// SPDX-License-Identifier: GPL-2.0+ /* * Contiguous Memory Allocator for DMA mapping framework * Copyright (c) 2010-2011 by Samsung Electronics. * Written by: * Marek Szyprowski <[email protected]> * Michal Nazarewicz <[email protected]> * * 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) … #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 … #else #define CMA_SIZE_MBYTES … #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 = …; static phys_addr_t size_cmdline __initdata = …; static phys_addr_t base_cmdline __initdata; static phys_addr_t limit_cmdline __initdata; static int __init early_cma(char *p) { … } early_param(…); #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) { … } early_param(…); static int __init early_cma_pernuma(char *p) { … } early_param(…); #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) { … } #endif #ifdef CONFIG_DMA_NUMA_CMA static void __init dma_numa_cma_reserve(void) { … } #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) { … } 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) { … } /** * 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) { … } /** * 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) { … } static struct page *cma_alloc_aligned(struct cma *cma, size_t size, gfp_t gfp) { … } /** * 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) { … } /** * 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) { … } /* * 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) … static int rmem_cma_device_init(struct reserved_mem *rmem, struct device *dev) { … } static void rmem_cma_device_release(struct reserved_mem *rmem, struct device *dev) { … } static const struct reserved_mem_ops rmem_cma_ops = …; static int __init rmem_cma_setup(struct reserved_mem *rmem) { … } RESERVEDMEM_OF_DECLARE(cma, "shared-dma-pool", rmem_cma_setup); #endif
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