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dma-mapping.c

/*
 * 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>

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, int nents,
         enum dma_data_direction direction)
{
      int i;

      for (i = 0; i < nents; i++, sg++) {
            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,
                      int nelems, enum dma_data_direction direction)
{
      int i;

      for (i = 0; i < nelems; i++, sg++) {
            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);

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