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dma.c

/*
 * DMA region bookkeeping routines
 *
 * Copyright (C) 2002 Maas Digital LLC
 *
 * This code is licensed under the GPL.  See the file COPYING in the root
 * directory of the kernel sources for details.
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/scatterlist.h>

#include "dma.h"

/* dma_prog_region */

void dma_prog_region_init(struct dma_prog_region *prog)
{
      prog->kvirt = NULL;
      prog->dev = NULL;
      prog->n_pages = 0;
      prog->bus_addr = 0;
}

int dma_prog_region_alloc(struct dma_prog_region *prog, unsigned long n_bytes,
                    struct pci_dev *dev)
{
      /* round up to page size */
      n_bytes = PAGE_ALIGN(n_bytes);

      prog->n_pages = n_bytes >> PAGE_SHIFT;

      prog->kvirt = pci_alloc_consistent(dev, n_bytes, &prog->bus_addr);
      if (!prog->kvirt) {
            printk(KERN_ERR
                   "dma_prog_region_alloc: pci_alloc_consistent() failed\n");
            dma_prog_region_free(prog);
            return -ENOMEM;
      }

      prog->dev = dev;

      return 0;
}

void dma_prog_region_free(struct dma_prog_region *prog)
{
      if (prog->kvirt) {
            pci_free_consistent(prog->dev, prog->n_pages << PAGE_SHIFT,
                            prog->kvirt, prog->bus_addr);
      }

      prog->kvirt = NULL;
      prog->dev = NULL;
      prog->n_pages = 0;
      prog->bus_addr = 0;
}

/* dma_region */

/**
 * dma_region_init - clear out all fields but do not allocate anything
 */
void dma_region_init(struct dma_region *dma)
{
      dma->kvirt = NULL;
      dma->dev = NULL;
      dma->n_pages = 0;
      dma->n_dma_pages = 0;
      dma->sglist = NULL;
}

/**
 * dma_region_alloc - allocate the buffer and map it to the IOMMU
 */
int dma_region_alloc(struct dma_region *dma, unsigned long n_bytes,
                 struct pci_dev *dev, int direction)
{
      unsigned int i;

      /* round up to page size */
      n_bytes = PAGE_ALIGN(n_bytes);

      dma->n_pages = n_bytes >> PAGE_SHIFT;

      dma->kvirt = vmalloc_32(n_bytes);
      if (!dma->kvirt) {
            printk(KERN_ERR "dma_region_alloc: vmalloc_32() failed\n");
            goto err;
      }

      /* Clear the ram out, no junk to the user */
      memset(dma->kvirt, 0, n_bytes);

      /* allocate scatter/gather list */
      dma->sglist = vmalloc(dma->n_pages * sizeof(*dma->sglist));
      if (!dma->sglist) {
            printk(KERN_ERR "dma_region_alloc: vmalloc(sglist) failed\n");
            goto err;
      }

      sg_init_table(dma->sglist, dma->n_pages);

      /* fill scatter/gather list with pages */
      for (i = 0; i < dma->n_pages; i++) {
            unsigned long va =
                (unsigned long)dma->kvirt + (i << PAGE_SHIFT);

            sg_set_page(&dma->sglist[i], vmalloc_to_page((void *)va),
                        PAGE_SIZE, 0);
      }

      /* map sglist to the IOMMU */
      dma->n_dma_pages =
          pci_map_sg(dev, dma->sglist, dma->n_pages, direction);

      if (dma->n_dma_pages == 0) {
            printk(KERN_ERR "dma_region_alloc: pci_map_sg() failed\n");
            goto err;
      }

      dma->dev = dev;
      dma->direction = direction;

      return 0;

      err:
      dma_region_free(dma);
      return -ENOMEM;
}

/**
 * dma_region_free - unmap and free the buffer
 */
void dma_region_free(struct dma_region *dma)
{
      if (dma->n_dma_pages) {
            pci_unmap_sg(dma->dev, dma->sglist, dma->n_pages,
                       dma->direction);
            dma->n_dma_pages = 0;
            dma->dev = NULL;
      }

      vfree(dma->sglist);
      dma->sglist = NULL;

      vfree(dma->kvirt);
      dma->kvirt = NULL;
      dma->n_pages = 0;
}

/* find the scatterlist index and remaining offset corresponding to a
   given offset from the beginning of the buffer */
static inline int dma_region_find(struct dma_region *dma, unsigned long offset,
                          unsigned int start, unsigned long *rem)
{
      int i;
      unsigned long off = offset;

      for (i = start; i < dma->n_dma_pages; i++) {
            if (off < sg_dma_len(&dma->sglist[i])) {
                  *rem = off;
                  break;
            }

            off -= sg_dma_len(&dma->sglist[i]);
      }

      BUG_ON(i >= dma->n_dma_pages);

      return i;
}

/**
 * dma_region_offset_to_bus - get bus address of an offset within a DMA region
 *
 * Returns the DMA bus address of the byte with the given @offset relative to
 * the beginning of the @dma.
 */
dma_addr_t dma_region_offset_to_bus(struct dma_region * dma,
                            unsigned long offset)
{
      unsigned long rem = 0;

      struct scatterlist *sg =
          &dma->sglist[dma_region_find(dma, offset, 0, &rem)];
      return sg_dma_address(sg) + rem;
}

/**
 * dma_region_sync_for_cpu - sync the CPU's view of the buffer
 */
void dma_region_sync_for_cpu(struct dma_region *dma, unsigned long offset,
                       unsigned long len)
{
      int first, last;
      unsigned long rem = 0;

      if (!len)
            len = 1;

      first = dma_region_find(dma, offset, 0, &rem);
      last = dma_region_find(dma, rem + len - 1, first, &rem);

      pci_dma_sync_sg_for_cpu(dma->dev, &dma->sglist[first], last - first + 1,
                        dma->direction);
}

/**
 * dma_region_sync_for_device - sync the IO bus' view of the buffer
 */
void dma_region_sync_for_device(struct dma_region *dma, unsigned long offset,
                        unsigned long len)
{
      int first, last;
      unsigned long rem = 0;

      if (!len)
            len = 1;

      first = dma_region_find(dma, offset, 0, &rem);
      last = dma_region_find(dma, rem + len - 1, first, &rem);

      pci_dma_sync_sg_for_device(dma->dev, &dma->sglist[first],
                           last - first + 1, dma->direction);
}

#ifdef CONFIG_MMU

/* nopage() handler for mmap access */

static struct page *dma_region_pagefault(struct vm_area_struct *area,
                               unsigned long address, int *type)
{
      unsigned long offset;
      unsigned long kernel_virt_addr;
      struct page *ret = NOPAGE_SIGBUS;

      struct dma_region *dma = (struct dma_region *)area->vm_private_data;

      if (!dma->kvirt)
            goto out;

      if ((address < (unsigned long)area->vm_start) ||
          (address >
           (unsigned long)area->vm_start + (dma->n_pages << PAGE_SHIFT)))
            goto out;

      if (type)
            *type = VM_FAULT_MINOR;
      offset = address - area->vm_start;
      kernel_virt_addr = (unsigned long)dma->kvirt + offset;
      ret = vmalloc_to_page((void *)kernel_virt_addr);
      get_page(ret);
      out:
      return ret;
}

static struct vm_operations_struct dma_region_vm_ops = {
      .nopage = dma_region_pagefault,
};

/**
 * dma_region_mmap - map the buffer into a user space process
 */
int dma_region_mmap(struct dma_region *dma, struct file *file,
                struct vm_area_struct *vma)
{
      unsigned long size;

      if (!dma->kvirt)
            return -EINVAL;

      /* must be page-aligned */
      if (vma->vm_pgoff != 0)
            return -EINVAL;

      /* check the length */
      size = vma->vm_end - vma->vm_start;
      if (size > (dma->n_pages << PAGE_SHIFT))
            return -EINVAL;

      vma->vm_ops = &dma_region_vm_ops;
      vma->vm_private_data = dma;
      vma->vm_file = file;
      vma->vm_flags |= VM_RESERVED;

      return 0;
}

#else                   /* CONFIG_MMU */

int dma_region_mmap(struct dma_region *dma, struct file *file,
                struct vm_area_struct *vma)
{
      return -EINVAL;
}

#endif                        /* CONFIG_MMU */

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