drivers/gpu/drm/qxl/qxl_cmd.c

   1 /*
   2  * Copyright 2013 Red Hat 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  * Authors: Dave Airlie
  23  *          Alon Levy
  24  */
  25
  26 /* QXL cmd/ring handling */
  27
  28 #include <linux/delay.h>
  29
  30 #include <drm/drm_util.h>
  31
  32 #include "qxl_drv.h"
  33 #include "qxl_object.h"
  34
  35 static int qxl_reap_surface_id(struct qxl_device *qdev, int max_to_reap);
  36
  37 struct ring {
  38         struct qxl_ring_header      header;
  39         uint8_t                     elements[];
  40 };
  41
  42 struct qxl_ring {
  43         struct ring            *ring;
  44         int                     element_size;
  45         int                     n_elements;
  46         int                     prod_notify;
  47         wait_queue_head_t      *push_event;
  48         spinlock_t             lock;
  49 };
  50
  51 void qxl_ring_free(struct qxl_ring *ring)
  52 {
  53         kfree(ring);
  54 }
  55
  56 void qxl_ring_init_hdr(struct qxl_ring *ring)
  57 {
  58         ring->ring->header.notify_on_prod = ring->n_elements;
  59 }
  60
  61 struct qxl_ring *
  62 qxl_ring_create(struct qxl_ring_header *header,
  63                 int element_size,
  64                 int n_elements,
  65                 int prod_notify,
  66                 bool set_prod_notify,
  67                 wait_queue_head_t *push_event)
  68 {
  69         struct qxl_ring *ring;
  70
  71         ring = kmalloc(sizeof(*ring), GFP_KERNEL);
  72         if (!ring)
  73                 return NULL;
  74
  75         ring->ring = (struct ring *)header;
  76         ring->element_size = element_size;
  77         ring->n_elements = n_elements;
  78         ring->prod_notify = prod_notify;
  79         ring->push_event = push_event;
  80         if (set_prod_notify)
  81                 qxl_ring_init_hdr(ring);
  82         spin_lock_init(&ring->lock);
  83         return ring;
  84 }
  85
  86 static int qxl_check_header(struct qxl_ring *ring)
  87 {
  88         int ret;
  89         struct qxl_ring_header *header = &(ring->ring->header);
  90         unsigned long flags;
  91
  92         spin_lock_irqsave(&ring->lock, flags);
  93         ret = header->prod - header->cons < header->num_items;
  94         if (ret == 0)
  95                 header->notify_on_cons = header->cons + 1;
  96         spin_unlock_irqrestore(&ring->lock, flags);
  97         return ret;
  98 }
  99
 100 int qxl_check_idle(struct qxl_ring *ring)
 101 {
 102         int ret;
 103         struct qxl_ring_header *header = &(ring->ring->header);
 104         unsigned long flags;
 105
 106         spin_lock_irqsave(&ring->lock, flags);
 107         ret = header->prod == header->cons;
 108         spin_unlock_irqrestore(&ring->lock, flags);
 109         return ret;
 110 }
 111
 112 int qxl_ring_push(struct qxl_ring *ring,
 113                   const void *new_elt, bool interruptible)
 114 {
 115         struct qxl_ring_header *header = &(ring->ring->header);
 116         uint8_t *elt;
 117         int idx, ret;
 118         unsigned long flags;
 119
 120         spin_lock_irqsave(&ring->lock, flags);
 121         if (header->prod - header->cons == header->num_items) {
 122                 header->notify_on_cons = header->cons + 1;
 123                 mb();
 124                 spin_unlock_irqrestore(&ring->lock, flags);
 125                 if (!drm_can_sleep()) {
 126                         while (!qxl_check_header(ring))
 127                                 udelay(1);
 128                 } else {
 129                         if (interruptible) {
 130                                 ret = wait_event_interruptible(*ring->push_event,
 131                                                                qxl_check_header(ring));
 132                                 if (ret)
 133                                         return ret;
 134                         } else {
 135                                 wait_event(*ring->push_event,
 136                                            qxl_check_header(ring));
 137                         }
 138
 139                 }
 140                 spin_lock_irqsave(&ring->lock, flags);
 141         }
 142
 143         idx = header->prod & (ring->n_elements - 1);
 144         elt = ring->ring->elements + idx * ring->element_size;
 145
 146         memcpy((void *)elt, new_elt, ring->element_size);
 147
 148         header->prod++;
 149
 150         mb();
 151
 152         if (header->prod == header->notify_on_prod)
 153                 outb(0, ring->prod_notify);
 154
 155         spin_unlock_irqrestore(&ring->lock, flags);
 156         return 0;
 157 }
 158
 159 static bool qxl_ring_pop(struct qxl_ring *ring,
 160                          void *element)
 161 {
 162         volatile struct qxl_ring_header *header = &(ring->ring->header);
 163         volatile uint8_t *ring_elt;
 164         int idx;
 165         unsigned long flags;
 166
 167         spin_lock_irqsave(&ring->lock, flags);
 168         if (header->cons == header->prod) {
 169                 header->notify_on_prod = header->cons + 1;
 170                 spin_unlock_irqrestore(&ring->lock, flags);
 171                 return false;
 172         }
 173
 174         idx = header->cons & (ring->n_elements - 1);
 175         ring_elt = ring->ring->elements + idx * ring->element_size;
 176
 177         memcpy(element, (void *)ring_elt, ring->element_size);
 178
 179         header->cons++;
 180
 181         spin_unlock_irqrestore(&ring->lock, flags);
 182         return true;
 183 }
 184
 185 int
 186 qxl_push_command_ring_release(struct qxl_device *qdev, struct qxl_release *release,
 187                               uint32_t type, bool interruptible)
 188 {
 189         struct qxl_command cmd;
 190
 191         cmd.type = type;
 192         cmd.data = qxl_bo_physical_address(qdev, release->release_bo, release->release_offset);
 193
 194         return qxl_ring_push(qdev->command_ring, &cmd, interruptible);
 195 }
 196
 197 int
 198 qxl_push_cursor_ring_release(struct qxl_device *qdev, struct qxl_release *release,
 199                              uint32_t type, bool interruptible)
 200 {
 201         struct qxl_command cmd;
 202
 203         cmd.type = type;
 204         cmd.data = qxl_bo_physical_address(qdev, release->release_bo, release->release_offset);
 205
 206         return qxl_ring_push(qdev->cursor_ring, &cmd, interruptible);
 207 }
 208
 209 bool qxl_queue_garbage_collect(struct qxl_device *qdev, bool flush)
 210 {
 211         if (!qxl_check_idle(qdev->release_ring)) {
 212                 schedule_work(&qdev->gc_work);
 213                 if (flush)
 214                         flush_work(&qdev->gc_work);
 215                 return true;
 216         }
 217         return false;
 218 }
 219
 220 int qxl_garbage_collect(struct qxl_device *qdev)
 221 {
 222         struct qxl_release *release;
 223         uint64_t id, next_id;
 224         int i = 0;
 225         union qxl_release_info *info;
 226
 227         while (qxl_ring_pop(qdev->release_ring, &id)) {
 228                 DRM_DEBUG_DRIVER("popped %lld\n", id);
 229                 while (id) {
 230                         release = qxl_release_from_id_locked(qdev, id);
 231                         if (release == NULL)
 232                                 break;
 233
 234                         info = qxl_release_map(qdev, release);
 235                         next_id = info->next;
 236                         qxl_release_unmap(qdev, release, info);
 237
 238                         DRM_DEBUG_DRIVER("popped %lld, next %lld\n", id,
 239                                          next_id);
 240
 241                         switch (release->type) {
 242                         case QXL_RELEASE_DRAWABLE:
 243                         case QXL_RELEASE_SURFACE_CMD:
 244                         case QXL_RELEASE_CURSOR_CMD:
 245                                 break;
 246                         default:
 247                                 DRM_ERROR("unexpected release type\n");
 248                                 break;
 249                         }
 250                         id = next_id;
 251
 252                         qxl_release_free(qdev, release);
 253                         ++i;
 254                 }
 255         }
 256
 257         DRM_DEBUG_DRIVER("%d\n", i);
 258
 259         return i;
 260 }
 261
 262 int qxl_alloc_bo_reserved(struct qxl_device *qdev,
 263                           struct qxl_release *release,
 264                           unsigned long size,
 265                           struct qxl_bo **_bo)
 266 {
 267         struct qxl_bo *bo;
 268         int ret;
 269
 270         ret = qxl_bo_create(qdev, size, false /* not kernel - device */,
 271                             false, QXL_GEM_DOMAIN_VRAM, NULL, &bo);
 272         if (ret) {
 273                 DRM_ERROR("failed to allocate VRAM BO\n");
 274                 return ret;
 275         }
 276         ret = qxl_release_list_add(release, bo);
 277         if (ret)
 278                 goto out_unref;
 279
 280         *_bo = bo;
 281         return 0;
 282 out_unref:
 283         qxl_bo_unref(&bo);
 284         return ret;
 285 }
 286
 287 static int wait_for_io_cmd_user(struct qxl_device *qdev, uint8_t val, long port, bool intr)
 288 {
 289         int irq_num;
 290         long addr = qdev->io_base + port;
 291         int ret;
 292
 293         mutex_lock(&qdev->async_io_mutex);
 294         irq_num = atomic_read(&qdev->irq_received_io_cmd);
 295         if (qdev->last_sent_io_cmd > irq_num) {
 296                 if (intr)
 297                         ret = wait_event_interruptible_timeout(qdev->io_cmd_event,
 298                                                                atomic_read(&qdev->irq_received_io_cmd) > irq_num, 5*HZ);
 299                 else
 300                         ret = wait_event_timeout(qdev->io_cmd_event,
 301                                                  atomic_read(&qdev->irq_received_io_cmd) > irq_num, 5*HZ);
 302                 /* 0 is timeout, just bail the "hw" has gone away */
 303                 if (ret <= 0)
 304                         goto out;
 305                 irq_num = atomic_read(&qdev->irq_received_io_cmd);
 306         }
 307         outb(val, addr);
 308         qdev->last_sent_io_cmd = irq_num + 1;
 309         if (intr)
 310                 ret = wait_event_interruptible_timeout(qdev->io_cmd_event,
 311                                                        atomic_read(&qdev->irq_received_io_cmd) > irq_num, 5*HZ);
 312         else
 313                 ret = wait_event_timeout(qdev->io_cmd_event,
 314                                          atomic_read(&qdev->irq_received_io_cmd) > irq_num, 5*HZ);
 315 out:
 316         if (ret > 0)
 317                 ret = 0;
 318         mutex_unlock(&qdev->async_io_mutex);
 319         return ret;
 320 }
 321
 322 static void wait_for_io_cmd(struct qxl_device *qdev, uint8_t val, long port)
 323 {
 324         int ret;
 325
 326 restart:
 327         ret = wait_for_io_cmd_user(qdev, val, port, false);
 328         if (ret == -ERESTARTSYS)
 329                 goto restart;
 330 }
 331
 332 int qxl_io_update_area(struct qxl_device *qdev, struct qxl_bo *surf,
 333                         const struct qxl_rect *area)
 334 {
 335         int surface_id;
 336         uint32_t surface_width, surface_height;
 337         int ret;
 338
 339         if (!surf->hw_surf_alloc)
 340                 DRM_ERROR("got io update area with no hw surface\n");
 341
 342         if (surf->is_primary)
 343                 surface_id = 0;
 344         else
 345                 surface_id = surf->surface_id;
 346         surface_width = surf->surf.width;
 347         surface_height = surf->surf.height;
 348
 349         if (area->left < 0 || area->top < 0 ||
 350             area->right > surface_width || area->bottom > surface_height)
 351                 return -EINVAL;
 352
 353         mutex_lock(&qdev->update_area_mutex);
 354         qdev->ram_header->update_area = *area;
 355         qdev->ram_header->update_surface = surface_id;
 356         ret = wait_for_io_cmd_user(qdev, 0, QXL_IO_UPDATE_AREA_ASYNC, true);
 357         mutex_unlock(&qdev->update_area_mutex);
 358         return ret;
 359 }
 360
 361 void qxl_io_notify_oom(struct qxl_device *qdev)
 362 {
 363         outb(0, qdev->io_base + QXL_IO_NOTIFY_OOM);
 364 }
 365
 366 void qxl_io_flush_release(struct qxl_device *qdev)
 367 {
 368         outb(0, qdev->io_base + QXL_IO_FLUSH_RELEASE);
 369 }
 370
 371 void qxl_io_flush_surfaces(struct qxl_device *qdev)
 372 {
 373         wait_for_io_cmd(qdev, 0, QXL_IO_FLUSH_SURFACES_ASYNC);
 374 }
 375
 376 void qxl_io_destroy_primary(struct qxl_device *qdev)
 377 {
 378         wait_for_io_cmd(qdev, 0, QXL_IO_DESTROY_PRIMARY_ASYNC);
 379         qdev->primary_bo->is_primary = false;
 380         drm_gem_object_put_unlocked(&qdev->primary_bo->tbo.base);
 381         qdev->primary_bo = NULL;
 382 }
 383
 384 void qxl_io_create_primary(struct qxl_device *qdev, struct qxl_bo *bo)
 385 {
 386         struct qxl_surface_create *create;
 387
 388         if (WARN_ON(qdev->primary_bo))
 389                 return;
 390
 391         DRM_DEBUG_DRIVER("qdev %p, ram_header %p\n", qdev, qdev->ram_header);
 392         create = &qdev->ram_header->create_surface;
 393         create->format = bo->surf.format;
 394         create->width = bo->surf.width;
 395         create->height = bo->surf.height;
 396         create->stride = bo->surf.stride;
 397         create->mem = qxl_bo_physical_address(qdev, bo, 0);
 398
 399         DRM_DEBUG_DRIVER("mem = %llx, from %p\n", create->mem, bo->kptr);
 400
 401         create->flags = QXL_SURF_FLAG_KEEP_DATA;
 402         create->type = QXL_SURF_TYPE_PRIMARY;
 403
 404         wait_for_io_cmd(qdev, 0, QXL_IO_CREATE_PRIMARY_ASYNC);
 405         qdev->primary_bo = bo;
 406         qdev->primary_bo->is_primary = true;
 407         drm_gem_object_get(&qdev->primary_bo->tbo.base);
 408 }
 409
 410 void qxl_io_memslot_add(struct qxl_device *qdev, uint8_t id)
 411 {
 412         DRM_DEBUG_DRIVER("qxl_memslot_add %d\n", id);
 413         wait_for_io_cmd(qdev, id, QXL_IO_MEMSLOT_ADD_ASYNC);
 414 }
 415
 416 void qxl_io_reset(struct qxl_device *qdev)
 417 {
 418         outb(0, qdev->io_base + QXL_IO_RESET);
 419 }
 420
 421 void qxl_io_monitors_config(struct qxl_device *qdev)
 422 {
 423         wait_for_io_cmd(qdev, 0, QXL_IO_MONITORS_CONFIG_ASYNC);
 424 }
 425
 426 int qxl_surface_id_alloc(struct qxl_device *qdev,
 427                       struct qxl_bo *surf)
 428 {
 429         uint32_t handle;
 430         int idr_ret;
 431         int count = 0;
 432 again:
 433         idr_preload(GFP_ATOMIC);
 434         spin_lock(&qdev->surf_id_idr_lock);
 435         idr_ret = idr_alloc(&qdev->surf_id_idr, NULL, 1, 0, GFP_NOWAIT);
 436         spin_unlock(&qdev->surf_id_idr_lock);
 437         idr_preload_end();
 438         if (idr_ret < 0)
 439                 return idr_ret;
 440         handle = idr_ret;
 441
 442         if (handle >= qdev->rom->n_surfaces) {
 443                 count++;
 444                 spin_lock(&qdev->surf_id_idr_lock);
 445                 idr_remove(&qdev->surf_id_idr, handle);
 446                 spin_unlock(&qdev->surf_id_idr_lock);
 447                 qxl_reap_surface_id(qdev, 2);
 448                 goto again;
 449         }
 450         surf->surface_id = handle;
 451
 452         spin_lock(&qdev->surf_id_idr_lock);
 453         qdev->last_alloced_surf_id = handle;
 454         spin_unlock(&qdev->surf_id_idr_lock);
 455         return 0;
 456 }
 457
 458 void qxl_surface_id_dealloc(struct qxl_device *qdev,
 459                             uint32_t surface_id)
 460 {
 461         spin_lock(&qdev->surf_id_idr_lock);
 462         idr_remove(&qdev->surf_id_idr, surface_id);
 463         spin_unlock(&qdev->surf_id_idr_lock);
 464 }
 465
 466 int qxl_hw_surface_alloc(struct qxl_device *qdev,
 467                          struct qxl_bo *surf)
 468 {
 469         struct qxl_surface_cmd *cmd;
 470         struct qxl_release *release;
 471         int ret;
 472
 473         if (surf->hw_surf_alloc)
 474                 return 0;
 475
 476         ret = qxl_alloc_surface_release_reserved(qdev, QXL_SURFACE_CMD_CREATE,
 477                                                  NULL,
 478                                                  &release);
 479         if (ret)
 480                 return ret;
 481
 482         ret = qxl_release_reserve_list(release, true);
 483         if (ret) {
 484                 qxl_release_free(qdev, release);
 485                 return ret;
 486         }
 487         cmd = (struct qxl_surface_cmd *)qxl_release_map(qdev, release);
 488         cmd->type = QXL_SURFACE_CMD_CREATE;
 489         cmd->flags = QXL_SURF_FLAG_KEEP_DATA;
 490         cmd->u.surface_create.format = surf->surf.format;
 491         cmd->u.surface_create.width = surf->surf.width;
 492         cmd->u.surface_create.height = surf->surf.height;
 493         cmd->u.surface_create.stride = surf->surf.stride;
 494         cmd->u.surface_create.data = qxl_bo_physical_address(qdev, surf, 0);
 495         cmd->surface_id = surf->surface_id;
 496         qxl_release_unmap(qdev, release, &cmd->release_info);
 497
 498         surf->surf_create = release;
 499
 500         /* no need to add a release to the fence for this surface bo,
 501            since it is only released when we ask to destroy the surface
 502            and it would never signal otherwise */
 503         qxl_release_fence_buffer_objects(release);
 504         qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);
 505
 506         surf->hw_surf_alloc = true;
 507         spin_lock(&qdev->surf_id_idr_lock);
 508         idr_replace(&qdev->surf_id_idr, surf, surf->surface_id);
 509         spin_unlock(&qdev->surf_id_idr_lock);
 510         return 0;
 511 }
 512
 513 int qxl_hw_surface_dealloc(struct qxl_device *qdev,
 514                            struct qxl_bo *surf)
 515 {
 516         struct qxl_surface_cmd *cmd;
 517         struct qxl_release *release;
 518         int ret;
 519         int id;
 520
 521         if (!surf->hw_surf_alloc)
 522                 return 0;
 523
 524         ret = qxl_alloc_surface_release_reserved(qdev, QXL_SURFACE_CMD_DESTROY,
 525                                                  surf->surf_create,
 526                                                  &release);
 527         if (ret)
 528                 return ret;
 529
 530         surf->surf_create = NULL;
 531         /* remove the surface from the idr, but not the surface id yet */
 532         spin_lock(&qdev->surf_id_idr_lock);
 533         idr_replace(&qdev->surf_id_idr, NULL, surf->surface_id);
 534         spin_unlock(&qdev->surf_id_idr_lock);
 535         surf->hw_surf_alloc = false;
 536
 537         id = surf->surface_id;
 538         surf->surface_id = 0;
 539
 540         release->surface_release_id = id;
 541         cmd = (struct qxl_surface_cmd *)qxl_release_map(qdev, release);
 542         cmd->type = QXL_SURFACE_CMD_DESTROY;
 543         cmd->surface_id = id;
 544         qxl_release_unmap(qdev, release, &cmd->release_info);
 545
 546         qxl_release_fence_buffer_objects(release);
 547         qxl_push_command_ring_release(qdev, release, QXL_CMD_SURFACE, false);
 548
 549         return 0;
 550 }
 551
 552 static int qxl_update_surface(struct qxl_device *qdev, struct qxl_bo *surf)
 553 {
 554         struct qxl_rect rect;
 555         int ret;
 556
 557         /* if we are evicting, we need to make sure the surface is up
 558            to date */
 559         rect.left = 0;
 560         rect.right = surf->surf.width;
 561         rect.top = 0;
 562         rect.bottom = surf->surf.height;
 563 retry:
 564         ret = qxl_io_update_area(qdev, surf, &rect);
 565         if (ret == -ERESTARTSYS)
 566                 goto retry;
 567         return ret;
 568 }
 569
 570 static void qxl_surface_evict_locked(struct qxl_device *qdev, struct qxl_bo *surf, bool do_update_area)
 571 {
 572         /* no need to update area if we are just freeing the surface normally */
 573         if (do_update_area)
 574                 qxl_update_surface(qdev, surf);
 575
 576         /* nuke the surface id at the hw */
 577         qxl_hw_surface_dealloc(qdev, surf);
 578 }
 579
 580 void qxl_surface_evict(struct qxl_device *qdev, struct qxl_bo *surf, bool do_update_area)
 581 {
 582         mutex_lock(&qdev->surf_evict_mutex);
 583         qxl_surface_evict_locked(qdev, surf, do_update_area);
 584         mutex_unlock(&qdev->surf_evict_mutex);
 585 }
 586
 587 static int qxl_reap_surf(struct qxl_device *qdev, struct qxl_bo *surf, bool stall)
 588 {
 589         int ret;
 590
 591         ret = qxl_bo_reserve(surf, false);
 592         if (ret)
 593                 return ret;
 594
 595         if (stall)
 596                 mutex_unlock(&qdev->surf_evict_mutex);
 597
 598         ret = ttm_bo_wait(&surf->tbo, true, !stall);
 599
 600         if (stall)
 601                 mutex_lock(&qdev->surf_evict_mutex);
 602         if (ret) {
 603                 qxl_bo_unreserve(surf);
 604                 return ret;
 605         }
 606
 607         qxl_surface_evict_locked(qdev, surf, true);
 608         qxl_bo_unreserve(surf);
 609         return 0;
 610 }
 611
 612 static int qxl_reap_surface_id(struct qxl_device *qdev, int max_to_reap)
 613 {
 614         int num_reaped = 0;
 615         int i, ret;
 616         bool stall = false;
 617         int start = 0;
 618
 619         mutex_lock(&qdev->surf_evict_mutex);
 620 again:
 621
 622         spin_lock(&qdev->surf_id_idr_lock);
 623         start = qdev->last_alloced_surf_id + 1;
 624         spin_unlock(&qdev->surf_id_idr_lock);
 625
 626         for (i = start; i < start + qdev->rom->n_surfaces; i++) {
 627                 void *objptr;
 628                 int surfid = i % qdev->rom->n_surfaces;
 629
 630                 /* this avoids the case where the objects is in the
 631                    idr but has been evicted half way - its makes
 632                    the idr lookup atomic with the eviction */
 633                 spin_lock(&qdev->surf_id_idr_lock);
 634                 objptr = idr_find(&qdev->surf_id_idr, surfid);
 635                 spin_unlock(&qdev->surf_id_idr_lock);
 636
 637                 if (!objptr)
 638                         continue;
 639
 640                 ret = qxl_reap_surf(qdev, objptr, stall);
 641                 if (ret == 0)
 642                         num_reaped++;
 643                 if (num_reaped >= max_to_reap)
 644                         break;
 645         }
 646         if (num_reaped == 0 && stall == false) {
 647                 stall = true;
 648                 goto again;
 649         }
 650
 651         mutex_unlock(&qdev->surf_evict_mutex);
 652         if (num_reaped) {
 653                 usleep_range(500, 1000);
 654                 qxl_queue_garbage_collect(qdev, true);
 655         }
 656
 657         return 0;
 658 }