kernel/dma/contiguous.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * 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>
  *
  * Contiguous Memory Allocator
  *
  *   The Contiguous Memory Allocator (CMA) makes it possible to
  *   allocate big contiguous chunks of memory after the system has
  *   booted.
  *
  * Why is it needed?
  *
  *   Various devices on embedded systems have no scatter-getter and/or
  *   IO map support and require contiguous blocks of memory to
  *   operate.  They include devices such as cameras, hardware video
  *   coders, etc.
  *
  *   Such devices often require big memory buffers (a full HD frame
  *   is, for instance, more than 2 mega pixels large, i.e. more than 6
  *   MB of memory), which makes mechanisms such as kmalloc() or
  *   alloc_page() ineffective.
  *
  *   At the same time, a solution where a big memory region is
  *   reserved for a device is suboptimal since often more memory is
  *   reserved then strictly required and, moreover, the memory is
  *   inaccessible to page system even if device drivers don't use it.
  *
  *   CMA tries to solve this issue by operating on memory regions
  *   where only movable pages can be allocated from.  This way, kernel
  *   can use the memory for pagecache and when device driver requests
  *   it, allocated pages can be migrated.
  */

 #define pr_fmt(fmt) "cma: " fmt

 #include <asm/page.h>

 #include <linux/memblock.h>
 #include <linux/err.h>
 #include <linux/sizes.h>
 #include <linux/dma-map-ops.h>
 #include <linux/cma.h>
 #include <linux/nospec.h>

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

 struct cma *dma_contiguous_default_area;

 /*
  * 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 __initconst =
 	(phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
 static phys_addr_t  size_cmdline __initdata = -1;
 static phys_addr_t base_cmdline __initdata;
 static phys_addr_t limit_cmdline __initdata;

 static int __init early_cma(char *p)
 {
 	if (!p) {
 		pr_err("Config string not provided\n");
 		return -EINVAL;
 	}

 	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_DMA_NUMA_CMA

 static struct cma *dma_contiguous_numa_area[MAX_NUMNODES];
 static phys_addr_t numa_cma_size[MAX_NUMNODES] __initdata;
 static struct cma *dma_contiguous_pernuma_area[MAX_NUMNODES];
 static phys_addr_t pernuma_size_bytes __initdata;

 static int __init early_numa_cma(char *p)
 {
 	int nid, count = 0;
 	unsigned long tmp;
 	char *s = p;

 	while (*s) {
 		if (sscanf(s, "%lu%n", &tmp, &count) != 1)
 			break;

 		if (s[count] == ':') {
 			if (tmp >= MAX_NUMNODES)
 				break;
 			nid = array_index_nospec(tmp, MAX_NUMNODES);

 			s += count + 1;
 			tmp = memparse(s, &s);
 			numa_cma_size[nid] = tmp;

 			if (*s == ',')
 				s++;
 			else
 				break;
 		} else
 			break;
 	}

 	return 0;
 }
 early_param("numa_cma", early_numa_cma);

 static int __init early_cma_pernuma(char *p)
 {
 	pernuma_size_bytes = memparse(p, &p);
 	return 0;
 }
 early_param("cma_pernuma", early_cma_pernuma);
 #endif

 #ifdef CONFIG_CMA_SIZE_PERCENTAGE

 static phys_addr_t __init __maybe_unused cma_early_percent_memory(void)
 {
 	unsigned long total_pages = PHYS_PFN(memblock_phys_mem_size());

 	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

 #ifdef CONFIG_DMA_NUMA_CMA
 static void __init dma_numa_cma_reserve(void)
 {
 	int nid;

 	for_each_node(nid) {
 		int ret;
 		char name[CMA_MAX_NAME];
 		struct cma **cma;

 		if (!node_online(nid)) {
 			if (pernuma_size_bytes || numa_cma_size[nid])
 				pr_warn("invalid node %d specified\n", nid);
 			continue;
 		}

 		if (pernuma_size_bytes) {

 			cma = &dma_contiguous_pernuma_area[nid];
 			snprintf(name, sizeof(name), "pernuma%d", nid);
 			ret = cma_declare_contiguous_nid(0, pernuma_size_bytes, 0, 0,
 							 0, false, name, cma, nid);
 			if (ret)
 				pr_warn("%s: reservation failed: err %d, node %d", __func__,
 					ret, nid);
 		}

 		if (numa_cma_size[nid]) {

 			cma = &dma_contiguous_numa_area[nid];
 			snprintf(name, sizeof(name), "numa%d", nid);
 			ret = cma_declare_contiguous_nid(0, numa_cma_size[nid], 0, 0, 0, false,
 							 name, cma, nid);
 			if (ret)
 				pr_warn("%s: reservation failed: err %d, node %d", __func__,
 					ret, nid);
 		}
 	}
 }
 #else
 static inline void __init dma_numa_cma_reserve(void)
 {
 }
 #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;

 	dma_numa_cma_reserve();

 	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);
 	}
 }

 void __weak
 dma_contiguous_early_fixup(phys_addr_t base, unsigned long size)
 {
 }

 /**
  * 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)
 {
 	int ret;

 	ret = cma_declare_contiguous(base, size, limit, 0, 0, fixed,
 					"reserved", res_cma);
 	if (ret)
 		return ret;

 	/* Architecture specific contiguous memory fixup. */
 	dma_contiguous_early_fixup(cma_get_base(*res_cma),
 				cma_get_size(*res_cma));

 	return 0;
 }

 /**
  * 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).
  * @no_warn: Avoid printing message about failed allocation.
  *
  * 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, size_t count,
 				       unsigned int align, bool no_warn)
 {
 	if (align > CONFIG_CMA_ALIGNMENT)
 		align = CONFIG_CMA_ALIGNMENT;

 	return cma_alloc(dev_get_cma_area(dev), count, align, no_warn);
 }

 /**
  * 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)
 {
 	return cma_release(dev_get_cma_area(dev), pages, count);
 }

 static struct page *cma_alloc_aligned(struct cma *cma, size_t size, gfp_t gfp)
 {
 	unsigned int align = min(get_order(size), CONFIG_CMA_ALIGNMENT);

 	return cma_alloc(cma, size >> PAGE_SHIFT, align, gfp & __GFP_NOWARN);
 }

 /**
  * dma_alloc_contiguous() - allocate contiguous pages
  * @dev:   Pointer to device for which the allocation is performed.
  * @size:  Requested allocation size.
  * @gfp:   Allocation flags.
  *
  * tries to use device specific contiguous memory area if available, or it
  * tries to use per-numa cma, if the allocation fails, it will fallback to
  * try default global one.
  *
  * Note that it bypass one-page size of allocations from the per-numa and
  * global area as the addresses within one page are always contiguous, so
  * there is no need to waste CMA pages for that kind; it also helps reduce
  * fragmentations.
  */
 struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
 {
 #ifdef CONFIG_DMA_NUMA_CMA
 	int nid = dev_to_node(dev);
 #endif

 	/* CMA can be used only in the context which permits sleeping */
 	if (!gfpflags_allow_blocking(gfp))
 		return NULL;
 	if (dev->cma_area)
 		return cma_alloc_aligned(dev->cma_area, size, gfp);
 	if (size <= PAGE_SIZE)
 		return NULL;

 #ifdef CONFIG_DMA_NUMA_CMA
 	if (nid != NUMA_NO_NODE && !(gfp & (GFP_DMA | GFP_DMA32))) {
 		struct cma *cma = dma_contiguous_pernuma_area[nid];
 		struct page *page;

 		if (cma) {
 			page = cma_alloc_aligned(cma, size, gfp);
 			if (page)
 				return page;
 		}

 		cma = dma_contiguous_numa_area[nid];
 		if (cma) {
 			page = cma_alloc_aligned(cma, size, gfp);
 			if (page)
 				return page;
 		}
 	}
 #endif
 	if (!dma_contiguous_default_area)
 		return NULL;

 	return cma_alloc_aligned(dma_contiguous_default_area, size, gfp);
 }

 /**
  * dma_free_contiguous() - release allocated pages
  * @dev:   Pointer to device for which the pages were allocated.
  * @page:  Pointer to the allocated pages.
  * @size:  Size of allocated pages.
  *
  * This function releases memory allocated by dma_alloc_contiguous(). As the
  * cma_release returns false when provided pages do not belong to contiguous
  * area and true otherwise, this function then does a fallback __free_pages()
  * upon a false-return.
  */
 void dma_free_contiguous(struct device *dev, struct page *page, size_t size)
 {
 	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;

 	/* if dev has its own cma, free page from there */
 	if (dev->cma_area) {
 		if (cma_release(dev->cma_area, page, count))
 			return;
 	} else {
 		/*
 		 * otherwise, page is from either per-numa cma or default cma
 		 */
 #ifdef CONFIG_DMA_NUMA_CMA
 		if (cma_release(dma_contiguous_pernuma_area[page_to_nid(page)],
 					page, count))
 			return;
 		if (cma_release(dma_contiguous_numa_area[page_to_nid(page)],
 					page, count))
 			return;
 #endif
 		if (cma_release(dma_contiguous_default_area, page, count))
 			return;
 	}

 	/* not in any cma, free from buddy */
 	__free_pages(page, get_order(size));
 }

 /*
  * Support for reserved memory regions defined in device tree
  */
 #ifdef CONFIG_OF_RESERVED_MEM
 #include <linux/of.h>
 #include <linux/of_fdt.h>
 #include <linux/of_reserved_mem.h>

 #undef pr_fmt
 #define pr_fmt(fmt) fmt

 static int rmem_cma_device_init(struct reserved_mem *rmem, struct device *dev)
 {
 	dev->cma_area = rmem->priv;
 	return 0;
 }

 static void rmem_cma_device_release(struct reserved_mem *rmem,
 				    struct device *dev)
 {
 	dev->cma_area = NULL;
 }

 static const struct reserved_mem_ops rmem_cma_ops = {
 	.device_init	= rmem_cma_device_init,
 	.device_release = rmem_cma_device_release,
 };

 static int __init rmem_cma_setup(struct reserved_mem *rmem)
 {
 	unsigned long node = rmem->fdt_node;
 	bool default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
 	struct cma *cma;
 	int err;

 	if (size_cmdline != -1 && default_cma) {
 		pr_info("Reserved memory: bypass %s node, using cmdline CMA params instead\n",
 			rmem->name);
 		return -EBUSY;
 	}

 	if (!of_get_flat_dt_prop(node, "reusable", NULL) ||
 	    of_get_flat_dt_prop(node, "no-map", NULL))
 		return -EINVAL;

 	if (!IS_ALIGNED(rmem->base | rmem->size, CMA_MIN_ALIGNMENT_BYTES)) {
 		pr_err("Reserved memory: incorrect alignment of CMA region\n");
 		return -EINVAL;
 	}

 	err = cma_init_reserved_mem(rmem->base, rmem->size, 0, rmem->name, &cma);
 	if (err) {
 		pr_err("Reserved memory: unable to setup CMA region\n");
 		return err;
 	}
 	/* Architecture specific contiguous memory fixup. */
 	dma_contiguous_early_fixup(rmem->base, rmem->size);

 	if (default_cma)
 		dma_contiguous_default_area = cma;

 	rmem->ops = &rmem_cma_ops;
 	rmem->priv = cma;

 	pr_info("Reserved memory: created CMA memory pool at %pa, size %ld MiB\n",
 		&rmem->base, (unsigned long)rmem->size / SZ_1M);

 	return 0;
 }
 RESERVEDMEM_OF_DECLARE(cma, "shared-dma-pool", rmem_cma_setup);
 #endif
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* 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>
	*
	* Contiguous Memory Allocator
	*
	* The Contiguous Memory Allocator (CMA) makes it possible to
	* allocate big contiguous chunks of memory after the system has
	* booted.
	*
	* Why is it needed?
	*
	* Various devices on embedded systems have no scatter-getter and/or
	* IO map support and require contiguous blocks of memory to
	* operate. They include devices such as cameras, hardware video
	* coders, etc.
	*
	* Such devices often require big memory buffers (a full HD frame
	* is, for instance, more than 2 mega pixels large, i.e. more than 6
	* MB of memory), which makes mechanisms such as kmalloc() or
	* alloc_page() ineffective.
	*
	* At the same time, a solution where a big memory region is
	* reserved for a device is suboptimal since often more memory is
	* reserved then strictly required and, moreover, the memory is
	* inaccessible to page system even if device drivers don't use it.
	*
	* CMA tries to solve this issue by operating on memory regions
	* where only movable pages can be allocated from. This way, kernel
	* can use the memory for pagecache and when device driver requests
	* it, allocated pages can be migrated.
	*/

	#define pr_fmt(fmt) "cma: " fmt

	#include <asm/page.h>

	#include <linux/memblock.h>
	#include <linux/err.h>
	#include <linux/sizes.h>
	#include <linux/dma-map-ops.h>
	#include <linux/cma.h>
	#include <linux/nospec.h>

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

	struct cma *dma_contiguous_default_area;

	/*
	* 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 __initconst =
	(phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
	static phys_addr_t size_cmdline __initdata = -1;
	static phys_addr_t base_cmdline __initdata;
	static phys_addr_t limit_cmdline __initdata;

	static int __init early_cma(char *p)
	{
	if (!p) {
	pr_err("Config string not provided\n");
	return -EINVAL;
	}

	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_DMA_NUMA_CMA

	static struct cma *dma_contiguous_numa_area[MAX_NUMNODES];
	static phys_addr_t numa_cma_size[MAX_NUMNODES] __initdata;
	static struct cma *dma_contiguous_pernuma_area[MAX_NUMNODES];
	static phys_addr_t pernuma_size_bytes __initdata;

	static int __init early_numa_cma(char *p)
	{
	int nid, count = 0;
	unsigned long tmp;
	char *s = p;

	while (*s) {
	if (sscanf(s, "%lu%n", &tmp, &count) != 1)
	break;

	if (s[count] == ':') {
	if (tmp >= MAX_NUMNODES)
	break;
	nid = array_index_nospec(tmp, MAX_NUMNODES);

	s += count + 1;
	tmp = memparse(s, &s);
	numa_cma_size[nid] = tmp;

	if (*s == ',')
	s++;
	else
	break;
	} else
	break;
	}

	return 0;
	}
	early_param("numa_cma", early_numa_cma);

	static int __init early_cma_pernuma(char *p)
	{
	pernuma_size_bytes = memparse(p, &p);
	return 0;
	}
	early_param("cma_pernuma", early_cma_pernuma);
	#endif

	#ifdef CONFIG_CMA_SIZE_PERCENTAGE

	static phys_addr_t __init __maybe_unused cma_early_percent_memory(void)
	{
	unsigned long total_pages = PHYS_PFN(memblock_phys_mem_size());

	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

	#ifdef CONFIG_DMA_NUMA_CMA
	static void __init dma_numa_cma_reserve(void)
	{
	int nid;

	for_each_node(nid) {
	int ret;
	char name[CMA_MAX_NAME];
	struct cma **cma;

	if (!node_online(nid)) {
	if (pernuma_size_bytes \|\| numa_cma_size[nid])
	pr_warn("invalid node %d specified\n", nid);
	continue;
	}

	if (pernuma_size_bytes) {

	cma = &dma_contiguous_pernuma_area[nid];
	snprintf(name, sizeof(name), "pernuma%d", nid);
	ret = cma_declare_contiguous_nid(0, pernuma_size_bytes, 0, 0,
	0, false, name, cma, nid);
	if (ret)
	pr_warn("%s: reservation failed: err %d, node %d", __func__,
	ret, nid);
	}

	if (numa_cma_size[nid]) {

	cma = &dma_contiguous_numa_area[nid];
	snprintf(name, sizeof(name), "numa%d", nid);
	ret = cma_declare_contiguous_nid(0, numa_cma_size[nid], 0, 0, 0, false,
	name, cma, nid);
	if (ret)
	pr_warn("%s: reservation failed: err %d, node %d", __func__,
	ret, nid);
	}
	}
	}
	#else
	static inline void __init dma_numa_cma_reserve(void)
	{
	}
	#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;

	dma_numa_cma_reserve();

	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);
	}
	}

	void __weak
	dma_contiguous_early_fixup(phys_addr_t base, unsigned long size)
	{
	}

	/**
	* 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)
	{
	int ret;

	ret = cma_declare_contiguous(base, size, limit, 0, 0, fixed,
	"reserved", res_cma);
	if (ret)
	return ret;

	/* Architecture specific contiguous memory fixup. */
	dma_contiguous_early_fixup(cma_get_base(*res_cma),
	cma_get_size(*res_cma));

	return 0;
	}

	/**
	* 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).
	* @no_warn: Avoid printing message about failed allocation.
	*
	* 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, size_t count,
	unsigned int align, bool no_warn)
	{
	if (align > CONFIG_CMA_ALIGNMENT)
	align = CONFIG_CMA_ALIGNMENT;

	return cma_alloc(dev_get_cma_area(dev), count, align, no_warn);
	}

	/**
	* 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)
	{
	return cma_release(dev_get_cma_area(dev), pages, count);
	}

	static struct page cma_alloc_aligned(struct cma cma, size_t size, gfp_t gfp)
	{
	unsigned int align = min(get_order(size), CONFIG_CMA_ALIGNMENT);

	return cma_alloc(cma, size >> PAGE_SHIFT, align, gfp & __GFP_NOWARN);
	}

	/**
	* dma_alloc_contiguous() - allocate contiguous pages
	* @dev: Pointer to device for which the allocation is performed.
	* @size: Requested allocation size.
	* @gfp: Allocation flags.
	*
	* tries to use device specific contiguous memory area if available, or it
	* tries to use per-numa cma, if the allocation fails, it will fallback to
	* try default global one.
	*
	* Note that it bypass one-page size of allocations from the per-numa and
	* global area as the addresses within one page are always contiguous, so
	* there is no need to waste CMA pages for that kind; it also helps reduce
	* fragmentations.
	*/
	struct page dma_alloc_contiguous(struct device dev, size_t size, gfp_t gfp)
	{
	#ifdef CONFIG_DMA_NUMA_CMA
	int nid = dev_to_node(dev);
	#endif

	/* CMA can be used only in the context which permits sleeping */
	if (!gfpflags_allow_blocking(gfp))
	return NULL;
	if (dev->cma_area)
	return cma_alloc_aligned(dev->cma_area, size, gfp);
	if (size <= PAGE_SIZE)
	return NULL;

	#ifdef CONFIG_DMA_NUMA_CMA
	if (nid != NUMA_NO_NODE && !(gfp & (GFP_DMA \| GFP_DMA32))) {
	struct cma *cma = dma_contiguous_pernuma_area[nid];
	struct page *page;

	if (cma) {
	page = cma_alloc_aligned(cma, size, gfp);
	if (page)
	return page;
	}

	cma = dma_contiguous_numa_area[nid];
	if (cma) {
	page = cma_alloc_aligned(cma, size, gfp);
	if (page)
	return page;
	}
	}
	#endif
	if (!dma_contiguous_default_area)
	return NULL;

	return cma_alloc_aligned(dma_contiguous_default_area, size, gfp);
	}

	/**
	* dma_free_contiguous() - release allocated pages
	* @dev: Pointer to device for which the pages were allocated.
	* @page: Pointer to the allocated pages.
	* @size: Size of allocated pages.
	*
	* This function releases memory allocated by dma_alloc_contiguous(). As the
	* cma_release returns false when provided pages do not belong to contiguous
	* area and true otherwise, this function then does a fallback __free_pages()
	* upon a false-return.
	*/
	void dma_free_contiguous(struct device dev, struct page page, size_t size)
	{
	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;

	/* if dev has its own cma, free page from there */
	if (dev->cma_area) {
	if (cma_release(dev->cma_area, page, count))
	return;
	} else {
	/*
	* otherwise, page is from either per-numa cma or default cma
	*/
	#ifdef CONFIG_DMA_NUMA_CMA
	if (cma_release(dma_contiguous_pernuma_area[page_to_nid(page)],
	page, count))
	return;
	if (cma_release(dma_contiguous_numa_area[page_to_nid(page)],
	page, count))
	return;
	#endif
	if (cma_release(dma_contiguous_default_area, page, count))
	return;
	}

	/* not in any cma, free from buddy */
	__free_pages(page, get_order(size));
	}

	/*
	* Support for reserved memory regions defined in device tree
	*/
	#ifdef CONFIG_OF_RESERVED_MEM
	#include <linux/of.h>
	#include <linux/of_fdt.h>
	#include <linux/of_reserved_mem.h>

	#undef pr_fmt
	#define pr_fmt(fmt) fmt

	static int rmem_cma_device_init(struct reserved_mem rmem, struct device dev)
	{
	dev->cma_area = rmem->priv;
	return 0;
	}

	static void rmem_cma_device_release(struct reserved_mem *rmem,
	struct device *dev)
	{
	dev->cma_area = NULL;
	}

	static const struct reserved_mem_ops rmem_cma_ops = {
	.device_init = rmem_cma_device_init,
	.device_release = rmem_cma_device_release,
	};

	static int __init rmem_cma_setup(struct reserved_mem *rmem)
	{
	unsigned long node = rmem->fdt_node;
	bool default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
	struct cma *cma;
	int err;

	if (size_cmdline != -1 && default_cma) {
	pr_info("Reserved memory: bypass %s node, using cmdline CMA params instead\n",
	rmem->name);
	return -EBUSY;
	}

	if (!of_get_flat_dt_prop(node, "reusable", NULL) \|\|
	of_get_flat_dt_prop(node, "no-map", NULL))
	return -EINVAL;

	if (!IS_ALIGNED(rmem->base \| rmem->size, CMA_MIN_ALIGNMENT_BYTES)) {
	pr_err("Reserved memory: incorrect alignment of CMA region\n");
	return -EINVAL;
	}

	err = cma_init_reserved_mem(rmem->base, rmem->size, 0, rmem->name, &cma);
	if (err) {
	pr_err("Reserved memory: unable to setup CMA region\n");
	return err;
	}
	/* Architecture specific contiguous memory fixup. */
	dma_contiguous_early_fixup(rmem->base, rmem->size);

	if (default_cma)
	dma_contiguous_default_area = cma;

	rmem->ops = &rmem_cma_ops;
	rmem->priv = cma;

	pr_info("Reserved memory: created CMA memory pool at %pa, size %ld MiB\n",
	&rmem->base, (unsigned long)rmem->size / SZ_1M);

	return 0;
	}
	RESERVEDMEM_OF_DECLARE(cma, "shared-dma-pool", rmem_cma_setup);
	#endif