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c64be2bb1c
The Contiguous Memory Allocator is a set of helper functions for DMA mapping framework that improves allocations of contiguous memory chunks. CMA grabs memory on system boot, marks it with MIGRATE_CMA migrate type and gives back to the system. Kernel is allowed to allocate only movable pages within CMA's managed memory so that it can be used for example for page cache when DMA mapping do not use it. On dma_alloc_from_contiguous() request such pages are migrated out of CMA area to free required contiguous block and fulfill the request. This allows to allocate large contiguous chunks of memory at any time assuming that there is enough free memory available in the system. This code is heavily based on earlier works by Michal Nazarewicz. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Michal Nazarewicz <mina86@mina86.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Tested-by: Rob Clark <rob.clark@linaro.org> Tested-by: Ohad Ben-Cohen <ohad@wizery.com> Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org> Tested-by: Robert Nelson <robertcnelson@gmail.com> Tested-by: Barry Song <Baohua.Song@csr.com>
111 lines
3.1 KiB
C
111 lines
3.1 KiB
C
#ifndef __LINUX_CMA_H
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#define __LINUX_CMA_H
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/*
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* Contiguous Memory Allocator for DMA mapping framework
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* Copyright (c) 2010-2011 by Samsung Electronics.
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* Written by:
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* Marek Szyprowski <m.szyprowski@samsung.com>
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* Michal Nazarewicz <mina86@mina86.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License or (at your optional) any later version of the license.
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*/
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/*
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* Contiguous Memory Allocator
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*
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* The Contiguous Memory Allocator (CMA) makes it possible to
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* allocate big contiguous chunks of memory after the system has
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* booted.
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*
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* Why is it needed?
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*
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* Various devices on embedded systems have no scatter-getter and/or
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* IO map support and require contiguous blocks of memory to
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* operate. They include devices such as cameras, hardware video
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* coders, etc.
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*
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* Such devices often require big memory buffers (a full HD frame
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* is, for instance, more then 2 mega pixels large, i.e. more than 6
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* MB of memory), which makes mechanisms such as kmalloc() or
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* alloc_page() ineffective.
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*
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* At the same time, a solution where a big memory region is
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* reserved for a device is suboptimal since often more memory is
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* reserved then strictly required and, moreover, the memory is
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* inaccessible to page system even if device drivers don't use it.
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*
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* CMA tries to solve this issue by operating on memory regions
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* where only movable pages can be allocated from. This way, kernel
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* can use the memory for pagecache and when device driver requests
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* it, allocated pages can be migrated.
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*
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* Driver usage
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*
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* CMA should not be used by the device drivers directly. It is
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* only a helper framework for dma-mapping subsystem.
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*
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* For more information, see kernel-docs in drivers/base/dma-contiguous.c
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*/
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#ifdef __KERNEL__
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struct cma;
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struct page;
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struct device;
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#ifdef CONFIG_CMA
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/*
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* There is always at least global CMA area and a few optional device
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* private areas configured in kernel .config.
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*/
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#define MAX_CMA_AREAS (1 + CONFIG_CMA_AREAS)
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extern struct cma *dma_contiguous_default_area;
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void dma_contiguous_reserve(phys_addr_t addr_limit);
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int dma_declare_contiguous(struct device *dev, unsigned long size,
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phys_addr_t base, phys_addr_t limit);
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struct page *dma_alloc_from_contiguous(struct device *dev, int count,
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unsigned int order);
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bool dma_release_from_contiguous(struct device *dev, struct page *pages,
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int count);
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#else
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#define MAX_CMA_AREAS (0)
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static inline void dma_contiguous_reserve(phys_addr_t limit) { }
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static inline
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int dma_declare_contiguous(struct device *dev, unsigned long size,
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phys_addr_t base, phys_addr_t limit)
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{
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return -ENOSYS;
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}
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static inline
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struct page *dma_alloc_from_contiguous(struct device *dev, int count,
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unsigned int order)
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{
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return NULL;
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}
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static inline
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bool dma_release_from_contiguous(struct device *dev, struct page *pages,
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int count)
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{
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return false;
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}
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#endif
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#endif
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#endif
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