arch/arm/plat-omap/iovmm.c

/*
 * omap iommu: simple virtual address space management
 *
 * Copyright (C) 2008-2009 Nokia Corporation
 *
 * Written by Hiroshi DOYU <Hiroshi.DOYU@nokia.com>
 *
 * 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.
 */

#include <linux/err.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/device.h>
#include <linux/scatterlist.h>

#include <asm/cacheflush.h>
#include <asm/mach/map.h>

#include <plat/iommu.h>
#include <plat/iovmm.h>

#include "iopgtable.h"

/*
 * A device driver needs to create address mappings between:
 *
 * - iommu/device address
 * - physical address
 * - mpu virtual address
 *
 * There are 4 possible patterns for them:
 *
 *    |iova/			  mapping		iommu_		page
 *    | da	pa	va	(d)-(p)-(v)		function	type
 *  ---------------------------------------------------------------------------
 *  1 | c	c	c	 1 - 1 - 1	  _kmap() / _kunmap()	s
 *  2 | c	c,a	c	 1 - 1 - 1	_kmalloc()/ _kfree()	s
 *  3 | c	d	c	 1 - n - 1	  _vmap() / _vunmap()	s
 *  4 | c	d,a	c	 1 - n - 1	_vmalloc()/ _vfree()	n*
 *
 *
 *	'iova':	device iommu virtual address
 *	'da':	alias of 'iova'
 *	'pa':	physical address
 *	'va':	mpu virtual address
 *
 *	'c':	contiguous memory area
 *	'd':	discontiguous memory area
 *	'a':	anonymous memory allocation
 *	'()':	optional feature
 *
 *	'n':	a normal page(4KB) size is used.
 *	's':	multiple iommu superpage(16MB, 1MB, 64KB, 4KB) size is used.
 *
 *	'*':	not yet, but feasible.
 */

static struct kmem_cache *iovm_area_cachep;

/* return total bytes of sg buffers */
static size_t sgtable_len(const struct sg_table *sgt)
{
	unsigned int i, total = 0;
	struct scatterlist *sg;

	if (!sgt)
		return 0;

	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
		size_t bytes;

		bytes = sg_dma_len(sg);

		if (!iopgsz_ok(bytes)) {
			pr_err("%s: sg[%d] not iommu pagesize(%x)\n",
			       __func__, i, bytes);
			return 0;
		}

		total += bytes;
	}

	return total;
}
#define sgtable_ok(x)	(!!sgtable_len(x))

/*
 * calculate the optimal number sg elements from total bytes based on
 * iommu superpages
 */
static unsigned int sgtable_nents(size_t bytes)
{
	int i;
	unsigned int nr_entries;
	const unsigned long pagesize[] = { SZ_16M, SZ_1M, SZ_64K, SZ_4K, };

	if (!IS_ALIGNED(bytes, PAGE_SIZE)) {
		pr_err("%s: wrong size %08x\n", __func__, bytes);
		return 0;
	}

	nr_entries = 0;
	for (i = 0; i < ARRAY_SIZE(pagesize); i++) {
		if (bytes >= pagesize[i]) {
			nr_entries += (bytes / pagesize[i]);
			bytes %= pagesize[i];
		}
	}
	BUG_ON(bytes);

	return nr_entries;
}

/* allocate and initialize sg_table header(a kind of 'superblock') */
static struct sg_table *sgtable_alloc(const size_t bytes, u32 flags)
{
	unsigned int nr_entries;
	int err;
	struct sg_table *sgt;

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

	if (!IS_ALIGNED(bytes, PAGE_SIZE))
		return ERR_PTR(-EINVAL);

	/* FIXME: IOVMF_DA_FIXED should support 'superpages' */
	if ((flags & IOVMF_LINEAR) && (flags & IOVMF_DA_ANON)) {
		nr_entries = sgtable_nents(bytes);
		if (!nr_entries)
			return ERR_PTR(-EINVAL);
	} else
		nr_entries =  bytes / PAGE_SIZE;

	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
	if (!sgt)
		return ERR_PTR(-ENOMEM);

	err = sg_alloc_table(sgt, nr_entries, GFP_KERNEL);
	if (err)
		return ERR_PTR(err);

	pr_debug("%s: sgt:%p(%d entries)\n", __func__, sgt, nr_entries);

	return sgt;
}

/* free sg_table header(a kind of superblock) */
static void sgtable_free(struct sg_table *sgt)
{
	if (!sgt)
		return;

	sg_free_table(sgt);
	kfree(sgt);

	pr_debug("%s: sgt:%p\n", __func__, sgt);
}

/* map 'sglist' to a contiguous mpu virtual area and return 'va' */
static void *vmap_sg(const struct sg_table *sgt)
{
	u32 va;
	size_t total;
	unsigned int i;
	struct scatterlist *sg;
	struct vm_struct *new;
	const struct mem_type *mtype;

	mtype = get_mem_type(MT_DEVICE);
	if (!mtype)
		return ERR_PTR(-EINVAL);

	total = sgtable_len(sgt);
	if (!total)
		return ERR_PTR(-EINVAL);

	new = __get_vm_area(total, VM_IOREMAP, VMALLOC_START, VMALLOC_END);
	if (!new)
		return ERR_PTR(-ENOMEM);
	va = (u32)new->addr;

	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
		size_t bytes;
		u32 pa;
		int err;

		pa = sg_phys(sg);
		bytes = sg_dma_len(sg);

		BUG_ON(bytes != PAGE_SIZE);

		err = ioremap_page(va,  pa, mtype);
		if (err)
			goto err_out;

		va += bytes;
	}

	flush_cache_vmap((unsigned long)new->addr,
				(unsigned long)(new->addr + total));
	return new->addr;

err_out:
	WARN_ON(1); /* FIXME: cleanup some mpu mappings */
	vunmap(new->addr);
	return ERR_PTR(-EAGAIN);
}

static inline void vunmap_sg(const void *va)
{
	vunmap(va);
}

static struct iovm_struct *__find_iovm_area(struct iommu *obj, const u32 da)
{
	struct iovm_struct *tmp;

	list_for_each_entry(tmp, &obj->mmap, list) {
		if ((da >= tmp->da_start) && (da < tmp->da_end)) {
			size_t len;

			len = tmp->da_end - tmp->da_start;

			dev_dbg(obj->dev, "%s: %08x-%08x-%08x(%x) %08x\n",
				__func__, tmp->da_start, da, tmp->da_end, len,
				tmp->flags);

			return tmp;
		}
	}

	return NULL;
}

/**
 * find_iovm_area  -  find iovma which includes @da
 * @da:		iommu device virtual address
 *
 * Find the existing iovma starting at @da
 */
struct iovm_struct *find_iovm_area(struct iommu *obj, u32 da)
{
	struct iovm_struct *area;

	mutex_lock(&obj->mmap_lock);
	area = __find_iovm_area(obj, da);
	mutex_unlock(&obj->mmap_lock);

	return area;
}
EXPORT_SYMBOL_GPL(find_iovm_area);

/*
 * This finds the hole(area) which fits the requested address and len
 * in iovmas mmap, and returns the new allocated iovma.
 */
static struct iovm_struct *alloc_iovm_area(struct iommu *obj, u32 da,
					   size_t bytes, u32 flags)
{
	struct iovm_struct *new, *tmp;
	u32 start, prev_end, alignement;

	if (!obj || !bytes)
		return ERR_PTR(-EINVAL);

	start = da;
	alignement = PAGE_SIZE;

	if (flags & IOVMF_DA_ANON) {
		/*
		 * Reserve the first page for NULL
		 */
		start = PAGE_SIZE;
		if (flags & IOVMF_LINEAR)
			alignement = iopgsz_max(bytes);
		start = roundup(start, alignement);
	}

	tmp = NULL;
	if (list_empty(&obj->mmap))
		goto found;

	prev_end = 0;
	list_for_each_entry(tmp, &obj->mmap, list) {

		if (prev_end >= start)
			break;

		if (start + bytes < tmp->da_start)
			goto found;

		if (flags & IOVMF_DA_ANON)
			start = roundup(tmp->da_end + 1, alignement);

		prev_end = tmp->da_end;
	}

	if ((start > prev_end) && (ULONG_MAX - start >= bytes))
		goto found;

	dev_dbg(obj->dev, "%s: no space to fit %08x(%x) flags: %08x\n",
		__func__, da, bytes, flags);

	return ERR_PTR(-EINVAL);

found:
	new = kmem_cache_zalloc(iovm_area_cachep, GFP_KERNEL);
	if (!new)
		return ERR_PTR(-ENOMEM);

	new->iommu = obj;
	new->da_start = start;
	new->da_end = start + bytes;
	new->flags = flags;

	/*
	 * keep ascending order of iovmas
	 */
	if (tmp)
		list_add_tail(&new->list, &tmp->list);
	else
		list_add(&new->list, &obj->mmap);

	dev_dbg(obj->dev, "%s: found %08x-%08x-%08x(%x) %08x\n",
		__func__, new->da_start, start, new->da_end, bytes, flags);

	return new;
}

static void free_iovm_area(struct iommu *obj, struct iovm_struct *area)
{
	size_t bytes;

	BUG_ON(!obj || !area);

	bytes = area->da_end - area->da_start;

	dev_dbg(obj->dev, "%s: %08x-%08x(%x) %08x\n",
		__func__, area->da_start, area->da_end, bytes, area->flags);

	list_del(&area->list);
	kmem_cache_free(iovm_area_cachep, area);
}

/**
 * da_to_va - convert (d) to (v)
 * @obj:	objective iommu
 * @da:		iommu device virtual address
 * @va:		mpu virtual address
 *
 * Returns mpu virtual addr which corresponds to a given device virtual addr
 */
void *da_to_va(struct iommu *obj, u32 da)
{
	void *va = NULL;
	struct iovm_struct *area;

	mutex_lock(&obj->mmap_lock);

	area = __find_iovm_area(obj, da);
	if (!area) {
		dev_dbg(obj->dev, "%s: no da area(%08x)\n", __func__, da);
		goto out;
	}
	va = area->va;
out:
	mutex_unlock(&obj->mmap_lock);

	return va;
}
EXPORT_SYMBOL_GPL(da_to_va);

static void sgtable_fill_vmalloc(struct sg_table *sgt, void *_va)
{
	unsigned int i;
	struct scatterlist *sg;
	void *va = _va;
	void *va_end;

	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
		struct page *pg;
		const size_t bytes = PAGE_SIZE;

		/*
		 * iommu 'superpage' isn't supported with 'iommu_vmalloc()'
		 */
		pg = vmalloc_to_page(va);
		BUG_ON(!pg);
		sg_set_page(sg, pg, bytes, 0);

		va += bytes;
	}

	va_end = _va + PAGE_SIZE * i;
}

static inline void sgtable_drain_vmalloc(struct sg_table *sgt)
{
	/*
	 * Actually this is not necessary at all, just exists for
	 * consistency of the code readability.
	 */
	BUG_ON(!sgt);
}

static void sgtable_fill_kmalloc(struct sg_table *sgt, u32 pa, size_t len)
{
	unsigned int i;
	struct scatterlist *sg;
	void *va;

	va = phys_to_virt(pa);

	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
		size_t bytes;

		bytes = iopgsz_max(len);

		BUG_ON(!iopgsz_ok(bytes));

		sg_set_buf(sg, phys_to_virt(pa), bytes);
		/*
		 * 'pa' is cotinuous(linear).
		 */
		pa += bytes;
		len -= bytes;
	}
	BUG_ON(len);
}

static inline void sgtable_drain_kmalloc(struct sg_table *sgt)
{
	/*
	 * Actually this is not necessary at all, just exists for
	 * consistency of the code readability
	 */
	BUG_ON(!sgt);
}

/* create 'da' <-> 'pa' mapping from 'sgt' */
static int map_iovm_area(struct iommu *obj, struct iovm_struct *new,
			 const struct sg_table *sgt, u32 flags)
{
	int err;
	unsigned int i, j;
	struct scatterlist *sg;
	u32 da = new->da_start;

	if (!obj || !sgt)
		return -EINVAL;

	BUG_ON(!sgtable_ok(sgt));

	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
		u32 pa;
		int pgsz;
		size_t bytes;
		struct iotlb_entry e;

		pa = sg_phys(sg);
		bytes = sg_dma_len(sg);

		flags &= ~IOVMF_PGSZ_MASK;
		pgsz = bytes_to_iopgsz(bytes);
		if (pgsz < 0)
			goto err_out;
		flags |= pgsz;

		pr_debug("%s: [%d] %08x %08x(%x)\n", __func__,
			 i, da, pa, bytes);

		iotlb_init_entry(&e, da, pa, flags);
		err = iopgtable_store_entry(obj, &e);
		if (err)
			goto err_out;

		da += bytes;
	}
	return 0;

err_out:
	da = new->da_start;

	for_each_sg(sgt->sgl, sg, i, j) {
		size_t bytes;

		bytes = iopgtable_clear_entry(obj, da);

		BUG_ON(!iopgsz_ok(bytes));

		da += bytes;
	}
	return err;
}

/* release 'da' <-> 'pa' mapping */
static void unmap_iovm_area(struct iommu *obj, struct iovm_struct *area)
{
	u32 start;
	size_t total = area->da_end - area->da_start;

	BUG_ON((!total) || !IS_ALIGNED(total, PAGE_SIZE));

	start = area->da_start;
	while (total > 0) {
		size_t bytes;

		bytes = iopgtable_clear_entry(obj, start);
		if (bytes == 0)
			bytes = PAGE_SIZE;
		else
			dev_dbg(obj->dev, "%s: unmap %08x(%x) %08x\n",
				__func__, start, bytes, area->flags);

		BUG_ON(!IS_ALIGNED(bytes, PAGE_SIZE));

		total -= bytes;
		start += bytes;
	}
	BUG_ON(total);
}

/* template function for all unmapping */
static struct sg_table *unmap_vm_area(struct iommu *obj, const u32 da,
				      void (*fn)(const void *), u32 flags)
{
	struct sg_table *sgt = NULL;
	struct iovm_struct *area;

	if (!IS_ALIGNED(da, PAGE_SIZE)) {
		dev_err(obj->dev, "%s: alignment err(%08x)\n", __func__, da);
		return NULL;
	}

	mutex_lock(&obj->mmap_lock);

	area = __find_iovm_area(obj, da);
	if (!area) {
		dev_dbg(obj->dev, "%s: no da area(%08x)\n", __func__, da);
		goto out;
	}

	if ((area->flags & flags) != flags) {
		dev_err(obj->dev, "%s: wrong flags(%08x)\n", __func__,
			area->flags);
		goto out;
	}
	sgt = (struct sg_table *)area->sgt;

	unmap_iovm_area(obj, area);

	fn(area->va);

	dev_dbg(obj->dev, "%s: %08x-%08x-%08x(%x) %08x\n", __func__,
		area->da_start, da, area->da_end,
		area->da_end - area->da_start, area->flags);

	free_iovm_area(obj, area);
out:
	mutex_unlock(&obj->mmap_lock);

	return sgt;
}

static u32 map_iommu_region(struct iommu *obj, u32 da,
	      const struct sg_table *sgt, void *va, size_t bytes, u32 flags)
{
	int err = -ENOMEM;
	struct iovm_struct *new;

	mutex_lock(&obj->mmap_lock);

	new = alloc_iovm_area(obj, da, bytes, flags);
	if (IS_ERR(new)) {
		err = PTR_ERR(new);
		goto err_alloc_iovma;
	}
	new->va = va;
	new->sgt = sgt;

	if (map_iovm_area(obj, new, sgt, new->flags))
		goto err_map;

	mutex_unlock(&obj->mmap_lock);

	dev_dbg(obj->dev, "%s: da:%08x(%x) flags:%08x va:%p\n",
		__func__, new->da_start, bytes, new->flags, va);

	return new->da_start;

err_map:
	free_iovm_area(obj, new);
err_alloc_iovma:
	mutex_unlock(&obj->mmap_lock);
	return err;
}

static inline u32 __iommu_vmap(struct iommu *obj, u32 da,
		 const struct sg_table *sgt, void *va, size_t bytes, u32 flags)
{
	return map_iommu_region(obj, da, sgt, va, bytes, flags);
}

/**
 * iommu_vmap  -  (d)-(p)-(v) address mapper
 * @obj:	objective iommu
 * @sgt:	address of scatter gather table
 * @flags:	iovma and page property
 *
 * Creates 1-n-1 mapping with given @sgt and returns @da.
 * All @sgt element must be io page size aligned.
 */
u32 iommu_vmap(struct iommu *obj, u32 da, const struct sg_table *sgt,
		 u32 flags)
{
	size_t bytes;
	void *va = NULL;

	if (!obj || !obj->dev || !sgt)
		return -EINVAL;

	bytes = sgtable_len(sgt);
	if (!bytes)
		return -EINVAL;
	bytes = PAGE_ALIGN(bytes);

	if (flags & IOVMF_MMIO) {
		va = vmap_sg(sgt);
		if (IS_ERR(va))
			return PTR_ERR(va);
	}

	flags &= IOVMF_HW_MASK;
	flags |= IOVMF_DISCONT;
	flags |= IOVMF_MMIO;
	flags |= (da ? IOVMF_DA_FIXED : IOVMF_DA_ANON);

	da = __iommu_vmap(obj, da, sgt, va, bytes, flags);
	if (IS_ERR_VALUE(da))
		vunmap_sg(va);

	return da;
}
EXPORT_SYMBOL_GPL(iommu_vmap);

/**
 * iommu_vunmap  -  release virtual mapping obtained by 'iommu_vmap()'
 * @obj:	objective iommu
 * @da:		iommu device virtual address
 *
 * Free the iommu virtually contiguous memory area starting at
 * @da, which was returned by 'iommu_vmap()'.
 */
struct sg_table *iommu_vunmap(struct iommu *obj, u32 da)
{
	struct sg_table *sgt;
	/*
	 * 'sgt' is allocated before 'iommu_vmalloc()' is called.
	 * Just returns 'sgt' to the caller to free
	 */
	sgt = unmap_vm_area(obj, da, vunmap_sg, IOVMF_DISCONT | IOVMF_MMIO);
	if (!sgt)
		dev_dbg(obj->dev, "%s: No sgt\n", __func__);
	return sgt;
}
EXPORT_SYMBOL_GPL(iommu_vunmap);

/**
 * iommu_vmalloc  -  (d)-(p)-(v) address allocator and mapper
 * @obj:	objective iommu
 * @da:		contiguous iommu virtual memory
 * @bytes:	allocation size
 * @flags:	iovma and page property
 *
 * Allocate @bytes linearly and creates 1-n-1 mapping and returns
 * @da again, which might be adjusted if 'IOVMF_DA_ANON' is set.
 */
u32 iommu_vmalloc(struct iommu *obj, u32 da, size_t bytes, u32 flags)
{
	void *va;
	struct sg_table *sgt;

	if (!obj || !obj->dev || !bytes)
		return -EINVAL;

	bytes = PAGE_ALIGN(bytes);

	va = vmalloc(bytes);
	if (!va)
		return -ENOMEM;

	sgt = sgtable_alloc(bytes, flags);
	if (IS_ERR(sgt)) {
		da = PTR_ERR(sgt);
		goto err_sgt_alloc;
	}
	sgtable_fill_vmalloc(sgt, va);

	flags &= IOVMF_HW_MASK;
	flags |= IOVMF_DISCONT;
	flags |= IOVMF_ALLOC;
	flags |= (da ? IOVMF_DA_FIXED : IOVMF_DA_ANON);

	da = __iommu_vmap(obj, da, sgt, va, bytes, flags);
	if (IS_ERR_VALUE(da))
		goto err_iommu_vmap;

	return da;

err_iommu_vmap:
	sgtable_drain_vmalloc(sgt);
	sgtable_free(sgt);
err_sgt_alloc:
	vfree(va);
	return da;
}
EXPORT_SYMBOL_GPL(iommu_vmalloc);

/**
 * iommu_vfree  -  release memory allocated by 'iommu_vmalloc()'
 * @obj:	objective iommu
 * @da:		iommu device virtual address
 *
 * Frees the iommu virtually continuous memory area starting at
 * @da, as obtained from 'iommu_vmalloc()'.
 */
void iommu_vfree(struct iommu *obj, const u32 da)
{
	struct sg_table *sgt;

	sgt = unmap_vm_area(obj, da, vfree, IOVMF_DISCONT | IOVMF_ALLOC);
	if (!sgt)
		dev_dbg(obj->dev, "%s: No sgt\n", __func__);
	sgtable_free(sgt);
}
EXPORT_SYMBOL_GPL(iommu_vfree);

static u32 __iommu_kmap(struct iommu *obj, u32 da, u32 pa, void *va,
			  size_t bytes, u32 flags)
{
	struct sg_table *sgt;

	sgt = sgtable_alloc(bytes, flags);
	if (IS_ERR(sgt))
		return PTR_ERR(sgt);

	sgtable_fill_kmalloc(sgt, pa, bytes);

	da = map_iommu_region(obj, da, sgt, va, bytes, flags);
	if (IS_ERR_VALUE(da)) {
		sgtable_drain_kmalloc(sgt);
		sgtable_free(sgt);
	}

	return da;
}

/**
 * iommu_kmap  -  (d)-(p)-(v) address mapper
 * @obj:	objective iommu
 * @da:		contiguous iommu virtual memory
 * @pa:		contiguous physical memory
 * @flags:	iovma and page property
 *
 * Creates 1-1-1 mapping and returns @da again, which can be
 * adjusted if 'IOVMF_DA_ANON' is set.
 */
u32 iommu_kmap(struct iommu *obj, u32 da, u32 pa, size_t bytes,
		 u32 flags)
{
	void *va;

	if (!obj || !obj->dev || !bytes)
		return -EINVAL;

	bytes = PAGE_ALIGN(bytes);

	va = ioremap(pa, bytes);
	if (!va)
		return -ENOMEM;

	flags &= IOVMF_HW_MASK;
	flags |= IOVMF_LINEAR;
	flags |= IOVMF_MMIO;
	flags |= (da ? IOVMF_DA_FIXED : IOVMF_DA_ANON);

	da = __iommu_kmap(obj, da, pa, va, bytes, flags);
	if (IS_ERR_VALUE(da))
		iounmap(va);

	return da;
}
EXPORT_SYMBOL_GPL(iommu_kmap);

/**
 * iommu_kunmap  -  release virtual mapping obtained by 'iommu_kmap()'
 * @obj:	objective iommu
 * @da:		iommu device virtual address
 *
 * Frees the iommu virtually contiguous memory area starting at
 * @da, which was passed to and was returned by'iommu_kmap()'.
 */
void iommu_kunmap(struct iommu *obj, u32 da)
{
	struct sg_table *sgt;
	typedef void (*func_t)(const void *);

	sgt = unmap_vm_area(obj, da, (func_t)__iounmap,
			    IOVMF_LINEAR | IOVMF_MMIO);
	if (!sgt)
		dev_dbg(obj->dev, "%s: No sgt\n", __func__);
	sgtable_free(sgt);
}
EXPORT_SYMBOL_GPL(iommu_kunmap);

/**
 * iommu_kmalloc  -  (d)-(p)-(v) address allocator and mapper
 * @obj:	objective iommu
 * @da:		contiguous iommu virtual memory
 * @bytes:	bytes for allocation
 * @flags:	iovma and page property
 *
 * Allocate @bytes linearly and creates 1-1-1 mapping and returns
 * @da again, which might be adjusted if 'IOVMF_DA_ANON' is set.
 */
u32 iommu_kmalloc(struct iommu *obj, u32 da, size_t bytes, u32 flags)
{
	void *va;
	u32 pa;

	if (!obj || !obj->dev || !bytes)
		return -EINVAL;

	bytes = PAGE_ALIGN(bytes);

	va = kmalloc(bytes, GFP_KERNEL | GFP_DMA);
	if (!va)
		return -ENOMEM;
	pa = virt_to_phys(va);

	flags &= IOVMF_HW_MASK;
	flags |= IOVMF_LINEAR;
	flags |= IOVMF_ALLOC;
	flags |= (da ? IOVMF_DA_FIXED : IOVMF_DA_ANON);

	da = __iommu_kmap(obj, da, pa, va, bytes, flags);
	if (IS_ERR_VALUE(da))
		kfree(va);

	return da;
}
EXPORT_SYMBOL_GPL(iommu_kmalloc);

/**
 * iommu_kfree  -  release virtual mapping obtained by 'iommu_kmalloc()'
 * @obj:	objective iommu
 * @da:		iommu device virtual address
 *
 * Frees the iommu virtually contiguous memory area starting at
 * @da, which was passed to and was returned by'iommu_kmalloc()'.
 */
void iommu_kfree(struct iommu *obj, u32 da)
{
	struct sg_table *sgt;

	sgt = unmap_vm_area(obj, da, kfree, IOVMF_LINEAR | IOVMF_ALLOC);
	if (!sgt)
		dev_dbg(obj->dev, "%s: No sgt\n", __func__);
	sgtable_free(sgt);
}
EXPORT_SYMBOL_GPL(iommu_kfree);


static int __init iovmm_init(void)
{
	const unsigned long flags = SLAB_HWCACHE_ALIGN;
	struct kmem_cache *p;

	p = kmem_cache_create("iovm_area_cache", sizeof(struct iovm_struct), 0,
			      flags, NULL);
	if (!p)
		return -ENOMEM;
	iovm_area_cachep = p;

	return 0;
}
module_init(iovmm_init);

static void __exit iovmm_exit(void)
{
	kmem_cache_destroy(iovm_area_cachep);
}
module_exit(iovmm_exit);

MODULE_DESCRIPTION("omap iommu: simple virtual address space management");
MODULE_AUTHOR("Hiroshi DOYU <Hiroshi.DOYU@nokia.com>");
MODULE_LICENSE("GPL v2");