arch/ia64/hp/common/hwsw_iommu.c

   1 /*
   2  * Copyright (c) 2004 Hewlett-Packard Development Company, L.P.
   3  *   Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
   4  *
   5  * This is a pseudo I/O MMU which dispatches to the hardware I/O MMU
   6  * whenever possible.  We assume that the hardware I/O MMU requires
   7  * full 32-bit addressability, as is the case, e.g., for HP zx1-based
   8  * systems (there, the I/O MMU window is mapped at 3-4GB).  If a
   9  * device doesn't provide full 32-bit addressability, we fall back on
  10  * the sw I/O TLB.  This is good enough to let us support broken
  11  * hardware such as soundcards which have a DMA engine that can
  12  * address only 28 bits.
  13  */
  14
  15 #include <linux/device.h>
  16 #include <linux/dma-mapping.h>
  17 #include <linux/swiotlb.h>
  18 #include <linux/export.h>
  19 #include <asm/machvec.h>
  20
  21 extern const struct dma_map_ops sba_dma_ops, swiotlb_dma_ops;
  22
  23 /* swiotlb declarations & definitions: */
  24 extern int swiotlb_late_init_with_default_size (size_t size);
  25
  26 /*
  27  * Note: we need to make the determination of whether or not to use
  28  * the sw I/O TLB based purely on the device structure.  Anything else
  29  * would be unreliable or would be too intrusive.
  30  */
  31 static inline int use_swiotlb(struct device *dev)
  32 {
  33         return dev && dev->dma_mask &&
  34                 !sba_dma_ops.dma_supported(dev, *dev->dma_mask);
  35 }
  36
  37 const struct dma_map_ops *hwsw_dma_get_ops(struct device *dev)
  38 {
  39         if (use_swiotlb(dev))
  40                 return &swiotlb_dma_ops;
  41         return &sba_dma_ops;
  42 }
  43 EXPORT_SYMBOL(hwsw_dma_get_ops);
  44
  45 void __init
  46 hwsw_init (void)
  47 {
  48         /* default to a smallish 2MB sw I/O TLB */
  49         if (swiotlb_late_init_with_default_size (2 * (1<<20)) != 0) {
  50 #ifdef CONFIG_IA64_GENERIC
  51                 /* Better to have normal DMA than panic */
  52                 printk(KERN_WARNING "%s: Failed to initialize software I/O TLB,"
  53                        " reverting to hpzx1 platform vector\n", __func__);
  54                 machvec_init("hpzx1");
  55 #else
  56                 panic("Unable to initialize software I/O TLB services");
  57 #endif
  58         }
  59 }