1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (c) 2004 Hewlett-Packard Development Company, L.P.
4  *   Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
5  *
6  * This is a pseudo I/O MMU which dispatches to the hardware I/O MMU
7  * whenever possible.  We assume that the hardware I/O MMU requires
8  * full 32-bit addressability, as is the case, e.g., for HP zx1-based
9  * systems (there, the I/O MMU window is mapped at 3-4GB).  If a
10  * device doesn't provide full 32-bit addressability, we fall back on
11  * the sw I/O TLB.  This is good enough to let us support broken
12  * hardware such as soundcards which have a DMA engine that can
13  * address only 28 bits.
14  */
15 
16 #include <linux/device.h>
17 #include <linux/dma-mapping.h>
18 #include <linux/swiotlb.h>
19 #include <linux/export.h>
20 #include <asm/machvec.h>
21 
22 extern const struct dma_map_ops sba_dma_ops;
23 
24 /* swiotlb declarations & definitions: */
25 extern int swiotlb_late_init_with_default_size (size_t size);
26 
27 /*
28  * Note: we need to make the determination of whether or not to use
29  * the sw I/O TLB based purely on the device structure.  Anything else
30  * would be unreliable or would be too intrusive.
31  */
use_swiotlb(struct device * dev)32 static inline int use_swiotlb(struct device *dev)
33 {
34 	return dev && dev->dma_mask &&
35 		!sba_dma_ops.dma_supported(dev, *dev->dma_mask);
36 }
37 
hwsw_dma_get_ops(struct device * dev)38 const struct dma_map_ops *hwsw_dma_get_ops(struct device *dev)
39 {
40 	if (use_swiotlb(dev))
41 		return &swiotlb_dma_ops;
42 	return &sba_dma_ops;
43 }
44 EXPORT_SYMBOL(hwsw_dma_get_ops);
45 
46 void __init
hwsw_init(void)47 hwsw_init (void)
48 {
49 	/* default to a smallish 2MB sw I/O TLB */
50 	if (swiotlb_late_init_with_default_size (2 * (1<<20)) != 0) {
51 #ifdef CONFIG_IA64_GENERIC
52 		/* Better to have normal DMA than panic */
53 		printk(KERN_WARNING "%s: Failed to initialize software I/O TLB,"
54 		       " reverting to hpzx1 platform vector\n", __func__);
55 		machvec_init("hpzx1");
56 #else
57 		panic("Unable to initialize software I/O TLB services");
58 #endif
59 	}
60 }
61