/*
 * Copyright 2014 Advanced Micro Devices, Inc.
 * All Rights Reserved.
 *
 * 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, sub license, 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 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 NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS 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.
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 */
/*
 * Authors:
 *    Christian König <christian.koenig@amd.com>
 */

#include <linux/firmware.h>
#include <linux/module.h>
#include <linux/mmu_notifier.h>

#include <drm/drm.h>

#include "radeon.h"

struct radeon_mn {
        /* constant after initialisation */
        struct radeon_device    *rdev;
        struct mm_struct        *mm;
        struct mmu_notifier     mn;

        /* only used on destruction */
        struct work_struct      work;

        /* protected by rdev->mn_lock */
        struct hlist_node       node;

        /* objects protected by lock */
        struct mutex            lock;
        struct rb_root_cached   objects;
};

struct radeon_mn_node {
        struct interval_tree_node       it;
        struct list_head                bos;
};

/**
 * radeon_mn_destroy - destroy the rmn
 *
 * @work: previously sheduled work item
 *
 * Lazy destroys the notifier from a work item
 */
static void radeon_mn_destroy(struct work_struct *work)
{
        struct radeon_mn *rmn = container_of(work, struct radeon_mn, work);
        struct radeon_device *rdev = rmn->rdev;
        struct radeon_mn_node *node, *next_node;
        struct radeon_bo *bo, *next_bo;

        mutex_lock(&rdev->mn_lock);
        mutex_lock(&rmn->lock);
        hash_del(&rmn->node);
        rbtree_postorder_for_each_entry_safe(node, next_node,
                                             &rmn->objects.rb_root, it.rb) {

                interval_tree_remove(&node->it, &rmn->objects);
                list_for_each_entry_safe(bo, next_bo, &node->bos, mn_list) {
                        bo->mn = NULL;
                        list_del_init(&bo->mn_list);
                }
                kfree(node);
        }
        mutex_unlock(&rmn->lock);
        mutex_unlock(&rdev->mn_lock);
        mmu_notifier_unregister(&rmn->mn, rmn->mm);
        kfree(rmn);
}

/**
 * radeon_mn_release - callback to notify about mm destruction
 *
 * @mn: our notifier
 * @mn: the mm this callback is about
 *
 * Shedule a work item to lazy destroy our notifier.
 */
static void radeon_mn_release(struct mmu_notifier *mn,
                              struct mm_struct *mm)
{
        struct radeon_mn *rmn = container_of(mn, struct radeon_mn, mn);
        INIT_WORK(&rmn->work, radeon_mn_destroy);
        schedule_work(&rmn->work);
}

/**
 * radeon_mn_invalidate_range_start - callback to notify about mm change
 *
 * @mn: our notifier
 * @mn: the mm this callback is about
 * @start: start of updated range
 * @end: end of updated range
 *
 * We block for all BOs between start and end to be idle and
 * unmap them by move them into system domain again.
 */
static int radeon_mn_invalidate_range_start(struct mmu_notifier *mn,
                                const struct mmu_notifier_range *range)
{
        struct radeon_mn *rmn = container_of(mn, struct radeon_mn, mn);
        struct ttm_operation_ctx ctx = { false, false };
        struct interval_tree_node *it;
        unsigned long end;
        int ret = 0;

        /* notification is exclusive, but interval is inclusive */
        end = range->end - 1;

        /* TODO we should be able to split locking for interval tree and
         * the tear down.
         */
        if (mmu_notifier_range_blockable(range))
                mutex_lock(&rmn->lock);
        else if (!mutex_trylock(&rmn->lock))
                return -EAGAIN;

        it = interval_tree_iter_first(&rmn->objects, range->start, end);
        while (it) {
                struct radeon_mn_node *node;
                struct radeon_bo *bo;
                long r;

                if (!mmu_notifier_range_blockable(range)) {
                        ret = -EAGAIN;
                        goto out_unlock;
                }

                node = container_of(it, struct radeon_mn_node, it);
                it = interval_tree_iter_next(it, range->start, end);

                list_for_each_entry(bo, &node->bos, mn_list) {

                        if (!bo->tbo.ttm || bo->tbo.ttm->state != tt_bound)
                                continue;

                        r = radeon_bo_reserve(bo, true);
                        if (r) {
                                DRM_ERROR("(%ld) failed to reserve user bo\n", r);
                                continue;
                        }

                        r = reservation_object_wait_timeout_rcu(bo->tbo.resv,
                                true, false, MAX_SCHEDULE_TIMEOUT);
                        if (r <= 0)
                                DRM_ERROR("(%ld) failed to wait for user bo\n", r);

                        radeon_ttm_placement_from_domain(bo, RADEON_GEM_DOMAIN_CPU);
                        r = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
                        if (r)
                                DRM_ERROR("(%ld) failed to validate user bo\n", r);

                        radeon_bo_unreserve(bo);
                }
        }
        
out_unlock:
        mutex_unlock(&rmn->lock);

        return ret;
}

static const struct mmu_notifier_ops radeon_mn_ops = {
        .release = radeon_mn_release,
        .invalidate_range_start = radeon_mn_invalidate_range_start,
};

/**
 * radeon_mn_get - create notifier context
 *
 * @rdev: radeon device pointer
 *
 * Creates a notifier context for current->mm.
 */
static struct radeon_mn *radeon_mn_get(struct radeon_device *rdev)
{
        struct mm_struct *mm = current->mm;
        struct radeon_mn *rmn;
        int r;

        if (down_write_killable(&mm->mmap_sem))
                return ERR_PTR(-EINTR);

        mutex_lock(&rdev->mn_lock);

        hash_for_each_possible(rdev->mn_hash, rmn, node, (unsigned long)mm)
                if (rmn->mm == mm)
                        goto release_locks;

        rmn = kzalloc(sizeof(*rmn), GFP_KERNEL);
        if (!rmn) {
                rmn = ERR_PTR(-ENOMEM);
                goto release_locks;
        }

        rmn->rdev = rdev;
        rmn->mm = mm;
        rmn->mn.ops = &radeon_mn_ops;
        mutex_init(&rmn->lock);
        rmn->objects = RB_ROOT_CACHED;
        
        r = __mmu_notifier_register(&rmn->mn, mm);
        if (r)
                goto free_rmn;

        hash_add(rdev->mn_hash, &rmn->node, (unsigned long)mm);

release_locks:
        mutex_unlock(&rdev->mn_lock);
        up_write(&mm->mmap_sem);

        return rmn;

free_rmn:
        mutex_unlock(&rdev->mn_lock);
        up_write(&mm->mmap_sem);
        kfree(rmn);

        return ERR_PTR(r);
}

/**
 * radeon_mn_register - register a BO for notifier updates
 *
 * @bo: radeon buffer object
 * @addr: userptr addr we should monitor
 *
 * Registers an MMU notifier for the given BO at the specified address.
 * Returns 0 on success, -ERRNO if anything goes wrong.
 */
int radeon_mn_register(struct radeon_bo *bo, unsigned long addr)
{
        unsigned long end = addr + radeon_bo_size(bo) - 1;
        struct radeon_device *rdev = bo->rdev;
        struct radeon_mn *rmn;
        struct radeon_mn_node *node = NULL;
        struct list_head bos;
        struct interval_tree_node *it;

        rmn = radeon_mn_get(rdev);
        if (IS_ERR(rmn))
                return PTR_ERR(rmn);

        INIT_LIST_HEAD(&bos);

        mutex_lock(&rmn->lock);

        while ((it = interval_tree_iter_first(&rmn->objects, addr, end))) {
                kfree(node);
                node = container_of(it, struct radeon_mn_node, it);
                interval_tree_remove(&node->it, &rmn->objects);
                addr = min(it->start, addr);
                end = max(it->last, end);
                list_splice(&node->bos, &bos);
        }

        if (!node) {
                node = kmalloc(sizeof(struct radeon_mn_node), GFP_KERNEL);
                if (!node) {
                        mutex_unlock(&rmn->lock);
                        return -ENOMEM;
                }
        }

        bo->mn = rmn;

        node->it.start = addr;
        node->it.last = end;
        INIT_LIST_HEAD(&node->bos);
        list_splice(&bos, &node->bos);
        list_add(&bo->mn_list, &node->bos);

        interval_tree_insert(&node->it, &rmn->objects);

        mutex_unlock(&rmn->lock);

        return 0;
}

/**
 * radeon_mn_unregister - unregister a BO for notifier updates
 *
 * @bo: radeon buffer object
 *
 * Remove any registration of MMU notifier updates from the buffer object.
 */
void radeon_mn_unregister(struct radeon_bo *bo)
{
        struct radeon_device *rdev = bo->rdev;
        struct radeon_mn *rmn;
        struct list_head *head;

        mutex_lock(&rdev->mn_lock);
        rmn = bo->mn;
        if (rmn == NULL) {
                mutex_unlock(&rdev->mn_lock);
                return;
        }

        mutex_lock(&rmn->lock);
        /* save the next list entry for later */
        head = bo->mn_list.next;

        bo->mn = NULL;
        list_del(&bo->mn_list);

        if (list_empty(head)) {
                struct radeon_mn_node *node;
                node = container_of(head, struct radeon_mn_node, bos);
                interval_tree_remove(&node->it, &rmn->objects);
                kfree(node);
        }

        mutex_unlock(&rmn->lock);
        mutex_unlock(&rdev->mn_lock);
}