drivers/gpu/drm/i915/i915_gem_fence.c

   1 /*
   2  * Copyright © 2008-2015 Intel Corporation
   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 (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include <drm/drmP.h>
  25 #include <drm/i915_drm.h>
  26 #include "i915_drv.h"
  27
  28 /**
  29  * DOC: fence register handling
  30  *
  31  * Important to avoid confusions: "fences" in the i915 driver are not execution
  32  * fences used to track command completion but hardware detiler objects which
  33  * wrap a given range of the global GTT. Each platform has only a fairly limited
  34  * set of these objects.
  35  *
  36  * Fences are used to detile GTT memory mappings. They're also connected to the
  37  * hardware frontbuffer render tracking and hence interract with frontbuffer
  38  * conmpression. Furthermore on older platforms fences are required for tiled
  39  * objects used by the display engine. They can also be used by the render
  40  * engine - they're required for blitter commands and are optional for render
  41  * commands. But on gen4+ both display (with the exception of fbc) and rendering
  42  * have their own tiling state bits and don't need fences.
  43  *
  44  * Also note that fences only support X and Y tiling and hence can't be used for
  45  * the fancier new tiling formats like W, Ys and Yf.
  46  *
  47  * Finally note that because fences are such a restricted resource they're
  48  * dynamically associated with objects. Furthermore fence state is committed to
  49  * the hardware lazily to avoid unecessary stalls on gen2/3. Therefore code must
  50  * explictly call i915_gem_object_get_fence() to synchronize fencing status
  51  * for cpu access. Also note that some code wants an unfenced view, for those
  52  * cases the fence can be removed forcefully with i915_gem_object_put_fence().
  53  *
  54  * Internally these functions will synchronize with userspace access by removing
  55  * CPU ptes into GTT mmaps (not the GTT ptes themselves) as needed.
  56  */
  57
  58 static void i965_write_fence_reg(struct drm_device *dev, int reg,
  59                                  struct drm_i915_gem_object *obj)
  60 {
  61         struct drm_i915_private *dev_priv = dev->dev_private;
  62         int fence_reg;
  63         int fence_pitch_shift;
  64
  65         if (INTEL_INFO(dev)->gen >= 6) {
  66                 fence_reg = FENCE_REG_SANDYBRIDGE_0;
  67                 fence_pitch_shift = SANDYBRIDGE_FENCE_PITCH_SHIFT;
  68         } else {
  69                 fence_reg = FENCE_REG_965_0;
  70                 fence_pitch_shift = I965_FENCE_PITCH_SHIFT;
  71         }
  72
  73         fence_reg += reg * 8;
  74
  75         /* To w/a incoherency with non-atomic 64-bit register updates,
  76          * we split the 64-bit update into two 32-bit writes. In order
  77          * for a partial fence not to be evaluated between writes, we
  78          * precede the update with write to turn off the fence register,
  79          * and only enable the fence as the last step.
  80          *
  81          * For extra levels of paranoia, we make sure each step lands
  82          * before applying the next step.
  83          */
  84         I915_WRITE(fence_reg, 0);
  85         POSTING_READ(fence_reg);
  86
  87         if (obj) {
  88                 u32 size = i915_gem_obj_ggtt_size(obj);
  89                 uint64_t val;
  90
  91                 /* Adjust fence size to match tiled area */
  92                 if (obj->tiling_mode != I915_TILING_NONE) {
  93                         uint32_t row_size = obj->stride *
  94                                 (obj->tiling_mode == I915_TILING_Y ? 32 : 8);
  95                         size = (size / row_size) * row_size;
  96                 }
  97
  98                 val = (uint64_t)((i915_gem_obj_ggtt_offset(obj) + size - 4096) &
  99                                  0xfffff000) << 32;
 100                 val |= i915_gem_obj_ggtt_offset(obj) & 0xfffff000;
 101                 val |= (uint64_t)((obj->stride / 128) - 1) << fence_pitch_shift;
 102                 if (obj->tiling_mode == I915_TILING_Y)
 103                         val |= 1 << I965_FENCE_TILING_Y_SHIFT;
 104                 val |= I965_FENCE_REG_VALID;
 105
 106                 I915_WRITE(fence_reg + 4, val >> 32);
 107                 POSTING_READ(fence_reg + 4);
 108
 109                 I915_WRITE(fence_reg + 0, val);
 110                 POSTING_READ(fence_reg);
 111         } else {
 112                 I915_WRITE(fence_reg + 4, 0);
 113                 POSTING_READ(fence_reg + 4);
 114         }
 115 }
 116
 117 static void i915_write_fence_reg(struct drm_device *dev, int reg,
 118                                  struct drm_i915_gem_object *obj)
 119 {
 120         struct drm_i915_private *dev_priv = dev->dev_private;
 121         u32 val;
 122
 123         if (obj) {
 124                 u32 size = i915_gem_obj_ggtt_size(obj);
 125                 int pitch_val;
 126                 int tile_width;
 127
 128                 WARN((i915_gem_obj_ggtt_offset(obj) & ~I915_FENCE_START_MASK) ||
 129                      (size & -size) != size ||
 130                      (i915_gem_obj_ggtt_offset(obj) & (size - 1)),
 131                      "object 0x%08lx [fenceable? %d] not 1M or pot-size (0x%08x) aligned\n",
 132                      i915_gem_obj_ggtt_offset(obj), obj->map_and_fenceable, size);
 133
 134                 if (obj->tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev))
 135                         tile_width = 128;
 136                 else
 137                         tile_width = 512;
 138
 139                 /* Note: pitch better be a power of two tile widths */
 140                 pitch_val = obj->stride / tile_width;
 141                 pitch_val = ffs(pitch_val) - 1;
 142
 143                 val = i915_gem_obj_ggtt_offset(obj);
 144                 if (obj->tiling_mode == I915_TILING_Y)
 145                         val |= 1 << I830_FENCE_TILING_Y_SHIFT;
 146                 val |= I915_FENCE_SIZE_BITS(size);
 147                 val |= pitch_val << I830_FENCE_PITCH_SHIFT;
 148                 val |= I830_FENCE_REG_VALID;
 149         } else
 150                 val = 0;
 151
 152         if (reg < 8)
 153                 reg = FENCE_REG_830_0 + reg * 4;
 154         else
 155                 reg = FENCE_REG_945_8 + (reg - 8) * 4;
 156
 157         I915_WRITE(reg, val);
 158         POSTING_READ(reg);
 159 }
 160
 161 static void i830_write_fence_reg(struct drm_device *dev, int reg,
 162                                 struct drm_i915_gem_object *obj)
 163 {
 164         struct drm_i915_private *dev_priv = dev->dev_private;
 165         uint32_t val;
 166
 167         if (obj) {
 168                 u32 size = i915_gem_obj_ggtt_size(obj);
 169                 uint32_t pitch_val;
 170
 171                 WARN((i915_gem_obj_ggtt_offset(obj) & ~I830_FENCE_START_MASK) ||
 172                      (size & -size) != size ||
 173                      (i915_gem_obj_ggtt_offset(obj) & (size - 1)),
 174                      "object 0x%08lx not 512K or pot-size 0x%08x aligned\n",
 175                      i915_gem_obj_ggtt_offset(obj), size);
 176
 177                 pitch_val = obj->stride / 128;
 178                 pitch_val = ffs(pitch_val) - 1;
 179
 180                 val = i915_gem_obj_ggtt_offset(obj);
 181                 if (obj->tiling_mode == I915_TILING_Y)
 182                         val |= 1 << I830_FENCE_TILING_Y_SHIFT;
 183                 val |= I830_FENCE_SIZE_BITS(size);
 184                 val |= pitch_val << I830_FENCE_PITCH_SHIFT;
 185                 val |= I830_FENCE_REG_VALID;
 186         } else
 187                 val = 0;
 188
 189         I915_WRITE(FENCE_REG_830_0 + reg * 4, val);
 190         POSTING_READ(FENCE_REG_830_0 + reg * 4);
 191 }
 192
 193 inline static bool i915_gem_object_needs_mb(struct drm_i915_gem_object *obj)
 194 {
 195         return obj && obj->base.read_domains & I915_GEM_DOMAIN_GTT;
 196 }
 197
 198 static void i915_gem_write_fence(struct drm_device *dev, int reg,
 199                                  struct drm_i915_gem_object *obj)
 200 {
 201         struct drm_i915_private *dev_priv = dev->dev_private;
 202
 203         /* Ensure that all CPU reads are completed before installing a fence
 204          * and all writes before removing the fence.
 205          */
 206         if (i915_gem_object_needs_mb(dev_priv->fence_regs[reg].obj))
 207                 mb();
 208
 209         WARN(obj && (!obj->stride || !obj->tiling_mode),
 210              "bogus fence setup with stride: 0x%x, tiling mode: %i\n",
 211              obj->stride, obj->tiling_mode);
 212
 213         if (IS_GEN2(dev))
 214                 i830_write_fence_reg(dev, reg, obj);
 215         else if (IS_GEN3(dev))
 216                 i915_write_fence_reg(dev, reg, obj);
 217         else if (INTEL_INFO(dev)->gen >= 4)
 218                 i965_write_fence_reg(dev, reg, obj);
 219
 220         /* And similarly be paranoid that no direct access to this region
 221          * is reordered to before the fence is installed.
 222          */
 223         if (i915_gem_object_needs_mb(obj))
 224                 mb();
 225 }
 226
 227 static inline int fence_number(struct drm_i915_private *dev_priv,
 228                                struct drm_i915_fence_reg *fence)
 229 {
 230         return fence - dev_priv->fence_regs;
 231 }
 232
 233 static void i915_gem_object_update_fence(struct drm_i915_gem_object *obj,
 234                                          struct drm_i915_fence_reg *fence,
 235                                          bool enable)
 236 {
 237         struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
 238         int reg = fence_number(dev_priv, fence);
 239
 240         i915_gem_write_fence(obj->base.dev, reg, enable ? obj : NULL);
 241
 242         if (enable) {
 243                 obj->fence_reg = reg;
 244                 fence->obj = obj;
 245                 list_move_tail(&fence->lru_list, &dev_priv->mm.fence_list);
 246         } else {
 247                 obj->fence_reg = I915_FENCE_REG_NONE;
 248                 fence->obj = NULL;
 249                 list_del_init(&fence->lru_list);
 250         }
 251         obj->fence_dirty = false;
 252 }
 253
 254 static inline void i915_gem_object_fence_lost(struct drm_i915_gem_object *obj)
 255 {
 256         if (obj->tiling_mode)
 257                 i915_gem_release_mmap(obj);
 258
 259         /* As we do not have an associated fence register, we will force
 260          * a tiling change if we ever need to acquire one.
 261          */
 262         obj->fence_dirty = false;
 263         obj->fence_reg = I915_FENCE_REG_NONE;
 264 }
 265
 266 static int
 267 i915_gem_object_wait_fence(struct drm_i915_gem_object *obj)
 268 {
 269         if (obj->last_fenced_req) {
 270                 int ret = i915_wait_request(obj->last_fenced_req);
 271                 if (ret)
 272                         return ret;
 273
 274                 i915_gem_request_assign(&obj->last_fenced_req, NULL);
 275         }
 276
 277         return 0;
 278 }
 279
 280 /**
 281  * i915_gem_object_put_fence - force-remove fence for an object
 282  * @obj: object to map through a fence reg
 283  *
 284  * This function force-removes any fence from the given object, which is useful
 285  * if the kernel wants to do untiled GTT access.
 286  *
 287  * Returns:
 288  *
 289  * 0 on success, negative error code on failure.
 290  */
 291 int
 292 i915_gem_object_put_fence(struct drm_i915_gem_object *obj)
 293 {
 294         struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
 295         struct drm_i915_fence_reg *fence;
 296         int ret;
 297
 298         ret = i915_gem_object_wait_fence(obj);
 299         if (ret)
 300                 return ret;
 301
 302         if (obj->fence_reg == I915_FENCE_REG_NONE)
 303                 return 0;
 304
 305         fence = &dev_priv->fence_regs[obj->fence_reg];
 306
 307         if (WARN_ON(fence->pin_count))
 308                 return -EBUSY;
 309
 310         i915_gem_object_fence_lost(obj);
 311         i915_gem_object_update_fence(obj, fence, false);
 312
 313         return 0;
 314 }
 315
 316 static struct drm_i915_fence_reg *
 317 i915_find_fence_reg(struct drm_device *dev)
 318 {
 319         struct drm_i915_private *dev_priv = dev->dev_private;
 320         struct drm_i915_fence_reg *reg, *avail;
 321         int i;
 322
 323         /* First try to find a free reg */
 324         avail = NULL;
 325         for (i = dev_priv->fence_reg_start; i < dev_priv->num_fence_regs; i++) {
 326                 reg = &dev_priv->fence_regs[i];
 327                 if (!reg->obj)
 328                         return reg;
 329
 330                 if (!reg->pin_count)
 331                         avail = reg;
 332         }
 333
 334         if (avail == NULL)
 335                 goto deadlock;
 336
 337         /* None available, try to steal one or wait for a user to finish */
 338         list_for_each_entry(reg, &dev_priv->mm.fence_list, lru_list) {
 339                 if (reg->pin_count)
 340                         continue;
 341
 342                 return reg;
 343         }
 344
 345 deadlock:
 346         /* Wait for completion of pending flips which consume fences */
 347         if (intel_has_pending_fb_unpin(dev))
 348                 return ERR_PTR(-EAGAIN);
 349
 350         return ERR_PTR(-EDEADLK);
 351 }
 352
 353 /**
 354  * i915_gem_object_get_fence - set up fencing for an object
 355  * @obj: object to map through a fence reg
 356  *
 357  * When mapping objects through the GTT, userspace wants to be able to write
 358  * to them without having to worry about swizzling if the object is tiled.
 359  * This function walks the fence regs looking for a free one for @obj,
 360  * stealing one if it can't find any.
 361  *
 362  * It then sets up the reg based on the object's properties: address, pitch
 363  * and tiling format.
 364  *
 365  * For an untiled surface, this removes any existing fence.
 366  *
 367  * Returns:
 368  *
 369  * 0 on success, negative error code on failure.
 370  */
 371 int
 372 i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
 373 {
 374         struct drm_device *dev = obj->base.dev;
 375         struct drm_i915_private *dev_priv = dev->dev_private;
 376         bool enable = obj->tiling_mode != I915_TILING_NONE;
 377         struct drm_i915_fence_reg *reg;
 378         int ret;
 379
 380         /* Have we updated the tiling parameters upon the object and so
 381          * will need to serialise the write to the associated fence register?
 382          */
 383         if (obj->fence_dirty) {
 384                 ret = i915_gem_object_wait_fence(obj);
 385                 if (ret)
 386                         return ret;
 387         }
 388
 389         /* Just update our place in the LRU if our fence is getting reused. */
 390         if (obj->fence_reg != I915_FENCE_REG_NONE) {
 391                 reg = &dev_priv->fence_regs[obj->fence_reg];
 392                 if (!obj->fence_dirty) {
 393                         list_move_tail(&reg->lru_list,
 394                                        &dev_priv->mm.fence_list);
 395                         return 0;
 396                 }
 397         } else if (enable) {
 398                 if (WARN_ON(!obj->map_and_fenceable))
 399                         return -EINVAL;
 400
 401                 reg = i915_find_fence_reg(dev);
 402                 if (IS_ERR(reg))
 403                         return PTR_ERR(reg);
 404
 405                 if (reg->obj) {
 406                         struct drm_i915_gem_object *old = reg->obj;
 407
 408                         ret = i915_gem_object_wait_fence(old);
 409                         if (ret)
 410                                 return ret;
 411
 412                         i915_gem_object_fence_lost(old);
 413                 }
 414         } else
 415                 return 0;
 416
 417         i915_gem_object_update_fence(obj, reg, enable);
 418
 419         return 0;
 420 }
 421
 422 /**
 423  * i915_gem_object_pin_fence - pin fencing state
 424  * @obj: object to pin fencing for
 425  *
 426  * This pins the fencing state (whether tiled or untiled) to make sure the
 427  * object is ready to be used as a scanout target. Fencing status must be
 428  * synchronize first by calling i915_gem_object_get_fence():
 429  *
 430  * The resulting fence pin reference must be released again with
 431  * i915_gem_object_unpin_fence().
 432  *
 433  * Returns:
 434  *
 435  * True if the object has a fence, false otherwise.
 436  */
 437 bool
 438 i915_gem_object_pin_fence(struct drm_i915_gem_object *obj)
 439 {
 440         if (obj->fence_reg != I915_FENCE_REG_NONE) {
 441                 struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
 442                 struct i915_vma *ggtt_vma = i915_gem_obj_to_ggtt(obj);
 443
 444                 WARN_ON(!ggtt_vma ||
 445                         dev_priv->fence_regs[obj->fence_reg].pin_count >
 446                         ggtt_vma->pin_count);
 447                 dev_priv->fence_regs[obj->fence_reg].pin_count++;
 448                 return true;
 449         } else
 450                 return false;
 451 }
 452
 453 /**
 454  * i915_gem_object_unpin_fence - unpin fencing state
 455  * @obj: object to unpin fencing for
 456  *
 457  * This releases the fence pin reference acquired through
 458  * i915_gem_object_pin_fence. It will handle both objects with and without an
 459  * attached fence correctly, callers do not need to distinguish this.
 460  */
 461 void
 462 i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)
 463 {
 464         if (obj->fence_reg != I915_FENCE_REG_NONE) {
 465                 struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
 466                 WARN_ON(dev_priv->fence_regs[obj->fence_reg].pin_count <= 0);
 467                 dev_priv->fence_regs[obj->fence_reg].pin_count--;
 468         }
 469 }
 470
 471 /**
 472  * i915_gem_restore_fences - restore fence state
 473  * @dev: DRM device
 474  *
 475  * Restore the hw fence state to match the software tracking again, to be called
 476  * after a gpu reset and on resume.
 477  */
 478 void i915_gem_restore_fences(struct drm_device *dev)
 479 {
 480         struct drm_i915_private *dev_priv = dev->dev_private;
 481         int i;
 482
 483         for (i = 0; i < dev_priv->num_fence_regs; i++) {
 484                 struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i];
 485
 486                 /*
 487                  * Commit delayed tiling changes if we have an object still
 488                  * attached to the fence, otherwise just clear the fence.
 489                  */
 490                 if (reg->obj) {
 491                         i915_gem_object_update_fence(reg->obj, reg,
 492                                                      reg->obj->tiling_mode);
 493                 } else {
 494                         i915_gem_write_fence(dev, i, NULL);
 495                 }
 496         }
 497 }