Hello,
I've just found two nasty bugs in this version of CMA. Sadly, both are the
results of posting the patches in a big hurry. I'm really sorry.
Alignment argument was not passed correctly to the
bitmap_find_next_zero_area() function and there was an ugly bug in the
dma_release_from_contiguous() function.
On Tuesday, July 05, 2011 9:42 AM Marek Szyprowski wrote:
> 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 CMA_MIGRATE_TYPE and
> gives back to the system. Kernel is allowed to allocate 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.szyprow...@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.p...@samsung.com>
> CC: Michal Nazarewicz <min...@mina86.com>
> ---
> drivers/base/Kconfig | 77 +++++++++
> drivers/base/Makefile | 1 +
> drivers/base/dma-contiguous.c | 367
> ++++++++++++++++++++++++++++++++++++++++
> include/linux/dma-contiguous.h | 104 +++++++++++
> 4 files changed, 549 insertions(+), 0 deletions(-)
> create mode 100644 drivers/base/dma-contiguous.c
> create mode 100644 include/linux/dma-contiguous.h
>
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index d57e8d0..95ae1a7 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -168,4 +168,81 @@ config SYS_HYPERVISOR
> bool
> default n
>
> +config CMA
> + bool "Contiguous Memory Allocator"
> + depends HAVE_DMA_CONTIGUOUS && HAVE_MEMBLOCK
> + select MIGRATION
> + select CMA_MIGRATE_TYPE
> + help
> + This enables the Contiguous Memory Allocator which allows drivers
> + to allocate big physically-contiguous blocks of memory for use with
> + hardware components that do not support I/O map nor scatter-gather.
> +
> + For more information see <include/linux/dma-contiguous.h>.
> + If unsure, say "n".
> +
> +if CMA
> +
> +config CMA_DEBUG
> + bool "CMA debug messages (DEVELOPEMENT)"
> + help
> + Turns on debug messages in CMA. This produces KERN_DEBUG
> + messages for every CMA call as well as various messages while
> + processing calls such as dma_alloc_from_contiguous().
> + This option does not affect warning and error messages.
> +
> +comment "Default contiguous memory area size:"
> +
> +config CMA_SIZE_ABSOLUTE
> + int "Absolute size (in MiB)"
> + default 16
> + help
> + Defines the size (in MiB) of the default memory area for Contiguous
> + Memory Allocator.
> +
> +config CMA_SIZE_PERCENTAGE
> + int "Percentage of total memory"
> + default 10
> + help
> + Defines the size of the default memory area for Contiguous Memory
> + Allocator as a percentage of the total memory in the system.
> +
> +choice
> + prompt "Selected region size"
> + default CMA_SIZE_SEL_ABSOLUTE
> +
> +config CMA_SIZE_SEL_ABSOLUTE
> + bool "Use absolute value only"
> +
> +config CMA_SIZE_SEL_PERCENTAGE
> + bool "Use percentage value only"
> +
> +config CMA_SIZE_SEL_MIN
> + bool "Use lower value (minimum)"
> +
> +config CMA_SIZE_SEL_MAX
> + bool "Use higher value (maximum)"
> +
> +endchoice
> +
> +config CMA_ALIGNMENT
> + int "Maximum PAGE_SIZE order of alignment for contiguous buffers"
> + range 4 9
> + default 8
> + help
> + DMA mapping framework by default aligns all buffers to the smallest
> + PAGE_SIZE order which is greater than or equal to the requested
> buffer
> + size. This works well for buffers up to a few hundreds kilobytes,
> but
> + for larger buffers it just a memory waste. With this parameter you
> can
> + specify the maximum PAGE_SIZE order for contiguous buffers. Larger
> + buffers will be aligned only to this specified order. The order is
> + expressed as a power of two multiplied by the PAGE_SIZE.
> +
> + For example, if your system defaults to 4KiB pages, the order value
> + of 8 means that the buffers will be aligned up to 1MiB only.
> +
> + If unsure, leave the default value "8".
> +
> +endif
> +
> endmenu
> diff --git a/drivers/base/Makefile b/drivers/base/Makefile
> index 4c5701c..be6aab4 100644
> --- a/drivers/base/Makefile
> +++ b/drivers/base/Makefile
> @@ -5,6 +5,7 @@ obj-y := core.o sys.o bus.o dd.o syscore.o \
> cpu.o firmware.o init.o map.o devres.o \
> attribute_container.o transport_class.o
> obj-$(CONFIG_DEVTMPFS) += devtmpfs.o
> +obj-$(CONFIG_CMA) += dma-contiguous.o
> obj-y += power/
> obj-$(CONFIG_HAS_DMA) += dma-mapping.o
> obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> new file mode 100644
> index 0000000..707b901
> --- /dev/null
> +++ b/drivers/base/dma-contiguous.c
> @@ -0,0 +1,367 @@
> +/*
> + * Contiguous Memory Allocator for DMA mapping framework
> + * Copyright (c) 2010-2011 by Samsung Electronics.
> + * Written by:
> + * Marek Szyprowski <m.szyprow...@samsung.com>
> + * Michal Nazarewicz <min...@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/sizes.h>
> +
> +#include <linux/memblock.h>
> +#include <linux/err.h>
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/page-isolation.h>
> +#include <linux/slab.h>
> +#include <linux/swap.h>
> +#include <linux/mm_types.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/dma-contiguous.h>
> +
> +struct cma {
> + unsigned long base_pfn;
> + unsigned long count;
> + unsigned long *bitmap;
> +};
> +
> +struct cma *dma_contiguous_default_area;
> +
> +static unsigned long size_abs = CONFIG_CMA_SIZE_ABSOLUTE * SZ_1M;
> +static unsigned long size_percent = CONFIG_CMA_SIZE_PERCENTAGE;
> +static long size_cmdline = -1;
> +
> +static int __init early_cma(char *p)
> +{
> + pr_debug("%s(%s)\n", __func__, p);
> + size_cmdline = memparse(p, &p);
> + return 0;
> +}
> +early_param("cma", early_cma);
> +
> +/**
> + * dma_contiguous_reserve() - reserve area for contiguous memory handling
> + *
> + * This funtion reserves memory from memblock subsystem. It should be
> + * called by arch specific code once a memblock allocator has been
> activated
> + * and all other subsystems have already allocated/reserved memory.
> + */
> +void __init dma_contiguous_reserve(void)
> +{
> + struct memblock_region *reg;
> + unsigned long selected_size = 0;
> + unsigned long total_pages = 0;
> +
> + pr_debug("%s()\n", __func__);
> +
> + /*
> + * 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);
> +
> + size_percent *= (total_pages << PAGE_SHIFT) / 100;
> +
> + pr_debug("%s: available phys mem: %ld MiB\n", __func__,
> + (total_pages << PAGE_SHIFT) / SZ_1M);
> +
> +#ifdef CONFIG_CMA_SIZE_SEL_ABSOLUTE
> + selected_size = size_abs;
> +#endif
> +#ifdef CONFIG_CMA_SIZE_SEL_PERCENTAGE
> + selected_size = size_percent;
> +#endif
> +#ifdef CONFIG_CMA_SIZE_SEL_MIN
> + selected_size = min(size_abs, size_percent);
> +#endif
> +#ifdef CONFIG_CMA_SIZE_SEL_MAX
> + selected_size = max(size_abs, size_percent);
> +#endif
> +
> + if (size_cmdline != -1)
> + selected_size = size_cmdline;
> +
> + if (!selected_size)
> + return;
> +
> + pr_debug("%s: reserving %ld MiB for global area\n", __func__,
> + selected_size / SZ_1M);
> +
> + dma_declare_contiguous(NULL, selected_size, 0);
> +};
> +
> +static DEFINE_MUTEX(cma_mutex);
> +
> +#ifdef CONFIG_DEBUG_VM
> +
> +static int __cma_activate_area(unsigned long base_pfn, unsigned long
> count)
> +{
> + unsigned long pfn = base_pfn;
> + unsigned i = count;
> + struct zone *zone;
> +
> + pr_debug("%s(0x%08lx+0x%lx)\n", __func__, base_pfn, count);
> +
> + VM_BUG_ON(!pfn_valid(pfn));
> + zone = page_zone(pfn_to_page(pfn));
> +
> + do {
> + VM_BUG_ON(!pfn_valid(pfn));
> + VM_BUG_ON(page_zone(pfn_to_page(pfn)) != zone);
> + if (!(pfn & (pageblock_nr_pages - 1)))
> + init_cma_reserved_pageblock(pfn_to_page(pfn));
> + ++pfn;
> + } while (--i);
> +
> + return 0;
> +}
> +
> +#else
> +
> +static int __cma_activate_area(unsigned long base_pfn, unsigned long
> count)
> +{
> + unsigned i = count >> pageblock_order;
> + struct page *p = pfn_to_page(base_pfn);
> +
> + pr_debug("%s(0x%08lx+0x%lx)\n", __func__, base_pfn, count);
> +
> + do {
> + init_cma_reserved_pageblock(p);
> + p += pageblock_nr_pages;
> + } while (--i);
> +
> + return 0;
> +}
> +
> +#endif
> +
> +static struct cma *__cma_create_area(unsigned long base_pfn,
> + unsigned long count)
> +{
> + int bitmap_size = BITS_TO_LONGS(count) * sizeof(long);
> + struct cma *cma;
> +
> + pr_debug("%s(0x%08lx+0x%lx)\n", __func__, base_pfn, count);
> +
> + cma = kmalloc(sizeof *cma, GFP_KERNEL);
> + if (!cma)
> + return ERR_PTR(-ENOMEM);
> +
> + cma->base_pfn = base_pfn;
> + cma->count = count;
> + cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> +
> + if (!cma->bitmap)
> + goto no_mem;
> +
> + __cma_activate_area(base_pfn, count);
> +
> + pr_debug("%s: returning <%p>\n", __func__, (void *)cma);
> + return cma;
> +
> +no_mem:
> + kfree(cma);
> + return ERR_PTR(-ENOMEM);
> +}
> +
> +static struct cma_reserved {
> + unsigned long start;
> + unsigned long size;
> + struct device *dev;
> +} cma_reserved[8] __initdata;
> +static unsigned cma_reserved_count __initdata;
> +
> +static int __init __cma_init_reserved_areas(void)
> +{
> + struct cma_reserved *r = cma_reserved;
> + unsigned i = cma_reserved_count;
> +
> + pr_debug("%s()\n", __func__);
> +
> + for (; i; --i, ++r) {
> + struct cma *cma;
> + cma = __cma_create_area(page_to_pfn(phys_to_page(r->start)),
> + r->size >> PAGE_SHIFT);
> + if (!IS_ERR(cma)) {
> + pr_debug("%s: created area %p\n", __func__, cma);
> + if (r->dev)
> + set_dev_cma_area(r->dev, cma);
> + else
> + dma_contiguous_default_area = cma;
> + }
> + }
> + return 0;
> +}
> +core_initcall(__cma_init_reserved_areas);
> +
> +/**
> + * dma_declare_contiguous() - reserve area for contiguous memory handling
> + * for particular device
> + * @dev: Pointer to device structure.
> + * @size: Size of the reserved memory.
> + * @start: Start address of the reserved memory (optional, 0 for any).
> + *
> + * This funtion reserves memory for specified device. It should be
> + * called by board specific code once a memblock allocator has been
> activated
> + * and all other subsystems have already allocated/reserved memory.
> + */
> +int __init dma_declare_contiguous(struct device *dev, unsigned long size,
> + phys_addr_t start)
> +{
> + struct cma_reserved *r = &cma_reserved[cma_reserved_count];
> + unsigned long alignment;
> +
> + pr_debug("%s(%p+%p)\n", __func__, (void *)start, (void *)size);
> +
> + /* Sanity checks */
> + if (cma_reserved_count == ARRAY_SIZE(cma_reserved))
> + return -ENOSPC;
> +
> + if (!size)
> + return -EINVAL;
> +
> + /* Sanitise input arguments */
> + alignment = PAGE_SIZE << (MAX_ORDER + 1);
> + start = ALIGN(start, alignment);
> + size = ALIGN(size , alignment);
> +
> + /* Reserve memory */
> + if (start) {
> + if (memblock_is_region_reserved(start, size) ||
> + memblock_reserve(start, size) < 0)
> + return -EBUSY;
> + } else {
> + /*
> + * Use __memblock_alloc_base() since
> + * memblock_alloc_base() panic()s.
> + */
> + u64 addr = __memblock_alloc_base(size, alignment, 0);
> + if (!addr) {
> + return -ENOMEM;
> + } else if (addr + size > ~(unsigned long)0) {
> + memblock_free(addr, size);
> + return -EOVERFLOW;
> + } else {
> + start = addr;
> + }
> + }
> +
> + /*
> + * Each reserved area must be initialised later, when more kernel
> + * subsystems (like slab allocator) are available.
> + */
> + r->start = start;
> + r->size = size;
> + r->dev = dev;
> + cma_reserved_count++;
> + printk(KERN_INFO "%s: reserved %ld MiB area at 0x%p\n", __func__,
> + size / SZ_1M, (void *)start);
> + 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).
> + *
> + * This funtion allocates memory buffer for specified device. It uses
> + * device specific contiguous memory area if available or the default
> + * global one. Requires architecture specific get_dev_cma_area() helper
> + * function.
> + */
> +struct page *dma_alloc_from_contiguous(struct device *dev, int count,
> + unsigned int align)
> +{
> + struct cma *cma = get_dev_cma_area(dev);
> + unsigned long pfn, pageno;
> + int ret;
> +
> + if (!cma)
> + return NULL;
> +
> + if (align > CONFIG_CMA_ALIGNMENT)
> + align = CONFIG_CMA_ALIGNMENT;
> +
> + pr_debug("%s(<%p>, %d/%d)\n", __func__, (void *)cma, count, align);
> +
> + if (!count)
> + return NULL;
> +
> + mutex_lock(&cma_mutex);
> +
> + pageno = bitmap_find_next_zero_area(cma->bitmap, cma->count, 0, count,
> + align);
Fixed version:
pageno = bitmap_find_next_zero_area(cma->bitmap, cma->count, 0, count,
(1 << align) - 1);
> + if (pageno >= cma->count) {
> + ret = -ENOMEM;
> + goto error;
> + }
> + bitmap_set(cma->bitmap, pageno, count);
> +
> + pfn = cma->base_pfn + pageno;
> + ret = alloc_contig_range(pfn, pfn + count, 0, MIGRATE_CMA);
> + if (ret)
> + goto free;
> +
> + mutex_unlock(&cma_mutex);
> +
> + pr_debug("%s(): returning [%ld]\n", __func__, pfn);
> + return pfn_to_page(pfn);
> +free:
> + bitmap_clear(cma->bitmap, pageno, count);
> +error:
> + mutex_unlock(&cma_mutex);
> + return NULL;
> +}
> +
> +/**
> + * 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 funtion reserves memory for specified device. It should be
> + * called by board specific code once a memblock allocator has been
> activated
> + * and all other subsystems have already allocated/reserved memory.
> + */
> +int dma_release_from_contiguous(struct device *dev, struct page *pages,
> + int count)
> +{
> + struct cma *cma = get_dev_cma_area(dev);
> + unsigned long pfn;
> +
> + if (!cma || !pages)
> + return 0;
> +
> + pr_debug("%s([%p])\n", __func__, (void *)pages);
> +
> + pfn = page_to_pfn(pages);
> +
> + if (pfn < cma->base_pfn || pfn >= cma->base_pfn + count)
Fixed version:
if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> + return 0;
> +
> + mutex_lock(&cma_mutex);
> +
> + bitmap_clear(cma->bitmap, pfn - cma->base_pfn, count);
> + free_contig_pages(pages, count);
> +
> + mutex_unlock(&cma_mutex);
> + return 1;
> +}
> diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-
> contiguous.h
> new file mode 100644
> index 0000000..98312c9
> --- /dev/null
> +++ b/include/linux/dma-contiguous.h
> @@ -0,0 +1,104 @@
> +#ifndef __LINUX_CMA_H
> +#define __LINUX_CMA_H
> +
> +/*
> + * Contiguous Memory Allocator for DMA mapping framework
> + * Copyright (c) 2010-2011 by Samsung Electronics.
> + * Written by:
> + * Marek Szyprowski <m.szyprow...@samsung.com>
> + * Michal Nazarewicz <min...@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.
> + */
> +
> +/*
> + * 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 then 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.
> + *
> + * Driver usage
> + *
> + * CMA should not be used by the device drivers directly. It is
> + * only a helper framework for dma-mapping subsystem.
> + *
> + * For more information, see kernel-docs in drivers/base/dma-
> contiguous.c
> + */
> +
> +#ifdef __KERNEL__
> +
> +struct cma;
> +struct page;
> +struct device;
> +
> +#ifdef CONFIG_CMA
> +
> +extern struct cma *dma_contiguous_default_area;
> +
> +void dma_contiguous_reserve(void);
> +int dma_declare_contiguous(struct device *dev, unsigned long size,
> + phys_addr_t base);
> +
> +struct page *dma_alloc_from_contiguous(struct device *dev, int count,
> + unsigned int order);
> +int dma_release_from_contiguous(struct device *dev, struct page *pages,
> + int count);
> +
> +#else
> +
> +#define dna_contiguous_default_area NULL
> +
> +static inline void dma_contiguous_reserve(void) { }
> +
> +static inline
> +int dma_declare_contiguous(struct device *dev, unsigned long size,
> + unsigned long base)
> +{
> + return -EINVAL;
> +}
> +
> +static inline
> +struct page *dma_alloc_from_contiguous(struct device *dev, int count,
> + unsigned int order)
> +{
> + return NULL;
> +}
> +
> +static inline
> +int dma_release_from_contiguous(struct device *dev, struct page *pages,
> + int count)
> +{
> + return 0;
> +}
> +
> +#endif
> +
> +#endif
> +
> +#endif
> --
> 1.7.1.569.g6f426
Best regards
--
Marek Szyprowski
Samsung Poland R&D Center
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