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

static int dma_region_pagefault(struct vm_area_struct *vma,
				struct vm_fault *vmf)
{
	struct dma_region *dma = (struct dma_region *)vma->vm_private_data;

	if (!dma->kvirt)
		return VM_FAULT_SIGBUS;

	if (vmf->pgoff >= dma->n_pages)
		return VM_FAULT_SIGBUS;

	vmf->page = vmalloc_to_page(dma->kvirt + (vmf->pgoff << PAGE_SHIFT));
	get_page(vmf->page);
	return 0;
}

static struct vm_operations_struct dma_region_vm_ops = {
	.fault = 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 (XXX: comment is wrong, we could allow pgoff) */
	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 | VM_ALWAYSDUMP;

	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 */