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Subject[PATCH 6/8] drivers: add Contiguous Memory Allocator
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.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
CC: Michal Nazarewicz <mina86@mina86.com>
---
arch/Kconfig | 3 +
drivers/base/Kconfig | 77 ++++++++
drivers/base/Makefile | 1 +
drivers/base/dma-contiguous.c | 396 ++++++++++++++++++++++++++++++++++++++++
include/linux/dma-contiguous.h | 102 ++++++++++
5 files changed, 579 insertions(+), 0 deletions(-)
create mode 100644 drivers/base/dma-contiguous.c
create mode 100644 include/linux/dma-contiguous.h
diff --git a/arch/Kconfig b/arch/Kconfig
index 26b0e23..228d761 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -124,6 +124,9 @@ config HAVE_ARCH_TRACEHOOK
config HAVE_DMA_ATTRS
bool

+config HAVE_DMA_CONTIGUOUS
+ bool
+
config USE_GENERIC_SMP_HELPERS
bool

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index d57e8d0..c690d05 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 on 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..7fdeaba
--- /dev/null
+++ b/drivers/base/dma-contiguous.c
@@ -0,0 +1,396 @@
+/*
+ * 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/slab.h>
+#include <linux/swap.h>
+#include <linux/mm_types.h>
+#include <linux/dma-contiguous.h>
+
+#ifndef SZ_1M
+#define SZ_1M (1 << 20)
+#endif
+
+#ifdef phys_to_pfn
+/* nothing to do */
+#elif defined __phys_to_pfn
+# define phys_to_pfn __phys_to_pfn
+#elif defined PFN_PHYS
+# define phys_to_pfn PFN_PHYS
+#else
+# error correct phys_to_pfn implementation needed
+#endif
+
+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);
+
+static unsigned long __init __cma_early_get_total_pages(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;
+}
+
+
+/**
+ * dma_contiguous_reserve() - reserve area for contiguous memory handling
+ *
+ * This funtion 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(void)
+{
+ unsigned long selected_size = 0;
+ unsigned long total_pages;
+
+ pr_debug("%s()\n", __func__);
+
+ total_pages = __cma_early_get_total_pages();
+ 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 {
+ phys_addr_t start;
+ unsigned long size;
+ struct device *dev;
+} cma_reserved[MAX_CMA_AREAS] __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(phys_to_pfn(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 when early allocator (memblock or bootmem)
+ * is still activate.
+ */
+int __init dma_declare_contiguous(struct device *dev, unsigned long size,
+ phys_addr_t base)
+{
+ struct cma_reserved *r = &cma_reserved[cma_reserved_count];
+ unsigned long alignment;
+
+ pr_debug("%s(%p+%p)\n", __func__, (void *)base, (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);
+ base = ALIGN(base, alignment);
+ size = ALIGN(size , alignment);
+
+ /* Reserve memory */
+ if (base) {
+ if (memblock_is_region_reserved(base, size) ||
+ memblock_reserve(base, size) < 0)
+ return -EBUSY;
+ } else {
+ /*
+ * Use __memblock_alloc_base() since
+ * memblock_alloc_base() panic()s.
+ */
+ phys_addr_t 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 {
+ base = addr;
+ }
+ }
+
+ /*
+ * Each reserved area must be initialised later, when more kernel
+ * subsystems (like slab allocator) are available.
+ */
+ r->start = base;
+ 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 *)base);
+
+ /*
+ * Architecture specific contiguous memory fixup.
+ */
+ dma_contiguous_early_fixup(base, size);
+ 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 order)
+{
+ struct cma *cma = get_dev_cma_area(dev);
+ unsigned long pfn, pageno;
+ unsigned int align;
+ int ret;
+
+ if (!cma)
+ return NULL;
+
+ if (order > CONFIG_CMA_ALIGNMENT)
+ order = CONFIG_CMA_ALIGNMENT;
+
+ pr_debug("%s(<%p>, %d/%d)\n", __func__, (void *)cma, count, order);
+
+ align = (1 << order) - 1;
+
+ if (!count)
+ return NULL;
+
+ mutex_lock(&cma_mutex);
+
+ pageno = bitmap_find_next_zero_area(cma->bitmap, cma->count, 0, count,
+ align);
+ 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 [%p]\n", __func__, pfn_to_page(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 releases memory allocated by dma_alloc_from_contiguous().
+ * It return 0 when provided pages doen't belongs to contiguous area and
+ * 1 on success.
+ */
+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 + 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..6f8e462
--- /dev/null
+++ b/include/linux/dma-contiguous.h
@@ -0,0 +1,102 @@
+#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.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.
+ */
+
+/*
+ * 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;
+
+extern struct cma *dma_contiguous_default_area;
+
+#ifdef CONFIG_CMA
+
+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
+
+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


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