/*
 * Copyright © 2008-2012 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>
 *    Chris Wilson <chris@chris-wilson.co.uk>
 *
 */

#include <drm/drmP.h>
#include <drm/i915_drm.h>
#include "i915_drv.h"

#define KB(x) ((x) * 1024)
#define MB(x) (KB(x) * 1024)

/*
 * The BIOS typically reserves some of the system's memory for the exclusive
 * use of the integrated graphics. This memory is no longer available for
 * use by the OS and so the user finds that his system has less memory
 * available than he put in. We refer to this memory as stolen.
 *
 * The BIOS will allocate its framebuffer from the stolen memory. Our
 * goal is try to reuse that object for our own fbcon which must always
 * be available for panics. Anything else we can reuse the stolen memory
 * for is a boon.
 */

int i915_gem_stolen_insert_node_in_range(struct drm_i915_private *dev_priv,
                                         struct drm_mm_node *node, u64 size,
                                         unsigned alignment, u64 start, u64 end)
{
        int ret;

        if (!drm_mm_initialized(&dev_priv->mm.stolen))
                return -ENODEV;

        /* See the comment at the drm_mm_init() call for more about this check.
         * WaSkipStolenMemoryFirstPage:bdw,chv,kbl (incomplete)
         */
        if (start < 4096 && (IS_GEN8(dev_priv) ||
                             IS_KBL_REVID(dev_priv, 0, KBL_REVID_A0)))
                start = 4096;

        mutex_lock(&dev_priv->mm.stolen_lock);
        ret = drm_mm_insert_node_in_range(&dev_priv->mm.stolen, node, size,
                                          alignment, start, end,
                                          DRM_MM_SEARCH_DEFAULT);
        mutex_unlock(&dev_priv->mm.stolen_lock);

        return ret;
}

int i915_gem_stolen_insert_node(struct drm_i915_private *dev_priv,
                                struct drm_mm_node *node, u64 size,
                                unsigned alignment)
{
        struct i915_ggtt *ggtt = &dev_priv->ggtt;

        return i915_gem_stolen_insert_node_in_range(dev_priv, node, size,
                                                    alignment, 0,
                                                    ggtt->stolen_usable_size);
}

void i915_gem_stolen_remove_node(struct drm_i915_private *dev_priv,
                                 struct drm_mm_node *node)
{
        mutex_lock(&dev_priv->mm.stolen_lock);
        drm_mm_remove_node(node);
        mutex_unlock(&dev_priv->mm.stolen_lock);
}

static unsigned long i915_stolen_to_physical(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct i915_ggtt *ggtt = &dev_priv->ggtt;
        struct resource *r;
        u32 base;

        /* Almost universally we can find the Graphics Base of Stolen Memory
         * at register BSM (0x5c) in the igfx configuration space. On a few
         * (desktop) machines this is also mirrored in the bridge device at
         * different locations, or in the MCHBAR.
         *
         * On 865 we just check the TOUD register.
         *
         * On 830/845/85x the stolen memory base isn't available in any
         * register. We need to calculate it as TOM-TSEG_SIZE-stolen_size.
         *
         */
        base = 0;
        if (INTEL_INFO(dev)->gen >= 3) {
                u32 bsm;

                pci_read_config_dword(dev->pdev, BSM, &bsm);

                base = bsm & BSM_MASK;
        } else if (IS_I865G(dev)) {
                u16 toud = 0;

                /*
                 * FIXME is the graphics stolen memory region
                 * always at TOUD? Ie. is it always the last
                 * one to be allocated by the BIOS?
                 */
                pci_bus_read_config_word(dev->pdev->bus, PCI_DEVFN(0, 0),
                                         I865_TOUD, &toud);

                base = toud << 16;
        } else if (IS_I85X(dev)) {
                u32 tseg_size = 0;
                u32 tom;
                u8 tmp;

                pci_bus_read_config_byte(dev->pdev->bus, PCI_DEVFN(0, 0),
                                         I85X_ESMRAMC, &tmp);

                if (tmp & TSEG_ENABLE)
                        tseg_size = MB(1);

                pci_bus_read_config_byte(dev->pdev->bus, PCI_DEVFN(0, 1),
                                         I85X_DRB3, &tmp);
                tom = tmp * MB(32);

                base = tom - tseg_size - ggtt->stolen_size;
        } else if (IS_845G(dev)) {
                u32 tseg_size = 0;
                u32 tom;
                u8 tmp;

                pci_bus_read_config_byte(dev->pdev->bus, PCI_DEVFN(0, 0),
                                         I845_ESMRAMC, &tmp);

                if (tmp & TSEG_ENABLE) {
                        switch (tmp & I845_TSEG_SIZE_MASK) {
                        case I845_TSEG_SIZE_512K:
                                tseg_size = KB(512);
                                break;
                        case I845_TSEG_SIZE_1M:
                                tseg_size = MB(1);
                                break;
                        }
                }

                pci_bus_read_config_byte(dev->pdev->bus, PCI_DEVFN(0, 0),
                                         I830_DRB3, &tmp);
                tom = tmp * MB(32);

                base = tom - tseg_size - ggtt->stolen_size;
        } else if (IS_I830(dev)) {
                u32 tseg_size = 0;
                u32 tom;
                u8 tmp;

                pci_bus_read_config_byte(dev->pdev->bus, PCI_DEVFN(0, 0),
                                         I830_ESMRAMC, &tmp);

                if (tmp & TSEG_ENABLE) {
                        if (tmp & I830_TSEG_SIZE_1M)
                                tseg_size = MB(1);
                        else
                                tseg_size = KB(512);
                }

                pci_bus_read_config_byte(dev->pdev->bus, PCI_DEVFN(0, 0),
                                         I830_DRB3, &tmp);
                tom = tmp * MB(32);

                base = tom - tseg_size - ggtt->stolen_size;
        }

        if (base == 0)
                return 0;

        /* make sure we don't clobber the GTT if it's within stolen memory */
        if (INTEL_INFO(dev)->gen <= 4 && !IS_G33(dev) && !IS_G4X(dev)) {
                struct {
                        u32 start, end;
                } stolen[2] = {
                        { .start = base, .end = base + ggtt->stolen_size, },
                        { .start = base, .end = base + ggtt->stolen_size, },
                };
                u64 ggtt_start, ggtt_end;

                ggtt_start = I915_READ(PGTBL_CTL);
                if (IS_GEN4(dev))
                        ggtt_start = (ggtt_start & PGTBL_ADDRESS_LO_MASK) |
                                     (ggtt_start & PGTBL_ADDRESS_HI_MASK) << 28;
                else
                        ggtt_start &= PGTBL_ADDRESS_LO_MASK;
                ggtt_end = ggtt_start + ggtt_total_entries(ggtt) * 4;

                if (ggtt_start >= stolen[0].start && ggtt_start < stolen[0].end)
                        stolen[0].end = ggtt_start;
                if (ggtt_end > stolen[1].start && ggtt_end <= stolen[1].end)
                        stolen[1].start = ggtt_end;

                /* pick the larger of the two chunks */
                if (stolen[0].end - stolen[0].start >
                    stolen[1].end - stolen[1].start) {
                        base = stolen[0].start;
                        ggtt->stolen_size = stolen[0].end - stolen[0].start;
                } else {
                        base = stolen[1].start;
                        ggtt->stolen_size = stolen[1].end - stolen[1].start;
                }

                if (stolen[0].start != stolen[1].start ||
                    stolen[0].end != stolen[1].end) {
                        DRM_DEBUG_KMS("GTT within stolen memory at 0x%llx-0x%llx\n",
                                      (unsigned long long)ggtt_start,
                                      (unsigned long long)ggtt_end - 1);
                        DRM_DEBUG_KMS("Stolen memory adjusted to 0x%x-0x%x\n",
                                      base, base + (u32)ggtt->stolen_size - 1);
                }
        }


        /* Verify that nothing else uses this physical address. Stolen
         * memory should be reserved by the BIOS and hidden from the
         * kernel. So if the region is already marked as busy, something
         * is seriously wrong.
         */
        r = devm_request_mem_region(dev->dev, base, ggtt->stolen_size,
                                    "Graphics Stolen Memory");
        if (r == NULL) {
                /*
                 * One more attempt but this time requesting region from
                 * base + 1, as we have seen that this resolves the region
                 * conflict with the PCI Bus.
                 * This is a BIOS w/a: Some BIOS wrap stolen in the root
                 * PCI bus, but have an off-by-one error. Hence retry the
                 * reservation starting from 1 instead of 0.
                 */
                r = devm_request_mem_region(dev->dev, base + 1,
                                            ggtt->stolen_size - 1,
                                            "Graphics Stolen Memory");
                /*
                 * GEN3 firmware likes to smash pci bridges into the stolen
                 * range. Apparently this works.
                 */
                if (r == NULL && !IS_GEN3(dev)) {
                        DRM_ERROR("conflict detected with stolen region: [0x%08x - 0x%08x]\n",
                                  base, base + (uint32_t)ggtt->stolen_size);
                        base = 0;
                }
        }

        return base;
}

void i915_gem_cleanup_stolen(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = dev->dev_private;

        if (!drm_mm_initialized(&dev_priv->mm.stolen))
                return;

        drm_mm_takedown(&dev_priv->mm.stolen);
}

static void g4x_get_stolen_reserved(struct drm_i915_private *dev_priv,
                                    unsigned long *base, unsigned long *size)
{
        struct i915_ggtt *ggtt = &dev_priv->ggtt;
        uint32_t reg_val = I915_READ(IS_GM45(dev_priv) ?
                                     CTG_STOLEN_RESERVED :
                                     ELK_STOLEN_RESERVED);
        unsigned long stolen_top = dev_priv->mm.stolen_base +
                                   ggtt->stolen_size;

        *base = (reg_val & G4X_STOLEN_RESERVED_ADDR2_MASK) << 16;

        WARN_ON((reg_val & G4X_STOLEN_RESERVED_ADDR1_MASK) < *base);

        /* On these platforms, the register doesn't have a size field, so the
         * size is the distance between the base and the top of the stolen
         * memory. We also have the genuine case where base is zero and there's
         * nothing reserved. */
        if (*base == 0)
                *size = 0;
        else
                *size = stolen_top - *base;
}

static void gen6_get_stolen_reserved(struct drm_i915_private *dev_priv,
                                     unsigned long *base, unsigned long *size)
{
        uint32_t reg_val = I915_READ(GEN6_STOLEN_RESERVED);

        *base = reg_val & GEN6_STOLEN_RESERVED_ADDR_MASK;

        switch (reg_val & GEN6_STOLEN_RESERVED_SIZE_MASK) {
        case GEN6_STOLEN_RESERVED_1M:
                *size = 1024 * 1024;
                break;
        case GEN6_STOLEN_RESERVED_512K:
                *size = 512 * 1024;
                break;
        case GEN6_STOLEN_RESERVED_256K:
                *size = 256 * 1024;
                break;
        case GEN6_STOLEN_RESERVED_128K:
                *size = 128 * 1024;
                break;
        default:
                *size = 1024 * 1024;
                MISSING_CASE(reg_val & GEN6_STOLEN_RESERVED_SIZE_MASK);
        }
}

static void gen7_get_stolen_reserved(struct drm_i915_private *dev_priv,
                                     unsigned long *base, unsigned long *size)
{
        uint32_t reg_val = I915_READ(GEN6_STOLEN_RESERVED);

        *base = reg_val & GEN7_STOLEN_RESERVED_ADDR_MASK;

        switch (reg_val & GEN7_STOLEN_RESERVED_SIZE_MASK) {
        case GEN7_STOLEN_RESERVED_1M:
                *size = 1024 * 1024;
                break;
        case GEN7_STOLEN_RESERVED_256K:
                *size = 256 * 1024;
                break;
        default:
                *size = 1024 * 1024;
                MISSING_CASE(reg_val & GEN7_STOLEN_RESERVED_SIZE_MASK);
        }
}

static void gen8_get_stolen_reserved(struct drm_i915_private *dev_priv,
                                     unsigned long *base, unsigned long *size)
{
        uint32_t reg_val = I915_READ(GEN6_STOLEN_RESERVED);

        *base = reg_val & GEN6_STOLEN_RESERVED_ADDR_MASK;

        switch (reg_val & GEN8_STOLEN_RESERVED_SIZE_MASK) {
        case GEN8_STOLEN_RESERVED_1M:
                *size = 1024 * 1024;
                break;
        case GEN8_STOLEN_RESERVED_2M:
                *size = 2 * 1024 * 1024;
                break;
        case GEN8_STOLEN_RESERVED_4M:
                *size = 4 * 1024 * 1024;
                break;
        case GEN8_STOLEN_RESERVED_8M:
                *size = 8 * 1024 * 1024;
                break;
        default:
                *size = 8 * 1024 * 1024;
                MISSING_CASE(reg_val & GEN8_STOLEN_RESERVED_SIZE_MASK);
        }
}

static void bdw_get_stolen_reserved(struct drm_i915_private *dev_priv,
                                    unsigned long *base, unsigned long *size)
{
        struct i915_ggtt *ggtt = &dev_priv->ggtt;
        uint32_t reg_val = I915_READ(GEN6_STOLEN_RESERVED);
        unsigned long stolen_top;

        stolen_top = dev_priv->mm.stolen_base + ggtt->stolen_size;

        *base = reg_val & GEN6_STOLEN_RESERVED_ADDR_MASK;

        /* On these platforms, the register doesn't have a size field, so the
         * size is the distance between the base and the top of the stolen
         * memory. We also have the genuine case where base is zero and there's
         * nothing reserved. */
        if (*base == 0)
                *size = 0;
        else
                *size = stolen_top - *base;
}

int i915_gem_init_stolen(struct drm_device *dev)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct i915_ggtt *ggtt = &dev_priv->ggtt;
        unsigned long reserved_total, reserved_base = 0, reserved_size;
        unsigned long stolen_top;

        mutex_init(&dev_priv->mm.stolen_lock);

#ifdef CONFIG_INTEL_IOMMU
        if (intel_iommu_gfx_mapped && INTEL_INFO(dev)->gen < 8) {
                DRM_INFO("DMAR active, disabling use of stolen memory\n");
                return 0;
        }
#endif

        if (ggtt->stolen_size == 0)
                return 0;

        dev_priv->mm.stolen_base = i915_stolen_to_physical(dev);
        if (dev_priv->mm.stolen_base == 0)
                return 0;

        stolen_top = dev_priv->mm.stolen_base + ggtt->stolen_size;

        switch (INTEL_INFO(dev_priv)->gen) {
        case 2:
        case 3:
                break;
        case 4:
                if (IS_G4X(dev))
                        g4x_get_stolen_reserved(dev_priv, &reserved_base,
                                                &reserved_size);
                break;
        case 5:
                /* Assume the gen6 maximum for the older platforms. */
                reserved_size = 1024 * 1024;
                reserved_base = stolen_top - reserved_size;
                break;
        case 6:
                gen6_get_stolen_reserved(dev_priv, &reserved_base,
                                         &reserved_size);
                break;
        case 7:
                gen7_get_stolen_reserved(dev_priv, &reserved_base,
                                         &reserved_size);
                break;
        default:
                if (IS_BROADWELL(dev_priv) ||
                    IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev))
                        bdw_get_stolen_reserved(dev_priv, &reserved_base,
                                                &reserved_size);
                else
                        gen8_get_stolen_reserved(dev_priv, &reserved_base,
                                                 &reserved_size);
                break;
        }

        /* It is possible for the reserved base to be zero, but the register
         * field for size doesn't have a zero option. */
        if (reserved_base == 0) {
                reserved_size = 0;
                reserved_base = stolen_top;
        }

        if (reserved_base < dev_priv->mm.stolen_base ||
            reserved_base + reserved_size > stolen_top) {
                DRM_DEBUG_KMS("Stolen reserved area [0x%08lx - 0x%08lx] outside stolen memory [0x%08lx - 0x%08lx]\n",
                              reserved_base, reserved_base + reserved_size,
                              dev_priv->mm.stolen_base, stolen_top);
                return 0;
        }

        ggtt->stolen_reserved_base = reserved_base;
        ggtt->stolen_reserved_size = reserved_size;

        /* It is possible for the reserved area to end before the end of stolen
         * memory, so just consider the start. */
        reserved_total = stolen_top - reserved_base;

        DRM_DEBUG_KMS("Memory reserved for graphics device: %zuK, usable: %luK\n",
                      ggtt->stolen_size >> 10,
                      (ggtt->stolen_size - reserved_total) >> 10);

        ggtt->stolen_usable_size = ggtt->stolen_size - reserved_total;

        /*
         * Basic memrange allocator for stolen space.
         *
         * TODO: Notice that some platforms require us to not use the first page
         * of the stolen memory but their BIOSes may still put the framebuffer
         * on the first page. So we don't reserve this page for now because of
         * that. Our current solution is to just prevent new nodes from being
         * inserted on the first page - see the check we have at
         * i915_gem_stolen_insert_node_in_range(). We may want to fix the fbcon
         * problem later.
         */
        drm_mm_init(&dev_priv->mm.stolen, 0, ggtt->stolen_usable_size);

        return 0;
}

static struct sg_table *
i915_pages_create_for_stolen(struct drm_device *dev,
                             u32 offset, u32 size)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct i915_ggtt *ggtt = &dev_priv->ggtt;
        struct sg_table *st;
        struct scatterlist *sg;

        DRM_DEBUG_DRIVER("offset=0x%x, size=%d\n", offset, size);
        BUG_ON(offset > ggtt->stolen_size - size);

        /* We hide that we have no struct page backing our stolen object
         * by wrapping the contiguous physical allocation with a fake
         * dma mapping in a single scatterlist.
         */

        st = kmalloc(sizeof(*st), GFP_KERNEL);
        if (st == NULL)
                return NULL;

        if (sg_alloc_table(st, 1, GFP_KERNEL)) {
                kfree(st);
                return NULL;
        }

        sg = st->sgl;
        sg->offset = 0;
        sg->length = size;

        sg_dma_address(sg) = (dma_addr_t)dev_priv->mm.stolen_base + offset;
        sg_dma_len(sg) = size;

        return st;
}

static int i915_gem_object_get_pages_stolen(struct drm_i915_gem_object *obj)
{
        BUG();
        return -EINVAL;
}

static void i915_gem_object_put_pages_stolen(struct drm_i915_gem_object *obj)
{
        /* Should only be called during free */
        sg_free_table(obj->pages);
        kfree(obj->pages);
}


static void
i915_gem_object_release_stolen(struct drm_i915_gem_object *obj)
{
        struct drm_i915_private *dev_priv = obj->base.dev->dev_private;

        if (obj->stolen) {
                i915_gem_stolen_remove_node(dev_priv, obj->stolen);
                kfree(obj->stolen);
                obj->stolen = NULL;
        }
}
static const struct drm_i915_gem_object_ops i915_gem_object_stolen_ops = {
        .get_pages = i915_gem_object_get_pages_stolen,
        .put_pages = i915_gem_object_put_pages_stolen,
        .release = i915_gem_object_release_stolen,
};

static struct drm_i915_gem_object *
_i915_gem_object_create_stolen(struct drm_device *dev,
                               struct drm_mm_node *stolen)
{
        struct drm_i915_gem_object *obj;

        obj = i915_gem_object_alloc(dev);
        if (obj == NULL)
                return NULL;

        drm_gem_private_object_init(dev, &obj->base, stolen->size);
        i915_gem_object_init(obj, &i915_gem_object_stolen_ops);

        obj->pages = i915_pages_create_for_stolen(dev,
                                                  stolen->start, stolen->size);
        if (obj->pages == NULL)
                goto cleanup;

        obj->get_page.sg = obj->pages->sgl;
        obj->get_page.last = 0;

        i915_gem_object_pin_pages(obj);
        obj->stolen = stolen;

        obj->base.read_domains = I915_GEM_DOMAIN_CPU | I915_GEM_DOMAIN_GTT;
        obj->cache_level = HAS_LLC(dev) ? I915_CACHE_LLC : I915_CACHE_NONE;

        return obj;

cleanup:
        i915_gem_object_free(obj);
        return NULL;
}

struct drm_i915_gem_object *
i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
{
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct drm_i915_gem_object *obj;
        struct drm_mm_node *stolen;
        int ret;

        if (!drm_mm_initialized(&dev_priv->mm.stolen))
                return NULL;

        DRM_DEBUG_KMS("creating stolen object: size=%x\n", size);
        if (size == 0)
                return NULL;

        stolen = kzalloc(sizeof(*stolen), GFP_KERNEL);
        if (!stolen)
                return NULL;

        ret = i915_gem_stolen_insert_node(dev_priv, stolen, size, 4096);
        if (ret) {
                kfree(stolen);
                return NULL;
        }

        obj = _i915_gem_object_create_stolen(dev, stolen);
        if (obj)
                return obj;

        i915_gem_stolen_remove_node(dev_priv, stolen);
        kfree(stolen);
        return NULL;
}

struct drm_i915_gem_object *
i915_gem_object_create_stolen_for_preallocated(struct drm_device *dev,
                                               u32 stolen_offset,
                                               u32 gtt_offset,
                                               u32 size)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct i915_ggtt *ggtt = &dev_priv->ggtt;
        struct drm_i915_gem_object *obj;
        struct drm_mm_node *stolen;
        struct i915_vma *vma;
        int ret;

        if (!drm_mm_initialized(&dev_priv->mm.stolen))
                return NULL;

        lockdep_assert_held(&dev->struct_mutex);

        DRM_DEBUG_KMS("creating preallocated stolen object: stolen_offset=%x, gtt_offset=%x, size=%x\n",
                        stolen_offset, gtt_offset, size);

        /* KISS and expect everything to be page-aligned */
        if (WARN_ON(size == 0) || WARN_ON(size & 4095) ||
            WARN_ON(stolen_offset & 4095))
                return NULL;

        stolen = kzalloc(sizeof(*stolen), GFP_KERNEL);
        if (!stolen)
                return NULL;

        stolen->start = stolen_offset;
        stolen->size = size;
        mutex_lock(&dev_priv->mm.stolen_lock);
        ret = drm_mm_reserve_node(&dev_priv->mm.stolen, stolen);
        mutex_unlock(&dev_priv->mm.stolen_lock);
        if (ret) {
                DRM_DEBUG_KMS("failed to allocate stolen space\n");
                kfree(stolen);
                return NULL;
        }

        obj = _i915_gem_object_create_stolen(dev, stolen);
        if (obj == NULL) {
                DRM_DEBUG_KMS("failed to allocate stolen object\n");
                i915_gem_stolen_remove_node(dev_priv, stolen);
                kfree(stolen);
                return NULL;
        }

        /* Some objects just need physical mem from stolen space */
        if (gtt_offset == I915_GTT_OFFSET_NONE)
                return obj;

        vma = i915_gem_obj_lookup_or_create_vma(obj, &ggtt->base);
        if (IS_ERR(vma)) {
                ret = PTR_ERR(vma);
                goto err;
        }

        /* To simplify the initialisation sequence between KMS and GTT,
         * we allow construction of the stolen object prior to
         * setting up the GTT space. The actual reservation will occur
         * later.
         */
        vma->node.start = gtt_offset;
        vma->node.size = size;
        if (drm_mm_initialized(&ggtt->base.mm)) {
                ret = drm_mm_reserve_node(&ggtt->base.mm, &vma->node);
                if (ret) {
                        DRM_DEBUG_KMS("failed to allocate stolen GTT space\n");
                        goto err;
                }

                vma->bound |= GLOBAL_BIND;
                __i915_vma_set_map_and_fenceable(vma);
                list_add_tail(&vma->vm_link, &ggtt->base.inactive_list);
        }

        list_add_tail(&obj->global_list, &dev_priv->mm.bound_list);
        i915_gem_object_pin_pages(obj);

        return obj;

err:
        drm_gem_object_unreference(&obj->base);
        return NULL;
}