hwsw_iommu.c

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/*
 * Copyright (c) 2004 Hewlett-Packard Development Company, L.P.
 *   Contributed by David Mosberger-Tang <[email protected]>
 *
 * 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
    }
}