Root/
1 | /* |
2 | * linux/kernel/dma.c: A DMA channel allocator. Inspired by linux/kernel/irq.c. |
3 | * |
4 | * Written by Hennus Bergman, 1992. |
5 | * |
6 | * 1994/12/26: Changes by Alex Nash to fix a minor bug in /proc/dma. |
7 | * In the previous version the reported device could end up being wrong, |
8 | * if a device requested a DMA channel that was already in use. |
9 | * [It also happened to remove the sizeof(char *) == sizeof(int) |
10 | * assumption introduced because of those /proc/dma patches. -- Hennus] |
11 | */ |
12 | #include <linux/export.h> |
13 | #include <linux/kernel.h> |
14 | #include <linux/errno.h> |
15 | #include <linux/spinlock.h> |
16 | #include <linux/string.h> |
17 | #include <linux/seq_file.h> |
18 | #include <linux/proc_fs.h> |
19 | #include <linux/init.h> |
20 | #include <asm/dma.h> |
21 | |
22 | |
23 | |
24 | /* A note on resource allocation: |
25 | * |
26 | * All drivers needing DMA channels, should allocate and release them |
27 | * through the public routines `request_dma()' and `free_dma()'. |
28 | * |
29 | * In order to avoid problems, all processes should allocate resources in |
30 | * the same sequence and release them in the reverse order. |
31 | * |
32 | * So, when allocating DMAs and IRQs, first allocate the IRQ, then the DMA. |
33 | * When releasing them, first release the DMA, then release the IRQ. |
34 | * If you don't, you may cause allocation requests to fail unnecessarily. |
35 | * This doesn't really matter now, but it will once we get real semaphores |
36 | * in the kernel. |
37 | */ |
38 | |
39 | |
40 | DEFINE_SPINLOCK(dma_spin_lock); |
41 | |
42 | /* |
43 | * If our port doesn't define this it has no PC like DMA |
44 | */ |
45 | |
46 | #ifdef MAX_DMA_CHANNELS |
47 | |
48 | |
49 | /* Channel n is busy iff dma_chan_busy[n].lock != 0. |
50 | * DMA0 used to be reserved for DRAM refresh, but apparently not any more... |
51 | * DMA4 is reserved for cascading. |
52 | */ |
53 | |
54 | struct dma_chan { |
55 | int lock; |
56 | const char *device_id; |
57 | }; |
58 | |
59 | static struct dma_chan dma_chan_busy[MAX_DMA_CHANNELS] = { |
60 | [4] = { 1, "cascade" }, |
61 | }; |
62 | |
63 | |
64 | /** |
65 | * request_dma - request and reserve a system DMA channel |
66 | * @dmanr: DMA channel number |
67 | * @device_id: reserving device ID string, used in /proc/dma |
68 | */ |
69 | int request_dma(unsigned int dmanr, const char * device_id) |
70 | { |
71 | if (dmanr >= MAX_DMA_CHANNELS) |
72 | return -EINVAL; |
73 | |
74 | if (xchg(&dma_chan_busy[dmanr].lock, 1) != 0) |
75 | return -EBUSY; |
76 | |
77 | dma_chan_busy[dmanr].device_id = device_id; |
78 | |
79 | /* old flag was 0, now contains 1 to indicate busy */ |
80 | return 0; |
81 | } /* request_dma */ |
82 | |
83 | /** |
84 | * free_dma - free a reserved system DMA channel |
85 | * @dmanr: DMA channel number |
86 | */ |
87 | void free_dma(unsigned int dmanr) |
88 | { |
89 | if (dmanr >= MAX_DMA_CHANNELS) { |
90 | printk(KERN_WARNING "Trying to free DMA%d\n", dmanr); |
91 | return; |
92 | } |
93 | |
94 | if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) { |
95 | printk(KERN_WARNING "Trying to free free DMA%d\n", dmanr); |
96 | return; |
97 | } |
98 | |
99 | } /* free_dma */ |
100 | |
101 | #else |
102 | |
103 | int request_dma(unsigned int dmanr, const char *device_id) |
104 | { |
105 | return -EINVAL; |
106 | } |
107 | |
108 | void free_dma(unsigned int dmanr) |
109 | { |
110 | } |
111 | |
112 | #endif |
113 | |
114 | #ifdef CONFIG_PROC_FS |
115 | |
116 | #ifdef MAX_DMA_CHANNELS |
117 | static int proc_dma_show(struct seq_file *m, void *v) |
118 | { |
119 | int i; |
120 | |
121 | for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) { |
122 | if (dma_chan_busy[i].lock) { |
123 | seq_printf(m, "%2d: %s\n", i, |
124 | dma_chan_busy[i].device_id); |
125 | } |
126 | } |
127 | return 0; |
128 | } |
129 | #else |
130 | static int proc_dma_show(struct seq_file *m, void *v) |
131 | { |
132 | seq_puts(m, "No DMA\n"); |
133 | return 0; |
134 | } |
135 | #endif /* MAX_DMA_CHANNELS */ |
136 | |
137 | static int proc_dma_open(struct inode *inode, struct file *file) |
138 | { |
139 | return single_open(file, proc_dma_show, NULL); |
140 | } |
141 | |
142 | static const struct file_operations proc_dma_operations = { |
143 | .open = proc_dma_open, |
144 | .read = seq_read, |
145 | .llseek = seq_lseek, |
146 | .release = single_release, |
147 | }; |
148 | |
149 | static int __init proc_dma_init(void) |
150 | { |
151 | proc_create("dma", 0, NULL, &proc_dma_operations); |
152 | return 0; |
153 | } |
154 | |
155 | __initcall(proc_dma_init); |
156 | #endif |
157 | |
158 | EXPORT_SYMBOL(request_dma); |
159 | EXPORT_SYMBOL(free_dma); |
160 | EXPORT_SYMBOL(dma_spin_lock); |
161 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9