dma-mapping.c

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/*
 * Dynamic DMA mapping support
 *
 * Copyright 2005-2009 Analog Devices Inc.
 *
 * Licensed under the GPL-2 or later
 */

#include <linux/types.h>
#include <linux/gfp.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/dma-mapping.h>
#include <linux/scatterlist.h>
#include <linux/export.h>

static spinlock_t dma_page_lock;
static unsigned long *dma_page;
static unsigned int dma_pages;
static unsigned long dma_base;
static unsigned long dma_size;
static unsigned int dma_initialized;

static void dma_alloc_init(unsigned long start, unsigned long end)
{
    spin_lock_init(&dma_page_lock);
    dma_initialized = 0;

    dma_page = (unsigned long *)__get_free_page(GFP_KERNEL);
    memset(dma_page, 0, PAGE_SIZE);
    dma_base = PAGE_ALIGN(start);
    dma_size = PAGE_ALIGN(end) - PAGE_ALIGN(start);
    dma_pages = dma_size >> PAGE_SHIFT;
    memset((void *)dma_base, 0, DMA_UNCACHED_REGION);
    dma_initialized = 1;

    printk(KERN_INFO "%s: dma_page @ 0x%p - %d pages at 0x%08lx\n", __func__,
           dma_page, dma_pages, dma_base);
}

static inline unsigned int get_pages(size_t size)
{
    return ((size - 1) >> PAGE_SHIFT) + 1;
}

static unsigned long __alloc_dma_pages(unsigned int pages)
{
    unsigned long ret = 0, flags;
    int i, count = 0;

    if (dma_initialized == 0)
        dma_alloc_init(_ramend - DMA_UNCACHED_REGION, _ramend);

    spin_lock_irqsave(&dma_page_lock, flags);

    for (i = 0; i < dma_pages;) {
        if (test_bit(i++, dma_page) == 0) {
            if (++count == pages) {
                while (count--)
                    __set_bit(--i, dma_page);

                ret = dma_base + (i << PAGE_SHIFT);
                break;
            }
        } else
            count = 0;
    }
    spin_unlock_irqrestore(&dma_page_lock, flags);
    return ret;
}

static void __free_dma_pages(unsigned long addr, unsigned int pages)
{
    unsigned long page = (addr - dma_base) >> PAGE_SHIFT;
    unsigned long flags;
    int i;

    if ((page + pages) > dma_pages) {
        printk(KERN_ERR "%s: freeing outside range.\n", __func__);
        BUG();
    }

    spin_lock_irqsave(&dma_page_lock, flags);
    for (i = page; i < page + pages; i++)
        __clear_bit(i, dma_page);

    spin_unlock_irqrestore(&dma_page_lock, flags);
}

void *dma_alloc_coherent(struct device *dev, size_t size,
             dma_addr_t *dma_handle, gfp_t gfp)
{
    void *ret;

    ret = (void *)__alloc_dma_pages(get_pages(size));

    if (ret) {
        memset(ret, 0, size);
        *dma_handle = virt_to_phys(ret);
    }

    return ret;
}
EXPORT_SYMBOL(dma_alloc_coherent);

void
dma_free_coherent(struct device *dev, size_t size, void *vaddr,
          dma_addr_t dma_handle)
{
    __free_dma_pages((unsigned long)vaddr, get_pages(size));
}
EXPORT_SYMBOL(dma_free_coherent);

/*
 * Streaming DMA mappings
 */
void __dma_sync(dma_addr_t addr, size_t size,
        enum dma_data_direction dir)
{
    __dma_sync_inline(addr, size, dir);
}
EXPORT_SYMBOL(__dma_sync);

int
dma_map_sg(struct device *dev, struct scatterlist *sg_list, int nents,
       enum dma_data_direction direction)
{
    struct scatterlist *sg;
    int i;

    for_each_sg(sg_list, sg, nents, i) {
        sg->dma_address = (dma_addr_t) sg_virt(sg);
        __dma_sync(sg_dma_address(sg), sg_dma_len(sg), direction);
    }

    return nents;
}
EXPORT_SYMBOL(dma_map_sg);

void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg_list,
                int nelems, enum dma_data_direction direction)
{
    struct scatterlist *sg;
    int i;

    for_each_sg(sg_list, sg, nelems, i) {
        sg->dma_address = (dma_addr_t) sg_virt(sg);
        __dma_sync(sg_dma_address(sg), sg_dma_len(sg), direction);
    }
}
EXPORT_SYMBOL(dma_sync_sg_for_device);