 if (cur_size <= kfd->gtt_sa_chunk_size)
 534                         cur_size = 0;
 535                 else
 536                         cur_size -= kfd->gtt_sa_chunk_size;
 537
 538         } while (cur_size > 0);
 539
 540         pr_debug("kfd: range_start = %d, range_end = %d\n",
 541                 (*mem_obj)->range_start, (*mem_obj)->range_end);
 542
 543         /* Mark the chunks as allocated */
 544         for (found = (*mem_obj)->range_start;
 545                 found <= (*mem_obj)->range_end;
 546                 found++)
 547                 set_bit(found, kfd->gtt_sa_bitmap);
 548
 549 kfd_gtt_out:
 550         mutex_unlock(&kfd->gtt_sa_lock);
 551         return 0;
 552
 553 kfd_gtt_no_free_chunk:
 554         pr_debug("kfd: allocation failed with mem_obj = %p\n", mem_obj);
 555         mutex_unlock(&kfd->gtt_sa_lock);
 556         kfree(mem_obj);
 557         return -ENOMEM;
 558 }
 559
 560 int kfd_gtt_sa_free(struct kfd_dev *kfd, struct kfd_mem_obj *mem_obj)
 561 {
 562         unsigned int bit;
 563
 564         BUG_ON(!kfd);
 565
 566         /* Act like kfree when trying to free a NULL object */
 567         if (!mem_obj)
 568                 return 0;
 569
 570         pr_debug("kfd: free mem_obj = %p, range_start = %d, range_end = %d\n",
 571                         mem_obj, mem_obj->range_start, mem_obj->range_end);
 572
 573         mutex_lock(&kfd->gtt_sa_lock);
 574
 575         /* Mark the chunks as free */
 576         for (bit = mem_obj->range_start;
 577                 bit <= mem_obj->range_end;
 578                 bit++)
 579                 clear_bit(bit, kfd->gtt_sa_bitmap);
 580
 581         mutex_unlock(&kfd->gtt_sa_lock);
 582
 583         kfree(mem_obj);
 584         return 0;
 585 }