1. 根目录:
2. arch
3. ia64
4. hp
5. common
6. hwsw_iommu.c

/*
 * Copyright (c) 2004 Hewlett-Packard Development Company, L.P.
 *   Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
 *
 * This is a pseudo I/O MMU which dispatches to the hardware I/O MMU
 * whenever possible.  We assume that the hardware I/O MMU requires
 * full 32-bit addressability, as is the case, e.g., for HP zx1-based
 * systems (there, the I/O MMU window is mapped at 3-4GB).  If a
 * device doesn't provide full 32-bit addressability, we fall back on
 * the sw I/O TLB.  This is good enough to let us support broken
 * hardware such as soundcards which have a DMA engine that can
 * address only 28 bits.
 */

#include <linux/device.h>
#include <linux/dma-mapping.h>
#include <linux/swiotlb.h>
#include <linux/export.h>
#include <asm/machvec.h>

extern struct dma_map_ops sba_dma_ops, swiotlb_dma_ops;

/* swiotlb declarations & definitions: */
extern int swiotlb_late_init_with_default_size (size_t size);

/*
 * Note: we need to make the determination of whether or not to use
 * the sw I/O TLB based purely on the device structure.  Anything else
 * would be unreliable or would be too intrusive.
 */
static inline int use_swiotlb(struct device *dev)
{
	return dev && dev->dma_mask &&
		!sba_dma_ops.dma_supported(dev, *dev->dma_mask);
}

struct dma_map_ops *hwsw_dma_get_ops(struct device *dev)
{
	if (use_swiotlb(dev))
		return &swiotlb_dma_ops;
	return &sba_dma_ops;
}
EXPORT_SYMBOL(hwsw_dma_get_ops);

void __init
hwsw_init (void)
{
	/* default to a smallish 2MB sw I/O TLB */
	if (swiotlb_late_init_with_default_size (2 * (1<<20)) != 0) {
#ifdef CONFIG_IA64_GENERIC
		/* Better to have normal DMA than panic */
		printk(KERN_WARNING "%s: Failed to initialize software I/O TLB,"
		       " reverting to hpzx1 platform vector\n", __func__);
		machvec_init("hpzx1");
#else
		panic("Unable to initialize software I/O TLB services");
#endif
	}
}