drivers/base/dma-contiguous.c - kernel/msm-4.9 - Gitiles

 /*
  * Contiguous Memory Allocator for DMA mapping framework
  * Copyright (c) 2010-2011 by Samsung Electronics.
  * Written by:
  *	Marek Szyprowski <m.szyprowski@samsung.com>
  *	Michal Nazarewicz <mina86@mina86.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation; either version 2 of the
  * License or (at your optional) any later version of the license.
  */

 #define pr_fmt(fmt) "cma: " fmt

 #ifdef CONFIG_CMA_DEBUG
 #ifndef DEBUG
 #  define DEBUG
 #endif
 #endif

 #include <asm/page.h>
 #include <asm/dma-contiguous.h>

 #include <linux/memblock.h>
 #include <linux/err.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
 #include <linux/page-isolation.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/mm_types.h>
 #include <linux/dma-contiguous.h>

 struct cma {
 	unsigned long	base_pfn;
 	unsigned long	count;
 	unsigned long	*bitmap;
 	struct mutex	lock;
 };

 struct cma *dma_contiguous_default_area;

 #ifdef CONFIG_CMA_SIZE_MBYTES
 #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES
 #else
 #define CMA_SIZE_MBYTES 0
 #endif

 /*
  * Default global CMA area size can be defined in kernel's .config.
  * This is useful mainly for distro maintainers to create a kernel
  * that works correctly for most supported systems.
  * The size can be set in bytes or as a percentage of the total memory
  * in the system.
  *
  * Users, who want to set the size of global CMA area for their system
  * should use cma= kernel parameter.
  */
 static const phys_addr_t size_bytes = CMA_SIZE_MBYTES * SZ_1M;
 static phys_addr_t size_cmdline = -1;
 static phys_addr_t base_cmdline;
 static phys_addr_t limit_cmdline;

 static int __init early_cma(char *p)
 {
 	pr_debug("%s(%s)\n", __func__, p);
 	size_cmdline = memparse(p, &p);
 	if (*p != '@')
 		return 0;
 	base_cmdline = memparse(p + 1, &p);
 	if (*p != '-') {
 		limit_cmdline = base_cmdline + size_cmdline;
 		return 0;
 	}
 	limit_cmdline = memparse(p + 1, &p);

 	return 0;
 }
 early_param("cma", early_cma);

 #ifdef CONFIG_CMA_SIZE_PERCENTAGE

 static phys_addr_t __init __maybe_unused cma_early_percent_memory(void)
 {
 	struct memblock_region *reg;
 	unsigned long total_pages = 0;

 	/*
 	 * We cannot use memblock_phys_mem_size() here, because
 	 * memblock_analyze() has not been called yet.
 	 */
 	for_each_memblock(memory, reg)
 		total_pages += memblock_region_memory_end_pfn(reg) -
 			       memblock_region_memory_base_pfn(reg);

 	return (total_pages * CONFIG_CMA_SIZE_PERCENTAGE / 100) << PAGE_SHIFT;
 }

 #else

 static inline __maybe_unused phys_addr_t cma_early_percent_memory(void)
 {
 	return 0;
 }

 #endif

 /**
  * dma_contiguous_reserve() - reserve area(s) for contiguous memory handling
  * @limit: End address of the reserved memory (optional, 0 for any).
  *
  * This function reserves memory from early allocator. It should be
  * called by arch specific code once the early allocator (memblock or bootmem)
  * has been activated and all other subsystems have already allocated/reserved
  * memory.
  */
 void __init dma_contiguous_reserve(phys_addr_t limit)
 {
 	phys_addr_t selected_size = 0;
 	phys_addr_t selected_base = 0;
 	phys_addr_t selected_limit = limit;
 	bool fixed = false;

 	pr_debug("%s(limit %08lx)\n", __func__, (unsigned long)limit);

 	if (size_cmdline != -1) {
 		selected_size = size_cmdline;
 		selected_base = base_cmdline;
 		selected_limit = min_not_zero(limit_cmdline, limit);
 		if (base_cmdline + size_cmdline == limit_cmdline)
 			fixed = true;
 	} else {
 #ifdef CONFIG_CMA_SIZE_SEL_MBYTES
 		selected_size = size_bytes;
 #elif defined(CONFIG_CMA_SIZE_SEL_PERCENTAGE)
 		selected_size = cma_early_percent_memory();
 #elif defined(CONFIG_CMA_SIZE_SEL_MIN)
 		selected_size = min(size_bytes, cma_early_percent_memory());
 #elif defined(CONFIG_CMA_SIZE_SEL_MAX)
 		selected_size = max(size_bytes, cma_early_percent_memory());
 #endif
 	}

 	if (selected_size && !dma_contiguous_default_area) {
 		pr_debug("%s: reserving %ld MiB for global area\n", __func__,
 			 (unsigned long)selected_size / SZ_1M);

 		dma_contiguous_reserve_area(selected_size, selected_base,
 					    selected_limit,
 					    &dma_contiguous_default_area,
 					    fixed);
 	}
 }

 static DEFINE_MUTEX(cma_mutex);

 static int __init cma_activate_area(struct cma *cma)
 {
 	int bitmap_size = BITS_TO_LONGS(cma->count) * sizeof(long);
 	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
 	unsigned i = cma->count >> pageblock_order;
 	struct zone *zone;

 	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);

 	if (!cma->bitmap)
 		return -ENOMEM;

 	WARN_ON_ONCE(!pfn_valid(pfn));
 	zone = page_zone(pfn_to_page(pfn));

 	do {
 		unsigned j;
 		base_pfn = pfn;
 		for (j = pageblock_nr_pages; j; --j, pfn++) {
 			WARN_ON_ONCE(!pfn_valid(pfn));
 			if (page_zone(pfn_to_page(pfn)) != zone)
 				return -EINVAL;
 		}
 		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
 	} while (--i);

 	mutex_init(&cma->lock);
 	return 0;
 }

 static struct cma cma_areas[MAX_CMA_AREAS];
 static unsigned cma_area_count;

 static int __init cma_init_reserved_areas(void)
 {
 	int i;

 	for (i = 0; i < cma_area_count; i++) {
 		int ret = cma_activate_area(&cma_areas[i]);
 		if (ret)
 			return ret;
 	}

 	return 0;
 }
 core_initcall(cma_init_reserved_areas);

 /**
  * dma_contiguous_reserve_area() - reserve custom contiguous area
  * @size: Size of the reserved area (in bytes),
  * @base: Base address of the reserved area optional, use 0 for any
  * @limit: End address of the reserved memory (optional, 0 for any).
  * @res_cma: Pointer to store the created cma region.
  * @fixed: hint about where to place the reserved area
  *
  * This function reserves memory from early allocator. It should be
  * called by arch specific code once the early allocator (memblock or bootmem)
  * has been activated and all other subsystems have already allocated/reserved
  * memory. This function allows to create custom reserved areas for specific
  * devices.
  *
  * If @fixed is true, reserve contiguous area at exactly @base.  If false,
  * reserve in range from @base to @limit.
  */
 int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
 				       phys_addr_t limit, struct cma **res_cma,
 				       bool fixed)
 {
 	struct cma *cma = &cma_areas[cma_area_count];
 	phys_addr_t alignment;
 	int ret = 0;

 	pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__,
 		 (unsigned long)size, (unsigned long)base,
 		 (unsigned long)limit);

 	/* Sanity checks */
 	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
 		pr_err("Not enough slots for CMA reserved regions!\n");
 		return -ENOSPC;
 	}

 	if (!size)
 		return -EINVAL;

 	/* Sanitise input arguments */
 	alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
 	base = ALIGN(base, alignment);
 	size = ALIGN(size, alignment);
 	limit &= ~(alignment - 1);

 	/* Reserve memory */
 	if (base && fixed) {
 		if (memblock_is_region_reserved(base, size) ||
 		    memblock_reserve(base, size) < 0) {
 			ret = -EBUSY;
 			goto err;
 		}
 	} else {
 		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
 							limit);
 		if (!addr) {
 			ret = -ENOMEM;
 			goto err;
 		} else {
 			base = addr;
 		}
 	}

 	/*
 	 * Each reserved area must be initialised later, when more kernel
 	 * subsystems (like slab allocator) are available.
 	 */
 	cma->base_pfn = PFN_DOWN(base);
 	cma->count = size >> PAGE_SHIFT;
 	*res_cma = cma;
 	cma_area_count++;

 	pr_info("CMA: reserved %ld MiB at %08lx\n", (unsigned long)size / SZ_1M,
 		(unsigned long)base);

 	/* Architecture specific contiguous memory fixup. */
 	dma_contiguous_early_fixup(base, size);
 	return 0;
 err:
 	pr_err("CMA: failed to reserve %ld MiB\n", (unsigned long)size / SZ_1M);
 	return ret;
 }

 static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
 {
 	mutex_lock(&cma->lock);
 	bitmap_clear(cma->bitmap, pfn - cma->base_pfn, count);
 	mutex_unlock(&cma->lock);
 }

 /**
  * dma_alloc_from_contiguous() - allocate pages from contiguous area
  * @dev:   Pointer to device for which the allocation is performed.
  * @count: Requested number of pages.
  * @align: Requested alignment of pages (in PAGE_SIZE order).
  *
  * This function allocates memory buffer for specified device. It uses
  * device specific contiguous memory area if available or the default
  * global one. Requires architecture specific dev_get_cma_area() helper
  * function.
  */
 struct page *dma_alloc_from_contiguous(struct device *dev, int count,
 				       unsigned int align)
 {
 	unsigned long mask, pfn, pageno, start = 0;
 	struct cma *cma = dev_get_cma_area(dev);
 	struct page *page = NULL;
 	int ret;

 	if (!cma || !cma->count)
 		return NULL;

 	if (align > CONFIG_CMA_ALIGNMENT)
 		align = CONFIG_CMA_ALIGNMENT;

 	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
 		 count, align);

 	if (!count)
 		return NULL;

 	mask = (1 << align) - 1;


 	for (;;) {
 		mutex_lock(&cma->lock);
 		pageno = bitmap_find_next_zero_area(cma->bitmap, cma->count,
 						    start, count, mask);
 		if (pageno >= cma->count) {
 			mutex_unlock(&cma->lock);
 			break;
 		}
 		bitmap_set(cma->bitmap, pageno, count);
 		/*
 		 * It's safe to drop the lock here. We've marked this region for
 		 * our exclusive use. If the migration fails we will take the
 		 * lock again and unmark it.
 		 */
 		mutex_unlock(&cma->lock);

 		pfn = cma->base_pfn + pageno;
 		mutex_lock(&cma_mutex);
 		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
 		mutex_unlock(&cma_mutex);
 		if (ret == 0) {
 			page = pfn_to_page(pfn);
 			break;
 		} else if (ret != -EBUSY) {
 			clear_cma_bitmap(cma, pfn, count);
 			break;
 		}
 		clear_cma_bitmap(cma, pfn, count);
 		pr_debug("%s(): memory range at %p is busy, retrying\n",
 			 __func__, pfn_to_page(pfn));
 		/* try again with a bit different memory target */
 		start = pageno + mask + 1;
 	}

 	pr_debug("%s(): returned %p\n", __func__, page);
 	return page;
 }

 /**
  * dma_release_from_contiguous() - release allocated pages
  * @dev:   Pointer to device for which the pages were allocated.
  * @pages: Allocated pages.
  * @count: Number of allocated pages.
  *
  * This function releases memory allocated by dma_alloc_from_contiguous().
  * It returns false when provided pages do not belong to contiguous area and
  * true otherwise.
  */
 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
 				 int count)
 {
 	struct cma *cma = dev_get_cma_area(dev);
 	unsigned long pfn;

 	if (!cma || !pages)
 		return false;

 	pr_debug("%s(page %p)\n", __func__, (void *)pages);

 	pfn = page_to_pfn(pages);

 	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
 		return false;

 	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);

 	free_contig_range(pfn, count);
 	clear_cma_bitmap(cma, pfn, count);

 	return true;
 }
	/*
	* Contiguous Memory Allocator for DMA mapping framework
	* Copyright (c) 2010-2011 by Samsung Electronics.
	* Written by:
	* Marek Szyprowski <m.szyprowski@samsung.com>
	* Michal Nazarewicz <mina86@mina86.com>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License as
	* published by the Free Software Foundation; either version 2 of the
	* License or (at your optional) any later version of the license.
	*/

	#define pr_fmt(fmt) "cma: " fmt

	#ifdef CONFIG_CMA_DEBUG
	#ifndef DEBUG
	# define DEBUG
	#endif
	#endif

	#include <asm/page.h>
	#include <asm/dma-contiguous.h>

	#include <linux/memblock.h>
	#include <linux/err.h>
	#include <linux/mm.h>
	#include <linux/mutex.h>
	#include <linux/page-isolation.h>
	#include <linux/sizes.h>
	#include <linux/slab.h>
	#include <linux/swap.h>
	#include <linux/mm_types.h>
	#include <linux/dma-contiguous.h>

	struct cma {
	unsigned long base_pfn;
	unsigned long count;
	unsigned long *bitmap;
	struct mutex lock;
	};

	struct cma *dma_contiguous_default_area;

	#ifdef CONFIG_CMA_SIZE_MBYTES
	#define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES
	#else
	#define CMA_SIZE_MBYTES 0
	#endif

	/*
	* Default global CMA area size can be defined in kernel's .config.
	* This is useful mainly for distro maintainers to create a kernel
	* that works correctly for most supported systems.
	* The size can be set in bytes or as a percentage of the total memory
	* in the system.
	*
	* Users, who want to set the size of global CMA area for their system
	* should use cma= kernel parameter.
	*/
	static const phys_addr_t size_bytes = CMA_SIZE_MBYTES * SZ_1M;
	static phys_addr_t size_cmdline = -1;
	static phys_addr_t base_cmdline;
	static phys_addr_t limit_cmdline;

	static int __init early_cma(char *p)
	{
	pr_debug("%s(%s)\n", __func__, p);
	size_cmdline = memparse(p, &p);
	if (*p != '@')
	return 0;
	base_cmdline = memparse(p + 1, &p);
	if (*p != '-') {
	limit_cmdline = base_cmdline + size_cmdline;
	return 0;
	}
	limit_cmdline = memparse(p + 1, &p);

	return 0;
	}
	early_param("cma", early_cma);

	#ifdef CONFIG_CMA_SIZE_PERCENTAGE

	static phys_addr_t __init __maybe_unused cma_early_percent_memory(void)
	{
	struct memblock_region *reg;
	unsigned long total_pages = 0;

	/*
	* We cannot use memblock_phys_mem_size() here, because
	* memblock_analyze() has not been called yet.
	*/
	for_each_memblock(memory, reg)
	total_pages += memblock_region_memory_end_pfn(reg) -
	memblock_region_memory_base_pfn(reg);

	return (total_pages * CONFIG_CMA_SIZE_PERCENTAGE / 100) << PAGE_SHIFT;
	}

	#else

	static inline __maybe_unused phys_addr_t cma_early_percent_memory(void)
	{
	return 0;
	}

	#endif

	/**
	* dma_contiguous_reserve() - reserve area(s) for contiguous memory handling
	* @limit: End address of the reserved memory (optional, 0 for any).
	*
	* This function reserves memory from early allocator. It should be
	* called by arch specific code once the early allocator (memblock or bootmem)
	* has been activated and all other subsystems have already allocated/reserved
	* memory.
	*/
	void __init dma_contiguous_reserve(phys_addr_t limit)
	{
	phys_addr_t selected_size = 0;
	phys_addr_t selected_base = 0;
	phys_addr_t selected_limit = limit;
	bool fixed = false;

	pr_debug("%s(limit %08lx)\n", __func__, (unsigned long)limit);

	if (size_cmdline != -1) {
	selected_size = size_cmdline;
	selected_base = base_cmdline;
	selected_limit = min_not_zero(limit_cmdline, limit);
	if (base_cmdline + size_cmdline == limit_cmdline)
	fixed = true;
	} else {
	#ifdef CONFIG_CMA_SIZE_SEL_MBYTES
	selected_size = size_bytes;
	#elif defined(CONFIG_CMA_SIZE_SEL_PERCENTAGE)
	selected_size = cma_early_percent_memory();
	#elif defined(CONFIG_CMA_SIZE_SEL_MIN)
	selected_size = min(size_bytes, cma_early_percent_memory());
	#elif defined(CONFIG_CMA_SIZE_SEL_MAX)
	selected_size = max(size_bytes, cma_early_percent_memory());
	#endif
	}

	if (selected_size && !dma_contiguous_default_area) {
	pr_debug("%s: reserving %ld MiB for global area\n", __func__,
	(unsigned long)selected_size / SZ_1M);

	dma_contiguous_reserve_area(selected_size, selected_base,
	selected_limit,
	&dma_contiguous_default_area,
	fixed);
	}
	}

	static DEFINE_MUTEX(cma_mutex);

	static int __init cma_activate_area(struct cma *cma)
	{
	int bitmap_size = BITS_TO_LONGS(cma->count) * sizeof(long);
	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
	unsigned i = cma->count >> pageblock_order;
	struct zone *zone;

	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);

	if (!cma->bitmap)
	return -ENOMEM;

	WARN_ON_ONCE(!pfn_valid(pfn));
	zone = page_zone(pfn_to_page(pfn));

	do {
	unsigned j;
	base_pfn = pfn;
	for (j = pageblock_nr_pages; j; --j, pfn++) {
	WARN_ON_ONCE(!pfn_valid(pfn));
	if (page_zone(pfn_to_page(pfn)) != zone)
	return -EINVAL;
	}
	init_cma_reserved_pageblock(pfn_to_page(base_pfn));
	} while (--i);

	mutex_init(&cma->lock);
	return 0;
	}

	static struct cma cma_areas[MAX_CMA_AREAS];
	static unsigned cma_area_count;

	static int __init cma_init_reserved_areas(void)
	{
	int i;

	for (i = 0; i < cma_area_count; i++) {
	int ret = cma_activate_area(&cma_areas[i]);
	if (ret)
	return ret;
	}

	return 0;
	}
	core_initcall(cma_init_reserved_areas);

	/**
	* dma_contiguous_reserve_area() - reserve custom contiguous area
	* @size: Size of the reserved area (in bytes),
	* @base: Base address of the reserved area optional, use 0 for any
	* @limit: End address of the reserved memory (optional, 0 for any).
	* @res_cma: Pointer to store the created cma region.
	* @fixed: hint about where to place the reserved area
	*
	* This function reserves memory from early allocator. It should be
	* called by arch specific code once the early allocator (memblock or bootmem)
	* has been activated and all other subsystems have already allocated/reserved
	* memory. This function allows to create custom reserved areas for specific
	* devices.
	*
	* If @fixed is true, reserve contiguous area at exactly @base. If false,
	* reserve in range from @base to @limit.
	*/
	int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
	phys_addr_t limit, struct cma **res_cma,
	bool fixed)
	{
	struct cma *cma = &cma_areas[cma_area_count];
	phys_addr_t alignment;
	int ret = 0;

	pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__,
	(unsigned long)size, (unsigned long)base,
	(unsigned long)limit);

	/* Sanity checks */
	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
	pr_err("Not enough slots for CMA reserved regions!\n");
	return -ENOSPC;
	}

	if (!size)
	return -EINVAL;

	/* Sanitise input arguments */
	alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
	base = ALIGN(base, alignment);
	size = ALIGN(size, alignment);
	limit &= ~(alignment - 1);

	/* Reserve memory */
	if (base && fixed) {
	if (memblock_is_region_reserved(base, size) \|\|
	memblock_reserve(base, size) < 0) {
	ret = -EBUSY;
	goto err;
	}
	} else {
	phys_addr_t addr = memblock_alloc_range(size, alignment, base,
	limit);
	if (!addr) {
	ret = -ENOMEM;
	goto err;
	} else {
	base = addr;
	}
	}

	/*
	* Each reserved area must be initialised later, when more kernel
	* subsystems (like slab allocator) are available.
	*/
	cma->base_pfn = PFN_DOWN(base);
	cma->count = size >> PAGE_SHIFT;
	*res_cma = cma;
	cma_area_count++;

	pr_info("CMA: reserved %ld MiB at %08lx\n", (unsigned long)size / SZ_1M,
	(unsigned long)base);

	/* Architecture specific contiguous memory fixup. */
	dma_contiguous_early_fixup(base, size);
	return 0;
	err:
	pr_err("CMA: failed to reserve %ld MiB\n", (unsigned long)size / SZ_1M);
	return ret;
	}

	static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
	{
	mutex_lock(&cma->lock);
	bitmap_clear(cma->bitmap, pfn - cma->base_pfn, count);
	mutex_unlock(&cma->lock);
	}

	/**
	* dma_alloc_from_contiguous() - allocate pages from contiguous area
	* @dev: Pointer to device for which the allocation is performed.
	* @count: Requested number of pages.
	* @align: Requested alignment of pages (in PAGE_SIZE order).
	*
	* This function allocates memory buffer for specified device. It uses
	* device specific contiguous memory area if available or the default
	* global one. Requires architecture specific dev_get_cma_area() helper
	* function.
	*/
	struct page dma_alloc_from_contiguous(struct device dev, int count,
	unsigned int align)
	{
	unsigned long mask, pfn, pageno, start = 0;
	struct cma *cma = dev_get_cma_area(dev);
	struct page *page = NULL;
	int ret;

	if (!cma \|\| !cma->count)
	return NULL;

	if (align > CONFIG_CMA_ALIGNMENT)
	align = CONFIG_CMA_ALIGNMENT;

	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
	count, align);

	if (!count)
	return NULL;

	mask = (1 << align) - 1;


	for (;;) {
	mutex_lock(&cma->lock);
	pageno = bitmap_find_next_zero_area(cma->bitmap, cma->count,
	start, count, mask);
	if (pageno >= cma->count) {
	mutex_unlock(&cma->lock);
	break;
	}
	bitmap_set(cma->bitmap, pageno, count);
	/*
	* It's safe to drop the lock here. We've marked this region for
	* our exclusive use. If the migration fails we will take the
	* lock again and unmark it.
	*/
	mutex_unlock(&cma->lock);

	pfn = cma->base_pfn + pageno;
	mutex_lock(&cma_mutex);
	ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
	mutex_unlock(&cma_mutex);
	if (ret == 0) {
	page = pfn_to_page(pfn);
	break;
	} else if (ret != -EBUSY) {
	clear_cma_bitmap(cma, pfn, count);
	break;
	}
	clear_cma_bitmap(cma, pfn, count);
	pr_debug("%s(): memory range at %p is busy, retrying\n",
	__func__, pfn_to_page(pfn));
	/* try again with a bit different memory target */
	start = pageno + mask + 1;
	}

	pr_debug("%s(): returned %p\n", __func__, page);
	return page;
	}

	/**
	* dma_release_from_contiguous() - release allocated pages
	* @dev: Pointer to device for which the pages were allocated.
	* @pages: Allocated pages.
	* @count: Number of allocated pages.
	*
	* This function releases memory allocated by dma_alloc_from_contiguous().
	* It returns false when provided pages do not belong to contiguous area and
	* true otherwise.
	*/
	bool dma_release_from_contiguous(struct device dev, struct page pages,
	int count)
	{
	struct cma *cma = dev_get_cma_area(dev);
	unsigned long pfn;

	if (!cma \|\| !pages)
	return false;

	pr_debug("%s(page %p)\n", __func__, (void *)pages);

	pfn = page_to_pfn(pages);

	if (pfn < cma->base_pfn \|\| pfn >= cma->base_pfn + cma->count)
	return false;

	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);

	free_contig_range(pfn, count);
	clear_cma_bitmap(cma, pfn, count);

	return true;
	}