/*
 * Copyright 2019 Advanced Micro Devices, Inc.
 *
 * 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 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
 *
 * based on nouveau_prime.c
 *
 * Authors: Alex Deucher
 */

/**
 * DOC: PRIME Buffer Sharing
 *
 * The following callback implementations are used for :ref:`sharing GEM buffer
 * objects between different devices via PRIME <prime_buffer_sharing>`.
 */

#include "amdgpu.h"
#include "amdgpu_display.h"
#include "amdgpu_gem.h"
#include "amdgpu_dma_buf.h"
#include <drm/amdgpu_drm.h>
#include <linux/dma-buf.h>
#include <linux/dma-fence-array.h>
#include <linux/pci-p2pdma.h>

/**
 * amdgpu_gem_prime_vmap - &dma_buf_ops.vmap implementation
 * @obj: GEM BO
 *
 * Sets up an in-kernel virtual mapping of the BO's memory.
 *
 * Returns:
 * The virtual address of the mapping or an error pointer.
 */
void *amdgpu_gem_prime_vmap(struct drm_gem_object *obj)
{
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
        int ret;

        ret = ttm_bo_kmap(&bo->tbo, 0, bo->tbo.num_pages,
                          &bo->dma_buf_vmap);
        if (ret)
                return ERR_PTR(ret);

        return bo->dma_buf_vmap.virtual;
}

/**
 * amdgpu_gem_prime_vunmap - &dma_buf_ops.vunmap implementation
 * @obj: GEM BO
 * @vaddr: Virtual address (unused)
 *
 * Tears down the in-kernel virtual mapping of the BO's memory.
 */
void amdgpu_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
{
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);

        ttm_bo_kunmap(&bo->dma_buf_vmap);
}

/**
 * amdgpu_gem_prime_mmap - &drm_driver.gem_prime_mmap implementation
 * @obj: GEM BO
 * @vma: Virtual memory area
 *
 * Sets up a userspace mapping of the BO's memory in the given
 * virtual memory area.
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 */
int amdgpu_gem_prime_mmap(struct drm_gem_object *obj,
                          struct vm_area_struct *vma)
{
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
        unsigned asize = amdgpu_bo_size(bo);
        int ret;

        if (!vma->vm_file)
                return -ENODEV;

        if (adev == NULL)
                return -ENODEV;

        /* Check for valid size. */
        if (asize < vma->vm_end - vma->vm_start)
                return -EINVAL;

        if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm) ||
            (bo->flags & AMDGPU_GEM_CREATE_NO_CPU_ACCESS)) {
                return -EPERM;
        }
        vma->vm_pgoff += amdgpu_bo_mmap_offset(bo) >> PAGE_SHIFT;

        /* prime mmap does not need to check access, so allow here */
        ret = drm_vma_node_allow(&obj->vma_node, vma->vm_file->private_data);
        if (ret)
                return ret;

        ret = ttm_bo_mmap(vma->vm_file, vma, &adev->mman.bdev);
        drm_vma_node_revoke(&obj->vma_node, vma->vm_file->private_data);

        return ret;
}

static int
__dma_resv_make_exclusive(struct dma_resv *obj)
{
        struct dma_fence **fences;
        unsigned int count;
        int r;

        if (!dma_resv_get_list(obj)) /* no shared fences to convert */
                return 0;

        r = dma_resv_get_fences_rcu(obj, NULL, &count, &fences);
        if (r)
                return r;

        if (count == 0) {
                /* Now that was unexpected. */
        } else if (count == 1) {
                dma_resv_add_excl_fence(obj, fences[0]);
                dma_fence_put(fences[0]);
                kfree(fences);
        } else {
                struct dma_fence_array *array;

                array = dma_fence_array_create(count, fences,
                                               dma_fence_context_alloc(1), 0,
                                               false);
                if (!array)
                        goto err_fences_put;

                dma_resv_add_excl_fence(obj, &array->base);
                dma_fence_put(&array->base);
        }

        return 0;

err_fences_put:
        while (count--)
                dma_fence_put(fences[count]);
        kfree(fences);
        return -ENOMEM;
}

/**
 * amdgpu_dma_buf_attach - &dma_buf_ops.attach implementation
 *
 * @dmabuf: DMA-buf where we attach to
 * @attach: attachment to add
 *
 * Add the attachment as user to the exported DMA-buf.
 */
static int amdgpu_dma_buf_attach(struct dma_buf *dmabuf,
                                 struct dma_buf_attachment *attach)
{
        struct drm_gem_object *obj = dmabuf->priv;
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
        int r;

        if (pci_p2pdma_distance_many(adev->pdev, &attach->dev, 1, true) < 0)
                attach->peer2peer = false;

        if (attach->dev->driver == adev->dev->driver)
                return 0;

        r = amdgpu_bo_reserve(bo, false);
        if (unlikely(r != 0))
                return r;

        /*
         * We only create shared fences for internal use, but importers
         * of the dmabuf rely on exclusive fences for implicitly
         * tracking write hazards. As any of the current fences may
         * correspond to a write, we need to convert all existing
         * fences on the reservation object into a single exclusive
         * fence.
         */
        r = __dma_resv_make_exclusive(bo->tbo.base.resv);
        if (r)
                return r;

        bo->prime_shared_count++;
        amdgpu_bo_unreserve(bo);
        return 0;
}

/**
 * amdgpu_dma_buf_detach - &dma_buf_ops.detach implementation
 *
 * @dmabuf: DMA-buf where we remove the attachment from
 * @attach: the attachment to remove
 *
 * Called when an attachment is removed from the DMA-buf.
 */
static void amdgpu_dma_buf_detach(struct dma_buf *dmabuf,
                                  struct dma_buf_attachment *attach)
{
        struct drm_gem_object *obj = dmabuf->priv;
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);

        if (attach->dev->driver != adev->dev->driver && bo->prime_shared_count)
                bo->prime_shared_count--;
}

/**
 * amdgpu_dma_buf_pin - &dma_buf_ops.pin implementation
 *
 * @attach: attachment to pin down
 *
 * Pin the BO which is backing the DMA-buf so that it can't move any more.
 */
static int amdgpu_dma_buf_pin(struct dma_buf_attachment *attach)
{
        struct drm_gem_object *obj = attach->dmabuf->priv;
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);

        /* pin buffer into GTT */
        return amdgpu_bo_pin(bo, AMDGPU_GEM_DOMAIN_GTT);
}

/**
 * amdgpu_dma_buf_unpin - &dma_buf_ops.unpin implementation
 *
 * @attach: attachment to unpin
 *
 * Unpin a previously pinned BO to make it movable again.
 */
static void amdgpu_dma_buf_unpin(struct dma_buf_attachment *attach)
{
        struct drm_gem_object *obj = attach->dmabuf->priv;
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);

        amdgpu_bo_unpin(bo);
}

/**
 * amdgpu_dma_buf_map - &dma_buf_ops.map_dma_buf implementation
 * @attach: DMA-buf attachment
 * @dir: DMA direction
 *
 * Makes sure that the shared DMA buffer can be accessed by the target device.
 * For now, simply pins it to the GTT domain, where it should be accessible by
 * all DMA devices.
 *
 * Returns:
 * sg_table filled with the DMA addresses to use or ERR_PRT with negative error
 * code.
 */
static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
                                           enum dma_data_direction dir)
{
        struct dma_buf *dma_buf = attach->dmabuf;
        struct drm_gem_object *obj = dma_buf->priv;
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
        struct sg_table *sgt;
        long r;

        if (!bo->pin_count) {
                /* move buffer into GTT or VRAM */
                struct ttm_operation_ctx ctx = { false, false };
                unsigned domains = AMDGPU_GEM_DOMAIN_GTT;

                if (bo->preferred_domains & AMDGPU_GEM_DOMAIN_VRAM &&
                    attach->peer2peer) {
                        bo->flags |= AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
                        domains |= AMDGPU_GEM_DOMAIN_VRAM;
                }
                amdgpu_bo_placement_from_domain(bo, domains);
                r = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
                if (r)
                        return ERR_PTR(r);

        } else if (!(amdgpu_mem_type_to_domain(bo->tbo.mem.mem_type) &
                     AMDGPU_GEM_DOMAIN_GTT)) {
                return ERR_PTR(-EBUSY);
        }

        switch (bo->tbo.mem.mem_type) {
        case TTM_PL_TT:
                sgt = drm_prime_pages_to_sg(bo->tbo.ttm->pages,
                                            bo->tbo.num_pages);
                if (IS_ERR(sgt))
                        return sgt;

                if (dma_map_sgtable(attach->dev, sgt, dir,
                                    DMA_ATTR_SKIP_CPU_SYNC))
                        goto error_free;
                break;

        case TTM_PL_VRAM:
                r = amdgpu_vram_mgr_alloc_sgt(adev, &bo->tbo.mem, attach->dev,
                                              dir, &sgt);
                if (r)
                        return ERR_PTR(r);
                break;
        default:
                return ERR_PTR(-EINVAL);
        }

        return sgt;

error_free:
        sg_free_table(sgt);
        kfree(sgt);
        return ERR_PTR(-EBUSY);
}

/**
 * amdgpu_dma_buf_unmap - &dma_buf_ops.unmap_dma_buf implementation
 * @attach: DMA-buf attachment
 * @sgt: sg_table to unmap
 * @dir: DMA direction
 *
 * This is called when a shared DMA buffer no longer needs to be accessible by
 * another device. For now, simply unpins the buffer from GTT.
 */
static void amdgpu_dma_buf_unmap(struct dma_buf_attachment *attach,
                                 struct sg_table *sgt,
                                 enum dma_data_direction dir)
{
        struct dma_buf *dma_buf = attach->dmabuf;
        struct drm_gem_object *obj = dma_buf->priv;
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);

        if (sgt->sgl->page_link) {
                dma_unmap_sgtable(attach->dev, sgt, dir, 0);
                sg_free_table(sgt);
                kfree(sgt);
        } else {
                amdgpu_vram_mgr_free_sgt(adev, attach->dev, dir, sgt);
        }
}

/**
 * amdgpu_dma_buf_begin_cpu_access - &dma_buf_ops.begin_cpu_access implementation
 * @dma_buf: Shared DMA buffer
 * @direction: Direction of DMA transfer
 *
 * This is called before CPU access to the shared DMA buffer's memory. If it's
 * a read access, the buffer is moved to the GTT domain if possible, for optimal
 * CPU read performance.
 *
 * Returns:
 * 0 on success or a negative error code on failure.
 */
static int amdgpu_dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
                                           enum dma_data_direction direction)
{
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(dma_buf->priv);
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
        struct ttm_operation_ctx ctx = { true, false };
        u32 domain = amdgpu_display_supported_domains(adev, bo->flags);
        int ret;
        bool reads = (direction == DMA_BIDIRECTIONAL ||
                      direction == DMA_FROM_DEVICE);

        if (!reads || !(domain & AMDGPU_GEM_DOMAIN_GTT))
                return 0;

        /* move to gtt */
        ret = amdgpu_bo_reserve(bo, false);
        if (unlikely(ret != 0))
                return ret;

        if (!bo->pin_count && (bo->allowed_domains & AMDGPU_GEM_DOMAIN_GTT)) {
                amdgpu_bo_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_GTT);
                ret = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
        }

        amdgpu_bo_unreserve(bo);
        return ret;
}

const struct dma_buf_ops amdgpu_dmabuf_ops = {
        .attach = amdgpu_dma_buf_attach,
        .detach = amdgpu_dma_buf_detach,
        .pin = amdgpu_dma_buf_pin,
        .unpin = amdgpu_dma_buf_unpin,
        .map_dma_buf = amdgpu_dma_buf_map,
        .unmap_dma_buf = amdgpu_dma_buf_unmap,
        .release = drm_gem_dmabuf_release,
        .begin_cpu_access = amdgpu_dma_buf_begin_cpu_access,
        .mmap = drm_gem_dmabuf_mmap,
        .vmap = drm_gem_dmabuf_vmap,
        .vunmap = drm_gem_dmabuf_vunmap,
};

/**
 * amdgpu_gem_prime_export - &drm_driver.gem_prime_export implementation
 * @gobj: GEM BO
 * @flags: Flags such as DRM_CLOEXEC and DRM_RDWR.
 *
 * The main work is done by the &drm_gem_prime_export helper.
 *
 * Returns:
 * Shared DMA buffer representing the GEM BO from the given device.
 */
struct dma_buf *amdgpu_gem_prime_export(struct drm_gem_object *gobj,
                                        int flags)
{
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(gobj);
        struct dma_buf *buf;

        if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm) ||
            bo->flags & AMDGPU_GEM_CREATE_VM_ALWAYS_VALID)
                return ERR_PTR(-EPERM);

        buf = drm_gem_prime_export(gobj, flags);
        if (!IS_ERR(buf))
                buf->ops = &amdgpu_dmabuf_ops;

        return buf;
}

/**
 * amdgpu_dma_buf_create_obj - create BO for DMA-buf import
 *
 * @dev: DRM device
 * @dma_buf: DMA-buf
 *
 * Creates an empty SG BO for DMA-buf import.
 *
 * Returns:
 * A new GEM BO of the given DRM device, representing the memory
 * described by the given DMA-buf attachment and scatter/gather table.
 */
static struct drm_gem_object *
amdgpu_dma_buf_create_obj(struct drm_device *dev, struct dma_buf *dma_buf)
{
        struct dma_resv *resv = dma_buf->resv;
        struct amdgpu_device *adev = dev->dev_private;
        struct amdgpu_bo *bo;
        struct amdgpu_bo_param bp;
        int ret;

        memset(&bp, 0, sizeof(bp));
        bp.size = dma_buf->size;
        bp.byte_align = PAGE_SIZE;
        bp.domain = AMDGPU_GEM_DOMAIN_CPU;
        bp.flags = 0;
        bp.type = ttm_bo_type_sg;
        bp.resv = resv;
        dma_resv_lock(resv, NULL);
        ret = amdgpu_bo_create(adev, &bp, &bo);
        if (ret)
                goto error;

        bo->allowed_domains = AMDGPU_GEM_DOMAIN_GTT;
        bo->preferred_domains = AMDGPU_GEM_DOMAIN_GTT;
        if (dma_buf->ops != &amdgpu_dmabuf_ops)
                bo->prime_shared_count = 1;

        dma_resv_unlock(resv);
        return &bo->tbo.base;

error:
        dma_resv_unlock(resv);
        return ERR_PTR(ret);
}

/**
 * amdgpu_dma_buf_move_notify - &attach.move_notify implementation
 *
 * @attach: the DMA-buf attachment
 *
 * Invalidate the DMA-buf attachment, making sure that the we re-create the
 * mapping before the next use.
 */
static void
amdgpu_dma_buf_move_notify(struct dma_buf_attachment *attach)
{
        struct drm_gem_object *obj = attach->importer_priv;
        struct ww_acquire_ctx *ticket = dma_resv_locking_ctx(obj->resv);
        struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
        struct ttm_operation_ctx ctx = { false, false };
        struct ttm_placement placement = {};
        struct amdgpu_vm_bo_base *bo_base;
        int r;

        if (bo->tbo.mem.mem_type == TTM_PL_SYSTEM)
                return;

        r = ttm_bo_validate(&bo->tbo, &placement, &ctx);
        if (r) {
                DRM_ERROR("Failed to invalidate DMA-buf import (%d))\n", r);
                return;
        }

        for (bo_base = bo->vm_bo; bo_base; bo_base = bo_base->next) {
                struct amdgpu_vm *vm = bo_base->vm;
                struct dma_resv *resv = vm->root.base.bo->tbo.base.resv;

                if (ticket) {
                        /* When we get an error here it means that somebody
                         * else is holding the VM lock and updating page tables
                         * So we can just continue here.
                         */
                        r = dma_resv_lock(resv, ticket);
                        if (r)
                                continue;

                } else {
                        /* TODO: This is more problematic and we actually need
                         * to allow page tables updates without holding the
                         * lock.
                         */
                        if (!dma_resv_trylock(resv))
                                continue;
                }

                r = amdgpu_vm_clear_freed(adev, vm, NULL);
                if (!r)
                        r = amdgpu_vm_handle_moved(adev, vm);

                if (r && r != -EBUSY)
                        DRM_ERROR("Failed to invalidate VM page tables (%d))\n",
                                  r);

                dma_resv_unlock(resv);
        }
}

static const struct dma_buf_attach_ops amdgpu_dma_buf_attach_ops = {
        .allow_peer2peer = true,
        .move_notify = amdgpu_dma_buf_move_notify
};

/**
 * amdgpu_gem_prime_import - &drm_driver.gem_prime_import implementation
 * @dev: DRM device
 * @dma_buf: Shared DMA buffer
 *
 * Import a dma_buf into a the driver and potentially create a new GEM object.
 *
 * Returns:
 * GEM BO representing the shared DMA buffer for the given device.
 */
struct drm_gem_object *amdgpu_gem_prime_import(struct drm_device *dev,
                                               struct dma_buf *dma_buf)
{
        struct dma_buf_attachment *attach;
        struct drm_gem_object *obj;

        if (dma_buf->ops == &amdgpu_dmabuf_ops) {
                obj = dma_buf->priv;
                if (obj->dev == dev) {
                        /*
                         * Importing dmabuf exported from out own gem increases
                         * refcount on gem itself instead of f_count of dmabuf.
                         */
                        drm_gem_object_get(obj);
                        return obj;
                }
        }

        obj = amdgpu_dma_buf_create_obj(dev, dma_buf);
        if (IS_ERR(obj))
                return obj;

        attach = dma_buf_dynamic_attach(dma_buf, dev->dev,
                                        &amdgpu_dma_buf_attach_ops, obj);
        if (IS_ERR(attach)) {
                drm_gem_object_put(obj);
                return ERR_CAST(attach);
        }

        get_dma_buf(dma_buf);
        obj->import_attach = attach;
        return obj;
}