dma-coherent.c

Go to the documentation of this file.

/*
 * Coherent per-device memory handling.
 * Borrowed from i386
 */
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/dma-mapping.h>

struct dma_coherent_mem {
    void        *virt_base;
    dma_addr_t  device_base;
    phys_addr_t pfn_base;
    int     size;
    int     flags;
    unsigned long   *bitmap;
};

int dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr,
                dma_addr_t device_addr, size_t size, int flags)
{
    void __iomem *mem_base = NULL;
    int pages = size >> PAGE_SHIFT;
    int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long);

    if ((flags & (DMA_MEMORY_MAP | DMA_MEMORY_IO)) == 0)
        goto out;
    if (!size)
        goto out;
    if (dev->dma_mem)
        goto out;

    /* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */

    mem_base = ioremap(bus_addr, size);
    if (!mem_base)
        goto out;

    dev->dma_mem = kzalloc(sizeof(struct dma_coherent_mem), GFP_KERNEL);
    if (!dev->dma_mem)
        goto out;
    dev->dma_mem->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
    if (!dev->dma_mem->bitmap)
        goto free1_out;

    dev->dma_mem->virt_base = mem_base;
    dev->dma_mem->device_base = device_addr;
    dev->dma_mem->pfn_base = PFN_DOWN(bus_addr);
    dev->dma_mem->size = pages;
    dev->dma_mem->flags = flags;

    if (flags & DMA_MEMORY_MAP)
        return DMA_MEMORY_MAP;

    return DMA_MEMORY_IO;

 free1_out:
    kfree(dev->dma_mem);
 out:
    if (mem_base)
        iounmap(mem_base);
    return 0;
}
EXPORT_SYMBOL(dma_declare_coherent_memory);

void dma_release_declared_memory(struct device *dev)
{
    struct dma_coherent_mem *mem = dev->dma_mem;

    if (!mem)
        return;
    dev->dma_mem = NULL;
    iounmap(mem->virt_base);
    kfree(mem->bitmap);
    kfree(mem);
}
EXPORT_SYMBOL(dma_release_declared_memory);

void *dma_mark_declared_memory_occupied(struct device *dev,
                    dma_addr_t device_addr, size_t size)
{
    struct dma_coherent_mem *mem = dev->dma_mem;
    int pos, err;

    size += device_addr & ~PAGE_MASK;

    if (!mem)
        return ERR_PTR(-EINVAL);

    pos = (device_addr - mem->device_base) >> PAGE_SHIFT;
    err = bitmap_allocate_region(mem->bitmap, pos, get_order(size));
    if (err != 0)
        return ERR_PTR(err);
    return mem->virt_base + (pos << PAGE_SHIFT);
}
EXPORT_SYMBOL(dma_mark_declared_memory_occupied);

int dma_alloc_from_coherent(struct device *dev, ssize_t size,
                       dma_addr_t *dma_handle, void **ret)
{
    struct dma_coherent_mem *mem;
    int order = get_order(size);
    int pageno;

    if (!dev)
        return 0;
    mem = dev->dma_mem;
    if (!mem)
        return 0;

    *ret = NULL;

    if (unlikely(size > (mem->size << PAGE_SHIFT)))
        goto err;

    pageno = bitmap_find_free_region(mem->bitmap, mem->size, order);
    if (unlikely(pageno < 0))
        goto err;

    /*
     * Memory was found in the per-device area.
     */
    *dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
    *ret = mem->virt_base + (pageno << PAGE_SHIFT);
    memset(*ret, 0, size);

    return 1;

err:
    /*
     * In the case where the allocation can not be satisfied from the
     * per-device area, try to fall back to generic memory if the
     * constraints allow it.
     */
    return mem->flags & DMA_MEMORY_EXCLUSIVE;
}
EXPORT_SYMBOL(dma_alloc_from_coherent);

int dma_release_from_coherent(struct device *dev, int order, void *vaddr)
{
    struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL;

    if (mem && vaddr >= mem->virt_base && vaddr <
           (mem->virt_base + (mem->size << PAGE_SHIFT))) {
        int page = (vaddr - mem->virt_base) >> PAGE_SHIFT;

        bitmap_release_region(mem->bitmap, page, order);
        return 1;
    }
    return 0;
}
EXPORT_SYMBOL(dma_release_from_coherent);

int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma,
               void *vaddr, size_t size, int *ret)
{
    struct dma_coherent_mem *mem = dev ? dev->dma_mem : NULL;

    if (mem && vaddr >= mem->virt_base && vaddr + size <=
           (mem->virt_base + (mem->size << PAGE_SHIFT))) {
        unsigned long off = vma->vm_pgoff;
        int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
        int user_count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
        int count = size >> PAGE_SHIFT;

        *ret = -ENXIO;
        if (off < count && user_count <= count - off) {
            unsigned pfn = mem->pfn_base + start + off;
            *ret = remap_pfn_range(vma, vma->vm_start, pfn,
                           user_count << PAGE_SHIFT,
                           vma->vm_page_prot);
        }
        return 1;
    }
    return 0;
}
EXPORT_SYMBOL(dma_mmap_from_coherent);