ttm_page_alloc_dma.c

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/*
 * Copyright 2011 (c) Oracle Corp.

 * 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 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 NON-INFRINGEMENT. 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.
 *
 * Author: Konrad Rzeszutek Wilk <[email protected]>
 */

/*
 * A simple DMA pool losely based on dmapool.c. It has certain advantages
 * over the DMA pools:
 * - Pool collects resently freed pages for reuse (and hooks up to
 *   the shrinker).
 * - Tracks currently in use pages
 * - Tracks whether the page is UC, WB or cached (and reverts to WB
 *   when freed).
 */

#define pr_fmt(fmt) "[TTM] " fmt

#include <linux/dma-mapping.h>
#include <linux/list.h>
#include <linux/seq_file.h> /* for seq_printf */
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/highmem.h>
#include <linux/mm_types.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/kthread.h>
#include <drm/ttm/ttm_bo_driver.h>
#include <drm/ttm/ttm_page_alloc.h>
#ifdef TTM_HAS_AGP
#include <asm/agp.h>
#endif

#define NUM_PAGES_TO_ALLOC      (PAGE_SIZE/sizeof(struct page *))
#define SMALL_ALLOCATION        4
#define FREE_ALL_PAGES          (~0U)
/* times are in msecs */
#define IS_UNDEFINED            (0)
#define IS_WC               (1<<1)
#define IS_UC               (1<<2)
#define IS_CACHED           (1<<3)
#define IS_DMA32            (1<<4)

enum pool_type {
    POOL_IS_UNDEFINED,
    POOL_IS_WC = IS_WC,
    POOL_IS_UC = IS_UC,
    POOL_IS_CACHED = IS_CACHED,
    POOL_IS_WC_DMA32 = IS_WC | IS_DMA32,
    POOL_IS_UC_DMA32 = IS_UC | IS_DMA32,
    POOL_IS_CACHED_DMA32 = IS_CACHED | IS_DMA32,
};
/*
 * The pool structure. There are usually six pools:
 *  - generic (not restricted to DMA32):
 *      - write combined, uncached, cached.
 *  - dma32 (up to 2^32 - so up 4GB):
 *      - write combined, uncached, cached.
 * for each 'struct device'. The 'cached' is for pages that are actively used.
 * The other ones can be shrunk by the shrinker API if neccessary.
 * @pools: The 'struct device->dma_pools' link.
 * @type: Type of the pool
 * @lock: Protects the inuse_list and free_list from concurrnet access. Must be
 * used with irqsave/irqrestore variants because pool allocator maybe called
 * from delayed work.
 * @inuse_list: Pool of pages that are in use. The order is very important and
 *   it is in the order that the TTM pages that are put back are in.
 * @free_list: Pool of pages that are free to be used. No order requirements.
 * @dev: The device that is associated with these pools.
 * @size: Size used during DMA allocation.
 * @npages_free: Count of available pages for re-use.
 * @npages_in_use: Count of pages that are in use.
 * @nfrees: Stats when pool is shrinking.
 * @nrefills: Stats when the pool is grown.
 * @gfp_flags: Flags to pass for alloc_page.
 * @name: Name of the pool.
 * @dev_name: Name derieved from dev - similar to how dev_info works.
 *   Used during shutdown as the dev_info during release is unavailable.
 */
struct dma_pool {
    struct list_head pools; /* The 'struct device->dma_pools link */
    enum pool_type type;
    spinlock_t lock;
    struct list_head inuse_list;
    struct list_head free_list;
    struct device *dev;
    unsigned size;
    unsigned npages_free;
    unsigned npages_in_use;
    unsigned long nfrees; /* Stats when shrunk. */
    unsigned long nrefills; /* Stats when grown. */
    gfp_t gfp_flags;
    char name[13]; /* "cached dma32" */
    char dev_name[64]; /* Constructed from dev */
};

/*
 * The accounting page keeping track of the allocated page along with
 * the DMA address.
 * @page_list: The link to the 'page_list' in 'struct dma_pool'.
 * @vaddr: The virtual address of the page
 * @dma: The bus address of the page. If the page is not allocated
 *   via the DMA API, it will be -1.
 */
struct dma_page {
    struct list_head page_list;
    void *vaddr;
    struct page *p;
    dma_addr_t dma;
};

/*
 * Limits for the pool. They are handled without locks because only place where
 * they may change is in sysfs store. They won't have immediate effect anyway
 * so forcing serialization to access them is pointless.
 */

struct ttm_pool_opts {
    unsigned    alloc_size;
    unsigned    max_size;
    unsigned    small;
};

/*
 * Contains the list of all of the 'struct device' and their corresponding
 * DMA pools. Guarded by _mutex->lock.
 * @pools: The link to 'struct ttm_pool_manager->pools'
 * @dev: The 'struct device' associated with the 'pool'
 * @pool: The 'struct dma_pool' associated with the 'dev'
 */
struct device_pools {
    struct list_head pools;
    struct device *dev;
    struct dma_pool *pool;
};

/*
 * struct ttm_pool_manager - Holds memory pools for fast allocation
 *
 * @lock: Lock used when adding/removing from pools
 * @pools: List of 'struct device' and 'struct dma_pool' tuples.
 * @options: Limits for the pool.
 * @npools: Total amount of pools in existence.
 * @shrinker: The structure used by [un|]register_shrinker
 */
struct ttm_pool_manager {
    struct mutex        lock;
    struct list_head    pools;
    struct ttm_pool_opts    options;
    unsigned        npools;
    struct shrinker     mm_shrink;
    struct kobject      kobj;
};

static struct ttm_pool_manager *_manager;

static struct attribute ttm_page_pool_max = {
    .name = "pool_max_size",
    .mode = S_IRUGO | S_IWUSR
};
static struct attribute ttm_page_pool_small = {
    .name = "pool_small_allocation",
    .mode = S_IRUGO | S_IWUSR
};
static struct attribute ttm_page_pool_alloc_size = {
    .name = "pool_allocation_size",
    .mode = S_IRUGO | S_IWUSR
};

static struct attribute *ttm_pool_attrs[] = {
    &ttm_page_pool_max,
    &ttm_page_pool_small,
    &ttm_page_pool_alloc_size,
    NULL
};

static void ttm_pool_kobj_release(struct kobject *kobj)
{
    struct ttm_pool_manager *m =
        container_of(kobj, struct ttm_pool_manager, kobj);
    kfree(m);
}

static ssize_t ttm_pool_store(struct kobject *kobj, struct attribute *attr,
                  const char *buffer, size_t size)
{
    struct ttm_pool_manager *m =
        container_of(kobj, struct ttm_pool_manager, kobj);
    int chars;
    unsigned val;
    chars = sscanf(buffer, "%u", &val);
    if (chars == 0)
        return size;

    /* Convert kb to number of pages */
    val = val / (PAGE_SIZE >> 10);

    if (attr == &ttm_page_pool_max)
        m->options.max_size = val;
    else if (attr == &ttm_page_pool_small)
        m->options.small = val;
    else if (attr == &ttm_page_pool_alloc_size) {
        if (val > NUM_PAGES_TO_ALLOC*8) {
            pr_err("Setting allocation size to %lu is not allowed. Recommended size is %lu\n",
                   NUM_PAGES_TO_ALLOC*(PAGE_SIZE >> 7),
                   NUM_PAGES_TO_ALLOC*(PAGE_SIZE >> 10));
            return size;
        } else if (val > NUM_PAGES_TO_ALLOC) {
            pr_warn("Setting allocation size to larger than %lu is not recommended\n",
                NUM_PAGES_TO_ALLOC*(PAGE_SIZE >> 10));
        }
        m->options.alloc_size = val;
    }

    return size;
}

static ssize_t ttm_pool_show(struct kobject *kobj, struct attribute *attr,
                 char *buffer)
{
    struct ttm_pool_manager *m =
        container_of(kobj, struct ttm_pool_manager, kobj);
    unsigned val = 0;

    if (attr == &ttm_page_pool_max)
        val = m->options.max_size;
    else if (attr == &ttm_page_pool_small)
        val = m->options.small;
    else if (attr == &ttm_page_pool_alloc_size)
        val = m->options.alloc_size;

    val = val * (PAGE_SIZE >> 10);

    return snprintf(buffer, PAGE_SIZE, "%u\n", val);
}

static const struct sysfs_ops ttm_pool_sysfs_ops = {
    .show = &ttm_pool_show,
    .store = &ttm_pool_store,
};

static struct kobj_type ttm_pool_kobj_type = {
    .release = &ttm_pool_kobj_release,
    .sysfs_ops = &ttm_pool_sysfs_ops,
    .default_attrs = ttm_pool_attrs,
};

#ifndef CONFIG_X86
static int set_pages_array_wb(struct page **pages, int addrinarray)
{
#ifdef TTM_HAS_AGP
    int i;

    for (i = 0; i < addrinarray; i++)
        unmap_page_from_agp(pages[i]);
#endif
    return 0;
}

static int set_pages_array_wc(struct page **pages, int addrinarray)
{
#ifdef TTM_HAS_AGP
    int i;

    for (i = 0; i < addrinarray; i++)
        map_page_into_agp(pages[i]);
#endif
    return 0;
}

static int set_pages_array_uc(struct page **pages, int addrinarray)
{
#ifdef TTM_HAS_AGP
    int i;

    for (i = 0; i < addrinarray; i++)
        map_page_into_agp(pages[i]);
#endif
    return 0;
}
#endif /* for !CONFIG_X86 */

static int ttm_set_pages_caching(struct dma_pool *pool,
                 struct page **pages, unsigned cpages)
{
    int r = 0;
    /* Set page caching */
    if (pool->type & IS_UC) {
        r = set_pages_array_uc(pages, cpages);
        if (r)
            pr_err("%s: Failed to set %d pages to uc!\n",
                   pool->dev_name, cpages);
    }
    if (pool->type & IS_WC) {
        r = set_pages_array_wc(pages, cpages);
        if (r)
            pr_err("%s: Failed to set %d pages to wc!\n",
                   pool->dev_name, cpages);
    }
    return r;
}

static void __ttm_dma_free_page(struct dma_pool *pool, struct dma_page *d_page)
{
    dma_addr_t dma = d_page->dma;
    dma_free_coherent(pool->dev, pool->size, d_page->vaddr, dma);

    kfree(d_page);
    d_page = NULL;
}
static struct dma_page *__ttm_dma_alloc_page(struct dma_pool *pool)
{
    struct dma_page *d_page;

    d_page = kmalloc(sizeof(struct dma_page), GFP_KERNEL);
    if (!d_page)
        return NULL;

    d_page->vaddr = dma_alloc_coherent(pool->dev, pool->size,
                       &d_page->dma,
                       pool->gfp_flags);
    if (d_page->vaddr)
        d_page->p = virt_to_page(d_page->vaddr);
    else {
        kfree(d_page);
        d_page = NULL;
    }
    return d_page;
}
static enum pool_type ttm_to_type(int flags, enum ttm_caching_state cstate)
{
    enum pool_type type = IS_UNDEFINED;

    if (flags & TTM_PAGE_FLAG_DMA32)
        type |= IS_DMA32;
    if (cstate == tt_cached)
        type |= IS_CACHED;
    else if (cstate == tt_uncached)
        type |= IS_UC;
    else
        type |= IS_WC;

    return type;
}

static void ttm_pool_update_free_locked(struct dma_pool *pool,
                    unsigned freed_pages)
{
    pool->npages_free -= freed_pages;
    pool->nfrees += freed_pages;

}

/* set memory back to wb and free the pages. */
static void ttm_dma_pages_put(struct dma_pool *pool, struct list_head *d_pages,
                  struct page *pages[], unsigned npages)
{
    struct dma_page *d_page, *tmp;

    /* Don't set WB on WB page pool. */
    if (npages && !(pool->type & IS_CACHED) &&
        set_pages_array_wb(pages, npages))
        pr_err("%s: Failed to set %d pages to wb!\n",
               pool->dev_name, npages);

    list_for_each_entry_safe(d_page, tmp, d_pages, page_list) {
        list_del(&d_page->page_list);
        __ttm_dma_free_page(pool, d_page);
    }
}

static void ttm_dma_page_put(struct dma_pool *pool, struct dma_page *d_page)
{
    /* Don't set WB on WB page pool. */
    if (!(pool->type & IS_CACHED) && set_pages_array_wb(&d_page->p, 1))
        pr_err("%s: Failed to set %d pages to wb!\n",
               pool->dev_name, 1);

    list_del(&d_page->page_list);
    __ttm_dma_free_page(pool, d_page);
}

/*
 * Free pages from pool.
 *
 * To prevent hogging the ttm_swap process we only free NUM_PAGES_TO_ALLOC
 * number of pages in one go.
 *
 * @pool: to free the pages from
 * @nr_free: If set to true will free all pages in pool
 **/
static unsigned ttm_dma_page_pool_free(struct dma_pool *pool, unsigned nr_free)
{
    unsigned long irq_flags;
    struct dma_page *dma_p, *tmp;
    struct page **pages_to_free;
    struct list_head d_pages;
    unsigned freed_pages = 0,
         npages_to_free = nr_free;

    if (NUM_PAGES_TO_ALLOC < nr_free)
        npages_to_free = NUM_PAGES_TO_ALLOC;
#if 0
    if (nr_free > 1) {
        pr_debug("%s: (%s:%d) Attempting to free %d (%d) pages\n",
             pool->dev_name, pool->name, current->pid,
             npages_to_free, nr_free);
    }
#endif
    pages_to_free = kmalloc(npages_to_free * sizeof(struct page *),
            GFP_KERNEL);

    if (!pages_to_free) {
        pr_err("%s: Failed to allocate memory for pool free operation\n",
               pool->dev_name);
        return 0;
    }
    INIT_LIST_HEAD(&d_pages);
restart:
    spin_lock_irqsave(&pool->lock, irq_flags);

    /* We picking the oldest ones off the list */
    list_for_each_entry_safe_reverse(dma_p, tmp, &pool->free_list,
                     page_list) {
        if (freed_pages >= npages_to_free)
            break;

        /* Move the dma_page from one list to another. */
        list_move(&dma_p->page_list, &d_pages);

        pages_to_free[freed_pages++] = dma_p->p;
        /* We can only remove NUM_PAGES_TO_ALLOC at a time. */
        if (freed_pages >= NUM_PAGES_TO_ALLOC) {

            ttm_pool_update_free_locked(pool, freed_pages);
            spin_unlock_irqrestore(&pool->lock, irq_flags);

            ttm_dma_pages_put(pool, &d_pages, pages_to_free,
                      freed_pages);

            INIT_LIST_HEAD(&d_pages);

            if (likely(nr_free != FREE_ALL_PAGES))
                nr_free -= freed_pages;

            if (NUM_PAGES_TO_ALLOC >= nr_free)
                npages_to_free = nr_free;
            else
                npages_to_free = NUM_PAGES_TO_ALLOC;

            freed_pages = 0;

            /* free all so restart the processing */
            if (nr_free)
                goto restart;

            /* Not allowed to fall through or break because
             * following context is inside spinlock while we are
             * outside here.
             */
            goto out;

        }
    }

    /* remove range of pages from the pool */
    if (freed_pages) {
        ttm_pool_update_free_locked(pool, freed_pages);
        nr_free -= freed_pages;
    }

    spin_unlock_irqrestore(&pool->lock, irq_flags);

    if (freed_pages)
        ttm_dma_pages_put(pool, &d_pages, pages_to_free, freed_pages);
out:
    kfree(pages_to_free);
    return nr_free;
}

static void ttm_dma_free_pool(struct device *dev, enum pool_type type)
{
    struct device_pools *p;
    struct dma_pool *pool;

    if (!dev)
        return;

    mutex_lock(&_manager->lock);
    list_for_each_entry_reverse(p, &_manager->pools, pools) {
        if (p->dev != dev)
            continue;
        pool = p->pool;
        if (pool->type != type)
            continue;

        list_del(&p->pools);
        kfree(p);
        _manager->npools--;
        break;
    }
    list_for_each_entry_reverse(pool, &dev->dma_pools, pools) {
        if (pool->type != type)
            continue;
        /* Takes a spinlock.. */
        ttm_dma_page_pool_free(pool, FREE_ALL_PAGES);
        WARN_ON(((pool->npages_in_use + pool->npages_free) != 0));
        /* This code path is called after _all_ references to the
         * struct device has been dropped - so nobody should be
         * touching it. In case somebody is trying to _add_ we are
         * guarded by the mutex. */
        list_del(&pool->pools);
        kfree(pool);
        break;
    }
    mutex_unlock(&_manager->lock);
}

/*
 * On free-ing of the 'struct device' this deconstructor is run.
 * Albeit the pool might have already been freed earlier.
 */
static void ttm_dma_pool_release(struct device *dev, void *res)
{
    struct dma_pool *pool = *(struct dma_pool **)res;

    if (pool)
        ttm_dma_free_pool(dev, pool->type);
}

static int ttm_dma_pool_match(struct device *dev, void *res, void *match_data)
{
    return *(struct dma_pool **)res == match_data;
}

static struct dma_pool *ttm_dma_pool_init(struct device *dev, gfp_t flags,
                      enum pool_type type)
{
    char *n[] = {"wc", "uc", "cached", " dma32", "unknown",};
    enum pool_type t[] = {IS_WC, IS_UC, IS_CACHED, IS_DMA32, IS_UNDEFINED};
    struct device_pools *sec_pool = NULL;
    struct dma_pool *pool = NULL, **ptr;
    unsigned i;
    int ret = -ENODEV;
    char *p;

    if (!dev)
        return NULL;

    ptr = devres_alloc(ttm_dma_pool_release, sizeof(*ptr), GFP_KERNEL);
    if (!ptr)
        return NULL;

    ret = -ENOMEM;

    pool = kmalloc_node(sizeof(struct dma_pool), GFP_KERNEL,
                dev_to_node(dev));
    if (!pool)
        goto err_mem;

    sec_pool = kmalloc_node(sizeof(struct device_pools), GFP_KERNEL,
                dev_to_node(dev));
    if (!sec_pool)
        goto err_mem;

    INIT_LIST_HEAD(&sec_pool->pools);
    sec_pool->dev = dev;
    sec_pool->pool =  pool;

    INIT_LIST_HEAD(&pool->free_list);
    INIT_LIST_HEAD(&pool->inuse_list);
    INIT_LIST_HEAD(&pool->pools);
    spin_lock_init(&pool->lock);
    pool->dev = dev;
    pool->npages_free = pool->npages_in_use = 0;
    pool->nfrees = 0;
    pool->gfp_flags = flags;
    pool->size = PAGE_SIZE;
    pool->type = type;
    pool->nrefills = 0;
    p = pool->name;
    for (i = 0; i < 5; i++) {
        if (type & t[i]) {
            p += snprintf(p, sizeof(pool->name) - (p - pool->name),
                      "%s", n[i]);
        }
    }
    *p = 0;
    /* We copy the name for pr_ calls b/c when dma_pool_destroy is called
     * - the kobj->name has already been deallocated.*/
    snprintf(pool->dev_name, sizeof(pool->dev_name), "%s %s",
         dev_driver_string(dev), dev_name(dev));
    mutex_lock(&_manager->lock);
    /* You can get the dma_pool from either the global: */
    list_add(&sec_pool->pools, &_manager->pools);
    _manager->npools++;
    /* or from 'struct device': */
    list_add(&pool->pools, &dev->dma_pools);
    mutex_unlock(&_manager->lock);

    *ptr = pool;
    devres_add(dev, ptr);

    return pool;
err_mem:
    devres_free(ptr);
    kfree(sec_pool);
    kfree(pool);
    return ERR_PTR(ret);
}

static struct dma_pool *ttm_dma_find_pool(struct device *dev,
                      enum pool_type type)
{
    struct dma_pool *pool, *tmp, *found = NULL;

    if (type == IS_UNDEFINED)
        return found;

    /* NB: We iterate on the 'struct dev' which has no spinlock, but
     * it does have a kref which we have taken. The kref is taken during
     * graphic driver loading - in the drm_pci_init it calls either
     * pci_dev_get or pci_register_driver which both end up taking a kref
     * on 'struct device'.
     *
     * On teardown, the graphic drivers end up quiescing the TTM (put_pages)
     * and calls the dev_res deconstructors: ttm_dma_pool_release. The nice
     * thing is at that point of time there are no pages associated with the
     * driver so this function will not be called.
     */
    list_for_each_entry_safe(pool, tmp, &dev->dma_pools, pools) {
        if (pool->type != type)
            continue;
        found = pool;
        break;
    }
    return found;
}

/*
 * Free pages the pages that failed to change the caching state. If there
 * are pages that have changed their caching state already put them to the
 * pool.
 */
static void ttm_dma_handle_caching_state_failure(struct dma_pool *pool,
                         struct list_head *d_pages,
                         struct page **failed_pages,
                         unsigned cpages)
{
    struct dma_page *d_page, *tmp;
    struct page *p;
    unsigned i = 0;

    p = failed_pages[0];
    if (!p)
        return;
    /* Find the failed page. */
    list_for_each_entry_safe(d_page, tmp, d_pages, page_list) {
        if (d_page->p != p)
            continue;
        /* .. and then progress over the full list. */
        list_del(&d_page->page_list);
        __ttm_dma_free_page(pool, d_page);
        if (++i < cpages)
            p = failed_pages[i];
        else
            break;
    }

}

/*
 * Allocate 'count' pages, and put 'need' number of them on the
 * 'pages' and as well on the 'dma_address' starting at 'dma_offset' offset.
 * The full list of pages should also be on 'd_pages'.
 * We return zero for success, and negative numbers as errors.
 */
static int ttm_dma_pool_alloc_new_pages(struct dma_pool *pool,
                    struct list_head *d_pages,
                    unsigned count)
{
    struct page **caching_array;
    struct dma_page *dma_p;
    struct page *p;
    int r = 0;
    unsigned i, cpages;
    unsigned max_cpages = min(count,
            (unsigned)(PAGE_SIZE/sizeof(struct page *)));

    /* allocate array for page caching change */
    caching_array = kmalloc(max_cpages*sizeof(struct page *), GFP_KERNEL);

    if (!caching_array) {
        pr_err("%s: Unable to allocate table for new pages\n",
               pool->dev_name);
        return -ENOMEM;
    }

    if (count > 1) {
        pr_debug("%s: (%s:%d) Getting %d pages\n",
             pool->dev_name, pool->name, current->pid, count);
    }

    for (i = 0, cpages = 0; i < count; ++i) {
        dma_p = __ttm_dma_alloc_page(pool);
        if (!dma_p) {
            pr_err("%s: Unable to get page %u\n",
                   pool->dev_name, i);

            /* store already allocated pages in the pool after
             * setting the caching state */
            if (cpages) {
                r = ttm_set_pages_caching(pool, caching_array,
                              cpages);
                if (r)
                    ttm_dma_handle_caching_state_failure(
                        pool, d_pages, caching_array,
                        cpages);
            }
            r = -ENOMEM;
            goto out;
        }
        p = dma_p->p;
#ifdef CONFIG_HIGHMEM
        /* gfp flags of highmem page should never be dma32 so we
         * we should be fine in such case
         */
        if (!PageHighMem(p))
#endif
        {
            caching_array[cpages++] = p;
            if (cpages == max_cpages) {
                /* Note: Cannot hold the spinlock */
                r = ttm_set_pages_caching(pool, caching_array,
                         cpages);
                if (r) {
                    ttm_dma_handle_caching_state_failure(
                        pool, d_pages, caching_array,
                        cpages);
                    goto out;
                }
                cpages = 0;
            }
        }
        list_add(&dma_p->page_list, d_pages);
    }

    if (cpages) {
        r = ttm_set_pages_caching(pool, caching_array, cpages);
        if (r)
            ttm_dma_handle_caching_state_failure(pool, d_pages,
                    caching_array, cpages);
    }
out:
    kfree(caching_array);
    return r;
}

/*
 * @return count of pages still required to fulfill the request.
 */
static int ttm_dma_page_pool_fill_locked(struct dma_pool *pool,
                     unsigned long *irq_flags)
{
    unsigned count = _manager->options.small;
    int r = pool->npages_free;

    if (count > pool->npages_free) {
        struct list_head d_pages;

        INIT_LIST_HEAD(&d_pages);

        spin_unlock_irqrestore(&pool->lock, *irq_flags);

        /* Returns how many more are neccessary to fulfill the
         * request. */
        r = ttm_dma_pool_alloc_new_pages(pool, &d_pages, count);

        spin_lock_irqsave(&pool->lock, *irq_flags);
        if (!r) {
            /* Add the fresh to the end.. */
            list_splice(&d_pages, &pool->free_list);
            ++pool->nrefills;
            pool->npages_free += count;
            r = count;
        } else {
            struct dma_page *d_page;
            unsigned cpages = 0;

            pr_err("%s: Failed to fill %s pool (r:%d)!\n",
                   pool->dev_name, pool->name, r);

            list_for_each_entry(d_page, &d_pages, page_list) {
                cpages++;
            }
            list_splice_tail(&d_pages, &pool->free_list);
            pool->npages_free += cpages;
            r = cpages;
        }
    }
    return r;
}

/*
 * @return count of pages still required to fulfill the request.
 * The populate list is actually a stack (not that is matters as TTM
 * allocates one page at a time.
 */
static int ttm_dma_pool_get_pages(struct dma_pool *pool,
                  struct ttm_dma_tt *ttm_dma,
                  unsigned index)
{
    struct dma_page *d_page;
    struct ttm_tt *ttm = &ttm_dma->ttm;
    unsigned long irq_flags;
    int count, r = -ENOMEM;

    spin_lock_irqsave(&pool->lock, irq_flags);
    count = ttm_dma_page_pool_fill_locked(pool, &irq_flags);
    if (count) {
        d_page = list_first_entry(&pool->free_list, struct dma_page, page_list);
        ttm->pages[index] = d_page->p;
        ttm_dma->dma_address[index] = d_page->dma;
        list_move_tail(&d_page->page_list, &ttm_dma->pages_list);
        r = 0;
        pool->npages_in_use += 1;
        pool->npages_free -= 1;
    }
    spin_unlock_irqrestore(&pool->lock, irq_flags);
    return r;
}

/*
 * On success pages list will hold count number of correctly
 * cached pages. On failure will hold the negative return value (-ENOMEM, etc).
 */
int ttm_dma_populate(struct ttm_dma_tt *ttm_dma, struct device *dev)
{
    struct ttm_tt *ttm = &ttm_dma->ttm;
    struct ttm_mem_global *mem_glob = ttm->glob->mem_glob;
    struct dma_pool *pool;
    enum pool_type type;
    unsigned i;
    gfp_t gfp_flags;
    int ret;

    if (ttm->state != tt_unpopulated)
        return 0;

    type = ttm_to_type(ttm->page_flags, ttm->caching_state);
    if (ttm->page_flags & TTM_PAGE_FLAG_DMA32)
        gfp_flags = GFP_USER | GFP_DMA32;
    else
        gfp_flags = GFP_HIGHUSER;
    if (ttm->page_flags & TTM_PAGE_FLAG_ZERO_ALLOC)
        gfp_flags |= __GFP_ZERO;

    pool = ttm_dma_find_pool(dev, type);
    if (!pool) {
        pool = ttm_dma_pool_init(dev, gfp_flags, type);
        if (IS_ERR_OR_NULL(pool)) {
            return -ENOMEM;
        }
    }

    INIT_LIST_HEAD(&ttm_dma->pages_list);
    for (i = 0; i < ttm->num_pages; ++i) {
        ret = ttm_dma_pool_get_pages(pool, ttm_dma, i);
        if (ret != 0) {
            ttm_dma_unpopulate(ttm_dma, dev);
            return -ENOMEM;
        }

        ret = ttm_mem_global_alloc_page(mem_glob, ttm->pages[i],
                        false, false);
        if (unlikely(ret != 0)) {
            ttm_dma_unpopulate(ttm_dma, dev);
            return -ENOMEM;
        }
    }

    if (unlikely(ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)) {
        ret = ttm_tt_swapin(ttm);
        if (unlikely(ret != 0)) {
            ttm_dma_unpopulate(ttm_dma, dev);
            return ret;
        }
    }

    ttm->state = tt_unbound;
    return 0;
}
EXPORT_SYMBOL_GPL(ttm_dma_populate);

/* Get good estimation how many pages are free in pools */
static int ttm_dma_pool_get_num_unused_pages(void)
{
    struct device_pools *p;
    unsigned total = 0;

    mutex_lock(&_manager->lock);
    list_for_each_entry(p, &_manager->pools, pools)
        total += p->pool->npages_free;
    mutex_unlock(&_manager->lock);
    return total;
}

/* Put all pages in pages list to correct pool to wait for reuse */
void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev)
{
    struct ttm_tt *ttm = &ttm_dma->ttm;
    struct dma_pool *pool;
    struct dma_page *d_page, *next;
    enum pool_type type;
    bool is_cached = false;
    unsigned count = 0, i, npages = 0;
    unsigned long irq_flags;

    type = ttm_to_type(ttm->page_flags, ttm->caching_state);
    pool = ttm_dma_find_pool(dev, type);
    if (!pool)
        return;

    is_cached = (ttm_dma_find_pool(pool->dev,
             ttm_to_type(ttm->page_flags, tt_cached)) == pool);

    /* make sure pages array match list and count number of pages */
    list_for_each_entry(d_page, &ttm_dma->pages_list, page_list) {
        ttm->pages[count] = d_page->p;
        count++;
    }

    spin_lock_irqsave(&pool->lock, irq_flags);
    pool->npages_in_use -= count;
    if (is_cached) {
        pool->nfrees += count;
    } else {
        pool->npages_free += count;
        list_splice(&ttm_dma->pages_list, &pool->free_list);
        npages = count;
        if (pool->npages_free > _manager->options.max_size) {
            npages = pool->npages_free - _manager->options.max_size;
            /* free at least NUM_PAGES_TO_ALLOC number of pages
             * to reduce calls to set_memory_wb */
            if (npages < NUM_PAGES_TO_ALLOC)
                npages = NUM_PAGES_TO_ALLOC;
        }
    }
    spin_unlock_irqrestore(&pool->lock, irq_flags);

    if (is_cached) {
        list_for_each_entry_safe(d_page, next, &ttm_dma->pages_list, page_list) {
            ttm_mem_global_free_page(ttm->glob->mem_glob,
                         d_page->p);
            ttm_dma_page_put(pool, d_page);
        }
    } else {
        for (i = 0; i < count; i++) {
            ttm_mem_global_free_page(ttm->glob->mem_glob,
                         ttm->pages[i]);
        }
    }

    INIT_LIST_HEAD(&ttm_dma->pages_list);
    for (i = 0; i < ttm->num_pages; i++) {
        ttm->pages[i] = NULL;
        ttm_dma->dma_address[i] = 0;
    }

    /* shrink pool if necessary (only on !is_cached pools)*/
    if (npages)
        ttm_dma_page_pool_free(pool, npages);
    ttm->state = tt_unpopulated;
}
EXPORT_SYMBOL_GPL(ttm_dma_unpopulate);

static int ttm_dma_pool_mm_shrink(struct shrinker *shrink,
                  struct shrink_control *sc)
{
    static atomic_t start_pool = ATOMIC_INIT(0);
    unsigned idx = 0;
    unsigned pool_offset = atomic_add_return(1, &start_pool);
    unsigned shrink_pages = sc->nr_to_scan;
    struct device_pools *p;

    if (list_empty(&_manager->pools))
        return 0;

    mutex_lock(&_manager->lock);
    pool_offset = pool_offset % _manager->npools;
    list_for_each_entry(p, &_manager->pools, pools) {
        unsigned nr_free;

        if (!p->dev)
            continue;
        if (shrink_pages == 0)
            break;
        /* Do it in round-robin fashion. */
        if (++idx < pool_offset)
            continue;
        nr_free = shrink_pages;
        shrink_pages = ttm_dma_page_pool_free(p->pool, nr_free);
        pr_debug("%s: (%s:%d) Asked to shrink %d, have %d more to go\n",
             p->pool->dev_name, p->pool->name, current->pid,
             nr_free, shrink_pages);
    }
    mutex_unlock(&_manager->lock);
    /* return estimated number of unused pages in pool */
    return ttm_dma_pool_get_num_unused_pages();
}

static void ttm_dma_pool_mm_shrink_init(struct ttm_pool_manager *manager)
{
    manager->mm_shrink.shrink = &ttm_dma_pool_mm_shrink;
    manager->mm_shrink.seeks = 1;
    register_shrinker(&manager->mm_shrink);
}

static void ttm_dma_pool_mm_shrink_fini(struct ttm_pool_manager *manager)
{
    unregister_shrinker(&manager->mm_shrink);
}

int ttm_dma_page_alloc_init(struct ttm_mem_global *glob, unsigned max_pages)
{
    int ret = -ENOMEM;

    WARN_ON(_manager);

    pr_info("Initializing DMA pool allocator\n");

    _manager = kzalloc(sizeof(*_manager), GFP_KERNEL);
    if (!_manager)
        goto err;

    mutex_init(&_manager->lock);
    INIT_LIST_HEAD(&_manager->pools);

    _manager->options.max_size = max_pages;
    _manager->options.small = SMALL_ALLOCATION;
    _manager->options.alloc_size = NUM_PAGES_TO_ALLOC;

    /* This takes care of auto-freeing the _manager */
    ret = kobject_init_and_add(&_manager->kobj, &ttm_pool_kobj_type,
                   &glob->kobj, "dma_pool");
    if (unlikely(ret != 0)) {
        kobject_put(&_manager->kobj);
        goto err;
    }
    ttm_dma_pool_mm_shrink_init(_manager);
    return 0;
err:
    return ret;
}

void ttm_dma_page_alloc_fini(void)
{
    struct device_pools *p, *t;

    pr_info("Finalizing DMA pool allocator\n");
    ttm_dma_pool_mm_shrink_fini(_manager);

    list_for_each_entry_safe_reverse(p, t, &_manager->pools, pools) {
        dev_dbg(p->dev, "(%s:%d) Freeing.\n", p->pool->name,
            current->pid);
        WARN_ON(devres_destroy(p->dev, ttm_dma_pool_release,
            ttm_dma_pool_match, p->pool));
        ttm_dma_free_pool(p->dev, p->pool->type);
    }
    kobject_put(&_manager->kobj);
    _manager = NULL;
}

int ttm_dma_page_alloc_debugfs(struct seq_file *m, void *data)
{
    struct device_pools *p;
    struct dma_pool *pool = NULL;
    char *h[] = {"pool", "refills", "pages freed", "inuse", "available",
             "name", "virt", "busaddr"};

    if (!_manager) {
        seq_printf(m, "No pool allocator running.\n");
        return 0;
    }
    seq_printf(m, "%13s %12s %13s %8s %8s %8s\n",
           h[0], h[1], h[2], h[3], h[4], h[5]);
    mutex_lock(&_manager->lock);
    list_for_each_entry(p, &_manager->pools, pools) {
        struct device *dev = p->dev;
        if (!dev)
            continue;
        pool = p->pool;
        seq_printf(m, "%13s %12ld %13ld %8d %8d %8s\n",
                pool->name, pool->nrefills,
                pool->nfrees, pool->npages_in_use,
                pool->npages_free,
                pool->dev_name);
    }
    mutex_unlock(&_manager->lock);
    return 0;
}
EXPORT_SYMBOL_GPL(ttm_dma_page_alloc_debugfs);