1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * ISA DMA support functions
4 * Copyright (c) by Jaroslav Kysela <perex@perex.cz>
5 */
6
7 /*
8 * Defining following add some delay. Maybe this helps for some broken
9 * ISA DMA controllers.
10 */
11
12 #undef HAVE_REALLY_SLOW_DMA_CONTROLLER
13
14 #include <linux/export.h>
15 #include <sound/core.h>
16 #include <asm/dma.h>
17
18 /**
19 * snd_dma_program - program an ISA DMA transfer
20 * @dma: the dma number
21 * @addr: the physical address of the buffer
22 * @size: the DMA transfer size
23 * @mode: the DMA transfer mode, DMA_MODE_XXX
24 *
25 * Programs an ISA DMA transfer for the given buffer.
26 */
snd_dma_program(unsigned long dma,unsigned long addr,unsigned int size,unsigned short mode)27 void snd_dma_program(unsigned long dma,
28 unsigned long addr, unsigned int size,
29 unsigned short mode)
30 {
31 unsigned long flags;
32
33 flags = claim_dma_lock();
34 disable_dma(dma);
35 clear_dma_ff(dma);
36 set_dma_mode(dma, mode);
37 set_dma_addr(dma, addr);
38 set_dma_count(dma, size);
39 if (!(mode & DMA_MODE_NO_ENABLE))
40 enable_dma(dma);
41 release_dma_lock(flags);
42 }
43 EXPORT_SYMBOL(snd_dma_program);
44
45 /**
46 * snd_dma_disable - stop the ISA DMA transfer
47 * @dma: the dma number
48 *
49 * Stops the ISA DMA transfer.
50 */
snd_dma_disable(unsigned long dma)51 void snd_dma_disable(unsigned long dma)
52 {
53 unsigned long flags;
54
55 flags = claim_dma_lock();
56 clear_dma_ff(dma);
57 disable_dma(dma);
58 release_dma_lock(flags);
59 }
60 EXPORT_SYMBOL(snd_dma_disable);
61
62 /**
63 * snd_dma_pointer - return the current pointer to DMA transfer buffer in bytes
64 * @dma: the dma number
65 * @size: the dma transfer size
66 *
67 * Return: The current pointer in DMA transfer buffer in bytes.
68 */
snd_dma_pointer(unsigned long dma,unsigned int size)69 unsigned int snd_dma_pointer(unsigned long dma, unsigned int size)
70 {
71 unsigned long flags;
72 unsigned int result, result1;
73
74 flags = claim_dma_lock();
75 clear_dma_ff(dma);
76 if (!isa_dma_bridge_buggy)
77 disable_dma(dma);
78 result = get_dma_residue(dma);
79 /*
80 * HACK - read the counter again and choose higher value in order to
81 * avoid reading during counter lower byte roll over if the
82 * isa_dma_bridge_buggy is set.
83 */
84 result1 = get_dma_residue(dma);
85 if (!isa_dma_bridge_buggy)
86 enable_dma(dma);
87 release_dma_lock(flags);
88 if (unlikely(result < result1))
89 result = result1;
90 #ifdef CONFIG_SND_DEBUG
91 if (result > size)
92 pr_err("ALSA: pointer (0x%x) for DMA #%ld is greater than transfer size (0x%x)\n", result, dma, size);
93 #endif
94 if (result >= size || result == 0)
95 return 0;
96 else
97 return size - result;
98 }
99 EXPORT_SYMBOL(snd_dma_pointer);
100