/*
 * drivers/gpu/ion/ion_mem_pool.c
 *
 * Copyright (C) 2011 Google, Inc.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/debugfs.h>
#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/fs.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/shrinker.h>
#include "ion_priv.h"

/* #define DEBUG_PAGE_POOL_SHRINKER */

static struct plist_head pools = PLIST_HEAD_INIT(pools);
static struct shrinker shrinker;

struct ion_page_pool_item {
	struct page *page;
	struct list_head list;
};

static void *ion_page_pool_alloc_pages(struct ion_page_pool *pool)
{
	struct page *page = alloc_pages(pool->gfp_mask, pool->order);

	if (!page)
		return NULL;
	/* this is only being used to flush the page for dma,
	   this api is not really suitable for calling from a driver
	   but no better way to flush a page for dma exist at this time */
	__dma_page_cpu_to_dev(page, 0, PAGE_SIZE << pool->order,
			      DMA_BIDIRECTIONAL);
	return page;
}

static void ion_page_pool_free_pages(struct ion_page_pool *pool,
				     struct page *page)
{
	__free_pages(page, pool->order);
}

static int ion_page_pool_add(struct ion_page_pool *pool, struct page *page)
{
	struct ion_page_pool_item *item;

	item = kmalloc(sizeof(struct ion_page_pool_item), GFP_KERNEL);
	if (!item)
		return -ENOMEM;

	mutex_lock(&pool->mutex);
	item->page = page;
	if (PageHighMem(page)) {
		list_add_tail(&item->list, &pool->high_items);
		pool->high_count++;
	} else {
		list_add_tail(&item->list, &pool->low_items);
		pool->low_count++;
	}
	mutex_unlock(&pool->mutex);
	return 0;
}

static struct page *ion_page_pool_remove(struct ion_page_pool *pool, bool high)
{
	struct ion_page_pool_item *item;
	struct page *page;

	if (high) {
		BUG_ON(!pool->high_count);
		item = list_first_entry(&pool->high_items,
					struct ion_page_pool_item, list);
		pool->high_count--;
	} else {
		BUG_ON(!pool->low_count);
		item = list_first_entry(&pool->low_items,
					struct ion_page_pool_item, list);
		pool->low_count--;
	}

	list_del(&item->list);
	page = item->page;
	kfree(item);
	return page;
}

void *ion_page_pool_alloc(struct ion_page_pool *pool)
{
	struct page *page = NULL;

	BUG_ON(!pool);

	mutex_lock(&pool->mutex);
	if (pool->high_count)
		page = ion_page_pool_remove(pool, true);
	else if (pool->low_count)
		page = ion_page_pool_remove(pool, false);
	mutex_unlock(&pool->mutex);

	if (!page)
		page = ion_page_pool_alloc_pages(pool);

	return page;
}

void ion_page_pool_free(struct ion_page_pool *pool, struct page* page)
{
	int ret;

	ret = ion_page_pool_add(pool, page);
	if (ret)
		ion_page_pool_free_pages(pool, page);
}

#ifdef DEBUG_PAGE_POOL_SHRINKER
static int debug_drop_pools_set(void *data, u64 val)
{
	struct shrink_control sc;
	int objs;

	sc.gfp_mask = -1;
	sc.nr_to_scan = 0;

	if (!val)
		return 0;

	objs = shrinker.shrink(&shrinker, &sc);
	sc.nr_to_scan = objs;

	shrinker.shrink(&shrinker, &sc);
	return 0;
}

static int debug_drop_pools_get(void *data, u64 *val)
{
	struct shrink_control sc;
	int objs;

	sc.gfp_mask = -1;
	sc.nr_to_scan = 0;

	objs = shrinker.shrink(&shrinker, &sc);
	*val = objs;
	return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(debug_drop_pools_fops, debug_drop_pools_get,
                        debug_drop_pools_set, "%llu\n");

static int debug_grow_pools_set(void *data, u64 val)
{
	struct ion_page_pool *pool;
	struct page *page;

	plist_for_each_entry(pool, &pools, list) {
		if (val != pool->list.prio)
			continue;
		page = ion_page_pool_alloc_pages(pool);
		if (page)
			ion_page_pool_add(pool, page);
	}

	return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(debug_grow_pools_fops, debug_drop_pools_get,
			debug_grow_pools_set, "%llu\n");
#endif

static int ion_page_pool_total(bool high)
{
	struct ion_page_pool *pool;
	int total = 0;

	plist_for_each_entry(pool, &pools, list) {
		total += high ? (pool->high_count + pool->low_count) *
			(1 << pool->order) :
			pool->low_count * (1 << pool->order);
	}
	return total;
}

static int ion_page_pool_shrink(struct shrinker *shrinker,
				 struct shrink_control *sc)
{
	struct ion_page_pool *pool;
	int nr_freed = 0;
	int i;
	bool high;
	int nr_to_scan = sc->nr_to_scan;

	if (sc->gfp_mask & __GFP_HIGHMEM)
		high = true;

	if (nr_to_scan == 0)
		return ion_page_pool_total(high);

	plist_for_each_entry(pool, &pools, list) {
		for (i = 0; i < nr_to_scan; i++) {
			struct page *page;

			mutex_lock(&pool->mutex);
			if (high && pool->high_count) {
				page = ion_page_pool_remove(pool, true);
			} else if (pool->low_count) {
				page = ion_page_pool_remove(pool, false);
			} else {
				mutex_unlock(&pool->mutex);
				break;
			}
			mutex_unlock(&pool->mutex);
			ion_page_pool_free_pages(pool, page);
			nr_freed += (1 << pool->order);
		}
		nr_to_scan -= i;
	}

	return ion_page_pool_total(high);
}

struct ion_page_pool *ion_page_pool_create(gfp_t gfp_mask, unsigned int order)
{
	struct ion_page_pool *pool = kmalloc(sizeof(struct ion_page_pool),
					     GFP_KERNEL);
	if (!pool)
		return NULL;
	pool->high_count = 0;
	pool->low_count = 0;
	INIT_LIST_HEAD(&pool->low_items);
	INIT_LIST_HEAD(&pool->high_items);
	pool->gfp_mask = gfp_mask;
	pool->order = order;
	mutex_init(&pool->mutex);
	plist_node_init(&pool->list, order);
	plist_add(&pool->list, &pools);

	return pool;
}

void ion_page_pool_destroy(struct ion_page_pool *pool)
{
	plist_del(&pool->list, &pools);
	kfree(pool);
}

static int __init ion_page_pool_init(void)
{
	shrinker.shrink = ion_page_pool_shrink;
	shrinker.seeks = DEFAULT_SEEKS;
	shrinker.batch = 0;
	register_shrinker(&shrinker);
#ifdef DEBUG_PAGE_POOL_SHRINKER
	debugfs_create_file("ion_pools_shrink", 0644, NULL, NULL,
			    &debug_drop_pools_fops);
	debugfs_create_file("ion_pools_grow", 0644, NULL, NULL,
			    &debug_grow_pools_fops);
#endif
	return 0;
}

static void __exit ion_page_pool_exit(void)
{
	unregister_shrinker(&shrinker);
}

module_init(ion_page_pool_init);
module_exit(ion_page_pool_exit);