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 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 */
use_swiotlb(struct device * dev)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
hwsw_dma_get_ops(struct device * dev)37 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
hwsw_init(void)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 }
60