[mirror_ubuntu-bionic-kernel.git] / kernel / dma.c

/*
 * 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/export.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <asm/dma.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.
 */


DEFINE_SPINLOCK(dma_spin_lock);

/*
 *	If our port doesn't define this it has no PC like DMA
 */

#ifdef MAX_DMA_CHANNELS


/* 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] = {
	[4] = { 1, "cascade" },
};


/**
 * request_dma - request and reserve a system DMA channel
 * @dmanr: DMA channel number
 * @device_id: reserving device ID string, used in /proc/dma
 */
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 */

/**
 * free_dma - free a reserved system DMA channel
 * @dmanr: DMA channel number
 */
void free_dma(unsigned int dmanr)
{
	if (dmanr >= MAX_DMA_CHANNELS) {
		printk(KERN_WARNING "Trying to free DMA%d\n", dmanr);
		return;
	}

	if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) {
		printk(KERN_WARNING "Trying to free free DMA%d\n", dmanr);
		return;
	}

} /* free_dma */

#else

int request_dma(unsigned int dmanr, const char *device_id)
{
	return -EINVAL;
}

void free_dma(unsigned int dmanr)
{
}

#endif

#ifdef CONFIG_PROC_FS

#ifdef MAX_DMA_CHANNELS
static int proc_dma_show(struct seq_file *m, void *v)
{
	int i;

	for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) {
		if (dma_chan_busy[i].lock) {
			seq_printf(m, "%2d: %s\n", i,
				   dma_chan_busy[i].device_id);
		}
	}
	return 0;
}
#else
static int proc_dma_show(struct seq_file *m, void *v)
{
	seq_puts(m, "No DMA\n");
	return 0;
}
#endif /* MAX_DMA_CHANNELS */

static int proc_dma_open(struct inode *inode, struct file *file)
{
	return single_open(file, proc_dma_show, NULL);
}

static const struct file_operations proc_dma_operations = {
	.open		= proc_dma_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int __init proc_dma_init(void)
{
	proc_create("dma", 0, NULL, &proc_dma_operations);
	return 0;
}

__initcall(proc_dma_init);
#endif

EXPORT_SYMBOL(request_dma);
EXPORT_SYMBOL(free_dma);
EXPORT_SYMBOL(dma_spin_lock);
Commit	Line	Data
d9f3216b	1	/*
1da177e4 LT	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	*/
9984de1a	12	#include <linux/export.h>
1da177e4 LT	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>
1da177e4	21
902749cd	22
1da177e4 LT	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
eed34d0f RD	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	*/
1da177e4 LT	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
eed34d0f RD	83	/**
	84	* free_dma - free a reserved system DMA channel
	85	* @dmanr: DMA channel number
	86	*/
1da177e4 LT	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;
902749cd	97	}
1da177e4 LT	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) {
902749cd DW	123	seq_printf(m, "%2d: %s\n", i,
902749cd DW	124	dma_chan_busy[i].device_id);
1da177e4 LT	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
15ad7cdc	142	static const struct file_operations proc_dma_operations = {
1da177e4 LT	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	{
c33fff0a	151	proc_create("dma", 0, NULL, &proc_dma_operations);
1da177e4 LT	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);