ARM: dma-mapping: remove custom consistent dma region

This patch changes dma-mapping subsystem to use generic vmalloc areas
for all consistent dma allocations. This increases the total size limit
of the consistent allocations and removes platform hacks and a lot of
duplicated code.

Atomic allocations are served from special pool preallocated on boot,
because vmalloc areas cannot be reliably created in atomic context.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>

2 files changed, 169 insertions, 320 deletions

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 655878bcc96d..f906d5f4cbd8 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -22,6 +22,7 @@
 #include <linux/memblock.h>
 #include <linux/slab.h>
 #include <linux/iommu.h>
+#include <linux/io.h>
 #include <linux/vmalloc.h>
 
 #include <asm/memory.h>
@@ -217,115 +218,70 @@ static void __dma_free_buffer(struct page *page, size_t size)
 }
 
 #ifdef CONFIG_MMU
+#ifdef CONFIG_HUGETLB_PAGE
+#error ARM Coherent DMA allocator does not (yet) support huge TLB
+#endif
 
-#define CONSISTENT_OFFSET(x)    (((unsigned long)(x) - consistent_base) >> PAGE_SHIFT)
-#define CONSISTENT_PTE_INDEX(x) (((unsigned long)(x) - consistent_base) >> PMD_SHIFT)
-
-/*
- * These are the page tables (2MB each) covering uncached, DMA consistent allocations
- */
-static pte_t **consistent_pte;
-
-#define DEFAULT_CONSISTENT_DMA_SIZE SZ_2M
+static void *__alloc_from_contiguous(struct device *dev, size_t size,
+                                     pgprot_t prot, struct page **ret_page);
 
-static unsigned long consistent_base = CONSISTENT_END - DEFAULT_CONSISTENT_DMA_SIZE;
+static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
+                                 pgprot_t prot, struct page **ret_page,
+                                 const void *caller);
 
-void __init init_consistent_dma_size(unsigned long size)
+static void *
+__dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
+        const void *caller)
 {
-        unsigned long base = CONSISTENT_END - ALIGN(size, SZ_2M);
+        struct vm_struct *area;
+        unsigned long addr;
 
-        BUG_ON(consistent_pte); /* Check we're called before DMA region init */
-        BUG_ON(base < VMALLOC_END);
+        /*
+         * DMA allocation can be mapped to user space, so lets
+         * set VM_USERMAP flags too.
+         */
+        area = get_vm_area_caller(size, VM_ARM_DMA_CONSISTENT | VM_USERMAP,
+                                  caller);
+        if (!area)
+                return NULL;
+        addr = (unsigned long)area->addr;
+        area->phys_addr = __pfn_to_phys(page_to_pfn(page));
 
-        /* Grow region to accommodate specified size  */
-        if (base < consistent_base)
-                consistent_base = base;
+        if (ioremap_page_range(addr, addr + size, area->phys_addr, prot)) {
+                vunmap((void *)addr);
+                return NULL;
+        }
+        return (void *)addr;
 }
 
-#include "vmregion.h"
-
-static struct arm_vmregion_head consistent_head = {
-        .vm_lock        = __SPIN_LOCK_UNLOCKED(&consistent_head.vm_lock),
-        .vm_list        = LIST_HEAD_INIT(consistent_head.vm_list),
-        .vm_end         = CONSISTENT_END,
-};
-
-#ifdef CONFIG_HUGETLB_PAGE
-#error ARM Coherent DMA allocator does not (yet) support huge TLB
-#endif
-
-/*
- * Initialise the consistent memory allocation.
- */
-static int __init consistent_init(void)
+static void __dma_free_remap(void *cpu_addr, size_t size)
 {
-        int ret = 0;
-        pgd_t *pgd;
-        pud_t *pud;
-        pmd_t *pmd;
-        pte_t *pte;
-        int i = 0;
-        unsigned long base = consistent_base;
-        unsigned long num_ptes = (CONSISTENT_END - base) >> PMD_SHIFT;
-
-        if (IS_ENABLED(CONFIG_CMA) && !IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU))
-                return 0;
-
-        consistent_pte = kmalloc(num_ptes * sizeof(pte_t), GFP_KERNEL);
-        if (!consistent_pte) {
-                pr_err("%s: no memory\n", __func__);
-                return -ENOMEM;
+        unsigned int flags = VM_ARM_DMA_CONSISTENT | VM_USERMAP;
+        struct vm_struct *area = find_vm_area(cpu_addr);
+        if (!area || (area->flags & flags) != flags) {
+                WARN(1, "trying to free invalid coherent area: %p\n", cpu_addr);
+                return;
         }
-
-        pr_debug("DMA memory: 0x%08lx - 0x%08lx:\n", base, CONSISTENT_END);
-        consistent_head.vm_start = base;
-
-        do {
-                pgd = pgd_offset(&init_mm, base);
-
-                pud = pud_alloc(&init_mm, pgd, base);
-                if (!pud) {
-                        pr_err("%s: no pud tables\n", __func__);
-                        ret = -ENOMEM;
-                        break;
-                }
-
-                pmd = pmd_alloc(&init_mm, pud, base);
-                if (!pmd) {
-                        pr_err("%s: no pmd tables\n", __func__);
-                        ret = -ENOMEM;
-                        break;
-                }
-                WARN_ON(!pmd_none(*pmd));
-
-                pte = pte_alloc_kernel(pmd, base);
-                if (!pte) {
-                        pr_err("%s: no pte tables\n", __func__);
-                        ret = -ENOMEM;
-                        break;
-                }
-
-                consistent_pte[i++] = pte;
-                base += PMD_SIZE;
-        } while (base < CONSISTENT_END);
-
-        return ret;
+        unmap_kernel_range((unsigned long)cpu_addr, size);
+        vunmap(cpu_addr);
 }
-core_initcall(consistent_init);
-
-static void *__alloc_from_contiguous(struct device *dev, size_t size,
-                                     pgprot_t prot, struct page **ret_page);
 
-static struct arm_vmregion_head coherent_head = {
-        .vm_lock        = __SPIN_LOCK_UNLOCKED(&coherent_head.vm_lock),
-        .vm_list        = LIST_HEAD_INIT(coherent_head.vm_list),
+struct dma_pool {
+        size_t size;
+        spinlock_t lock;
+        unsigned long *bitmap;
+        unsigned long nr_pages;
+        void *vaddr;
+        struct page *page;
 };
 
-static size_t coherent_pool_size = DEFAULT_CONSISTENT_DMA_SIZE / 8;
+static struct dma_pool atomic_pool = {
+        .size = SZ_256K,
+};
 
 static int __init early_coherent_pool(char *p)
 {
-        coherent_pool_size = memparse(p, &p);
+        atomic_pool.size = memparse(p, &p);
         return 0;
 }
 early_param("coherent_pool", early_coherent_pool);
@@ -333,32 +289,45 @@ early_param("coherent_pool", early_coherent_pool);
 /*
  * Initialise the coherent pool for atomic allocations.
  */
-static int __init coherent_init(void)
+static int __init atomic_pool_init(void)
 {
+        struct dma_pool *pool = &atomic_pool;
         pgprot_t prot = pgprot_dmacoherent(pgprot_kernel);
-        size_t size = coherent_pool_size;
+        unsigned long nr_pages = pool->size >> PAGE_SHIFT;
+        unsigned long *bitmap;
         struct page *page;
         void *ptr;
+        int bitmap_size = BITS_TO_LONGS(nr_pages) * sizeof(long);
 
-        if (!IS_ENABLED(CONFIG_CMA))
-                return 0;
+        bitmap = kzalloc(bitmap_size, GFP_KERNEL);
+        if (!bitmap)
+                goto no_bitmap;
 
-        ptr = __alloc_from_contiguous(NULL, size, prot, &page);
+        if (IS_ENABLED(CONFIG_CMA))
+                ptr = __alloc_from_contiguous(NULL, pool->size, prot, &page);
+        else
+                ptr = __alloc_remap_buffer(NULL, pool->size, GFP_KERNEL, prot,
+                                           &page, NULL);
         if (ptr) {
-                coherent_head.vm_start = (unsigned long) ptr;
-                coherent_head.vm_end = (unsigned long) ptr + size;
-                printk(KERN_INFO "DMA: preallocated %u KiB pool for atomic coherent allocations\n",
-                       (unsigned)size / 1024);
+                spin_lock_init(&pool->lock);
+                pool->vaddr = ptr;
+                pool->page = page;
+                pool->bitmap = bitmap;
+                pool->nr_pages = nr_pages;
+                pr_info("DMA: preallocated %u KiB pool for atomic coherent allocations\n",
+                       (unsigned)pool->size / 1024);
                 return 0;
         }
-        printk(KERN_ERR "DMA: failed to allocate %u KiB pool for atomic coherent allocation\n",
-               (unsigned)size / 1024);
+        kfree(bitmap);
+no_bitmap:
+        pr_err("DMA: failed to allocate %u KiB pool for atomic coherent allocation\n",
+               (unsigned)pool->size / 1024);
         return -ENOMEM;
 }
 /*
  * CMA is activated by core_initcall, so we must be called after it.
  */
-postcore_initcall(coherent_init);
+postcore_initcall(atomic_pool_init);
 
 struct dma_contig_early_reserve {
         phys_addr_t base;
@@ -406,112 +375,6 @@ void __init dma_contiguous_remap(void)
         }
 }
 
-static void *
-__dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
-        const void *caller)
-{
-        struct arm_vmregion *c;
-        size_t align;
-        int bit;
-
-        if (!consistent_pte) {
-                pr_err("%s: not initialised\n", __func__);
-                dump_stack();
-                return NULL;
-        }
-
-        /*
-         * Align the virtual region allocation - maximum alignment is
-         * a section size, minimum is a page size.  This helps reduce
-         * fragmentation of the DMA space, and also prevents allocations
-         * smaller than a section from crossing a section boundary.
-         */
-        bit = fls(size - 1);
-        if (bit > SECTION_SHIFT)
-                bit = SECTION_SHIFT;
-        align = 1 << bit;
-
-        /*
-         * Allocate a virtual address in the consistent mapping region.
-         */
-        c = arm_vmregion_alloc(&consistent_head, align, size,
-                            gfp & ~(__GFP_DMA | __GFP_HIGHMEM), caller);
-        if (c) {
-                pte_t *pte;
-                int idx = CONSISTENT_PTE_INDEX(c->vm_start);
-                u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
-
-                pte = consistent_pte[idx] + off;
-                c->priv = page;
-
-                do {
-                        BUG_ON(!pte_none(*pte));
-
-                        set_pte_ext(pte, mk_pte(page, prot), 0);
-                        page++;
-                        pte++;
-                        off++;
-                        if (off >= PTRS_PER_PTE) {
-                                off = 0;
-                                pte = consistent_pte[++idx];
-                        }
-                } while (size -= PAGE_SIZE);
-
-                dsb();
-
-                return (void *)c->vm_start;
-        }
-        return NULL;
-}
-
-static void __dma_free_remap(void *cpu_addr, size_t size)
-{
-        struct arm_vmregion *c;
-        unsigned long addr;
-        pte_t *ptep;
-        int idx;
-        u32 off;
-
-        c = arm_vmregion_find_remove(&consistent_head, (unsigned long)cpu_addr);
-        if (!c) {
-                pr_err("%s: trying to free invalid coherent area: %p\n",
-                       __func__, cpu_addr);
-                dump_stack();
-                return;
-        }
-
-        if ((c->vm_end - c->vm_start) != size) {
-                pr_err("%s: freeing wrong coherent size (%ld != %d)\n",
-                       __func__, c->vm_end - c->vm_start, size);
-                dump_stack();
-                size = c->vm_end - c->vm_start;
-        }
-
-        idx = CONSISTENT_PTE_INDEX(c->vm_start);
-        off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
-        ptep = consistent_pte[idx] + off;
-        addr = c->vm_start;
-        do {
-                pte_t pte = ptep_get_and_clear(&init_mm, addr, ptep);
-
-                ptep++;
-                addr += PAGE_SIZE;
-                off++;
-                if (off >= PTRS_PER_PTE) {
-                        off = 0;
-                        ptep = consistent_pte[++idx];
-                }
-
-                if (pte_none(pte) || !pte_present(pte))
-                        pr_crit("%s: bad page in kernel page table\n",
-                                __func__);
-        } while (size -= PAGE_SIZE);
-
-        flush_tlb_kernel_range(c->vm_start, c->vm_end);
-
-        arm_vmregion_free(&consistent_head, c);
-}
-
 static int __dma_update_pte(pte_t *pte, pgtable_t token, unsigned long addr,
                             void *data)
 {
@@ -552,16 +415,17 @@ static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
         return ptr;
 }
 
-static void *__alloc_from_pool(struct device *dev, size_t size,
-                               struct page **ret_page, const void *caller)
+static void *__alloc_from_pool(size_t size, struct page **ret_page)
 {
-        struct arm_vmregion *c;
+        struct dma_pool *pool = &atomic_pool;
+        unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+        unsigned int pageno;
+        unsigned long flags;
+        void *ptr = NULL;
         size_t align;
 
-        if (!coherent_head.vm_start) {
-                printk(KERN_ERR "%s: coherent pool not initialised!\n",
-                       __func__);
-                dump_stack();
+        if (!pool->vaddr) {
+                WARN(1, "coherent pool not initialised!\n");
                 return NULL;
         }
 
@@ -571,35 +435,41 @@ static void *__alloc_from_pool(struct device *dev, size_t size,
          * size. This helps reduce fragmentation of the DMA space.
          */
         align = PAGE_SIZE << get_order(size);
-        c = arm_vmregion_alloc(&coherent_head, align, size, 0, caller);
-        if (c) {
-                void *ptr = (void *)c->vm_start;
-                struct page *page = virt_to_page(ptr);
-                *ret_page = page;
-                return ptr;
+
+        spin_lock_irqsave(&pool->lock, flags);
+        pageno = bitmap_find_next_zero_area(pool->bitmap, pool->nr_pages,
+                                            0, count, (1 << align) - 1);
+        if (pageno < pool->nr_pages) {
+                bitmap_set(pool->bitmap, pageno, count);
+                ptr = pool->vaddr + PAGE_SIZE * pageno;
+                *ret_page = pool->page + pageno;
         }
-        return NULL;
+        spin_unlock_irqrestore(&pool->lock, flags);
+
+        return ptr;
 }
 
-static int __free_from_pool(void *cpu_addr, size_t size)
+static int __free_from_pool(void *start, size_t size)
 {
-        unsigned long start = (unsigned long)cpu_addr;
-        unsigned long end = start + size;
-        struct arm_vmregion *c;
+        struct dma_pool *pool = &atomic_pool;
+        unsigned long pageno, count;
+        unsigned long flags;
 
-        if (start < coherent_head.vm_start || end > coherent_head.vm_end)
+        if (start < pool->vaddr || start > pool->vaddr + pool->size)
                 return 0;
 
-        c = arm_vmregion_find_remove(&coherent_head, (unsigned long)start);
-
-        if ((c->vm_end - c->vm_start) != size) {
-                printk(KERN_ERR "%s: freeing wrong coherent size (%ld != %d)\n",
-                       __func__, c->vm_end - c->vm_start, size);
-                dump_stack();
-                size = c->vm_end - c->vm_start;
+        if (start + size > pool->vaddr + pool->size) {
+                WARN(1, "freeing wrong coherent size from pool\n");
+                return 0;
         }
 
-        arm_vmregion_free(&coherent_head, c);
+        pageno = (start - pool->vaddr) >> PAGE_SHIFT;
+        count = size >> PAGE_SHIFT;
+
+        spin_lock_irqsave(&pool->lock, flags);
+        bitmap_clear(pool->bitmap, pageno, count);
+        spin_unlock_irqrestore(&pool->lock, flags);
+
         return 1;
 }
 
@@ -644,7 +514,7 @@ static inline pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot)
 
 #define __get_dma_pgprot(attrs, prot)   __pgprot(0)
 #define __alloc_remap_buffer(dev, size, gfp, prot, ret, c)      NULL
-#define __alloc_from_pool(dev, size, ret_page, c)               NULL
+#define __alloc_from_pool(size, ret_page)                       NULL
 #define __alloc_from_contiguous(dev, size, prot, ret)           NULL
 #define __free_from_pool(cpu_addr, size)                        0
 #define __free_from_contiguous(dev, page, size)                 do { } while (0)
@@ -702,10 +572,10 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 
         if (arch_is_coherent() || nommu())
                 addr = __alloc_simple_buffer(dev, size, gfp, &page);
+        else if (gfp & GFP_ATOMIC)
+                addr = __alloc_from_pool(size, &page);
         else if (!IS_ENABLED(CONFIG_CMA))
                 addr = __alloc_remap_buffer(dev, size, gfp, prot, &page, caller);
-        else if (gfp & GFP_ATOMIC)
-                addr = __alloc_from_pool(dev, size, &page, caller);
         else
                 addr = __alloc_from_contiguous(dev, size, prot, &page);
 
@@ -998,9 +868,6 @@ static int arm_dma_set_mask(struct device *dev, u64 dma_mask)
 
 static int __init dma_debug_do_init(void)
 {
-#ifdef CONFIG_MMU
-        arm_vmregion_create_proc("dma-mappings", &consistent_head);
-#endif
         dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
         return 0;
 }
@@ -1117,61 +984,32 @@ static int __iommu_free_buffer(struct device *dev, struct page **pages, size_t s
  * 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)
+__iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot,
+                    const void *caller)
 {
-        struct arm_vmregion *c;
-        size_t align;
-        size_t count = size >> PAGE_SHIFT;
-        int bit;
+        unsigned int i, nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
+        struct vm_struct *area;
+        unsigned long p;
 
-        if (!consistent_pte[0]) {
-                pr_err("%s: not initialised\n", __func__);
-                dump_stack();
+        area = get_vm_area_caller(size, VM_ARM_DMA_CONSISTENT | VM_USERMAP,
+                                  caller);
+        if (!area)
                 return NULL;
-        }
 
-        /*
-         * Align the virtual region allocation - maximum alignment is
-         * a section size, minimum is a page size.  This helps reduce
-         * fragmentation of the DMA space, and also prevents allocations
-         * smaller than a section from crossing a section boundary.
-         */
-        bit = fls(size - 1);
-        if (bit > SECTION_SHIFT)
-                bit = SECTION_SHIFT;
-        align = 1 << bit;
-
-        /*
-         * Allocate a virtual address in the consistent mapping region.
-         */
-        c = arm_vmregion_alloc(&consistent_head, align, size,
-                            gfp & ~(__GFP_DMA | __GFP_HIGHMEM), NULL);
-        if (c) {
-                pte_t *pte;
-                int idx = CONSISTENT_PTE_INDEX(c->vm_start);
-                int i = 0;
-                u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
-
-                pte = consistent_pte[idx] + off;
-                c->priv = pages;
-
-                do {
-                        BUG_ON(!pte_none(*pte));
-
-                        set_pte_ext(pte, mk_pte(pages[i], prot), 0);
-                        pte++;
-                        off++;
-                        i++;
-                        if (off >= PTRS_PER_PTE) {
-                                off = 0;
-                                pte = consistent_pte[++idx];
-                        }
-                } while (i < count);
-
-                dsb();
+        area->pages = pages;
+        area->nr_pages = nr_pages;
+        p = (unsigned long)area->addr;
 
-                return (void *)c->vm_start;
+        for (i = 0; i < nr_pages; i++) {
+                phys_addr_t phys = __pfn_to_phys(page_to_pfn(pages[i]));
+                if (ioremap_page_range(p, p + PAGE_SIZE, phys, prot))
+                        goto err;
+                p += PAGE_SIZE;
         }
+        return area->addr;
+err:
+        unmap_kernel_range((unsigned long)area->addr, size);
+        vunmap(area->addr);
         return NULL;
 }
 
@@ -1230,6 +1068,16 @@ static int __iommu_remove_mapping(struct device *dev, dma_addr_t iova, size_t si
         return 0;
 }
 
+static struct page **__iommu_get_pages(void *cpu_addr)
+{
+        struct vm_struct *area;
+
+        area = find_vm_area(cpu_addr);
+        if (area && (area->flags & VM_ARM_DMA_CONSISTENT))
+                return area->pages;
+        return NULL;
+}
+
 static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
             dma_addr_t *handle, gfp_t gfp, struct dma_attrs *attrs)
 {
@@ -1248,7 +1096,8 @@ static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
         if (*handle == DMA_ERROR_CODE)
                 goto err_buffer;
 
-        addr = __iommu_alloc_remap(pages, size, gfp, prot);
+        addr = __iommu_alloc_remap(pages, size, gfp, prot,
+                                   __builtin_return_address(0));
         if (!addr)
                 goto err_mapping;
 
@@ -1265,31 +1114,25 @@ 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,
                     struct dma_attrs *attrs)
 {
-        struct arm_vmregion *c;
+        unsigned long uaddr = vma->vm_start;
+        unsigned long usize = vma->vm_end - vma->vm_start;
+        struct page **pages = __iommu_get_pages(cpu_addr);
 
         vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
-        c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr);
 
-        if (c) {
-                struct page **pages = c->priv;
-
-                unsigned long uaddr = vma->vm_start;
-                unsigned long usize = vma->vm_end - vma->vm_start;
-                int i = 0;
-
-                do {
-                        int ret;
+        if (!pages)
+                return -ENXIO;
 
-                        ret = vm_insert_page(vma, uaddr, pages[i++]);
-                        if (ret) {
-                                pr_err("Remapping memory, error: %d\n", ret);
-                                return ret;
-                        }
+        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);
 
-                        uaddr += PAGE_SIZE;
-                        usize -= PAGE_SIZE;
-                } while (usize > 0);
-        }
         return 0;
 }
 
@@ -1300,16 +1143,19 @@ static int arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 void arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
                           dma_addr_t handle, struct dma_attrs *attrs)
 {
-        struct arm_vmregion *c;
+        struct page **pages = __iommu_get_pages(cpu_addr);
         size = PAGE_ALIGN(size);
 
-        c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr);
-        if (c) {
-                struct page **pages = c->priv;
-                __dma_free_remap(cpu_addr, size);
-                __iommu_remove_mapping(dev, handle, size);
-                __iommu_free_buffer(dev, pages, size);
+        if (!pages) {
+                WARN(1, "trying to free invalid coherent area: %p\n", cpu_addr);
+                return;
         }
+
+        unmap_kernel_range((unsigned long)cpu_addr, size);
+        vunmap(cpu_addr);
+
+        __iommu_remove_mapping(dev, handle, size);
+        __iommu_free_buffer(dev, pages, size);
 }
 
 /*
diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
index 2e8a1efdf7b8..6776160618ef 100644
--- a/arch/arm/mm/mm.h
+++ b/arch/arm/mm/mm.h
@@ -59,6 +59,9 @@ extern void __flush_dcache_page(struct address_space *mapping, struct page *page
 #define VM_ARM_MTYPE(mt)                ((mt) << 20)
 #define VM_ARM_MTYPE_MASK       (0x1f << 20)
 
+/* consistent regions used by dma_alloc_attrs() */
+#define VM_ARM_DMA_CONSISTENT   0x20000000
+
 #endif
 
 #ifdef CONFIG_ZONE_DMA