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 interact with frontbuffer
  38  * compression. 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 unnecessary stalls on gen2/3. Therefore code must
  50  * explicitly 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 #define pipelined 0
  59
  60 static void i965_write_fence_reg(struct drm_i915_fence_reg *fence,
  61                                  struct i915_vma *vma)
  62 {
  63         i915_reg_t fence_reg_lo, fence_reg_hi;
  64         int fence_pitch_shift;
  65         u64 val;
  66
  67         if (INTEL_INFO(fence->i915)->gen >= 6) {
  68                 fence_reg_lo = FENCE_REG_GEN6_LO(fence->id);
  69                 fence_reg_hi = FENCE_REG_GEN6_HI(fence->id);
  70                 fence_pitch_shift = GEN6_FENCE_PITCH_SHIFT;
  71
  72         } else {
  73                 fence_reg_lo = FENCE_REG_965_LO(fence->id);
  74                 fence_reg_hi = FENCE_REG_965_HI(fence->id);
  75                 fence_pitch_shift = I965_FENCE_PITCH_SHIFT;
  76         }
  77
  78         val = 0;
  79         if (vma) {
  80                 unsigned int tiling = i915_gem_object_get_tiling(vma->obj);
  81                 bool is_y_tiled = tiling == I915_TILING_Y;
  82                 unsigned int stride = i915_gem_object_get_stride(vma->obj);
  83                 u32 row_size = stride * (is_y_tiled ? 32 : 8);
  84                 u32 size = rounddown((u32)vma->node.size, row_size);
  85
  86                 val = ((vma->node.start + size - 4096) & 0xfffff000) << 32;
  87                 val |= vma->node.start & 0xfffff000;
  88                 val |= (u64)((stride / 128) - 1) << fence_pitch_shift;
  89                 if (is_y_tiled)
  90                         val |= BIT(I965_FENCE_TILING_Y_SHIFT);
  91                 val |= I965_FENCE_REG_VALID;
  92         }
  93
  94         if (!pipelined) {
  95                 struct drm_i915_private *dev_priv = fence->i915;
  96
  97                 /* To w/a incoherency with non-atomic 64-bit register updates,
  98                  * we split the 64-bit update into two 32-bit writes. In order
  99                  * for a partial fence not to be evaluated between writes, we
 100                  * precede the update with write to turn off the fence register,
 101                  * and only enable the fence as the last step.
 102                  *
 103                  * For extra levels of paranoia, we make sure each step lands
 104                  * before applying the next step.
 105                  */
 106                 I915_WRITE(fence_reg_lo, 0);
 107                 POSTING_READ(fence_reg_lo);
 108
 109                 I915_WRITE(fence_reg_hi, upper_32_bits(val));
 110                 I915_WRITE(fence_reg_lo, lower_32_bits(val));
 111                 POSTING_READ(fence_reg_lo);
 112         }
 113 }
 114
 115 static void i915_write_fence_reg(struct drm_i915_fence_reg *fence,
 116                                  struct i915_vma *vma)
 117 {
 118         u32 val;
 119
 120         val = 0;
 121         if (vma) {
 122                 unsigned int tiling = i915_gem_object_get_tiling(vma->obj);
 123                 bool is_y_tiled = tiling == I915_TILING_Y;
 124                 unsigned int stride = i915_gem_object_get_stride(vma->obj);
 125                 int pitch_val;
 126                 int tile_width;
 127
 128                 WARN((vma->node.start & ~I915_FENCE_START_MASK) ||
 129                      !is_power_of_2(vma->node.size) ||
 130                      (vma->node.start & (vma->node.size - 1)),
 131                      "object 0x%08llx [fenceable? %d] not 1M or pot-size (0x%08llx) aligned\n",
 132                      vma->node.start,
 133                      i915_vma_is_map_and_fenceable(vma),
 134                      vma->node.size);
 135
 136                 if (is_y_tiled && HAS_128_BYTE_Y_TILING(fence->i915))
 137                         tile_width = 128;
 138                 else
 139                         tile_width = 512;
 140
 141                 /* Note: pitch better be a power of two tile widths */
 142                 pitch_val = stride / tile_width;
 143                 pitch_val = ffs(pitch_val) - 1;
 144
 145                 val = vma->node.start;
 146                 if (is_y_tiled)
 147                         val |= BIT(I830_FENCE_TILING_Y_SHIFT);
 148                 val |= I915_FENCE_SIZE_BITS(vma->node.size);
 149                 val |= pitch_val << I830_FENCE_PITCH_SHIFT;
 150                 val |= I830_FENCE_REG_VALID;
 151         }
 152
 153         if (!pipelined) {
 154                 struct drm_i915_private *dev_priv = fence->i915;
 155                 i915_reg_t reg = FENCE_REG(fence->id);
 156
 157                 I915_WRITE(reg, val);
 158                 POSTING_READ(reg);
 159         }
 160 }
 161
 162 static void i830_write_fence_reg(struct drm_i915_fence_reg *fence,
 163                                  struct i915_vma *vma)
 164 {
 165         u32 val;
 166
 167         val = 0;
 168         if (vma) {
 169                 unsigned int tiling = i915_gem_object_get_tiling(vma->obj);
 170                 bool is_y_tiled = tiling == I915_TILING_Y;
 171                 unsigned int stride = i915_gem_object_get_stride(vma->obj);
 172                 u32 pitch_val;
 173
 174                 WARN((vma->node.start & ~I830_FENCE_START_MASK) ||
 175                      !is_power_of_2(vma->node.size) ||
 176                      (vma->node.start & (vma->node.size - 1)),
 177                      "object 0x%08llx not 512K or pot-size 0x%08llx aligned\n",
 178                      vma->node.start, vma->node.size);
 179
 180                 pitch_val = stride / 128;
 181                 pitch_val = ffs(pitch_val) - 1;
 182
 183                 val = vma->node.start;
 184                 if (is_y_tiled)
 185                         val |= BIT(I830_FENCE_TILING_Y_SHIFT);
 186                 val |= I830_FENCE_SIZE_BITS(vma->node.size);
 187                 val |= pitch_val << I830_FENCE_PITCH_SHIFT;
 188                 val |= I830_FENCE_REG_VALID;
 189         }
 190
 191         if (!pipelined) {
 192                 struct drm_i915_private *dev_priv = fence->i915;
 193                 i915_reg_t reg = FENCE_REG(fence->id);
 194
 195                 I915_WRITE(reg, val);
 196                 POSTING_READ(reg);
 197         }
 198 }
 199
 200 static void fence_write(struct drm_i915_fence_reg *fence,
 201                         struct i915_vma *vma)
 202 {
 203         /* Previous access through the fence register is marshalled by
 204          * the mb() inside the fault handlers (i915_gem_release_mmaps)
 205          * and explicitly managed for internal users.
 206          */
 207
 208         if (IS_GEN2(fence->i915))
 209                 i830_write_fence_reg(fence, vma);
 210         else if (IS_GEN3(fence->i915))
 211                 i915_write_fence_reg(fence, vma);
 212         else
 213                 i965_write_fence_reg(fence, vma);
 214
 215         /* Access through the fenced region afterwards is
 216          * ordered by the posting reads whilst writing the registers.
 217          */
 218
 219         fence->dirty = false;
 220 }
 221
 222 static int fence_update(struct drm_i915_fence_reg *fence,
 223                         struct i915_vma *vma)
 224 {
 225         int ret;
 226
 227         if (vma) {
 228                 if (!i915_vma_is_map_and_fenceable(vma))
 229                         return -EINVAL;
 230
 231                 if (WARN(!i915_gem_object_get_stride(vma->obj) ||
 232                          !i915_gem_object_get_tiling(vma->obj),
 233                          "bogus fence setup with stride: 0x%x, tiling mode: %i\n",
 234                          i915_gem_object_get_stride(vma->obj),
 235                          i915_gem_object_get_tiling(vma->obj)))
 236                         return -EINVAL;
 237
 238                 ret = i915_gem_active_retire(&vma->last_fence,
 239                                              &vma->obj->base.dev->struct_mutex);
 240                 if (ret)
 241                         return ret;
 242         }
 243
 244         if (fence->vma) {
 245                 ret = i915_gem_active_retire(&fence->vma->last_fence,
 246                                       &fence->vma->obj->base.dev->struct_mutex);
 247                 if (ret)
 248                         return ret;
 249         }
 250
 251         if (fence->vma && fence->vma != vma) {
 252                 /* Ensure that all userspace CPU access is completed before
 253                  * stealing the fence.
 254                  */
 255                 i915_gem_release_mmap(fence->vma->obj);
 256
 257                 fence->vma->fence = NULL;
 258                 fence->vma = NULL;
 259
 260                 list_move(&fence->link, &fence->i915->mm.fence_list);
 261         }
 262
 263         fence_write(fence, vma);
 264
 265         if (vma) {
 266                 if (fence->vma != vma) {
 267                         vma->fence = fence;
 268                         fence->vma = vma;
 269                 }
 270
 271                 list_move_tail(&fence->link, &fence->i915->mm.fence_list);
 272         }
 273
 274         return 0;
 275 }
 276
 277 /**
 278  * i915_vma_put_fence - force-remove fence for a VMA
 279  * @vma: vma to map linearly (not through a fence reg)
 280  *
 281  * This function force-removes any fence from the given object, which is useful
 282  * if the kernel wants to do untiled GTT access.
 283  *
 284  * Returns:
 285  *
 286  * 0 on success, negative error code on failure.
 287  */
 288 int
 289 i915_vma_put_fence(struct i915_vma *vma)
 290 {
 291         struct drm_i915_fence_reg *fence = vma->fence;
 292
 293         assert_rpm_wakelock_held(to_i915(vma->vm->dev));
 294
 295         if (!fence)
 296                 return 0;
 297
 298         if (fence->pin_count)
 299                 return -EBUSY;
 300
 301         return fence_update(fence, NULL);
 302 }
 303
 304 static struct drm_i915_fence_reg *fence_find(struct drm_i915_private *dev_priv)
 305 {
 306         struct drm_i915_fence_reg *fence;
 307
 308         list_for_each_entry(fence, &dev_priv->mm.fence_list, link) {
 309                 if (fence->pin_count)
 310                         continue;
 311
 312                 return fence;
 313         }
 314
 315         /* Wait for completion of pending flips which consume fences */
 316         if (intel_has_pending_fb_unpin(&dev_priv->drm))
 317                 return ERR_PTR(-EAGAIN);
 318
 319         return ERR_PTR(-EDEADLK);
 320 }
 321
 322 /**
 323  * i915_vma_get_fence - set up fencing for a vma
 324  * @vma: vma to map through a fence reg
 325  *
 326  * When mapping objects through the GTT, userspace wants to be able to write
 327  * to them without having to worry about swizzling if the object is tiled.
 328  * This function walks the fence regs looking for a free one for @obj,
 329  * stealing one if it can't find any.
 330  *
 331  * It then sets up the reg based on the object's properties: address, pitch
 332  * and tiling format.
 333  *
 334  * For an untiled surface, this removes any existing fence.
 335  *
 336  * Returns:
 337  *
 338  * 0 on success, negative error code on failure.
 339  */
 340 int
 341 i915_vma_get_fence(struct i915_vma *vma)
 342 {
 343         struct drm_i915_fence_reg *fence;
 344         struct i915_vma *set = i915_gem_object_is_tiled(vma->obj) ? vma : NULL;
 345
 346         /* Note that we revoke fences on runtime suspend. Therefore the user
 347          * must keep the device awake whilst using the fence.
 348          */
 349         assert_rpm_wakelock_held(to_i915(vma->vm->dev));
 350
 351         /* Just update our place in the LRU if our fence is getting reused. */
 352         if (vma->fence) {
 353                 fence = vma->fence;
 354                 if (!fence->dirty) {
 355                         list_move_tail(&fence->link,
 356                                        &fence->i915->mm.fence_list);
 357                         return 0;
 358                 }
 359         } else if (set) {
 360                 fence = fence_find(to_i915(vma->vm->dev));
 361                 if (IS_ERR(fence))
 362                         return PTR_ERR(fence);
 363         } else
 364                 return 0;
 365
 366         return fence_update(fence, set);
 367 }
 368
 369 /**
 370  * i915_gem_restore_fences - restore fence state
 371  * @dev: DRM device
 372  *
 373  * Restore the hw fence state to match the software tracking again, to be called
 374  * after a gpu reset and on resume. Note that on runtime suspend we only cancel
 375  * the fences, to be reacquired by the user later.
 376  */
 377 void i915_gem_restore_fences(struct drm_device *dev)
 378 {
 379         struct drm_i915_private *dev_priv = to_i915(dev);
 380         int i;
 381
 382         for (i = 0; i < dev_priv->num_fence_regs; i++) {
 383                 struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i];
 384                 struct i915_vma *vma = reg->vma;
 385
 386                 /*
 387                  * Commit delayed tiling changes if we have an object still
 388                  * attached to the fence, otherwise just clear the fence.
 389                  */
 390                 if (vma && !i915_gem_object_is_tiled(vma->obj)) {
 391                         GEM_BUG_ON(!reg->dirty);
 392                         GEM_BUG_ON(!list_empty(&vma->obj->userfault_link));
 393
 394                         list_move(&reg->link, &dev_priv->mm.fence_list);
 395                         vma->fence = NULL;
 396                         vma = NULL;
 397                 }
 398
 399                 fence_write(reg, vma);
 400                 reg->vma = vma;
 401         }
 402 }
 403
 404 /**
 405  * DOC: tiling swizzling details
 406  *
 407  * The idea behind tiling is to increase cache hit rates by rearranging
 408  * pixel data so that a group of pixel accesses are in the same cacheline.
 409  * Performance improvement from doing this on the back/depth buffer are on
 410  * the order of 30%.
 411  *
 412  * Intel architectures make this somewhat more complicated, though, by
 413  * adjustments made to addressing of data when the memory is in interleaved
 414  * mode (matched pairs of DIMMS) to improve memory bandwidth.
 415  * For interleaved memory, the CPU sends every sequential 64 bytes
 416  * to an alternate memory channel so it can get the bandwidth from both.
 417  *
 418  * The GPU also rearranges its accesses for increased bandwidth to interleaved
 419  * memory, and it matches what the CPU does for non-tiled.  However, when tiled
 420  * it does it a little differently, since one walks addresses not just in the
 421  * X direction but also Y.  So, along with alternating channels when bit
 422  * 6 of the address flips, it also alternates when other bits flip --  Bits 9
 423  * (every 512 bytes, an X tile scanline) and 10 (every two X tile scanlines)
 424  * are common to both the 915 and 965-class hardware.
 425  *
 426  * The CPU also sometimes XORs in higher bits as well, to improve
 427  * bandwidth doing strided access like we do so frequently in graphics.  This
 428  * is called "Channel XOR Randomization" in the MCH documentation.  The result
 429  * is that the CPU is XORing in either bit 11 or bit 17 to bit 6 of its address
 430  * decode.
 431  *
 432  * All of this bit 6 XORing has an effect on our memory management,
 433  * as we need to make sure that the 3d driver can correctly address object
 434  * contents.
 435  *
 436  * If we don't have interleaved memory, all tiling is safe and no swizzling is
 437  * required.
 438  *
 439  * When bit 17 is XORed in, we simply refuse to tile at all.  Bit
 440  * 17 is not just a page offset, so as we page an object out and back in,
 441  * individual pages in it will have different bit 17 addresses, resulting in
 442  * each 64 bytes being swapped with its neighbor!
 443  *
 444  * Otherwise, if interleaved, we have to tell the 3d driver what the address
 445  * swizzling it needs to do is, since it's writing with the CPU to the pages
 446  * (bit 6 and potentially bit 11 XORed in), and the GPU is reading from the
 447  * pages (bit 6, 9, and 10 XORed in), resulting in a cumulative bit swizzling
 448  * required by the CPU of XORing in bit 6, 9, 10, and potentially 11, in order
 449  * to match what the GPU expects.
 450  */
 451
 452 /**
 453  * i915_gem_detect_bit_6_swizzle - detect bit 6 swizzling pattern
 454  * @dev: DRM device
 455  *
 456  * Detects bit 6 swizzling of address lookup between IGD access and CPU
 457  * access through main memory.
 458  */
 459 void
 460 i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
 461 {
 462         struct drm_i915_private *dev_priv = to_i915(dev);
 463         uint32_t swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
 464         uint32_t swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
 465
 466         if (INTEL_GEN(dev_priv) >= 8 || IS_VALLEYVIEW(dev_priv)) {
 467                 /*
 468                  * On BDW+, swizzling is not used. We leave the CPU memory
 469                  * controller in charge of optimizing memory accesses without
 470                  * the extra address manipulation GPU side.
 471                  *
 472                  * VLV and CHV don't have GPU swizzling.
 473                  */
 474                 swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 475                 swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 476         } else if (INTEL_INFO(dev)->gen >= 6) {
 477                 if (dev_priv->preserve_bios_swizzle) {
 478                         if (I915_READ(DISP_ARB_CTL) &
 479                             DISP_TILE_SURFACE_SWIZZLING) {
 480                                 swizzle_x = I915_BIT_6_SWIZZLE_9_10;
 481                                 swizzle_y = I915_BIT_6_SWIZZLE_9;
 482                         } else {
 483                                 swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 484                                 swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 485                         }
 486                 } else {
 487                         uint32_t dimm_c0, dimm_c1;
 488                         dimm_c0 = I915_READ(MAD_DIMM_C0);
 489                         dimm_c1 = I915_READ(MAD_DIMM_C1);
 490                         dimm_c0 &= MAD_DIMM_A_SIZE_MASK | MAD_DIMM_B_SIZE_MASK;
 491                         dimm_c1 &= MAD_DIMM_A_SIZE_MASK | MAD_DIMM_B_SIZE_MASK;
 492                         /* Enable swizzling when the channels are populated
 493                          * with identically sized dimms. We don't need to check
 494                          * the 3rd channel because no cpu with gpu attached
 495                          * ships in that configuration. Also, swizzling only
 496                          * makes sense for 2 channels anyway. */
 497                         if (dimm_c0 == dimm_c1) {
 498                                 swizzle_x = I915_BIT_6_SWIZZLE_9_10;
 499                                 swizzle_y = I915_BIT_6_SWIZZLE_9;
 500                         } else {
 501                                 swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 502                                 swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 503                         }
 504                 }
 505         } else if (IS_GEN5(dev_priv)) {
 506                 /* On Ironlake whatever DRAM config, GPU always do
 507                  * same swizzling setup.
 508                  */
 509                 swizzle_x = I915_BIT_6_SWIZZLE_9_10;
 510                 swizzle_y = I915_BIT_6_SWIZZLE_9;
 511         } else if (IS_GEN2(dev_priv)) {
 512                 /* As far as we know, the 865 doesn't have these bit 6
 513                  * swizzling issues.
 514                  */
 515                 swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 516                 swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 517         } else if (IS_MOBILE(dev_priv) || (IS_GEN3(dev_priv) &&
 518                    !IS_G33(dev_priv))) {
 519                 uint32_t dcc;
 520
 521                 /* On 9xx chipsets, channel interleave by the CPU is
 522                  * determined by DCC.  For single-channel, neither the CPU
 523                  * nor the GPU do swizzling.  For dual channel interleaved,
 524                  * the GPU's interleave is bit 9 and 10 for X tiled, and bit
 525                  * 9 for Y tiled.  The CPU's interleave is independent, and
 526                  * can be based on either bit 11 (haven't seen this yet) or
 527                  * bit 17 (common).
 528                  */
 529                 dcc = I915_READ(DCC);
 530                 switch (dcc & DCC_ADDRESSING_MODE_MASK) {
 531                 case DCC_ADDRESSING_MODE_SINGLE_CHANNEL:
 532                 case DCC_ADDRESSING_MODE_DUAL_CHANNEL_ASYMMETRIC:
 533                         swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 534                         swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 535                         break;
 536                 case DCC_ADDRESSING_MODE_DUAL_CHANNEL_INTERLEAVED:
 537                         if (dcc & DCC_CHANNEL_XOR_DISABLE) {
 538                                 /* This is the base swizzling by the GPU for
 539                                  * tiled buffers.
 540                                  */
 541                                 swizzle_x = I915_BIT_6_SWIZZLE_9_10;
 542                                 swizzle_y = I915_BIT_6_SWIZZLE_9;
 543                         } else if ((dcc & DCC_CHANNEL_XOR_BIT_17) == 0) {
 544                                 /* Bit 11 swizzling by the CPU in addition. */
 545                                 swizzle_x = I915_BIT_6_SWIZZLE_9_10_11;
 546                                 swizzle_y = I915_BIT_6_SWIZZLE_9_11;
 547                         } else {
 548                                 /* Bit 17 swizzling by the CPU in addition. */
 549                                 swizzle_x = I915_BIT_6_SWIZZLE_9_10_17;
 550                                 swizzle_y = I915_BIT_6_SWIZZLE_9_17;
 551                         }
 552                         break;
 553                 }
 554
 555                 /* check for L-shaped memory aka modified enhanced addressing */
 556                 if (IS_GEN4(dev_priv) &&
 557                     !(I915_READ(DCC2) & DCC2_MODIFIED_ENHANCED_DISABLE)) {
 558                         swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
 559                         swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
 560                 }
 561
 562                 if (dcc == 0xffffffff) {
 563                         DRM_ERROR("Couldn't read from MCHBAR.  "
 564                                   "Disabling tiling.\n");
 565                         swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
 566                         swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
 567                 }
 568         } else {
 569                 /* The 965, G33, and newer, have a very flexible memory
 570                  * configuration.  It will enable dual-channel mode
 571                  * (interleaving) on as much memory as it can, and the GPU
 572                  * will additionally sometimes enable different bit 6
 573                  * swizzling for tiled objects from the CPU.
 574                  *
 575                  * Here's what I found on the G965:
 576                  *    slot fill         memory size  swizzling
 577                  * 0A   0B   1A   1B    1-ch   2-ch
 578                  * 512  0    0    0     512    0     O
 579                  * 512  0    512  0     16     1008  X
 580                  * 512  0    0    512   16     1008  X
 581                  * 0    512  0    512   16     1008  X
 582                  * 1024 1024 1024 0     2048   1024  O
 583                  *
 584                  * We could probably detect this based on either the DRB
 585                  * matching, which was the case for the swizzling required in
 586                  * the table above, or from the 1-ch value being less than
 587                  * the minimum size of a rank.
 588                  *
 589                  * Reports indicate that the swizzling actually
 590                  * varies depending upon page placement inside the
 591                  * channels, i.e. we see swizzled pages where the
 592                  * banks of memory are paired and unswizzled on the
 593                  * uneven portion, so leave that as unknown.
 594                  */
 595                 if (I915_READ16(C0DRB3) == I915_READ16(C1DRB3)) {
 596                         swizzle_x = I915_BIT_6_SWIZZLE_9_10;
 597                         swizzle_y = I915_BIT_6_SWIZZLE_9;
 598                 }
 599         }
 600
 601         if (swizzle_x == I915_BIT_6_SWIZZLE_UNKNOWN ||
 602             swizzle_y == I915_BIT_6_SWIZZLE_UNKNOWN) {
 603                 /* Userspace likes to explode if it sees unknown swizzling,
 604                  * so lie. We will finish the lie when reporting through
 605                  * the get-tiling-ioctl by reporting the physical swizzle
 606                  * mode as unknown instead.
 607                  *
 608                  * As we don't strictly know what the swizzling is, it may be
 609                  * bit17 dependent, and so we need to also prevent the pages
 610                  * from being moved.
 611                  */
 612                 dev_priv->quirks |= QUIRK_PIN_SWIZZLED_PAGES;
 613                 swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 614                 swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 615         }
 616
 617         dev_priv->mm.bit_6_swizzle_x = swizzle_x;
 618         dev_priv->mm.bit_6_swizzle_y = swizzle_y;
 619 }
 620
 621 /*
 622  * Swap every 64 bytes of this page around, to account for it having a new
 623  * bit 17 of its physical address and therefore being interpreted differently
 624  * by the GPU.
 625  */
 626 static void
 627 i915_gem_swizzle_page(struct page *page)
 628 {
 629         char temp[64];
 630         char *vaddr;
 631         int i;
 632
 633         vaddr = kmap(page);
 634
 635         for (i = 0; i < PAGE_SIZE; i += 128) {
 636                 memcpy(temp, &vaddr[i], 64);
 637                 memcpy(&vaddr[i], &vaddr[i + 64], 64);
 638                 memcpy(&vaddr[i + 64], temp, 64);
 639         }
 640
 641         kunmap(page);
 642 }
 643
 644 /**
 645  * i915_gem_object_do_bit_17_swizzle - fixup bit 17 swizzling
 646  * @obj: i915 GEM buffer object
 647  *
 648  * This function fixes up the swizzling in case any page frame number for this
 649  * object has changed in bit 17 since that state has been saved with
 650  * i915_gem_object_save_bit_17_swizzle().
 651  *
 652  * This is called when pinning backing storage again, since the kernel is free
 653  * to move unpinned backing storage around (either by directly moving pages or
 654  * by swapping them out and back in again).
 655  */
 656 void
 657 i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj)
 658 {
 659         struct sgt_iter sgt_iter;
 660         struct page *page;
 661         int i;
 662
 663         if (obj->bit_17 == NULL)
 664                 return;
 665
 666         i = 0;
 667         for_each_sgt_page(page, sgt_iter, obj->pages) {
 668                 char new_bit_17 = page_to_phys(page) >> 17;
 669                 if ((new_bit_17 & 0x1) !=
 670                     (test_bit(i, obj->bit_17) != 0)) {
 671                         i915_gem_swizzle_page(page);
 672                         set_page_dirty(page);
 673                 }
 674                 i++;
 675         }
 676 }
 677
 678 /**
 679  * i915_gem_object_save_bit_17_swizzle - save bit 17 swizzling
 680  * @obj: i915 GEM buffer object
 681  *
 682  * This function saves the bit 17 of each page frame number so that swizzling
 683  * can be fixed up later on with i915_gem_object_do_bit_17_swizzle(). This must
 684  * be called before the backing storage can be unpinned.
 685  */
 686 void
 687 i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj)
 688 {
 689         struct sgt_iter sgt_iter;
 690         struct page *page;
 691         int page_count = obj->base.size >> PAGE_SHIFT;
 692         int i;
 693
 694         if (obj->bit_17 == NULL) {
 695                 obj->bit_17 = kcalloc(BITS_TO_LONGS(page_count),
 696                                       sizeof(long), GFP_KERNEL);
 697                 if (obj->bit_17 == NULL) {
 698                         DRM_ERROR("Failed to allocate memory for bit 17 "
 699                                   "record\n");
 700                         return;
 701                 }
 702         }
 703
 704         i = 0;
 705
 706         for_each_sgt_page(page, sgt_iter, obj->pages) {
 707                 if (page_to_phys(page) & (1 << 17))
 708                         __set_bit(i, obj->bit_17);
 709                 else
 710                         __clear_bit(i, obj->bit_17);
 711                 i++;
 712         }
 713 }