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/* $Id: dma.c,v 1.1 2005-12-20 11:46:56 jcastillo Exp $
 * linux/kernel/dma.c: A DMA channel allocator. Inspired by linux/kernel/irq.c.
 *
 * Written by Hennus Bergman, 1992.
 *
 * 1994/12/26: Changes by Alex Nash to fix a minor bug in /proc/dma.
 *   In the previous version the reported device could end up being wrong,
 *   if a device requested a DMA channel that was already in use.
 *   [It also happened to remove the sizeof(char *) == sizeof(int)
 *   assumption introduced because of those /proc/dma patches. -- Hennus]
 */
 
#include <linux/kernel.h>
#include <linux/errno.h>
#include <asm/dma.h>
#include <asm/system.h>
 
 
/* A note on resource allocation:
 *
 * All drivers needing DMA channels, should allocate and release them
 * through the public routines `request_dma()' and `free_dma()'.
 *
 * In order to avoid problems, all processes should allocate resources in
 * the same sequence and release them in the reverse order.
 *
 * So, when allocating DMAs and IRQs, first allocate the IRQ, then the DMA.
 * When releasing them, first release the DMA, then release the IRQ.
 * If you don't, you may cause allocation requests to fail unnecessarily.
 * This doesn't really matter now, but it will once we get real semaphores
 * in the kernel.
 */
 
 
 
/* Channel n is busy iff dma_chan_busy[n].lock != 0.
 * DMA0 used to be reserved for DRAM refresh, but apparently not any more...
 * DMA4 is reserved for cascading.
 */
 
struct dma_chan {
        int  lock;
        const char *device_id;
};
 
static struct dma_chan dma_chan_busy[MAX_DMA_CHANNELS] = {
        { 0, 0 },
#ifdef CONFIG_M5307
        { 0, 0 },
        { 0, 0 },
#endif
#ifndef CONFIG_UCLINUX
        { 0, 0 },
        { 0, 0 },
        { 1, "cascade" },
        { 0, 0 },
        { 0, 0 },
#endif
        { 0, 0 }
};
 
int get_dma_list(char *buf)
{
        int i, len = 0;
 
        for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) {
                if (dma_chan_busy[i].lock) {
                    len += sprintf(buf+len, "%2d: %s\n",
                                   i,
                                   dma_chan_busy[i].device_id);
                }
        }
        return len;
} /* get_dma_list */
 
 
int request_dma(unsigned int dmanr, const char * device_id)
{
        if (dmanr >= MAX_DMA_CHANNELS)
                return -EINVAL;
 
        if (xchg(&dma_chan_busy[dmanr].lock, 1) != 0)
                return -EBUSY;
 
        dma_chan_busy[dmanr].device_id = device_id;
 
        /* old flag was 0, now contains 1 to indicate busy */
        return 0;
} /* request_dma */
 
 
void free_dma(unsigned int dmanr)
{
        if (dmanr >= MAX_DMA_CHANNELS) {
                printk("Trying to free DMA%d\n", dmanr);
                return;
        }
 
        if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) {
                printk("Trying to free free DMA%d\n", dmanr);
                return;
        }
 
} /* free_dma */

Line No.	Rev	Author	Line
1	1634	jcastillo	`/* $Id: dma.c,v 1.1 2005-12-20 11:46:56 jcastillo Exp $`
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
13			`#include <linux/kernel.h>`
14			`#include <linux/errno.h>`
15			`#include <asm/dma.h>`
16			`#include <asm/system.h>`
17
18
19			`/* A note on resource allocation:`
20			`*`
21			`* All drivers needing DMA channels, should allocate and release them`
22			* through the public routines `request_dma()' and `free_dma()'.
23			`*`
24			`* In order to avoid problems, all processes should allocate resources in`
25			`* the same sequence and release them in the reverse order.`
26			`*`
27			`* So, when allocating DMAs and IRQs, first allocate the IRQ, then the DMA.`
28			`* When releasing them, first release the DMA, then release the IRQ.`
29			`* If you don't, you may cause allocation requests to fail unnecessarily.`
30			`* This doesn't really matter now, but it will once we get real semaphores`
31			`* in the kernel.`
32			`*/`
33
34
35
36			`/* Channel n is busy iff dma_chan_busy[n].lock != 0.`
37			`* DMA0 used to be reserved for DRAM refresh, but apparently not any more...`
38			`* DMA4 is reserved for cascading.`
39			`*/`
40
41			`struct dma_chan {`
42			`int lock;`
43			`const char *device_id;`
44			`};`
45
46			`static struct dma_chan dma_chan_busy[MAX_DMA_CHANNELS] = {`
47			`{ 0, 0 },`
48			`#ifdef CONFIG_M5307`
49			`{ 0, 0 },`
50			`{ 0, 0 },`
51			`#endif`
52			`#ifndef CONFIG_UCLINUX`
53			`{ 0, 0 },`
54			`{ 0, 0 },`
55			`{ 1, "cascade" },`
56			`{ 0, 0 },`
57			`{ 0, 0 },`
58			`#endif`
59			`{ 0, 0 }`
60			`};`
61
62			`int get_dma_list(char *buf)`
63			`{`
64			`int i, len = 0;`
65
66			`for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) {`
67			`if (dma_chan_busy[i].lock) {`
68			`len += sprintf(buf+len, "%2d: %s\n",`
69			`i,`
70			`dma_chan_busy[i].device_id);`
71			`}`
72			`}`
73			`return len;`
74			`} /* get_dma_list */`
75
76
77			`int request_dma(unsigned int dmanr, const char * device_id)`
78			`{`
79			`if (dmanr >= MAX_DMA_CHANNELS)`
80			`return -EINVAL;`
81
82			`if (xchg(&dma_chan_busy[dmanr].lock, 1) != 0)`
83			`return -EBUSY;`
84
85			`dma_chan_busy[dmanr].device_id = device_id;`
86
87			`/* old flag was 0, now contains 1 to indicate busy */`
88			`return 0;`
89			`} /* request_dma */`
90
91
92			`void free_dma(unsigned int dmanr)`
93			`{`
94			`if (dmanr >= MAX_DMA_CHANNELS) {`
95			`printk("Trying to free DMA%d\n", dmanr);`
96			`return;`
97			`}`
98
99			`if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) {`
100			`printk("Trying to free free DMA%d\n", dmanr);`
101			`return;`
102			`}`
103
104			`} /* free_dma */`

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[/] [or1k/] [trunk/] [rc203soc/] [sw/] [uClinux/] [kernel/] [dma.c] - Blame information for rev 1777