dma-coherent.c

Go to the documentation of this file.

/*
 *  Port on Texas Instruments TMS320C6x architecture
 *
 *  Copyright (C) 2004, 2009, 2010, 2011 Texas Instruments Incorporated
 *  Author: Aurelien Jacquiot <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 *
 *  DMA uncached mapping support.
 *
 *  Using code pulled from ARM
 *  Copyright (C) 2000-2004 Russell King
 *
 */
#include <linux/slab.h>
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/dma-mapping.h>
#include <linux/memblock.h>

#include <asm/page.h>

/*
 * DMA coherent memory management, can be redefined using the memdma=
 * kernel command line
 */

/* none by default */
static phys_addr_t dma_base;
static u32 dma_size;
static u32 dma_pages;

static unsigned long *dma_bitmap;

/* bitmap lock */
static DEFINE_SPINLOCK(dma_lock);

/*
 * Return a DMA coherent and contiguous memory chunk from the DMA memory
 */
static inline u32 __alloc_dma_pages(int order)
{
    unsigned long flags;
    u32 pos;

    spin_lock_irqsave(&dma_lock, flags);
    pos = bitmap_find_free_region(dma_bitmap, dma_pages, order);
    spin_unlock_irqrestore(&dma_lock, flags);

    return dma_base + (pos << PAGE_SHIFT);
}

static void __free_dma_pages(u32 addr, int order)
{
    unsigned long flags;
    u32 pos = (addr - dma_base) >> PAGE_SHIFT;

    if (addr < dma_base || (pos + (1 << order)) >= dma_pages) {
        printk(KERN_ERR "%s: freeing outside range.\n", __func__);
        BUG();
    }

    spin_lock_irqsave(&dma_lock, flags);
    bitmap_release_region(dma_bitmap, pos, order);
    spin_unlock_irqrestore(&dma_lock, flags);
}

/*
 * Allocate DMA coherent memory space and return both the kernel
 * virtual and DMA address for that space.
 */
void *dma_alloc_coherent(struct device *dev, size_t size,
             dma_addr_t *handle, gfp_t gfp)
{
    u32 paddr;
    int order;

    if (!dma_size || !size)
        return NULL;

    order = get_count_order(((size - 1) >> PAGE_SHIFT) + 1);

    paddr = __alloc_dma_pages(order);

    if (handle)
        *handle = paddr;

    if (!paddr)
        return NULL;

    return phys_to_virt(paddr);
}
EXPORT_SYMBOL(dma_alloc_coherent);

/*
 * Free DMA coherent memory as defined by the above mapping.
 */
void dma_free_coherent(struct device *dev, size_t size, void *vaddr,
               dma_addr_t dma_handle)
{
    int order;

    if (!dma_size || !size)
        return;

    order = get_count_order(((size - 1) >> PAGE_SHIFT) + 1);

    __free_dma_pages(virt_to_phys(vaddr), order);
}
EXPORT_SYMBOL(dma_free_coherent);

/*
 * Initialise the coherent DMA memory allocator using the given uncached region.
 */
void __init coherent_mem_init(phys_addr_t start, u32 size)
{
    phys_addr_t bitmap_phys;

    if (!size)
        return;

    printk(KERN_INFO
           "Coherent memory (DMA) region start=0x%x size=0x%x\n",
           start, size);

    dma_base = start;
    dma_size = size;

    /* allocate bitmap */
    dma_pages = dma_size >> PAGE_SHIFT;
    if (dma_size & (PAGE_SIZE - 1))
        ++dma_pages;

    bitmap_phys = memblock_alloc(BITS_TO_LONGS(dma_pages) * sizeof(long),
                     sizeof(long));

    dma_bitmap = phys_to_virt(bitmap_phys);
    memset(dma_bitmap, 0, dma_pages * PAGE_SIZE);
}