Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux

[sfrench/cifs-2.6.git] / arch / arm / mm / dma-mapping.c

/*
 *  linux/arch/arm/mm/dma-mapping.c
 *
 *  Copyright (C) 2000-2004 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  DMA uncached mapping support.
 */
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/genalloc.h>
#include <linux/gfp.h>
#include <linux/errno.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/dma-mapping.h>
#include <linux/dma-contiguous.h>
#include <linux/highmem.h>
#include <linux/memblock.h>
#include <linux/slab.h>
#include <linux/iommu.h>
#include <linux/io.h>
#include <linux/vmalloc.h>
#include <linux/sizes.h>
#include <linux/cma.h>

#include <asm/memory.h>
#include <asm/highmem.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/mach/arch.h>
#include <asm/dma-iommu.h>
#include <asm/mach/map.h>
#include <asm/system_info.h>
#include <asm/dma-contiguous.h>

#include "dma.h"
#include "mm.h"

struct arm_dma_alloc_args {
        struct device *dev;
        size_t size;
        gfp_t gfp;
        pgprot_t prot;
        const void *caller;
        bool want_vaddr;
        int coherent_flag;
};

struct arm_dma_free_args {
        struct device *dev;
        size_t size;
        void *cpu_addr;
        struct page *page;
        bool want_vaddr;
};

#define NORMAL      0
#define COHERENT    1

struct arm_dma_allocator {
        void *(*alloc)(struct arm_dma_alloc_args *args,
                       struct page **ret_page);
        void (*free)(struct arm_dma_free_args *args);
};

struct arm_dma_buffer {
        struct list_head list;
        void *virt;
        struct arm_dma_allocator *allocator;
};

static LIST_HEAD(arm_dma_bufs);
static DEFINE_SPINLOCK(arm_dma_bufs_lock);

static struct arm_dma_buffer *arm_dma_buffer_find(void *virt)
{
        struct arm_dma_buffer *buf, *found = NULL;
        unsigned long flags;

        spin_lock_irqsave(&arm_dma_bufs_lock, flags);
        list_for_each_entry(buf, &arm_dma_bufs, list) {
                if (buf->virt == virt) {
                        list_del(&buf->list);
                        found = buf;
                        break;
                }
        }
        spin_unlock_irqrestore(&arm_dma_bufs_lock, flags);
        return found;
}

/*
 * The DMA API is built upon the notion of "buffer ownership".  A buffer
 * is either exclusively owned by the CPU (and therefore may be accessed
 * by it) or exclusively owned by the DMA device.  These helper functions
 * represent the transitions between these two ownership states.
 *
 * Note, however, that on later ARMs, this notion does not work due to
 * speculative prefetches.  We model our approach on the assumption that
 * the CPU does do speculative prefetches, which means we clean caches
 * before transfers and delay cache invalidation until transfer completion.
 *
 */
static void __dma_page_cpu_to_dev(struct page *, unsigned long,
                size_t, enum dma_data_direction);
static void __dma_page_dev_to_cpu(struct page *, unsigned long,
                size_t, enum dma_data_direction);

/**
 * arm_dma_map_page - map a portion of a page for streaming DMA
 * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
 * @page: page that buffer resides in
 * @offset: offset into page for start of buffer
 * @size: size of buffer to map
 * @dir: DMA transfer direction
 *
 * Ensure that any data held in the cache is appropriately discarded
 * or written back.
 *
 * The device owns this memory once this call has completed.  The CPU
 * can regain ownership by calling dma_unmap_page().
 */
static dma_addr_t arm_dma_map_page(struct device *dev, struct page *page,
             unsigned long offset, size_t size, enum dma_data_direction dir,
             unsigned long attrs)
{
        if ((attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
                __dma_page_cpu_to_dev(page, offset, size, dir);
        return pfn_to_dma(dev, page_to_pfn(page)) + offset;
}

static dma_addr_t arm_coherent_dma_map_page(struct device *dev, struct page *page,
             unsigned long offset, size_t size, enum dma_data_direction dir,
             unsigned long attrs)
{
        return pfn_to_dma(dev, page_to_pfn(page)) + offset;
}

/**
 * arm_dma_unmap_page - unmap a buffer previously mapped through dma_map_page()
 * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
 * @handle: DMA address of buffer
 * @size: size of buffer (same as passed to dma_map_page)
 * @dir: DMA transfer direction (same as passed to dma_map_page)
 *
 * Unmap a page streaming mode DMA translation.  The handle and size
 * must match what was provided in the previous dma_map_page() call.
 * All other usages are undefined.
 *
 * After this call, reads by the CPU to the buffer are guaranteed to see
 * whatever the device wrote there.
 */
static void arm_dma_unmap_page(struct device *dev, dma_addr_t handle,
                size_t size, enum dma_data_direction dir, unsigned long attrs)
{
        if ((attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
                __dma_page_dev_to_cpu(pfn_to_page(dma_to_pfn(dev, handle)),
                                      handle & ~PAGE_MASK, size, dir);
}

static void arm_dma_sync_single_for_cpu(struct device *dev,
                dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
        unsigned int offset = handle & (PAGE_SIZE - 1);
        struct page *page = pfn_to_page(dma_to_pfn(dev, handle-offset));
        __dma_page_dev_to_cpu(page, offset, size, dir);
}

static void arm_dma_sync_single_for_device(struct device *dev,
                dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
        unsigned int offset = handle & (PAGE_SIZE - 1);
        struct page *page = pfn_to_page(dma_to_pfn(dev, handle-offset));
        __dma_page_cpu_to_dev(page, offset, size, dir);
}

static int arm_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
{
        return dma_addr == ARM_MAPPING_ERROR;
}

const struct dma_map_ops arm_dma_ops = {
        .alloc                  = arm_dma_alloc,
        .free                   = arm_dma_free,
        .mmap                   = arm_dma_mmap,
        .get_sgtable            = arm_dma_get_sgtable,
        .map_page               = arm_dma_map_page,
        .unmap_page             = arm_dma_unmap_page,
        .map_sg                 = arm_dma_map_sg,
        .unmap_sg               = arm_dma_unmap_sg,
        .sync_single_for_cpu    = arm_dma_sync_single_for_cpu,
        .sync_single_for_device = arm_dma_sync_single_for_device,
        .sync_sg_for_cpu        = arm_dma_sync_sg_for_cpu,
        .sync_sg_for_device     = arm_dma_sync_sg_for_device,
        .mapping_error          = arm_dma_mapping_error,
        .dma_supported          = arm_dma_supported,
};
EXPORT_SYMBOL(arm_dma_ops);

static void *arm_coherent_dma_alloc(struct device *dev, size_t size,
        dma_addr_t *handle, gfp_t gfp, unsigned long attrs);
static void arm_coherent_dma_free(struct device *dev, size_t size, void *cpu_addr,
                                  dma_addr_t handle, unsigned long attrs);
static int arm_coherent_dma_mmap(struct device *dev, struct vm_area_struct *vma,
                 void *cpu_addr, dma_addr_t dma_addr, size_t size,
                 unsigned long attrs);

const struct dma_map_ops arm_coherent_dma_ops = {
        .alloc                  = arm_coherent_dma_alloc,
        .free                   = arm_coherent_dma_free,
        .mmap                   = arm_coherent_dma_mmap,
        .get_sgtable            = arm_dma_get_sgtable,
        .map_page               = arm_coherent_dma_map_page,
        .map_sg                 = arm_dma_map_sg,
        .mapping_error          = arm_dma_mapping_error,
        .dma_supported          = arm_dma_supported,
};
EXPORT_SYMBOL(arm_coherent_dma_ops);

static int __dma_supported(struct device *dev, u64 mask, bool warn)
{
        unsigned long max_dma_pfn;

        /*
         * If the mask allows for more memory than we can address,
         * and we actually have that much memory, then we must
         * indicate that DMA to this device is not supported.
         */
        if (sizeof(mask) != sizeof(dma_addr_t) &&
            mask > (dma_addr_t)~0 &&
            dma_to_pfn(dev, ~0) < max_pfn - 1) {
                if (warn) {
                        dev_warn(dev, "Coherent DMA mask %#llx is larger than dma_addr_t allows\n",
                                 mask);
                        dev_warn(dev, "Driver did not use or check the return value from dma_set_coherent_mask()?\n");
                }
                return 0;
        }

        max_dma_pfn = min(max_pfn, arm_dma_pfn_limit);

        /*
         * Translate the device's DMA mask to a PFN limit.  This
         * PFN number includes the page which we can DMA to.
         */
        if (dma_to_pfn(dev, mask) < max_dma_pfn) {
                if (warn)
                        dev_warn(dev, "Coherent DMA mask %#llx (pfn %#lx-%#lx) covers a smaller range of system memory than the DMA zone pfn 0x0-%#lx\n",
                                 mask,
                                 dma_to_pfn(dev, 0), dma_to_pfn(dev, mask) + 1,
                                 max_dma_pfn + 1);
                return 0;
        }

        return 1;
}

static u64 get_coherent_dma_mask(struct device *dev)
{
        u64 mask = (u64)DMA_BIT_MASK(32);

        if (dev) {
                mask = dev->coherent_dma_mask;

                /*
                 * Sanity check the DMA mask - it must be non-zero, and
                 * must be able to be satisfied by a DMA allocation.
                 */
                if (mask == 0) {
                        dev_warn(dev, "coherent DMA mask is unset\n");
                        return 0;
                }

                if (!__dma_supported(dev, mask, true))
                        return 0;
        }

        return mask;
}

static void __dma_clear_buffer(struct page *page, size_t size, int coherent_flag)
{
        /*
         * Ensure that the allocated pages are zeroed, and that any data
         * lurking in the kernel direct-mapped region is invalidated.
         */
        if (PageHighMem(page)) {
                phys_addr_t base = __pfn_to_phys(page_to_pfn(page));
                phys_addr_t end = base + size;
                while (size > 0) {
                        void *ptr = kmap_atomic(page);
                        memset(ptr, 0, PAGE_SIZE);
                        if (coherent_flag != COHERENT)
                                dmac_flush_range(ptr, ptr + PAGE_SIZE);
                        kunmap_atomic(ptr);
                        page++;
                        size -= PAGE_SIZE;
                }
                if (coherent_flag != COHERENT)
                        outer_flush_range(base, end);
        } else {
                void *ptr = page_address(page);
                memset(ptr, 0, size);
                if (coherent_flag != COHERENT) {
                        dmac_flush_range(ptr, ptr + size);
                        outer_flush_range(__pa(ptr), __pa(ptr) + size);
                }
        }
}

/*
 * Allocate a DMA buffer for 'dev' of size 'size' using the
 * specified gfp mask.  Note that 'size' must be page aligned.
 */
static struct page *__dma_alloc_buffer(struct device *dev, size_t size,
                                       gfp_t gfp, int coherent_flag)
{
        unsigned long order = get_order(size);
        struct page *page, *p, *e;

        page = alloc_pages(gfp, order);
        if (!page)
                return NULL;

        /*
         * Now split the huge page and free the excess pages
         */
        split_page(page, order);
        for (p = page + (size >> PAGE_SHIFT), e = page + (1 << order); p < e; p++)
                __free_page(p);

        __dma_clear_buffer(page, size, coherent_flag);

        return page;
}

/*
 * Free a DMA buffer.  'size' must be page aligned.
 */
static void __dma_free_buffer(struct page *page, size_t size)
{
        struct page *e = page + (size >> PAGE_SHIFT);

        while (page < e) {
                __free_page(page);
                page++;
        }
}

static void *__alloc_from_contiguous(struct device *dev, size_t size,
                                     pgprot_t prot, struct page **ret_page,
                                     const void *caller, bool want_vaddr,
                                     int coherent_flag, gfp_t gfp);

static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
                                 pgprot_t prot, struct page **ret_page,
                                 const void *caller, bool want_vaddr);

static void *
__dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
        const void *caller)
{
        /*
         * DMA allocation can be mapped to user space, so lets
         * set VM_USERMAP flags too.
         */
        return dma_common_contiguous_remap(page, size,
                        VM_ARM_DMA_CONSISTENT | VM_USERMAP,
                        prot, caller);
}

static void __dma_free_remap(void *cpu_addr, size_t size)
{
        dma_common_free_remap(cpu_addr, size,
                        VM_ARM_DMA_CONSISTENT | VM_USERMAP);
}

#define DEFAULT_DMA_COHERENT_POOL_SIZE  SZ_256K
static struct gen_pool *atomic_pool __ro_after_init;

static size_t atomic_pool_size __initdata = DEFAULT_DMA_COHERENT_POOL_SIZE;

static int __init early_coherent_pool(char *p)
{
        atomic_pool_size = memparse(p, &p);
        return 0;
}
early_param("coherent_pool", early_coherent_pool);

/*
 * Initialise the coherent pool for atomic allocations.
 */
static int __init atomic_pool_init(void)
{
        pgprot_t prot = pgprot_dmacoherent(PAGE_KERNEL);
        gfp_t gfp = GFP_KERNEL | GFP_DMA;
        struct page *page;
        void *ptr;

        atomic_pool = gen_pool_create(PAGE_SHIFT, -1);
        if (!atomic_pool)
                goto out;
        /*
         * The atomic pool is only used for non-coherent allocations
         * so we must pass NORMAL for coherent_flag.
         */
        if (dev_get_cma_area(NULL))
                ptr = __alloc_from_contiguous(NULL, atomic_pool_size, prot,
                                      &page, atomic_pool_init, true, NORMAL,
                                      GFP_KERNEL);
        else
                ptr = __alloc_remap_buffer(NULL, atomic_pool_size, gfp, prot,
                                           &page, atomic_pool_init, true);
        if (ptr) {
                int ret;

                ret = gen_pool_add_virt(atomic_pool, (unsigned long)ptr,
                                        page_to_phys(page),
                                        atomic_pool_size, -1);
                if (ret)
                        goto destroy_genpool;

                gen_pool_set_algo(atomic_pool,
                                gen_pool_first_fit_order_align,
                                NULL);
                pr_info("DMA: preallocated %zu KiB pool for atomic coherent allocations\n",
                       atomic_pool_size / 1024);
                return 0;
        }

destroy_genpool:
        gen_pool_destroy(atomic_pool);
        atomic_pool = NULL;
out:
        pr_err("DMA: failed to allocate %zu KiB pool for atomic coherent allocation\n",
               atomic_pool_size / 1024);
        return -ENOMEM;
}
/*
 * CMA is activated by core_initcall, so we must be called after it.
 */
postcore_initcall(atomic_pool_init);

struct dma_contig_early_reserve {
        phys_addr_t base;
        unsigned long size;
};

static struct dma_contig_early_reserve dma_mmu_remap[MAX_CMA_AREAS] __initdata;

static int dma_mmu_remap_num __initdata;

void __init dma_contiguous_early_fixup(phys_addr_t base, unsigned long size)
{
        dma_mmu_remap[dma_mmu_remap_num].base = base;
        dma_mmu_remap[dma_mmu_remap_num].size = size;
        dma_mmu_remap_num++;
}

void __init dma_contiguous_remap(void)
{
        int i;
        for (i = 0; i < dma_mmu_remap_num; i++) {
                phys_addr_t start = dma_mmu_remap[i].base;
                phys_addr_t end = start + dma_mmu_remap[i].size;
                struct map_desc map;
                unsigned long addr;

                if (end > arm_lowmem_limit)
                        end = arm_lowmem_limit;
                if (start >= end)
                        continue;

                map.pfn = __phys_to_pfn(start);
                map.virtual = __phys_to_virt(start);
                map.length = end - start;
                map.type = MT_MEMORY_DMA_READY;

                /*
                 * Clear previous low-memory mapping to ensure that the
                 * TLB does not see any conflicting entries, then flush
                 * the TLB of the old entries before creating new mappings.
                 *
                 * This ensures that any speculatively loaded TLB entries
                 * (even though they may be rare) can not cause any problems,
                 * and ensures that this code is architecturally compliant.
                 */
                for (addr = __phys_to_virt(start); addr < __phys_to_virt(end);
                     addr += PMD_SIZE)
                        pmd_clear(pmd_off_k(addr));

                flush_tlb_kernel_range(__phys_to_virt(start),
                                       __phys_to_virt(end));

                iotable_init(&map, 1);
        }
}

static int __dma_update_pte(pte_t *pte, pgtable_t token, unsigned long addr,
                            void *data)
{
        struct page *page = virt_to_page(addr);
        pgprot_t prot = *(pgprot_t *)data;

        set_pte_ext(pte, mk_pte(page, prot), 0);
        return 0;
}

static void __dma_remap(struct page *page, size_t size, pgprot_t prot)
{
        unsigned long start = (unsigned long) page_address(page);
        unsigned end = start + size;

        apply_to_page_range(&init_mm, start, size, __dma_update_pte, &prot);
        flush_tlb_kernel_range(start, end);
}

static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
                                 pgprot_t prot, struct page **ret_page,
                                 const void *caller, bool want_vaddr)
{
        struct page *page;
        void *ptr = NULL;
        /*
         * __alloc_remap_buffer is only called when the device is
         * non-coherent
         */
        page = __dma_alloc_buffer(dev, size, gfp, NORMAL);
        if (!page)
                return NULL;
        if (!want_vaddr)
                goto out;

        ptr = __dma_alloc_remap(page, size, gfp, prot, caller);
        if (!ptr) {
                __dma_free_buffer(page, size);
                return NULL;
        }

 out:
        *ret_page = page;
        return ptr;
}

static void *__alloc_from_pool(size_t size, struct page **ret_page)
{
        unsigned long val;
        void *ptr = NULL;

        if (!atomic_pool) {
                WARN(1, "coherent pool not initialised!\n");
                return NULL;
        }

        val = gen_pool_alloc(atomic_pool, size);
        if (val) {
                phys_addr_t phys = gen_pool_virt_to_phys(atomic_pool, val);

                *ret_page = phys_to_page(phys);
                ptr = (void *)val;
        }

        return ptr;
}

static bool __in_atomic_pool(void *start, size_t size)
{
        return addr_in_gen_pool(atomic_pool, (unsigned long)start, size);
}

static int __free_from_pool(void *start, size_t size)
{
        if (!__in_atomic_pool(start, size))
                return 0;

        gen_pool_free(atomic_pool, (unsigned long)start, size);

        return 1;
}

static void *__alloc_from_contiguous(struct device *dev, size_t size,
                                     pgprot_t prot, struct page **ret_page,
                                     const void *caller, bool want_vaddr,
                                     int coherent_flag, gfp_t gfp)
{
        unsigned long order = get_order(size);
        size_t count = size >> PAGE_SHIFT;
        struct page *page;
        void *ptr = NULL;

        page = dma_alloc_from_contiguous(dev, count, order, gfp & __GFP_NOWARN);
        if (!page)
                return NULL;

        __dma_clear_buffer(page, size, coherent_flag);

        if (!want_vaddr)
                goto out;

        if (PageHighMem(page)) {
                ptr = __dma_alloc_remap(page, size, GFP_KERNEL, prot, caller);
                if (!ptr) {
                        dma_release_from_contiguous(dev, page, count);
                        return NULL;
                }
        } else {
                __dma_remap(page, size, prot);
                ptr = page_address(page);
        }

 out:
        *ret_page = page;
        return ptr;
}

static void __free_from_contiguous(struct device *dev, struct page *page,
                                   void *cpu_addr, size_t size, bool want_vaddr)
{
        if (want_vaddr) {
                if (PageHighMem(page))
                        __dma_free_remap(cpu_addr, size);
                else
                        __dma_remap(page, size, PAGE_KERNEL);
        }
        dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT);
}

static inline pgprot_t __get_dma_pgprot(unsigned long attrs, pgprot_t prot)
{
        prot = (attrs & DMA_ATTR_WRITE_COMBINE) ?
                        pgprot_writecombine(prot) :
                        pgprot_dmacoherent(prot);
        return prot;
}

static void *__alloc_simple_buffer(struct device *dev, size_t size, gfp_t gfp,
                                   struct page **ret_page)
{
        struct page *page;
        /* __alloc_simple_buffer is only called when the device is coherent */
        page = __dma_alloc_buffer(dev, size, gfp, COHERENT);
        if (!page)
                return NULL;

        *ret_page = page;
        return page_address(page);
}

static void *simple_allocator_alloc(struct arm_dma_alloc_args *args,
                                    struct page **ret_page)
{
        return __alloc_simple_buffer(args->dev, args->size, args->gfp,
                                     ret_page);
}

static void simple_allocator_free(struct arm_dma_free_args *args)
{
        __dma_free_buffer(args->page, args->size);
}

static struct arm_dma_allocator simple_allocator = {
        .alloc = simple_allocator_alloc,
        .free = simple_allocator_free,
};

static void *cma_allocator_alloc(struct arm_dma_alloc_args *args,
                                 struct page **ret_page)
{
        return __alloc_from_contiguous(args->dev, args->size, args->prot,
                                       ret_page, args->caller,
                                       args->want_vaddr, args->coherent_flag,
                                       args->gfp);
}

static void cma_allocator_free(struct arm_dma_free_args *args)
{
        __free_from_contiguous(args->dev, args->page, args->cpu_addr,
                               args->size, args->want_vaddr);
}

static struct arm_dma_allocator cma_allocator = {
        .alloc = cma_allocator_alloc,
        .free = cma_allocator_free,
};

static void *pool_allocator_alloc(struct arm_dma_alloc_args *args,
                                  struct page **ret_page)
{
        return __alloc_from_pool(args->size, ret_page);
}

static void pool_allocator_free(struct arm_dma_free_args *args)
{
        __free_from_pool(args->cpu_addr, args->size);
}

static struct arm_dma_allocator pool_allocator = {
        .alloc = pool_allocator_alloc,
        .free = pool_allocator_free,
};

static void *remap_allocator_alloc(struct arm_dma_alloc_args *args,
                                   struct page **ret_page)
{
        return __alloc_remap_buffer(args->dev, args->size, args->gfp,
                                    args->prot, ret_page, args->caller,
                                    args->want_vaddr);
}

static void remap_allocator_free(struct arm_dma_free_args *args)
{
        if (args->want_vaddr)
                __dma_free_remap(args->cpu_addr, args->size);

        __dma_free_buffer(args->page, args->size);
}

static struct arm_dma_allocator remap_allocator = {
        .alloc = remap_allocator_alloc,
        .free = remap_allocator_free,
};

static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
                         gfp_t gfp, pgprot_t prot, bool is_coherent,
                         unsigned long attrs, const void *caller)
{
        u64 mask = get_coherent_dma_mask(dev);
        struct page *page = NULL;
        void *addr;
        bool allowblock, cma;
        struct arm_dma_buffer *buf;
        struct arm_dma_alloc_args args = {
                .dev = dev,
                .size = PAGE_ALIGN(size),
                .gfp = gfp,
                .prot = prot,
                .caller = caller,
                .want_vaddr = ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0),
                .coherent_flag = is_coherent ? COHERENT : NORMAL,
        };

#ifdef CONFIG_DMA_API_DEBUG
        u64 limit = (mask + 1) & ~mask;
        if (limit && size >= limit) {
                dev_warn(dev, "coherent allocation too big (requested %#x mask %#llx)\n",
                        size, mask);
                return NULL;
        }
#endif

        if (!mask)
                return NULL;

        buf = kzalloc(sizeof(*buf),
                      gfp & ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM));
        if (!buf)
                return NULL;

        if (mask < 0xffffffffULL)
                gfp |= GFP_DMA;

        /*
         * Following is a work-around (a.k.a. hack) to prevent pages
         * with __GFP_COMP being passed to split_page() which cannot
         * handle them.  The real problem is that this flag probably
         * should be 0 on ARM as it is not supported on this
         * platform; see CONFIG_HUGETLBFS.
         */
        gfp &= ~(__GFP_COMP);
        args.gfp = gfp;

        *handle = ARM_MAPPING_ERROR;
        allowblock = gfpflags_allow_blocking(gfp);
        cma = allowblock ? dev_get_cma_area(dev) : false;

        if (cma)
                buf->allocator = &cma_allocator;
        else if (is_coherent)
                buf->allocator = &simple_allocator;
        else if (allowblock)
                buf->allocator = &remap_allocator;
        else
                buf->allocator = &pool_allocator;

        addr = buf->allocator->alloc(&args, &page);

        if (page) {
                unsigned long flags;

                *handle = pfn_to_dma(dev, page_to_pfn(page));
                buf->virt = args.want_vaddr ? addr : page;

                spin_lock_irqsave(&arm_dma_bufs_lock, flags);
                list_add(&buf->list, &arm_dma_bufs);
                spin_unlock_irqrestore(&arm_dma_bufs_lock, flags);
        } else {
                kfree(buf);
        }

        return args.want_vaddr ? addr : page;
}

/*
 * Allocate DMA-coherent memory space and return both the kernel remapped
 * virtual and bus address for that space.
 */
void *arm_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
                    gfp_t gfp, unsigned long attrs)
{
        pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL);

        return __dma_alloc(dev, size, handle, gfp, prot, false,
                           attrs, __builtin_return_address(0));
}

static void *arm_coherent_dma_alloc(struct device *dev, size_t size,
        dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
{
        return __dma_alloc(dev, size, handle, gfp, PAGE_KERNEL, true,
                           attrs, __builtin_return_address(0));
}

static int __arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
                 void *cpu_addr, dma_addr_t dma_addr, size_t size,
                 unsigned long attrs)
{
        int ret;
        unsigned long nr_vma_pages = vma_pages(vma);
        unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
        unsigned long pfn = dma_to_pfn(dev, dma_addr);
        unsigned long off = vma->vm_pgoff;

        if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
                return ret;

        if (off < nr_pages && nr_vma_pages <= (nr_pages - off)) {
                ret = remap_pfn_range(vma, vma->vm_start,
                                      pfn + off,
                                      vma->vm_end - vma->vm_start,
                                      vma->vm_page_prot);
        }

        return ret;
}

/*
 * Create userspace mapping for the DMA-coherent memory.
 */
static int arm_coherent_dma_mmap(struct device *dev, struct vm_area_struct *vma,
                 void *cpu_addr, dma_addr_t dma_addr, size_t size,
                 unsigned long attrs)
{
        return __arm_dma_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
}

int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
                 void *cpu_addr, dma_addr_t dma_addr, size_t size,
                 unsigned long attrs)
{
        vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
        return __arm_dma_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
}

/*
 * Free a buffer as defined by the above mapping.
 */
static void __arm_dma_free(struct device *dev, size_t size, void *cpu_addr,
                           dma_addr_t handle, unsigned long attrs,
                           bool is_coherent)
{
        struct page *page = pfn_to_page(dma_to_pfn(dev, handle));
        struct arm_dma_buffer *buf;
        struct arm_dma_free_args args = {
                .dev = dev,
                .size = PAGE_ALIGN(size),
                .cpu_addr = cpu_addr,
                .page = page,
                .want_vaddr = ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0),
        };

        buf = arm_dma_buffer_find(cpu_addr);
        if (WARN(!buf, "Freeing invalid buffer %p\n", cpu_addr))
                return;

        buf->allocator->free(&args);
        kfree(buf);
}

void arm_dma_free(struct device *dev, size_t size, void *cpu_addr,
                  dma_addr_t handle, unsigned long attrs)
{
        __arm_dma_free(dev, size, cpu_addr, handle, attrs, false);
}

static void arm_coherent_dma_free(struct device *dev, size_t size, void *cpu_addr,
                                  dma_addr_t handle, unsigned long attrs)
{
        __arm_dma_free(dev, size, cpu_addr, handle, attrs, true);
}

/*
 * The whole dma_get_sgtable() idea is fundamentally unsafe - it seems
 * that the intention is to allow exporting memory allocated via the
 * coherent DMA APIs through the dma_buf API, which only accepts a
 * scattertable.  This presents a couple of problems:
 * 1. Not all memory allocated via the coherent DMA APIs is backed by
 *    a struct page
 * 2. Passing coherent DMA memory into the streaming APIs is not allowed
 *    as we will try to flush the memory through a different alias to that
 *    actually being used (and the flushes are redundant.)
 */
int arm_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
                 void *cpu_addr, dma_addr_t handle, size_t size,
                 unsigned long attrs)
{
        unsigned long pfn = dma_to_pfn(dev, handle);
        struct page *page;
        int ret;

        /* If the PFN is not valid, we do not have a struct page */
        if (!pfn_valid(pfn))
                return -ENXIO;

        page = pfn_to_page(pfn);

        ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
        if (unlikely(ret))
                return ret;

        sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
        return 0;
}

static void dma_cache_maint_page(struct page *page, unsigned long offset,
        size_t size, enum dma_data_direction dir,
        void (*op)(const void *, size_t, int))
{
        unsigned long pfn;
        size_t left = size;

        pfn = page_to_pfn(page) + offset / PAGE_SIZE;
        offset %= PAGE_SIZE;

        /*
         * A single sg entry may refer to multiple physically contiguous
         * pages.  But we still need to process highmem pages individually.
         * If highmem is not configured then the bulk of this loop gets
         * optimized out.
         */
        do {
                size_t len = left;
                void *vaddr;

                page = pfn_to_page(pfn);

                if (PageHighMem(page)) {
                        if (len + offset > PAGE_SIZE)
                                len = PAGE_SIZE - offset;

                        if (cache_is_vipt_nonaliasing()) {
                                vaddr = kmap_atomic(page);
                                op(vaddr + offset, len, dir);
                                kunmap_atomic(vaddr);
                        } else {
                                vaddr = kmap_high_get(page);
                                if (vaddr) {
                                        op(vaddr + offset, len, dir);
                                        kunmap_high(page);
                                }
                        }
                } else {
                        vaddr = page_address(page) + offset;
                        op(vaddr, len, dir);
                }
                offset = 0;
                pfn++;
                left -= len;
        } while (left);
}

/*
 * Make an area consistent for devices.
 * Note: Drivers should NOT use this function directly, as it will break
 * platforms with CONFIG_DMABOUNCE.
 * Use the driver DMA support - see dma-mapping.h (dma_sync_*)
 */
static void __dma_page_cpu_to_dev(struct page *page, unsigned long off,
        size_t size, enum dma_data_direction dir)
{
        phys_addr_t paddr;

        dma_cache_maint_page(page, off, size, dir, dmac_map_area);

        paddr = page_to_phys(page) + off;
        if (dir == DMA_FROM_DEVICE) {
                outer_inv_range(paddr, paddr + size);
        } else {
                outer_clean_range(paddr, paddr + size);
        }
        /* FIXME: non-speculating: flush on bidirectional mappings? */
}

static void __dma_page_dev_to_cpu(struct page *page, unsigned long off,
        size_t size, enum dma_data_direction dir)
{
        phys_addr_t paddr = page_to_phys(page) + off;

        /* FIXME: non-speculating: not required */
        /* in any case, don't bother invalidating if DMA to device */
        if (dir != DMA_TO_DEVICE) {
                outer_inv_range(paddr, paddr + size);

                dma_cache_maint_page(page, off, size, dir, dmac_unmap_area);
        }

        /*
         * Mark the D-cache clean for these pages to avoid extra flushing.
         */
        if (dir != DMA_TO_DEVICE && size >= PAGE_SIZE) {
                unsigned long pfn;
                size_t left = size;

                pfn = page_to_pfn(page) + off / PAGE_SIZE;
                off %= PAGE_SIZE;
                if (off) {
                        pfn++;
                        left -= PAGE_SIZE - off;
                }
                while (left >= PAGE_SIZE) {
                        page = pfn_to_page(pfn++);
                        set_bit(PG_dcache_clean, &page->flags);
                        left -= PAGE_SIZE;
                }
        }
}

/**
 * arm_dma_map_sg - map a set of SG buffers for streaming mode DMA
 * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
 * @sg: list of buffers
 * @nents: number of buffers to map
 * @dir: DMA transfer direction
 *
 * Map a set of buffers described by scatterlist in streaming mode for DMA.
 * This is the scatter-gather version of the dma_map_single interface.
 * Here the scatter gather list elements are each tagged with the
 * appropriate dma address and length.  They are obtained via
 * sg_dma_{address,length}.
 *
 * Device ownership issues as mentioned for dma_map_single are the same
 * here.
 */
int arm_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
                enum dma_data_direction dir, unsigned long attrs)
{
        const struct dma_map_ops *ops = get_dma_ops(dev);
        struct scatterlist *s;
        int i, j;

        for_each_sg(sg, s, nents, i) {
#ifdef CONFIG_NEED_SG_DMA_LENGTH
                s->dma_length = s->length;
#endif
                s->dma_address = ops->map_page(dev, sg_page(s), s->offset,
                                                s->length, dir, attrs);
                if (dma_mapping_error(dev, s->dma_address))
                        goto bad_mapping;
        }
        return nents;

 bad_mapping:
        for_each_sg(sg, s, i, j)
                ops->unmap_page(dev, sg_dma_address(s), sg_dma_len(s), dir, attrs);
        return 0;
}

/**
 * arm_dma_unmap_sg - unmap a set of SG buffers mapped by dma_map_sg
 * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
 * @sg: list of buffers
 * @nents: number of buffers to unmap (same as was passed to dma_map_sg)
 * @dir: DMA transfer direction (same as was passed to dma_map_sg)
 *
 * Unmap a set of streaming mode DMA translations.  Again, CPU access
 * rules concerning calls here are the same as for dma_unmap_single().
 */
void arm_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
                enum dma_data_direction dir, unsigned long attrs)
{
        const struct dma_map_ops *ops = get_dma_ops(dev);
        struct scatterlist *s;

        int i;

        for_each_sg(sg, s, nents, i)
                ops->unmap_page(dev, sg_dma_address(s), sg_dma_len(s), dir, attrs);
}

/**
 * arm_dma_sync_sg_for_cpu
 * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
 * @sg: list of buffers
 * @nents: number of buffers to map (returned from dma_map_sg)
 * @dir: DMA transfer direction (same as was passed to dma_map_sg)
 */
void arm_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
                        int nents, enum dma_data_direction dir)
{
        const struct dma_map_ops *ops = get_dma_ops(dev);
        struct scatterlist *s;
        int i;

        for_each_sg(sg, s, nents, i)
                ops->sync_single_for_cpu(dev, sg_dma_address(s), s->length,
                                         dir);
}

/**
 * arm_dma_sync_sg_for_device
 * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
 * @sg: list of buffers
 * @nents: number of buffers to map (returned from dma_map_sg)
 * @dir: DMA transfer direction (same as was passed to dma_map_sg)
 */
void arm_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
                        int nents, enum dma_data_direction dir)
{
        const struct dma_map_ops *ops = get_dma_ops(dev);
        struct scatterlist *s;
        int i;

        for_each_sg(sg, s, nents, i)
                ops->sync_single_for_device(dev, sg_dma_address(s), s->length,
                                            dir);
}

/*
 * Return whether the given device DMA address mask can be supported
 * properly.  For example, if your device can only drive the low 24-bits
 * during bus mastering, then you would pass 0x00ffffff as the mask
 * to this function.
 */
int arm_dma_supported(struct device *dev, u64 mask)
{
        return __dma_supported(dev, mask, false);
}

static const struct dma_map_ops *arm_get_dma_map_ops(bool coherent)
{
        return coherent ? &arm_coherent_dma_ops : &arm_dma_ops;
}

#ifdef CONFIG_ARM_DMA_USE_IOMMU

static int __dma_info_to_prot(enum dma_data_direction dir, unsigned long attrs)
{
        int prot = 0;

        if (attrs & DMA_ATTR_PRIVILEGED)
                prot |= IOMMU_PRIV;

        switch (dir) {
        case DMA_BIDIRECTIONAL:
                return prot | IOMMU_READ | IOMMU_WRITE;
        case DMA_TO_DEVICE:
                return prot | IOMMU_READ;
        case DMA_FROM_DEVICE:
                return prot | IOMMU_WRITE;
        default:
                return prot;
        }
}

/* IOMMU */

static int extend_iommu_mapping(struct dma_iommu_mapping *mapping);

static inline dma_addr_t __alloc_iova(struct dma_iommu_mapping *mapping,
                                      size_t size)
{
        unsigned int order = get_order(size);
        unsigned int align = 0;
        unsigned int count, start;
        size_t mapping_size = mapping->bits << PAGE_SHIFT;
        unsigned long flags;
        dma_addr_t iova;
        int i;

        if (order > CONFIG_ARM_DMA_IOMMU_ALIGNMENT)
                order = CONFIG_ARM_DMA_IOMMU_ALIGNMENT;

        count = PAGE_ALIGN(size) >> PAGE_SHIFT;
        align = (1 << order) - 1;

        spin_lock_irqsave(&mapping->lock, flags);
        for (i = 0; i < mapping->nr_bitmaps; i++) {
                start = bitmap_find_next_zero_area(mapping->bitmaps[i],
                                mapping->bits, 0, count, align);

                if (start > mapping->bits)
                        continue;

                bitmap_set(mapping->bitmaps[i], start, count);
                break;
        }

        /*
         * No unused range found. Try to extend the existing mapping
         * and perform a second attempt to reserve an IO virtual
         * address range of size bytes.
         */
        if (i == mapping->nr_bitmaps) {
                if (extend_iommu_mapping(mapping)) {
                        spin_unlock_irqrestore(&mapping->lock, flags);
                        return ARM_MAPPING_ERROR;
                }

                start = bitmap_find_next_zero_area(mapping->bitmaps[i],
                                mapping->bits, 0, count, align);

                if (start > mapping->bits) {
                        spin_unlock_irqrestore(&mapping->lock, flags);
                        return ARM_MAPPING_ERROR;
                }

                bitmap_set(mapping->bitmaps[i], start, count);
        }
        spin_unlock_irqrestore(&mapping->lock, flags);

        iova = mapping->base + (mapping_size * i);
        iova += start << PAGE_SHIFT;

        return iova;
}

static inline void __free_iova(struct dma_iommu_mapping *mapping,
                               dma_addr_t addr, size_t size)
{
        unsigned int start, count;
        size_t mapping_size = mapping->bits << PAGE_SHIFT;
        unsigned long flags;
        dma_addr_t bitmap_base;
        u32 bitmap_index;

        if (!size)
                return;

        bitmap_index = (u32) (addr - mapping->base) / (u32) mapping_size;
        BUG_ON(addr < mapping->base || bitmap_index > mapping->extensions);

        bitmap_base = mapping->base + mapping_size * bitmap_index;

        start = (addr - bitmap_base) >> PAGE_SHIFT;

        if (addr + size > bitmap_base + mapping_size) {
                /*
                 * The address range to be freed reaches into the iova
                 * range of the next bitmap. This should not happen as
                 * we don't allow this in __alloc_iova (at the
                 * moment).
                 */
                BUG();
        } else
                count = size >> PAGE_SHIFT;

        spin_lock_irqsave(&mapping->lock, flags);
        bitmap_clear(mapping->bitmaps[bitmap_index], start, count);
        spin_unlock_irqrestore(&mapping->lock, flags);
}

/* We'll try 2M, 1M, 64K, and finally 4K; array must end with 0! */
static const int iommu_order_array[] = { 9, 8, 4, 0 };

static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
                                          gfp_t gfp, unsigned long attrs,
                                          int coherent_flag)
{
        struct page **pages;
        int count = size >> PAGE_SHIFT;
        int array_size = count * sizeof(struct page *);
        int i = 0;
        int order_idx = 0;

        if (array_size <= PAGE_SIZE)
                pages = kzalloc(array_size, GFP_KERNEL);
        else
                pages = vzalloc(array_size);
        if (!pages)
                return NULL;

        if (attrs & DMA_ATTR_FORCE_CONTIGUOUS)
        {
                unsigned long order = get_order(size);
                struct page *page;

                page = dma_alloc_from_contiguous(dev, count, order,
                                                 gfp & __GFP_NOWARN);
                if (!page)
                        goto error;

                __dma_clear_buffer(page, size, coherent_flag);

                for (i = 0; i < count; i++)
                        pages[i] = page + i;

                return pages;
        }

        /* Go straight to 4K chunks if caller says it's OK. */
        if (attrs & DMA_ATTR_ALLOC_SINGLE_PAGES)
                order_idx = ARRAY_SIZE(iommu_order_array) - 1;

        /*
         * IOMMU can map any pages, so himem can also be used here
         */
        gfp |= __GFP_NOWARN | __GFP_HIGHMEM;

        while (count) {
                int j, order;

                order = iommu_order_array[order_idx];

                /* Drop down when we get small */
                if (__fls(count) < order) {
                        order_idx++;
                        continue;
                }

                if (order) {
                        /* See if it's easy to allocate a high-order chunk */
                        pages[i] = alloc_pages(gfp | __GFP_NORETRY, order);

                        /* Go down a notch at first sign of pressure */
                        if (!pages[i]) {
                                order_idx++;
                                continue;
                        }
                } else {
                        pages[i] = alloc_pages(gfp, 0);
                        if (!pages[i])
                                goto error;
                }

                if (order) {
                        split_page(pages[i], order);
                        j = 1 << order;
                        while (--j)
                                pages[i + j] = pages[i] + j;
                }

                __dma_clear_buffer(pages[i], PAGE_SIZE << order, coherent_flag);
                i += 1 << order;
                count -= 1 << order;
        }

        return pages;
error:
        while (i--)
                if (pages[i])
                        __free_pages(pages[i], 0);
        kvfree(pages);
        return NULL;
}

static int __iommu_free_buffer(struct device *dev, struct page **pages,
                               size_t size, unsigned long attrs)
{
        int count = size >> PAGE_SHIFT;
        int i;

        if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
                dma_release_from_contiguous(dev, pages[0], count);
        } else {
                for (i = 0; i < count; i++)
                        if (pages[i])
                                __free_pages(pages[i], 0);
        }

        kvfree(pages);
        return 0;
}

/*
 * Create a CPU mapping for a specified pages
 */
static void *
__iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot,
                    const void *caller)
{
        return dma_common_pages_remap(pages, size,
                        VM_ARM_DMA_CONSISTENT | VM_USERMAP, prot, caller);
}

/*
 * Create a mapping in device IO address space for specified pages
 */
static dma_addr_t
__iommu_create_mapping(struct device *dev, struct page **pages, size_t size,
                       unsigned long attrs)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
        unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
        dma_addr_t dma_addr, iova;
        int i;

        dma_addr = __alloc_iova(mapping, size);
        if (dma_addr == ARM_MAPPING_ERROR)
                return dma_addr;

        iova = dma_addr;
        for (i = 0; i < count; ) {
                int ret;

                unsigned int next_pfn = page_to_pfn(pages[i]) + 1;
                phys_addr_t phys = page_to_phys(pages[i]);
                unsigned int len, j;

                for (j = i + 1; j < count; j++, next_pfn++)
                        if (page_to_pfn(pages[j]) != next_pfn)
                                break;

                len = (j - i) << PAGE_SHIFT;
                ret = iommu_map(mapping->domain, iova, phys, len,
                                __dma_info_to_prot(DMA_BIDIRECTIONAL, attrs));
                if (ret < 0)
                        goto fail;
                iova += len;
                i = j;
        }
        return dma_addr;
fail:
        iommu_unmap(mapping->domain, dma_addr, iova-dma_addr);
        __free_iova(mapping, dma_addr, size);
        return ARM_MAPPING_ERROR;
}

static int __iommu_remove_mapping(struct device *dev, dma_addr_t iova, size_t size)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);

        /*
         * add optional in-page offset from iova to size and align
         * result to page size
         */
        size = PAGE_ALIGN((iova & ~PAGE_MASK) + size);
        iova &= PAGE_MASK;

        iommu_unmap(mapping->domain, iova, size);
        __free_iova(mapping, iova, size);
        return 0;
}

static struct page **__atomic_get_pages(void *addr)
{
        struct page *page;
        phys_addr_t phys;

        phys = gen_pool_virt_to_phys(atomic_pool, (unsigned long)addr);
        page = phys_to_page(phys);

        return (struct page **)page;
}

static struct page **__iommu_get_pages(void *cpu_addr, unsigned long attrs)
{
        struct vm_struct *area;

        if (__in_atomic_pool(cpu_addr, PAGE_SIZE))
                return __atomic_get_pages(cpu_addr);

        if (attrs & DMA_ATTR_NO_KERNEL_MAPPING)
                return cpu_addr;

        area = find_vm_area(cpu_addr);
        if (area && (area->flags & VM_ARM_DMA_CONSISTENT))
                return area->pages;
        return NULL;
}

static void *__iommu_alloc_simple(struct device *dev, size_t size, gfp_t gfp,
                                  dma_addr_t *handle, int coherent_flag,
                                  unsigned long attrs)
{
        struct page *page;
        void *addr;

        if (coherent_flag  == COHERENT)
                addr = __alloc_simple_buffer(dev, size, gfp, &page);
        else
                addr = __alloc_from_pool(size, &page);
        if (!addr)
                return NULL;

        *handle = __iommu_create_mapping(dev, &page, size, attrs);
        if (*handle == ARM_MAPPING_ERROR)
                goto err_mapping;

        return addr;

err_mapping:
        __free_from_pool(addr, size);
        return NULL;
}

static void __iommu_free_atomic(struct device *dev, void *cpu_addr,
                        dma_addr_t handle, size_t size, int coherent_flag)
{
        __iommu_remove_mapping(dev, handle, size);
        if (coherent_flag == COHERENT)
                __dma_free_buffer(virt_to_page(cpu_addr), size);
        else
                __free_from_pool(cpu_addr, size);
}

static void *__arm_iommu_alloc_attrs(struct device *dev, size_t size,
            dma_addr_t *handle, gfp_t gfp, unsigned long attrs,
            int coherent_flag)
{
        pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL);
        struct page **pages;
        void *addr = NULL;

        *handle = ARM_MAPPING_ERROR;
        size = PAGE_ALIGN(size);

        if (coherent_flag  == COHERENT || !gfpflags_allow_blocking(gfp))
                return __iommu_alloc_simple(dev, size, gfp, handle,
                                            coherent_flag, attrs);

        /*
         * Following is a work-around (a.k.a. hack) to prevent pages
         * with __GFP_COMP being passed to split_page() which cannot
         * handle them.  The real problem is that this flag probably
         * should be 0 on ARM as it is not supported on this
         * platform; see CONFIG_HUGETLBFS.
         */
        gfp &= ~(__GFP_COMP);

        pages = __iommu_alloc_buffer(dev, size, gfp, attrs, coherent_flag);
        if (!pages)
                return NULL;

        *handle = __iommu_create_mapping(dev, pages, size, attrs);
        if (*handle == ARM_MAPPING_ERROR)
                goto err_buffer;

        if (attrs & DMA_ATTR_NO_KERNEL_MAPPING)
                return pages;

        addr = __iommu_alloc_remap(pages, size, gfp, prot,
                                   __builtin_return_address(0));
        if (!addr)
                goto err_mapping;

        return addr;

err_mapping:
        __iommu_remove_mapping(dev, *handle, size);
err_buffer:
        __iommu_free_buffer(dev, pages, size, attrs);
        return NULL;
}

static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
            dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
{
        return __arm_iommu_alloc_attrs(dev, size, handle, gfp, attrs, NORMAL);
}

static void *arm_coherent_iommu_alloc_attrs(struct device *dev, size_t size,
                    dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
{
        return __arm_iommu_alloc_attrs(dev, size, handle, gfp, attrs, COHERENT);
}

static int __arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
                    void *cpu_addr, dma_addr_t dma_addr, size_t size,
                    unsigned long attrs)
{
        unsigned long uaddr = vma->vm_start;
        unsigned long usize = vma->vm_end - vma->vm_start;
        struct page **pages = __iommu_get_pages(cpu_addr, attrs);
        unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
        unsigned long off = vma->vm_pgoff;

        if (!pages)
                return -ENXIO;

        if (off >= nr_pages || (usize >> PAGE_SHIFT) > nr_pages - off)
                return -ENXIO;

        pages += off;

        do {
                int ret = vm_insert_page(vma, uaddr, *pages++);
                if (ret) {
                        pr_err("Remapping memory failed: %d\n", ret);
                        return ret;
                }
                uaddr += PAGE_SIZE;
                usize -= PAGE_SIZE;
        } while (usize > 0);

        return 0;
}
static int arm_iommu_mmap_attrs(struct device *dev,
                struct vm_area_struct *vma, void *cpu_addr,
                dma_addr_t dma_addr, size_t size, unsigned long attrs)
{
        vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);

        return __arm_iommu_mmap_attrs(dev, vma, cpu_addr, dma_addr, size, attrs);
}

static int arm_coherent_iommu_mmap_attrs(struct device *dev,
                struct vm_area_struct *vma, void *cpu_addr,
                dma_addr_t dma_addr, size_t size, unsigned long attrs)
{
        return __arm_iommu_mmap_attrs(dev, vma, cpu_addr, dma_addr, size, attrs);
}

/*
 * free a page as defined by the above mapping.
 * Must not be called with IRQs disabled.
 */
void __arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
        dma_addr_t handle, unsigned long attrs, int coherent_flag)
{
        struct page **pages;
        size = PAGE_ALIGN(size);

        if (coherent_flag == COHERENT || __in_atomic_pool(cpu_addr, size)) {
                __iommu_free_atomic(dev, cpu_addr, handle, size, coherent_flag);
                return;
        }

        pages = __iommu_get_pages(cpu_addr, attrs);
        if (!pages) {
                WARN(1, "trying to free invalid coherent area: %p\n", cpu_addr);
                return;
        }

        if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0) {
                dma_common_free_remap(cpu_addr, size,
                        VM_ARM_DMA_CONSISTENT | VM_USERMAP);
        }

        __iommu_remove_mapping(dev, handle, size);
        __iommu_free_buffer(dev, pages, size, attrs);
}

void arm_iommu_free_attrs(struct device *dev, size_t size,
                    void *cpu_addr, dma_addr_t handle, unsigned long attrs)
{
        __arm_iommu_free_attrs(dev, size, cpu_addr, handle, attrs, NORMAL);
}

void arm_coherent_iommu_free_attrs(struct device *dev, size_t size,
                    void *cpu_addr, dma_addr_t handle, unsigned long attrs)
{
        __arm_iommu_free_attrs(dev, size, cpu_addr, handle, attrs, COHERENT);
}

static int arm_iommu_get_sgtable(struct device *dev, struct sg_table *sgt,
                                 void *cpu_addr, dma_addr_t dma_addr,
                                 size_t size, unsigned long attrs)
{
        unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
        struct page **pages = __iommu_get_pages(cpu_addr, attrs);

        if (!pages)
                return -ENXIO;

        return sg_alloc_table_from_pages(sgt, pages, count, 0, size,
                                         GFP_KERNEL);
}

/*
 * Map a part of the scatter-gather list into contiguous io address space
 */
static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
                          size_t size, dma_addr_t *handle,
                          enum dma_data_direction dir, unsigned long attrs,
                          bool is_coherent)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
        dma_addr_t iova, iova_base;
        int ret = 0;
        unsigned int count;
        struct scatterlist *s;
        int prot;

        size = PAGE_ALIGN(size);
        *handle = ARM_MAPPING_ERROR;

        iova_base = iova = __alloc_iova(mapping, size);
        if (iova == ARM_MAPPING_ERROR)
                return -ENOMEM;

        for (count = 0, s = sg; count < (size >> PAGE_SHIFT); s = sg_next(s)) {
                phys_addr_t phys = page_to_phys(sg_page(s));
                unsigned int len = PAGE_ALIGN(s->offset + s->length);

                if (!is_coherent && (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
                        __dma_page_cpu_to_dev(sg_page(s), s->offset, s->length, dir);

                prot = __dma_info_to_prot(dir, attrs);

                ret = iommu_map(mapping->domain, iova, phys, len, prot);
                if (ret < 0)
                        goto fail;
                count += len >> PAGE_SHIFT;
                iova += len;
        }
        *handle = iova_base;

        return 0;
fail:
        iommu_unmap(mapping->domain, iova_base, count * PAGE_SIZE);
        __free_iova(mapping, iova_base, size);
        return ret;
}

static int __iommu_map_sg(struct device *dev, struct scatterlist *sg, int nents,
                     enum dma_data_direction dir, unsigned long attrs,
                     bool is_coherent)
{
        struct scatterlist *s = sg, *dma = sg, *start = sg;
        int i, count = 0;
        unsigned int offset = s->offset;
        unsigned int size = s->offset + s->length;
        unsigned int max = dma_get_max_seg_size(dev);

        for (i = 1; i < nents; i++) {
                s = sg_next(s);

                s->dma_address = ARM_MAPPING_ERROR;
                s->dma_length = 0;

                if (s->offset || (size & ~PAGE_MASK) || size + s->length > max) {
                        if (__map_sg_chunk(dev, start, size, &dma->dma_address,
                            dir, attrs, is_coherent) < 0)
                                goto bad_mapping;

                        dma->dma_address += offset;
                        dma->dma_length = size - offset;

                        size = offset = s->offset;
                        start = s;
                        dma = sg_next(dma);
                        count += 1;
                }
                size += s->length;
        }
        if (__map_sg_chunk(dev, start, size, &dma->dma_address, dir, attrs,
                is_coherent) < 0)
                goto bad_mapping;

        dma->dma_address += offset;
        dma->dma_length = size - offset;

        return count+1;

bad_mapping:
        for_each_sg(sg, s, count, i)
                __iommu_remove_mapping(dev, sg_dma_address(s), sg_dma_len(s));
        return 0;
}

/**
 * arm_coherent_iommu_map_sg - map a set of SG buffers for streaming mode DMA
 * @dev: valid struct device pointer
 * @sg: list of buffers
 * @nents: number of buffers to map
 * @dir: DMA transfer direction
 *
 * Map a set of i/o coherent buffers described by scatterlist in streaming
 * mode for DMA. The scatter gather list elements are merged together (if
 * possible) and tagged with the appropriate dma address and length. They are
 * obtained via sg_dma_{address,length}.
 */
int arm_coherent_iommu_map_sg(struct device *dev, struct scatterlist *sg,
                int nents, enum dma_data_direction dir, unsigned long attrs)
{
        return __iommu_map_sg(dev, sg, nents, dir, attrs, true);
}

/**
 * arm_iommu_map_sg - map a set of SG buffers for streaming mode DMA
 * @dev: valid struct device pointer
 * @sg: list of buffers
 * @nents: number of buffers to map
 * @dir: DMA transfer direction
 *
 * Map a set of buffers described by scatterlist in streaming mode for DMA.
 * The scatter gather list elements are merged together (if possible) and
 * tagged with the appropriate dma address and length. They are obtained via
 * sg_dma_{address,length}.
 */
int arm_iommu_map_sg(struct device *dev, struct scatterlist *sg,
                int nents, enum dma_data_direction dir, unsigned long attrs)
{
        return __iommu_map_sg(dev, sg, nents, dir, attrs, false);
}

static void __iommu_unmap_sg(struct device *dev, struct scatterlist *sg,
                int nents, enum dma_data_direction dir,
                unsigned long attrs, bool is_coherent)
{
        struct scatterlist *s;
        int i;

        for_each_sg(sg, s, nents, i) {
                if (sg_dma_len(s))
                        __iommu_remove_mapping(dev, sg_dma_address(s),
                                               sg_dma_len(s));
                if (!is_coherent && (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
                        __dma_page_dev_to_cpu(sg_page(s), s->offset,
                                              s->length, dir);
        }
}

/**
 * arm_coherent_iommu_unmap_sg - unmap a set of SG buffers mapped by dma_map_sg
 * @dev: valid struct device pointer
 * @sg: list of buffers
 * @nents: number of buffers to unmap (same as was passed to dma_map_sg)
 * @dir: DMA transfer direction (same as was passed to dma_map_sg)
 *
 * Unmap a set of streaming mode DMA translations.  Again, CPU access
 * rules concerning calls here are the same as for dma_unmap_single().
 */
void arm_coherent_iommu_unmap_sg(struct device *dev, struct scatterlist *sg,
                int nents, enum dma_data_direction dir,
                unsigned long attrs)
{
        __iommu_unmap_sg(dev, sg, nents, dir, attrs, true);
}

/**
 * arm_iommu_unmap_sg - unmap a set of SG buffers mapped by dma_map_sg
 * @dev: valid struct device pointer
 * @sg: list of buffers
 * @nents: number of buffers to unmap (same as was passed to dma_map_sg)
 * @dir: DMA transfer direction (same as was passed to dma_map_sg)
 *
 * Unmap a set of streaming mode DMA translations.  Again, CPU access
 * rules concerning calls here are the same as for dma_unmap_single().
 */
void arm_iommu_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
                        enum dma_data_direction dir,
                        unsigned long attrs)
{
        __iommu_unmap_sg(dev, sg, nents, dir, attrs, false);
}

/**
 * arm_iommu_sync_sg_for_cpu
 * @dev: valid struct device pointer
 * @sg: list of buffers
 * @nents: number of buffers to map (returned from dma_map_sg)
 * @dir: DMA transfer direction (same as was passed to dma_map_sg)
 */
void arm_iommu_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
                        int nents, enum dma_data_direction dir)
{
        struct scatterlist *s;
        int i;

        for_each_sg(sg, s, nents, i)
                __dma_page_dev_to_cpu(sg_page(s), s->offset, s->length, dir);

}

/**
 * arm_iommu_sync_sg_for_device
 * @dev: valid struct device pointer
 * @sg: list of buffers
 * @nents: number of buffers to map (returned from dma_map_sg)
 * @dir: DMA transfer direction (same as was passed to dma_map_sg)
 */
void arm_iommu_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
                        int nents, enum dma_data_direction dir)
{
        struct scatterlist *s;
        int i;

        for_each_sg(sg, s, nents, i)
                __dma_page_cpu_to_dev(sg_page(s), s->offset, s->length, dir);
}


/**
 * arm_coherent_iommu_map_page
 * @dev: valid struct device pointer
 * @page: page that buffer resides in
 * @offset: offset into page for start of buffer
 * @size: size of buffer to map
 * @dir: DMA transfer direction
 *
 * Coherent IOMMU aware version of arm_dma_map_page()
 */
static dma_addr_t arm_coherent_iommu_map_page(struct device *dev, struct page *page,
             unsigned long offset, size_t size, enum dma_data_direction dir,
             unsigned long attrs)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
        dma_addr_t dma_addr;
        int ret, prot, len = PAGE_ALIGN(size + offset);

        dma_addr = __alloc_iova(mapping, len);
        if (dma_addr == ARM_MAPPING_ERROR)
                return dma_addr;

        prot = __dma_info_to_prot(dir, attrs);

        ret = iommu_map(mapping->domain, dma_addr, page_to_phys(page), len, prot);
        if (ret < 0)
                goto fail;

        return dma_addr + offset;
fail:
        __free_iova(mapping, dma_addr, len);
        return ARM_MAPPING_ERROR;
}

/**
 * arm_iommu_map_page
 * @dev: valid struct device pointer
 * @page: page that buffer resides in
 * @offset: offset into page for start of buffer
 * @size: size of buffer to map
 * @dir: DMA transfer direction
 *
 * IOMMU aware version of arm_dma_map_page()
 */
static dma_addr_t arm_iommu_map_page(struct device *dev, struct page *page,
             unsigned long offset, size_t size, enum dma_data_direction dir,
             unsigned long attrs)
{
        if ((attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
                __dma_page_cpu_to_dev(page, offset, size, dir);

        return arm_coherent_iommu_map_page(dev, page, offset, size, dir, attrs);
}

/**
 * arm_coherent_iommu_unmap_page
 * @dev: valid struct device pointer
 * @handle: DMA address of buffer
 * @size: size of buffer (same as passed to dma_map_page)
 * @dir: DMA transfer direction (same as passed to dma_map_page)
 *
 * Coherent IOMMU aware version of arm_dma_unmap_page()
 */
static void arm_coherent_iommu_unmap_page(struct device *dev, dma_addr_t handle,
                size_t size, enum dma_data_direction dir, unsigned long attrs)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
        dma_addr_t iova = handle & PAGE_MASK;
        int offset = handle & ~PAGE_MASK;
        int len = PAGE_ALIGN(size + offset);

        if (!iova)
                return;

        iommu_unmap(mapping->domain, iova, len);
        __free_iova(mapping, iova, len);
}

/**
 * arm_iommu_unmap_page
 * @dev: valid struct device pointer
 * @handle: DMA address of buffer
 * @size: size of buffer (same as passed to dma_map_page)
 * @dir: DMA transfer direction (same as passed to dma_map_page)
 *
 * IOMMU aware version of arm_dma_unmap_page()
 */
static void arm_iommu_unmap_page(struct device *dev, dma_addr_t handle,
                size_t size, enum dma_data_direction dir, unsigned long attrs)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
        dma_addr_t iova = handle & PAGE_MASK;
        struct page *page = phys_to_page(iommu_iova_to_phys(mapping->domain, iova));
        int offset = handle & ~PAGE_MASK;
        int len = PAGE_ALIGN(size + offset);

        if (!iova)
                return;

        if ((attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
                __dma_page_dev_to_cpu(page, offset, size, dir);

        iommu_unmap(mapping->domain, iova, len);
        __free_iova(mapping, iova, len);
}

/**
 * arm_iommu_map_resource - map a device resource for DMA
 * @dev: valid struct device pointer
 * @phys_addr: physical address of resource
 * @size: size of resource to map
 * @dir: DMA transfer direction
 */
static dma_addr_t arm_iommu_map_resource(struct device *dev,
                phys_addr_t phys_addr, size_t size,
                enum dma_data_direction dir, unsigned long attrs)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
        dma_addr_t dma_addr;
        int ret, prot;
        phys_addr_t addr = phys_addr & PAGE_MASK;
        unsigned int offset = phys_addr & ~PAGE_MASK;
        size_t len = PAGE_ALIGN(size + offset);

        dma_addr = __alloc_iova(mapping, len);
        if (dma_addr == ARM_MAPPING_ERROR)
                return dma_addr;

        prot = __dma_info_to_prot(dir, attrs) | IOMMU_MMIO;

        ret = iommu_map(mapping->domain, dma_addr, addr, len, prot);
        if (ret < 0)
                goto fail;

        return dma_addr + offset;
fail:
        __free_iova(mapping, dma_addr, len);
        return ARM_MAPPING_ERROR;
}

/**
 * arm_iommu_unmap_resource - unmap a device DMA resource
 * @dev: valid struct device pointer
 * @dma_handle: DMA address to resource
 * @size: size of resource to map
 * @dir: DMA transfer direction
 */
static void arm_iommu_unmap_resource(struct device *dev, dma_addr_t dma_handle,
                size_t size, enum dma_data_direction dir,
                unsigned long attrs)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
        dma_addr_t iova = dma_handle & PAGE_MASK;
        unsigned int offset = dma_handle & ~PAGE_MASK;
        size_t len = PAGE_ALIGN(size + offset);

        if (!iova)
                return;

        iommu_unmap(mapping->domain, iova, len);
        __free_iova(mapping, iova, len);
}

static void arm_iommu_sync_single_for_cpu(struct device *dev,
                dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
        dma_addr_t iova = handle & PAGE_MASK;
        struct page *page = phys_to_page(iommu_iova_to_phys(mapping->domain, iova));
        unsigned int offset = handle & ~PAGE_MASK;

        if (!iova)
                return;

        __dma_page_dev_to_cpu(page, offset, size, dir);
}

static void arm_iommu_sync_single_for_device(struct device *dev,
                dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
        dma_addr_t iova = handle & PAGE_MASK;
        struct page *page = phys_to_page(iommu_iova_to_phys(mapping->domain, iova));
        unsigned int offset = handle & ~PAGE_MASK;

        if (!iova)
                return;

        __dma_page_cpu_to_dev(page, offset, size, dir);
}

const struct dma_map_ops iommu_ops = {
        .alloc          = arm_iommu_alloc_attrs,
        .free           = arm_iommu_free_attrs,
        .mmap           = arm_iommu_mmap_attrs,
        .get_sgtable    = arm_iommu_get_sgtable,

        .map_page               = arm_iommu_map_page,
        .unmap_page             = arm_iommu_unmap_page,
        .sync_single_for_cpu    = arm_iommu_sync_single_for_cpu,
        .sync_single_for_device = arm_iommu_sync_single_for_device,

        .map_sg                 = arm_iommu_map_sg,
        .unmap_sg               = arm_iommu_unmap_sg,
        .sync_sg_for_cpu        = arm_iommu_sync_sg_for_cpu,
        .sync_sg_for_device     = arm_iommu_sync_sg_for_device,

        .map_resource           = arm_iommu_map_resource,
        .unmap_resource         = arm_iommu_unmap_resource,

        .mapping_error          = arm_dma_mapping_error,
        .dma_supported          = arm_dma_supported,
};

const struct dma_map_ops iommu_coherent_ops = {
        .alloc          = arm_coherent_iommu_alloc_attrs,
        .free           = arm_coherent_iommu_free_attrs,
        .mmap           = arm_coherent_iommu_mmap_attrs,
        .get_sgtable    = arm_iommu_get_sgtable,

        .map_page       = arm_coherent_iommu_map_page,
        .unmap_page     = arm_coherent_iommu_unmap_page,

        .map_sg         = arm_coherent_iommu_map_sg,
        .unmap_sg       = arm_coherent_iommu_unmap_sg,

        .map_resource   = arm_iommu_map_resource,
        .unmap_resource = arm_iommu_unmap_resource,

        .mapping_error          = arm_dma_mapping_error,
        .dma_supported          = arm_dma_supported,
};

/**
 * arm_iommu_create_mapping
 * @bus: pointer to the bus holding the client device (for IOMMU calls)
 * @base: start address of the valid IO address space
 * @size: maximum size of the valid IO address space
 *
 * Creates a mapping structure which holds information about used/unused
 * IO address ranges, which is required to perform memory allocation and
 * mapping with IOMMU aware functions.
 *
 * The client device need to be attached to the mapping with
 * arm_iommu_attach_device function.
 */
struct dma_iommu_mapping *
arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, u64 size)
{
        unsigned int bits = size >> PAGE_SHIFT;
        unsigned int bitmap_size = BITS_TO_LONGS(bits) * sizeof(long);
        struct dma_iommu_mapping *mapping;
        int extensions = 1;
        int err = -ENOMEM;

        /* currently only 32-bit DMA address space is supported */
        if (size > DMA_BIT_MASK(32) + 1)
                return ERR_PTR(-ERANGE);

        if (!bitmap_size)
                return ERR_PTR(-EINVAL);

        if (bitmap_size > PAGE_SIZE) {
                extensions = bitmap_size / PAGE_SIZE;
                bitmap_size = PAGE_SIZE;
        }

        mapping = kzalloc(sizeof(struct dma_iommu_mapping), GFP_KERNEL);
        if (!mapping)
                goto err;

        mapping->bitmap_size = bitmap_size;
        mapping->bitmaps = kcalloc(extensions, sizeof(unsigned long *),
                                   GFP_KERNEL);
        if (!mapping->bitmaps)
                goto err2;

        mapping->bitmaps[0] = kzalloc(bitmap_size, GFP_KERNEL);
        if (!mapping->bitmaps[0])
                goto err3;

        mapping->nr_bitmaps = 1;
        mapping->extensions = extensions;
        mapping->base = base;
        mapping->bits = BITS_PER_BYTE * bitmap_size;

        spin_lock_init(&mapping->lock);

        mapping->domain = iommu_domain_alloc(bus);
        if (!mapping->domain)
                goto err4;

        kref_init(&mapping->kref);
        return mapping;
err4:
        kfree(mapping->bitmaps[0]);
err3:
        kfree(mapping->bitmaps);
err2:
        kfree(mapping);
err:
        return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(arm_iommu_create_mapping);

static void release_iommu_mapping(struct kref *kref)
{
        int i;
        struct dma_iommu_mapping *mapping =
                container_of(kref, struct dma_iommu_mapping, kref);

        iommu_domain_free(mapping->domain);
        for (i = 0; i < mapping->nr_bitmaps; i++)
                kfree(mapping->bitmaps[i]);
        kfree(mapping->bitmaps);
        kfree(mapping);
}

static int extend_iommu_mapping(struct dma_iommu_mapping *mapping)
{
        int next_bitmap;

        if (mapping->nr_bitmaps >= mapping->extensions)
                return -EINVAL;

        next_bitmap = mapping->nr_bitmaps;
        mapping->bitmaps[next_bitmap] = kzalloc(mapping->bitmap_size,
                                                GFP_ATOMIC);
        if (!mapping->bitmaps[next_bitmap])
                return -ENOMEM;

        mapping->nr_bitmaps++;

        return 0;
}

void arm_iommu_release_mapping(struct dma_iommu_mapping *mapping)
{
        if (mapping)
                kref_put(&mapping->kref, release_iommu_mapping);
}
EXPORT_SYMBOL_GPL(arm_iommu_release_mapping);

static int __arm_iommu_attach_device(struct device *dev,
                                     struct dma_iommu_mapping *mapping)
{
        int err;

        err = iommu_attach_device(mapping->domain, dev);
        if (err)
                return err;

        kref_get(&mapping->kref);
        to_dma_iommu_mapping(dev) = mapping;

        pr_debug("Attached IOMMU controller to %s device.\n", dev_name(dev));
        return 0;
}

/**
 * arm_iommu_attach_device
 * @dev: valid struct device pointer
 * @mapping: io address space mapping structure (returned from
 *      arm_iommu_create_mapping)
 *
 * Attaches specified io address space mapping to the provided device.
 * This replaces the dma operations (dma_map_ops pointer) with the
 * IOMMU aware version.
 *
 * More than one client might be attached to the same io address space
 * mapping.
 */
int arm_iommu_attach_device(struct device *dev,
                            struct dma_iommu_mapping *mapping)
{
        int err;

        err = __arm_iommu_attach_device(dev, mapping);
        if (err)
                return err;

        set_dma_ops(dev, &iommu_ops);
        return 0;
}
EXPORT_SYMBOL_GPL(arm_iommu_attach_device);

/**
 * arm_iommu_detach_device
 * @dev: valid struct device pointer
 *
 * Detaches the provided device from a previously attached map.
 * This voids the dma operations (dma_map_ops pointer)
 */
void arm_iommu_detach_device(struct device *dev)
{
        struct dma_iommu_mapping *mapping;

        mapping = to_dma_iommu_mapping(dev);
        if (!mapping) {
                dev_warn(dev, "Not attached\n");
                return;
        }

        iommu_detach_device(mapping->domain, dev);
        kref_put(&mapping->kref, release_iommu_mapping);
        to_dma_iommu_mapping(dev) = NULL;
        set_dma_ops(dev, arm_get_dma_map_ops(dev->archdata.dma_coherent));

        pr_debug("Detached IOMMU controller from %s device.\n", dev_name(dev));
}
EXPORT_SYMBOL_GPL(arm_iommu_detach_device);

static const struct dma_map_ops *arm_get_iommu_dma_map_ops(bool coherent)
{
        return coherent ? &iommu_coherent_ops : &iommu_ops;
}

static bool arm_setup_iommu_dma_ops(struct device *dev, u64 dma_base, u64 size,
                                    const struct iommu_ops *iommu)
{
        struct dma_iommu_mapping *mapping;

        if (!iommu)
                return false;

        mapping = arm_iommu_create_mapping(dev->bus, dma_base, size);
        if (IS_ERR(mapping)) {
                pr_warn("Failed to create %llu-byte IOMMU mapping for device %s\n",
                                size, dev_name(dev));
                return false;
        }

        if (__arm_iommu_attach_device(dev, mapping)) {
                pr_warn("Failed to attached device %s to IOMMU_mapping\n",
                                dev_name(dev));
                arm_iommu_release_mapping(mapping);
                return false;
        }

        return true;
}

static void arm_teardown_iommu_dma_ops(struct device *dev)
{
        struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);

        if (!mapping)
                return;

        arm_iommu_detach_device(dev);
        arm_iommu_release_mapping(mapping);
}

#else

static bool arm_setup_iommu_dma_ops(struct device *dev, u64 dma_base, u64 size,
                                    const struct iommu_ops *iommu)
{
        return false;
}

static void arm_teardown_iommu_dma_ops(struct device *dev) { }

#define arm_get_iommu_dma_map_ops arm_get_dma_map_ops

#endif  /* CONFIG_ARM_DMA_USE_IOMMU */

void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
                        const struct iommu_ops *iommu, bool coherent)
{
        const struct dma_map_ops *dma_ops;

        dev->archdata.dma_coherent = coherent;

        /*
         * Don't override the dma_ops if they have already been set. Ideally
         * this should be the only location where dma_ops are set, remove this
         * check when all other callers of set_dma_ops will have disappeared.
         */
        if (dev->dma_ops)
                return;

        if (arm_setup_iommu_dma_ops(dev, dma_base, size, iommu))
                dma_ops = arm_get_iommu_dma_map_ops(coherent);
        else
                dma_ops = arm_get_dma_map_ops(coherent);

        set_dma_ops(dev, dma_ops);

#ifdef CONFIG_XEN
        if (xen_initial_domain()) {
                dev->archdata.dev_dma_ops = dev->dma_ops;
                dev->dma_ops = xen_dma_ops;
        }
#endif
        dev->archdata.dma_ops_setup = true;
}

void arch_teardown_dma_ops(struct device *dev)
{
        if (!dev->archdata.dma_ops_setup)
                return;

        arm_teardown_iommu_dma_ops(dev);
}