// SPDX-License-Identifier: MIT
/*
 * Copyright © 2021 Intel Corporation
 */

#include <drm/ttm/ttm_bo_driver.h>
#include <drm/ttm/ttm_placement.h>

#include "i915_drv.h"
#include "intel_memory_region.h"
#include "intel_region_ttm.h"

#include "gem/i915_gem_object.h"
#include "gem/i915_gem_region.h"
#include "gem/i915_gem_ttm.h"
#include "gem/i915_gem_mman.h"

#include "gt/intel_migrate.h"
#include "gt/intel_engine_pm.h"

#define I915_PL_LMEM0 TTM_PL_PRIV
#define I915_PL_SYSTEM TTM_PL_SYSTEM
#define I915_PL_STOLEN TTM_PL_VRAM
#define I915_PL_GGTT TTM_PL_TT

#define I915_TTM_PRIO_PURGE     0
#define I915_TTM_PRIO_NO_PAGES  1
#define I915_TTM_PRIO_HAS_PAGES 2

/*
 * Size of struct ttm_place vector in on-stack struct ttm_placement allocs
 */
#define I915_TTM_MAX_PLACEMENTS INTEL_REGION_UNKNOWN

/**
 * struct i915_ttm_tt - TTM page vector with additional private information
 * @ttm: The base TTM page vector.
 * @dev: The struct device used for dma mapping and unmapping.
 * @cached_st: The cached scatter-gather table.
 *
 * Note that DMA may be going on right up to the point where the page-
 * vector is unpopulated in delayed destroy. Hence keep the
 * scatter-gather table mapped and cached up to that point. This is
 * different from the cached gem object io scatter-gather table which
 * doesn't have an associated dma mapping.
 */
struct i915_ttm_tt {
        struct ttm_tt ttm;
        struct device *dev;
        struct sg_table *cached_st;
};

static const struct ttm_place sys_placement_flags = {
        .fpfn = 0,
        .lpfn = 0,
        .mem_type = I915_PL_SYSTEM,
        .flags = 0,
};

static struct ttm_placement i915_sys_placement = {
        .num_placement = 1,
        .placement = &sys_placement_flags,
        .num_busy_placement = 1,
        .busy_placement = &sys_placement_flags,
};

static int i915_ttm_err_to_gem(int err)
{
        /* Fastpath */
        if (likely(!err))
                return 0;

        switch (err) {
        case -EBUSY:
                /*
                 * TTM likes to convert -EDEADLK to -EBUSY, and wants us to
                 * restart the operation, since we don't record the contending
                 * lock. We use -EAGAIN to restart.
                 */
                return -EAGAIN;
        case -ENOSPC:
                /*
                 * Memory type / region is full, and we can't evict.
                 * Except possibly system, that returns -ENOMEM;
                 */
                return -ENXIO;
        default:
                break;
        }

        return err;
}

static bool gpu_binds_iomem(struct ttm_resource *mem)
{
        return mem->mem_type != TTM_PL_SYSTEM;
}

static bool cpu_maps_iomem(struct ttm_resource *mem)
{
        /* Once / if we support GGTT, this is also false for cached ttm_tts */
        return mem->mem_type != TTM_PL_SYSTEM;
}

static enum i915_cache_level
i915_ttm_cache_level(struct drm_i915_private *i915, struct ttm_resource *res,
                     struct ttm_tt *ttm)
{
        return ((HAS_LLC(i915) || HAS_SNOOP(i915)) && !gpu_binds_iomem(res) &&
                ttm->caching == ttm_cached) ? I915_CACHE_LLC :
                I915_CACHE_NONE;
}

static void i915_ttm_adjust_lru(struct drm_i915_gem_object *obj);

static enum ttm_caching
i915_ttm_select_tt_caching(const struct drm_i915_gem_object *obj)
{
        /*
         * Objects only allowed in system get cached cpu-mappings.
         * Other objects get WC mapping for now. Even if in system.
         */
        if (obj->mm.region->type == INTEL_MEMORY_SYSTEM &&
            obj->mm.n_placements <= 1)
                return ttm_cached;

        return ttm_write_combined;
}

static void
i915_ttm_place_from_region(const struct intel_memory_region *mr,
                           struct ttm_place *place,
                           unsigned int flags)
{
        memset(place, 0, sizeof(*place));
        place->mem_type = intel_region_to_ttm_type(mr);

        if (flags & I915_BO_ALLOC_CONTIGUOUS)
                place->flags = TTM_PL_FLAG_CONTIGUOUS;
}

static void
i915_ttm_placement_from_obj(const struct drm_i915_gem_object *obj,
                            struct ttm_place *requested,
                            struct ttm_place *busy,
                            struct ttm_placement *placement)
{
        unsigned int num_allowed = obj->mm.n_placements;
        unsigned int flags = obj->flags;
        unsigned int i;

        placement->num_placement = 1;
        i915_ttm_place_from_region(num_allowed ? obj->mm.placements[0] :
                                   obj->mm.region, requested, flags);

        /* Cache this on object? */
        placement->num_busy_placement = num_allowed;
        for (i = 0; i < placement->num_busy_placement; ++i)
                i915_ttm_place_from_region(obj->mm.placements[i], busy + i, flags);

        if (num_allowed == 0) {
                *busy = *requested;
                placement->num_busy_placement = 1;
        }

        placement->placement = requested;
        placement->busy_placement = busy;
}

static struct ttm_tt *i915_ttm_tt_create(struct ttm_buffer_object *bo,
                                         uint32_t page_flags)
{
        struct ttm_resource_manager *man =
                ttm_manager_type(bo->bdev, bo->resource->mem_type);
        struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
        struct i915_ttm_tt *i915_tt;
        int ret;

        i915_tt = kzalloc(sizeof(*i915_tt), GFP_KERNEL);
        if (!i915_tt)
                return NULL;

        if (obj->flags & I915_BO_ALLOC_CPU_CLEAR &&
            man->use_tt)
                page_flags |= TTM_PAGE_FLAG_ZERO_ALLOC;

        ret = ttm_tt_init(&i915_tt->ttm, bo, page_flags,
                          i915_ttm_select_tt_caching(obj));
        if (ret) {
                kfree(i915_tt);
                return NULL;
        }

        i915_tt->dev = obj->base.dev->dev;

        return &i915_tt->ttm;
}

static void i915_ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
{
        struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);

        if (i915_tt->cached_st) {
                dma_unmap_sgtable(i915_tt->dev, i915_tt->cached_st,
                                  DMA_BIDIRECTIONAL, 0);
                sg_free_table(i915_tt->cached_st);
                kfree(i915_tt->cached_st);
                i915_tt->cached_st = NULL;
        }
        ttm_pool_free(&bdev->pool, ttm);
}

static void i915_ttm_tt_destroy(struct ttm_device *bdev, struct ttm_tt *ttm)
{
        struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);

        ttm_tt_destroy_common(bdev, ttm);
        ttm_tt_fini(ttm);
        kfree(i915_tt);
}

static bool i915_ttm_eviction_valuable(struct ttm_buffer_object *bo,
                                       const struct ttm_place *place)
{
        struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);

        /* Will do for now. Our pinned objects are still on TTM's LRU lists */
        return i915_gem_object_evictable(obj);
}

static void i915_ttm_evict_flags(struct ttm_buffer_object *bo,
                                 struct ttm_placement *placement)
{
        *placement = i915_sys_placement;
}

static int i915_ttm_move_notify(struct ttm_buffer_object *bo)
{
        struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
        int ret;

        ret = i915_gem_object_unbind(obj, I915_GEM_OBJECT_UNBIND_ACTIVE);
        if (ret)
                return ret;

        ret = __i915_gem_object_put_pages(obj);
        if (ret)
                return ret;

        return 0;
}

static void i915_ttm_free_cached_io_st(struct drm_i915_gem_object *obj)
{
        struct radix_tree_iter iter;
        void __rcu **slot;

        if (!obj->ttm.cached_io_st)
                return;

        rcu_read_lock();
        radix_tree_for_each_slot(slot, &obj->ttm.get_io_page.radix, &iter, 0)
                radix_tree_delete(&obj->ttm.get_io_page.radix, iter.index);
        rcu_read_unlock();

        sg_free_table(obj->ttm.cached_io_st);
        kfree(obj->ttm.cached_io_st);
        obj->ttm.cached_io_st = NULL;
}

static void
i915_ttm_adjust_domains_after_move(struct drm_i915_gem_object *obj)
{
        struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);

        if (cpu_maps_iomem(bo->resource) || bo->ttm->caching != ttm_cached) {
                obj->write_domain = I915_GEM_DOMAIN_WC;
                obj->read_domains = I915_GEM_DOMAIN_WC;
        } else {
                obj->write_domain = I915_GEM_DOMAIN_CPU;
                obj->read_domains = I915_GEM_DOMAIN_CPU;
        }
}

static void i915_ttm_adjust_gem_after_move(struct drm_i915_gem_object *obj)
{
        struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
        unsigned int cache_level;
        unsigned int i;

        /*
         * If object was moved to an allowable region, update the object
         * region to consider it migrated. Note that if it's currently not
         * in an allowable region, it's evicted and we don't update the
         * object region.
         */
        if (intel_region_to_ttm_type(obj->mm.region) != bo->resource->mem_type) {
                for (i = 0; i < obj->mm.n_placements; ++i) {
                        struct intel_memory_region *mr = obj->mm.placements[i];

                        if (intel_region_to_ttm_type(mr) == bo->resource->mem_type &&
                            mr != obj->mm.region) {
                                i915_gem_object_release_memory_region(obj);
                                i915_gem_object_init_memory_region(obj, mr);
                                break;
                        }
                }
        }

        obj->mem_flags &= ~(I915_BO_FLAG_STRUCT_PAGE | I915_BO_FLAG_IOMEM);

        obj->mem_flags |= cpu_maps_iomem(bo->resource) ? I915_BO_FLAG_IOMEM :
                I915_BO_FLAG_STRUCT_PAGE;

        cache_level = i915_ttm_cache_level(to_i915(bo->base.dev), bo->resource,
                                           bo->ttm);
        i915_gem_object_set_cache_coherency(obj, cache_level);
}

static void i915_ttm_purge(struct drm_i915_gem_object *obj)
{
        struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
        struct ttm_operation_ctx ctx = {
                .interruptible = true,
                .no_wait_gpu = false,
        };
        struct ttm_placement place = {};
        int ret;

        if (obj->mm.madv == __I915_MADV_PURGED)
                return;

        /* TTM's purge interface. Note that we might be reentering. */
        ret = ttm_bo_validate(bo, &place, &ctx);
        if (!ret) {
                obj->write_domain = 0;
                obj->read_domains = 0;
                i915_ttm_adjust_gem_after_move(obj);
                i915_ttm_free_cached_io_st(obj);
                obj->mm.madv = __I915_MADV_PURGED;
        }
}

static void i915_ttm_swap_notify(struct ttm_buffer_object *bo)
{
        struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
        int ret = i915_ttm_move_notify(bo);

        GEM_WARN_ON(ret);
        GEM_WARN_ON(obj->ttm.cached_io_st);
        if (!ret && obj->mm.madv != I915_MADV_WILLNEED)
                i915_ttm_purge(obj);
}

static void i915_ttm_delete_mem_notify(struct ttm_buffer_object *bo)
{
        struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);

        if (likely(obj))
                i915_ttm_free_cached_io_st(obj);
}

static struct intel_memory_region *
i915_ttm_region(struct ttm_device *bdev, int ttm_mem_type)
{
        struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);

        /* There's some room for optimization here... */
        GEM_BUG_ON(ttm_mem_type != I915_PL_SYSTEM &&
                   ttm_mem_type < I915_PL_LMEM0);
        if (ttm_mem_type == I915_PL_SYSTEM)
                return intel_memory_region_lookup(i915, INTEL_MEMORY_SYSTEM,
                                                  0);

        return intel_memory_region_lookup(i915, INTEL_MEMORY_LOCAL,
                                          ttm_mem_type - I915_PL_LMEM0);
}

static struct sg_table *i915_ttm_tt_get_st(struct ttm_tt *ttm)
{
        struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
        struct sg_table *st;
        int ret;

        if (i915_tt->cached_st)
                return i915_tt->cached_st;

        st = kzalloc(sizeof(*st), GFP_KERNEL);
        if (!st)
                return ERR_PTR(-ENOMEM);

        ret = sg_alloc_table_from_pages_segment(st,
                        ttm->pages, ttm->num_pages,
                        0, (unsigned long)ttm->num_pages << PAGE_SHIFT,
                        i915_sg_segment_size(), GFP_KERNEL);
        if (ret) {
                kfree(st);
                return ERR_PTR(ret);
        }

        ret = dma_map_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL, 0);
        if (ret) {
                sg_free_table(st);
                kfree(st);
                return ERR_PTR(ret);
        }

        i915_tt->cached_st = st;
        return st;
}

static struct sg_table *
i915_ttm_resource_get_st(struct drm_i915_gem_object *obj,
                         struct ttm_resource *res)
{
        struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);

        if (!gpu_binds_iomem(res))
                return i915_ttm_tt_get_st(bo->ttm);

        /*
         * If CPU mapping differs, we need to add the ttm_tt pages to
         * the resulting st. Might make sense for GGTT.
         */
        GEM_WARN_ON(!cpu_maps_iomem(res));
        return intel_region_ttm_resource_to_st(obj->mm.region, res);
}

static int i915_ttm_accel_move(struct ttm_buffer_object *bo,
                               struct ttm_resource *dst_mem,
                               struct sg_table *dst_st)
{
        struct drm_i915_private *i915 = container_of(bo->bdev, typeof(*i915),
                                                     bdev);
        struct ttm_resource_manager *src_man =
                ttm_manager_type(bo->bdev, bo->resource->mem_type);
        struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
        struct sg_table *src_st;
        struct i915_request *rq;
        struct ttm_tt *ttm = bo->ttm;
        enum i915_cache_level src_level, dst_level;
        int ret;

        if (!i915->gt.migrate.context)
                return -EINVAL;

        dst_level = i915_ttm_cache_level(i915, dst_mem, ttm);
        if (!ttm || !ttm_tt_is_populated(ttm)) {
                if (bo->type == ttm_bo_type_kernel)
                        return -EINVAL;

                if (ttm && !(ttm->page_flags & TTM_PAGE_FLAG_ZERO_ALLOC))
                        return 0;

                intel_engine_pm_get(i915->gt.migrate.context->engine);
                ret = intel_context_migrate_clear(i915->gt.migrate.context, NULL,
                                                  dst_st->sgl, dst_level,
                                                  gpu_binds_iomem(dst_mem),
                                                  0, &rq);

                if (!ret && rq) {
                        i915_request_wait(rq, 0, MAX_SCHEDULE_TIMEOUT);
                        i915_request_put(rq);
                }
                intel_engine_pm_put(i915->gt.migrate.context->engine);
        } else {
                src_st = src_man->use_tt ? i915_ttm_tt_get_st(ttm) :
                        obj->ttm.cached_io_st;

                src_level = i915_ttm_cache_level(i915, bo->resource, ttm);
                intel_engine_pm_get(i915->gt.migrate.context->engine);
                ret = intel_context_migrate_copy(i915->gt.migrate.context,
                                                 NULL, src_st->sgl, src_level,
                                                 gpu_binds_iomem(bo->resource),
                                                 dst_st->sgl, dst_level,
                                                 gpu_binds_iomem(dst_mem),
                                                 &rq);
                if (!ret && rq) {
                        i915_request_wait(rq, 0, MAX_SCHEDULE_TIMEOUT);
                        i915_request_put(rq);
                }
                intel_engine_pm_put(i915->gt.migrate.context->engine);
        }

        return ret;
}

static int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,
                         struct ttm_operation_ctx *ctx,
                         struct ttm_resource *dst_mem,
                         struct ttm_place *hop)
{
        struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
        struct ttm_resource_manager *dst_man =
                ttm_manager_type(bo->bdev, dst_mem->mem_type);
        struct intel_memory_region *dst_reg, *src_reg;
        union {
                struct ttm_kmap_iter_tt tt;
                struct ttm_kmap_iter_iomap io;
        } _dst_iter, _src_iter;
        struct ttm_kmap_iter *dst_iter, *src_iter;
        struct sg_table *dst_st;
        int ret;

        dst_reg = i915_ttm_region(bo->bdev, dst_mem->mem_type);
        src_reg = i915_ttm_region(bo->bdev, bo->resource->mem_type);
        GEM_BUG_ON(!dst_reg || !src_reg);

        /* Sync for now. We could do the actual copy async. */
        ret = ttm_bo_wait_ctx(bo, ctx);
        if (ret)
                return ret;

        ret = i915_ttm_move_notify(bo);
        if (ret)
                return ret;

        if (obj->mm.madv != I915_MADV_WILLNEED) {
                i915_ttm_purge(obj);
                ttm_resource_free(bo, &dst_mem);
                return 0;
        }

        /* Populate ttm with pages if needed. Typically system memory. */
        if (bo->ttm && (dst_man->use_tt ||
                        (bo->ttm->page_flags & TTM_PAGE_FLAG_SWAPPED))) {
                ret = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
                if (ret)
                        return ret;
        }

        dst_st = i915_ttm_resource_get_st(obj, dst_mem);
        if (IS_ERR(dst_st))
                return PTR_ERR(dst_st);

        ret = i915_ttm_accel_move(bo, dst_mem, dst_st);
        if (ret) {
                /* If we start mapping GGTT, we can no longer use man::use_tt here. */
                dst_iter = !cpu_maps_iomem(dst_mem) ?
                        ttm_kmap_iter_tt_init(&_dst_iter.tt, bo->ttm) :
                        ttm_kmap_iter_iomap_init(&_dst_iter.io, &dst_reg->iomap,
                                                 dst_st, dst_reg->region.start);

                src_iter = !cpu_maps_iomem(bo->resource) ?
                        ttm_kmap_iter_tt_init(&_src_iter.tt, bo->ttm) :
                        ttm_kmap_iter_iomap_init(&_src_iter.io, &src_reg->iomap,
                                                 obj->ttm.cached_io_st,
                                                 src_reg->region.start);

                ttm_move_memcpy(bo, dst_mem->num_pages, dst_iter, src_iter);
        }
        /* Below dst_mem becomes bo->resource. */
        ttm_bo_move_sync_cleanup(bo, dst_mem);
        i915_ttm_adjust_domains_after_move(obj);
        i915_ttm_free_cached_io_st(obj);

        if (gpu_binds_iomem(dst_mem) || cpu_maps_iomem(dst_mem)) {
                obj->ttm.cached_io_st = dst_st;
                obj->ttm.get_io_page.sg_pos = dst_st->sgl;
                obj->ttm.get_io_page.sg_idx = 0;
        }

        i915_ttm_adjust_gem_after_move(obj);
        return 0;
}

static int i915_ttm_io_mem_reserve(struct ttm_device *bdev, struct ttm_resource *mem)
{
        if (!cpu_maps_iomem(mem))
                return 0;

        mem->bus.caching = ttm_write_combined;
        mem->bus.is_iomem = true;

        return 0;
}

static unsigned long i915_ttm_io_mem_pfn(struct ttm_buffer_object *bo,
                                         unsigned long page_offset)
{
        struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
        unsigned long base = obj->mm.region->iomap.base - obj->mm.region->region.start;
        struct scatterlist *sg;
        unsigned int ofs;

        GEM_WARN_ON(bo->ttm);

        sg = __i915_gem_object_get_sg(obj, &obj->ttm.get_io_page, page_offset, &ofs, true);

        return ((base + sg_dma_address(sg)) >> PAGE_SHIFT) + ofs;
}

static struct ttm_device_funcs i915_ttm_bo_driver = {
        .ttm_tt_create = i915_ttm_tt_create,
        .ttm_tt_unpopulate = i915_ttm_tt_unpopulate,
        .ttm_tt_destroy = i915_ttm_tt_destroy,
        .eviction_valuable = i915_ttm_eviction_valuable,
        .evict_flags = i915_ttm_evict_flags,
        .move = i915_ttm_move,
        .swap_notify = i915_ttm_swap_notify,
        .delete_mem_notify = i915_ttm_delete_mem_notify,
        .io_mem_reserve = i915_ttm_io_mem_reserve,
        .io_mem_pfn = i915_ttm_io_mem_pfn,
};

/**
 * i915_ttm_driver - Return a pointer to the TTM device funcs
 *
 * Return: Pointer to statically allocated TTM device funcs.
 */
struct ttm_device_funcs *i915_ttm_driver(void)
{
        return &i915_ttm_bo_driver;
}

static int __i915_ttm_get_pages(struct drm_i915_gem_object *obj,
                                struct ttm_placement *placement)
{
        struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
        struct ttm_operation_ctx ctx = {
                .interruptible = true,
                .no_wait_gpu = false,
        };
        struct sg_table *st;
        int real_num_busy;
        int ret;

        /* First try only the requested placement. No eviction. */
        real_num_busy = fetch_and_zero(&placement->num_busy_placement);
        ret = ttm_bo_validate(bo, placement, &ctx);
        if (ret) {
                ret = i915_ttm_err_to_gem(ret);
                /*
                 * Anything that wants to restart the operation gets to
                 * do that.
                 */
                if (ret == -EDEADLK || ret == -EINTR || ret == -ERESTARTSYS ||
                    ret == -EAGAIN)
                        return ret;

                /*
                 * If the initial attempt fails, allow all accepted placements,
                 * evicting if necessary.
                 */
                placement->num_busy_placement = real_num_busy;
                ret = ttm_bo_validate(bo, placement, &ctx);
                if (ret)
                        return i915_ttm_err_to_gem(ret);
        }

        i915_ttm_adjust_lru(obj);
        if (bo->ttm && !ttm_tt_is_populated(bo->ttm)) {
                ret = ttm_tt_populate(bo->bdev, bo->ttm, &ctx);
                if (ret)
                        return ret;

                i915_ttm_adjust_domains_after_move(obj);
                i915_ttm_adjust_gem_after_move(obj);
        }

        if (!i915_gem_object_has_pages(obj)) {
                /* Object either has a page vector or is an iomem object */
                st = bo->ttm ? i915_ttm_tt_get_st(bo->ttm) : obj->ttm.cached_io_st;
                if (IS_ERR(st))
                        return PTR_ERR(st);

                __i915_gem_object_set_pages(obj, st, i915_sg_dma_sizes(st->sgl));
        }

        return ret;
}

static int i915_ttm_get_pages(struct drm_i915_gem_object *obj)
{
        struct ttm_place requested, busy[I915_TTM_MAX_PLACEMENTS];
        struct ttm_placement placement;

        GEM_BUG_ON(obj->mm.n_placements > I915_TTM_MAX_PLACEMENTS);

        /* Move to the requested placement. */
        i915_ttm_placement_from_obj(obj, &requested, busy, &placement);

        return __i915_ttm_get_pages(obj, &placement);
}

/**
 * DOC: Migration vs eviction
 *
 * GEM migration may not be the same as TTM migration / eviction. If
 * the TTM core decides to evict an object it may be evicted to a
 * TTM memory type that is not in the object's allowable GEM regions, or
 * in fact theoretically to a TTM memory type that doesn't correspond to
 * a GEM memory region. In that case the object's GEM region is not
 * updated, and the data is migrated back to the GEM region at
 * get_pages time. TTM may however set up CPU ptes to the object even
 * when it is evicted.
 * Gem forced migration using the i915_ttm_migrate() op, is allowed even
 * to regions that are not in the object's list of allowable placements.
 */
static int i915_ttm_migrate(struct drm_i915_gem_object *obj,
                            struct intel_memory_region *mr)
{
        struct ttm_place requested;
        struct ttm_placement placement;
        int ret;

        i915_ttm_place_from_region(mr, &requested, obj->flags);
        placement.num_placement = 1;
        placement.num_busy_placement = 1;
        placement.placement = &requested;
        placement.busy_placement = &requested;

        ret = __i915_ttm_get_pages(obj, &placement);
        if (ret)
                return ret;

        /*
         * Reinitialize the region bindings. This is primarily
         * required for objects where the new region is not in
         * its allowable placements.
         */
        if (obj->mm.region != mr) {
                i915_gem_object_release_memory_region(obj);
                i915_gem_object_init_memory_region(obj, mr);
        }

        return 0;
}

static void i915_ttm_put_pages(struct drm_i915_gem_object *obj,
                               struct sg_table *st)
{
        /*
         * We're currently not called from a shrinker, so put_pages()
         * typically means the object is about to destroyed, or called
         * from move_notify(). So just avoid doing much for now.
         * If the object is not destroyed next, The TTM eviction logic
         * and shrinkers will move it out if needed.
         */

        i915_ttm_adjust_lru(obj);
}

static void i915_ttm_adjust_lru(struct drm_i915_gem_object *obj)
{
        struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);

        /*
         * Don't manipulate the TTM LRUs while in TTM bo destruction.
         * We're called through i915_ttm_delete_mem_notify().
         */
        if (!kref_read(&bo->kref))
                return;

        /*
         * Put on the correct LRU list depending on the MADV status
         */
        spin_lock(&bo->bdev->lru_lock);
        if (obj->mm.madv != I915_MADV_WILLNEED) {
                bo->priority = I915_TTM_PRIO_PURGE;
        } else if (!i915_gem_object_has_pages(obj)) {
                if (bo->priority < I915_TTM_PRIO_HAS_PAGES)
                        bo->priority = I915_TTM_PRIO_HAS_PAGES;
        } else {
                if (bo->priority > I915_TTM_PRIO_NO_PAGES)
                        bo->priority = I915_TTM_PRIO_NO_PAGES;
        }

        ttm_bo_move_to_lru_tail(bo, bo->resource, NULL);
        spin_unlock(&bo->bdev->lru_lock);
}

/*
 * TTM-backed gem object destruction requires some clarification.
 * Basically we have two possibilities here. We can either rely on the
 * i915 delayed destruction and put the TTM object when the object
 * is idle. This would be detected by TTM which would bypass the
 * TTM delayed destroy handling. The other approach is to put the TTM
 * object early and rely on the TTM destroyed handling, and then free
 * the leftover parts of the GEM object once TTM's destroyed list handling is
 * complete. For now, we rely on the latter for two reasons:
 * a) TTM can evict an object even when it's on the delayed destroy list,
 * which in theory allows for complete eviction.
 * b) There is work going on in TTM to allow freeing an object even when
 * it's not idle, and using the TTM destroyed list handling could help us
 * benefit from that.
 */
static void i915_ttm_delayed_free(struct drm_i915_gem_object *obj)
{
        if (obj->ttm.created) {
                ttm_bo_put(i915_gem_to_ttm(obj));
        } else {
                __i915_gem_free_object(obj);
                call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
        }
}

static vm_fault_t vm_fault_ttm(struct vm_fault *vmf)
{
        struct vm_area_struct *area = vmf->vma;
        struct drm_i915_gem_object *obj =
                i915_ttm_to_gem(area->vm_private_data);

        /* Sanity check that we allow writing into this object */
        if (unlikely(i915_gem_object_is_readonly(obj) &&
                     area->vm_flags & VM_WRITE))
                return VM_FAULT_SIGBUS;

        return ttm_bo_vm_fault(vmf);
}

static int
vm_access_ttm(struct vm_area_struct *area, unsigned long addr,
              void *buf, int len, int write)
{
        struct drm_i915_gem_object *obj =
                i915_ttm_to_gem(area->vm_private_data);

        if (i915_gem_object_is_readonly(obj) && write)
                return -EACCES;

        return ttm_bo_vm_access(area, addr, buf, len, write);
}

static void ttm_vm_open(struct vm_area_struct *vma)
{
        struct drm_i915_gem_object *obj =
                i915_ttm_to_gem(vma->vm_private_data);

        GEM_BUG_ON(!obj);
        i915_gem_object_get(obj);
}

static void ttm_vm_close(struct vm_area_struct *vma)
{
        struct drm_i915_gem_object *obj =
                i915_ttm_to_gem(vma->vm_private_data);

        GEM_BUG_ON(!obj);
        i915_gem_object_put(obj);
}

static const struct vm_operations_struct vm_ops_ttm = {
        .fault = vm_fault_ttm,
        .access = vm_access_ttm,
        .open = ttm_vm_open,
        .close = ttm_vm_close,
};

static u64 i915_ttm_mmap_offset(struct drm_i915_gem_object *obj)
{
        /* The ttm_bo must be allocated with I915_BO_ALLOC_USER */
        GEM_BUG_ON(!drm_mm_node_allocated(&obj->base.vma_node.vm_node));

        return drm_vma_node_offset_addr(&obj->base.vma_node);
}

static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
        .name = "i915_gem_object_ttm",

        .get_pages = i915_ttm_get_pages,
        .put_pages = i915_ttm_put_pages,
        .truncate = i915_ttm_purge,
        .adjust_lru = i915_ttm_adjust_lru,
        .delayed_free = i915_ttm_delayed_free,
        .migrate = i915_ttm_migrate,
        .mmap_offset = i915_ttm_mmap_offset,
        .mmap_ops = &vm_ops_ttm,
};

void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
{
        struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);

        /* This releases all gem object bindings to the backend. */
        __i915_gem_free_object(obj);

        i915_gem_object_release_memory_region(obj);
        mutex_destroy(&obj->ttm.get_io_page.lock);

        if (obj->ttm.created)
                call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
}

/**
 * __i915_gem_ttm_object_init - Initialize a ttm-backed i915 gem object
 * @mem: The initial memory region for the object.
 * @obj: The gem object.
 * @size: Object size in bytes.
 * @flags: gem object flags.
 *
 * Return: 0 on success, negative error code on failure.
 */
int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
                               struct drm_i915_gem_object *obj,
                               resource_size_t size,
                               resource_size_t page_size,
                               unsigned int flags)
{
        static struct lock_class_key lock_class;
        struct drm_i915_private *i915 = mem->i915;
        struct ttm_operation_ctx ctx = {
                .interruptible = true,
                .no_wait_gpu = false,
        };
        enum ttm_bo_type bo_type;
        int ret;

        drm_gem_private_object_init(&i915->drm, &obj->base, size);
        i915_gem_object_init(obj, &i915_gem_ttm_obj_ops, &lock_class, flags);
        i915_gem_object_init_memory_region(obj, mem);
        i915_gem_object_make_unshrinkable(obj);
        INIT_RADIX_TREE(&obj->ttm.get_io_page.radix, GFP_KERNEL | __GFP_NOWARN);
        mutex_init(&obj->ttm.get_io_page.lock);
        bo_type = (obj->flags & I915_BO_ALLOC_USER) ? ttm_bo_type_device :
                ttm_bo_type_kernel;

        obj->base.vma_node.driver_private = i915_gem_to_ttm(obj);

        /* Forcing the page size is kernel internal only */
        GEM_BUG_ON(page_size && obj->mm.n_placements);

        /*
         * If this function fails, it will call the destructor, but
         * our caller still owns the object. So no freeing in the
         * destructor until obj->ttm.created is true.
         * Similarly, in delayed_destroy, we can't call ttm_bo_put()
         * until successful initialization.
         */
        ret = ttm_bo_init_reserved(&i915->bdev, i915_gem_to_ttm(obj), size,
                                   bo_type, &i915_sys_placement,
                                   page_size >> PAGE_SHIFT,
                                   &ctx, NULL, NULL, i915_ttm_bo_destroy);
        if (ret)
                return i915_ttm_err_to_gem(ret);

        obj->ttm.created = true;
        i915_ttm_adjust_domains_after_move(obj);
        i915_ttm_adjust_gem_after_move(obj);
        i915_gem_object_unlock(obj);

        return 0;
}

static const struct intel_memory_region_ops ttm_system_region_ops = {
        .init_object = __i915_gem_ttm_object_init,
};

struct intel_memory_region *
i915_gem_ttm_system_setup(struct drm_i915_private *i915,
                          u16 type, u16 instance)
{
        struct intel_memory_region *mr;

        mr = intel_memory_region_create(i915, 0,
                                        totalram_pages() << PAGE_SHIFT,
                                        PAGE_SIZE, 0,
                                        type, instance,
                                        &ttm_system_region_ops);
        if (IS_ERR(mr))
                return mr;

        intel_memory_region_set_name(mr, "system-ttm");
        return mr;
}