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/*
* Copyright © 2008 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* Authors:
* Eric Anholt <eric@anholt.net>
*
*/
#include "drmP.h"
#include "drm.h"
#include "i915_drm.h"
#include "i915_drv.h"
/** @file i915_gem_tiling.c
*
* Support for managing tiling state of buffer objects.
*
* The idea behind tiling is to increase cache hit rates by rearranging
* pixel data so that a group of pixel accesses are in the same cacheline.
* Performance improvement from doing this on the back/depth buffer are on
* the order of 30%.
*
* Intel architectures make this somewhat more complicated, though, by
* adjustments made to addressing of data when the memory is in interleaved
* mode (matched pairs of DIMMS) to improve memory bandwidth.
* For interleaved memory, the CPU sends every sequential 64 bytes
* to an alternate memory channel so it can get the bandwidth from both.
*
* The GPU also rearranges its accesses for increased bandwidth to interleaved
* memory, and it matches what the CPU does for non-tiled. However, when tiled
* it does it a little differently, since one walks addresses not just in the
* X direction but also Y. So, along with alternating channels when bit
* 6 of the address flips, it also alternates when other bits flip -- Bits 9
* (every 512 bytes, an X tile scanline) and 10 (every two X tile scanlines)
* are common to both the 915 and 965-class hardware.
*
* The CPU also sometimes XORs in higher bits as well, to improve
* bandwidth doing strided access like we do so frequently in graphics. This
* is called "Channel XOR Randomization" in the MCH documentation. The result
* is that the CPU is XORing in either bit 11 or bit 17 to bit 6 of its address
* decode.
*
* All of this bit 6 XORing has an effect on our memory management,
* as we need to make sure that the 3d driver can correctly address object
* contents.
*
* If we don't have interleaved memory, all tiling is safe and no swizzling is
* required.
*
* When bit 17 is XORed in, we simply refuse to tile at all. Bit
* 17 is not just a page offset, so as we page an objet out and back in,
* individual pages in it will have different bit 17 addresses, resulting in
* each 64 bytes being swapped with its neighbor!
*
* Otherwise, if interleaved, we have to tell the 3d driver what the address
* swizzling it needs to do is, since it's writing with the CPU to the pages
* (bit 6 and potentially bit 11 XORed in), and the GPU is reading from the
* pages (bit 6, 9, and 10 XORed in), resulting in a cumulative bit swizzling
* required by the CPU of XORing in bit 6, 9, 10, and potentially 11, in order
* to match what the GPU expects.
*/
/**
* Detects bit 6 swizzling of address lookup between IGD access and CPU
* access through main memory.
*/
void
i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
{
drm_i915_private_t *dev_priv = dev->dev_private;
uint32_t swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
uint32_t swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
if (!IS_I9XX(dev)) {
/* As far as we know, the 865 doesn't have these bit 6
* swizzling issues.
*/
swizzle_x = I915_BIT_6_SWIZZLE_NONE;
swizzle_y = I915_BIT_6_SWIZZLE_NONE;
} else if ((!IS_I965G(dev) && !IS_G33(dev)) || IS_I965GM(dev) ||
IS_GM45(dev)) {
uint32_t dcc;
/* On 915-945 and GM965, channel interleave by the CPU is
* determined by DCC. The CPU will alternate based on bit 6
* in interleaved mode, and the GPU will then also alternate
* on bit 6, 9, and 10 for X, but the CPU may also optionally
* alternate based on bit 17 (XOR not disabled and XOR
* bit == 17).
*/
dcc = I915_READ(DCC);
switch (dcc & DCC_ADDRESSING_MODE_MASK) {
case DCC_ADDRESSING_MODE_SINGLE_CHANNEL:
case DCC_ADDRESSING_MODE_DUAL_CHANNEL_ASYMMETRIC:
swizzle_x = I915_BIT_6_SWIZZLE_NONE;
swizzle_y = I915_BIT_6_SWIZZLE_NONE;
break;
case DCC_ADDRESSING_MODE_DUAL_CHANNEL_INTERLEAVED:
if (IS_I915G(dev) || IS_I915GM(dev) ||
dcc & DCC_CHANNEL_XOR_DISABLE) {
swizzle_x = I915_BIT_6_SWIZZLE_9_10;
swizzle_y = I915_BIT_6_SWIZZLE_9;
} else if (IS_I965GM(dev) || IS_GM45(dev)) {
/* GM965 only does bit 11-based channel
* randomization
*/
swizzle_x = I915_BIT_6_SWIZZLE_9_10_11;
swizzle_y = I915_BIT_6_SWIZZLE_9_11;
} else {
/* Bit 17 or perhaps other swizzling */
swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
}
break;
}
if (dcc == 0xffffffff) {
DRM_ERROR("Couldn't read from MCHBAR. "
"Disabling tiling.\n");
swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
}
} else {
/* The 965, G33, and newer, have a very flexible memory
* configuration. It will enable dual-channel mode
* (interleaving) on as much memory as it can, and the GPU
* will additionally sometimes enable different bit 6
* swizzling for tiled objects from the CPU.
*
* Here's what I found on the G965:
* slot fill memory size swizzling
* 0A 0B 1A 1B 1-ch 2-ch
* 512 0 0 0 512 0 O
* 512 0 512 0 16 1008 X
* 512 0 0 512 16 1008 X
* 0 512 0 512 16 1008 X
* 1024 1024 1024 0 2048 1024 O
*
* We could probably detect this based on either the DRB
* matching, which was the case for the swizzling required in
* the table above, or from the 1-ch value being less than
* the minimum size of a rank.
*/
if (I915_READ16(C0DRB3) != I915_READ16(C1DRB3)) {
swizzle_x = I915_BIT_6_SWIZZLE_NONE;
swizzle_y = I915_BIT_6_SWIZZLE_NONE;
} else {
swizzle_x = I915_BIT_6_SWIZZLE_9_10;
swizzle_y = I915_BIT_6_SWIZZLE_9;
}
}
dev_priv->mm.bit_6_swizzle_x = swizzle_x;
dev_priv->mm.bit_6_swizzle_y = swizzle_y;
}
/**
* Sets the tiling mode of an object, returning the required swizzling of
* bit 6 of addresses in the object.
*/
int
i915_gem_set_tiling(struct drm_device *dev, void *data,
struct drm_file *file_priv)
{
struct drm_i915_gem_set_tiling *args = data;
drm_i915_private_t *dev_priv = dev->dev_private;
struct drm_gem_object *obj;
struct drm_i915_gem_object *obj_priv;
obj = drm_gem_object_lookup(dev, file_priv, args->handle);
if (obj == NULL)
return -EINVAL;
obj_priv = obj->driver_private;
mutex_lock(&dev->struct_mutex);
if (args->tiling_mode == I915_TILING_NONE) {
obj_priv->tiling_mode = I915_TILING_NONE;
args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
} else {
if (args->tiling_mode == I915_TILING_X)
args->swizzle_mode = dev_priv->mm.bit_6_swizzle_x;
else
args->swizzle_mode = dev_priv->mm.bit_6_swizzle_y;
/* If we can't handle the swizzling, make it untiled. */
if (args->swizzle_mode == I915_BIT_6_SWIZZLE_UNKNOWN) {
args->tiling_mode = I915_TILING_NONE;
args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
}
}
obj_priv->tiling_mode = args->tiling_mode;
mutex_unlock(&dev->struct_mutex);
drm_gem_object_unreference(obj);
return 0;
}
/**
* Returns the current tiling mode and required bit 6 swizzling for the object.
*/
int
i915_gem_get_tiling(struct drm_device *dev, void *data,
struct drm_file *file_priv)
{
struct drm_i915_gem_get_tiling *args = data;
drm_i915_private_t *dev_priv = dev->dev_private;
struct drm_gem_object *obj;
struct drm_i915_gem_object *obj_priv;
obj = drm_gem_object_lookup(dev, file_priv, args->handle);
if (obj == NULL)
return -EINVAL;
obj_priv = obj->driver_private;
mutex_lock(&dev->struct_mutex);
args->tiling_mode = obj_priv->tiling_mode;
switch (obj_priv->tiling_mode) {
case I915_TILING_X:
args->swizzle_mode = dev_priv->mm.bit_6_swizzle_x;
break;
case I915_TILING_Y:
args->swizzle_mode = dev_priv->mm.bit_6_swizzle_y;
break;
case I915_TILING_NONE:
args->swizzle_mode = I915_BIT_6_SWIZZLE_NONE;
break;
default:
DRM_ERROR("unknown tiling mode\n");
}
mutex_unlock(&dev->struct_mutex);
drm_gem_object_unreference(obj);
return 0;
}
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