summaryrefslogtreecommitdiffstats
path: root/arch/arm/mach-sa1100/dma.c
blob: f990a3e858462d6324d85e469e50ea2d66604c1c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
/*
 * arch/arm/mach-sa1100/dma.c
 *
 * Support functions for the SA11x0 internal DMA channels.
 *
 * Copyright (C) 2000, 2001 by Nicolas Pitre
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/errno.h>

#include <asm/system.h>
#include <asm/irq.h>
#include <mach/hardware.h>
#include <asm/dma.h>


#undef DEBUG
#ifdef DEBUG
#define DPRINTK( s, arg... )  printk( "dma<%p>: " s, regs , ##arg )
#else
#define DPRINTK( x... )
#endif


typedef struct {
	const char *device_id;		/* device name */
	u_long device;			/* this channel device, 0  if unused*/
	dma_callback_t callback;	/* to call when DMA completes */
	void *data;			/* ... with private data ptr */
} sa1100_dma_t;

static sa1100_dma_t dma_chan[SA1100_DMA_CHANNELS];

static spinlock_t dma_list_lock;


static irqreturn_t dma_irq_handler(int irq, void *dev_id)
{
	dma_regs_t *dma_regs = dev_id;
	sa1100_dma_t *dma = dma_chan + (((u_int)dma_regs >> 5) & 7);
	int status = dma_regs->RdDCSR;

	if (status & (DCSR_ERROR)) {
		printk(KERN_CRIT "DMA on \"%s\" caused an error\n", dma->device_id);
		dma_regs->ClrDCSR = DCSR_ERROR;
	}

	dma_regs->ClrDCSR = status & (DCSR_DONEA | DCSR_DONEB);
	if (dma->callback) {
		if (status & DCSR_DONEA)
			dma->callback(dma->data);
		if (status & DCSR_DONEB)
			dma->callback(dma->data);
	}
	return IRQ_HANDLED;
}


/**
 *	sa1100_request_dma - allocate one of the SA11x0's DMA chanels
 *	@device: The SA11x0 peripheral targeted by this request
 *	@device_id: An ascii name for the claiming device
 *	@callback: Function to be called when the DMA completes
 *	@data: A cookie passed back to the callback function
 *	@dma_regs: Pointer to the location of the allocated channel's identifier
 *
 * 	This function will search for a free DMA channel and returns the
 * 	address of the hardware registers for that channel as the channel
 * 	identifier. This identifier is written to the location pointed by
 * 	@dma_regs. The list of possible values for @device are listed into
 * 	arch/arm/mach-sa1100/include/mach/dma.h as a dma_device_t enum.
 *
 * 	Note that reading from a port and writing to the same port are
 * 	actually considered as two different streams requiring separate
 * 	DMA registrations.
 *
 * 	The @callback function is called from interrupt context when one
 * 	of the two possible DMA buffers in flight has terminated. That
 * 	function has to be small and efficient while posponing more complex
 * 	processing to a lower priority execution context.
 *
 * 	If no channels are available, or if the desired @device is already in
 * 	use by another DMA channel, then an error code is returned.  This
 * 	function must be called before any other DMA calls.
 **/

int sa1100_request_dma (dma_device_t device, const char *device_id,
			dma_callback_t callback, void *data,
			dma_regs_t **dma_regs)
{
	sa1100_dma_t *dma = NULL;
	dma_regs_t *regs;
	int i, err;

	*dma_regs = NULL;

	err = 0;
	spin_lock(&dma_list_lock);
	for (i = 0; i < SA1100_DMA_CHANNELS; i++) {
		if (dma_chan[i].device == device) {
			err = -EBUSY;
			break;
		} else if (!dma_chan[i].device && !dma) {
			dma = &dma_chan[i];
		}
	}
	if (!err) {
	       if (dma)
		       dma->device = device;
	       else
		       err = -ENOSR;
	}
	spin_unlock(&dma_list_lock);
	if (err)
		return err;

	i = dma - dma_chan;
	regs = (dma_regs_t *)&DDAR(i);
	err = request_irq(IRQ_DMA0 + i, dma_irq_handler, IRQF_DISABLED,
			  device_id, regs);
	if (err) {
		printk(KERN_ERR
		       "%s: unable to request IRQ %d for %s\n",
		       __func__, IRQ_DMA0 + i, device_id);
		dma->device = 0;
		return err;
	}

	*dma_regs = regs;
	dma->device_id = device_id;
	dma->callback = callback;
	dma->data = data;

	regs->ClrDCSR =
		(DCSR_DONEA | DCSR_DONEB | DCSR_STRTA | DCSR_STRTB |
		 DCSR_IE | DCSR_ERROR | DCSR_RUN);
	regs->DDAR = device;

	return 0;
}


/**
 * 	sa1100_free_dma - free a SA11x0 DMA channel
 * 	@regs: identifier for the channel to free
 *
 * 	This clears all activities on a given DMA channel and releases it
 * 	for future requests.  The @regs identifier is provided by a
 * 	successful call to sa1100_request_dma().
 **/

void sa1100_free_dma(dma_regs_t *regs)
{
	int i;

	for (i = 0; i < SA1100_DMA_CHANNELS; i++)
		if (regs == (dma_regs_t *)&DDAR(i))
			break;
	if (i >= SA1100_DMA_CHANNELS) {
		printk(KERN_ERR "%s: bad DMA identifier\n", __func__);
		return;
	}

	if (!dma_chan[i].device) {
		printk(KERN_ERR "%s: Trying to free free DMA\n", __func__);
		return;
	}

	regs->ClrDCSR =
		(DCSR_DONEA | DCSR_DONEB | DCSR_STRTA | DCSR_STRTB |
		 DCSR_IE | DCSR_ERROR | DCSR_RUN);
	free_irq(IRQ_DMA0 + i, regs);
	dma_chan[i].device = 0;
}


/**
 * 	sa1100_start_dma - submit a data buffer for DMA
 * 	@regs: identifier for the channel to use
 * 	@dma_ptr: buffer physical (or bus) start address
 * 	@size: buffer size
 *
 * 	This function hands the given data buffer to the hardware for DMA
 * 	access. If another buffer is already in flight then this buffer
 * 	will be queued so the DMA engine will switch to it automatically
 * 	when the previous one is done.  The DMA engine is actually toggling
 * 	between two buffers so at most 2 successful calls can be made before
 * 	one of them terminates and the callback function is called.
 *
 * 	The @regs identifier is provided by a successful call to
 * 	sa1100_request_dma().
 *
 * 	The @size must not be larger than %MAX_DMA_SIZE.  If a given buffer
 * 	is larger than that then it's the caller's responsibility to split
 * 	it into smaller chunks and submit them separately. If this is the
 * 	case then a @size of %CUT_DMA_SIZE is recommended to avoid ending
 * 	up with too small chunks. The callback function can be used to chain
 * 	submissions of buffer chunks.
 *
 * 	Error return values:
 * 	%-EOVERFLOW:	Given buffer size is too big.
 * 	%-EBUSY:	Both DMA buffers are already in use.
 * 	%-EAGAIN:	Both buffers were busy but one of them just completed
 * 			but the interrupt handler has to execute first.
 *
 * 	This function returs 0 on success.
 **/

int sa1100_start_dma(dma_regs_t *regs, dma_addr_t dma_ptr, u_int size)
{
	unsigned long flags;
	u_long status;
	int ret;

	if (dma_ptr & 3)
		printk(KERN_WARNING "DMA: unaligned start address (0x%08lx)\n",
		       (unsigned long)dma_ptr);

	if (size > MAX_DMA_SIZE)
		return -EOVERFLOW;

	local_irq_save(flags);
	status = regs->RdDCSR;

	/* If both DMA buffers are started, there's nothing else we can do. */
	if ((status & (DCSR_STRTA | DCSR_STRTB)) == (DCSR_STRTA | DCSR_STRTB)) {
		DPRINTK("start: st %#x busy\n", status);
		ret = -EBUSY;
		goto out;
	}

	if (((status & DCSR_BIU) && (status & DCSR_STRTB)) ||
	    (!(status & DCSR_BIU) && !(status & DCSR_STRTA))) {
		if (status & DCSR_DONEA) {
			/* give a chance for the interrupt to be processed */
			ret = -EAGAIN;
			goto out;
		}
		regs->DBSA = dma_ptr;
		regs->DBTA = size;
		regs->SetDCSR = DCSR_STRTA | DCSR_IE | DCSR_RUN;
		DPRINTK("start a=%#x s=%d on A\n", dma_ptr, size);
	} else {
		if (status & DCSR_DONEB) {
			/* give a chance for the interrupt to be processed */
			ret = -EAGAIN;
			goto out;
		}
		regs->DBSB = dma_ptr;
		regs->DBTB = size;
		regs->SetDCSR = DCSR_STRTB | DCSR_IE | DCSR_RUN;
		DPRINTK("start a=%#x s=%d on B\n", dma_ptr, size);
	}
	ret = 0;

out:
	local_irq_restore(flags);
	return ret;
}


/**
 * 	sa1100_get_dma_pos - return current DMA position
 * 	@regs: identifier for the channel to use
 *
 * 	This function returns the current physical (or bus) address for the
 * 	given DMA channel.  If the channel is running i.e. not in a stopped
 * 	state then the caller must disable interrupts prior calling this
 * 	function and process the returned value before re-enabling them to
 * 	prevent races with the completion interrupt handler and the callback
 * 	function. The validation of the returned value is the caller's
 * 	responsibility as well -- the hardware seems to return out of range
 * 	values when the DMA engine completes a buffer.
 *
 * 	The @regs identifier is provided by a successful call to
 * 	sa1100_request_dma().
 **/

dma_addr_t sa1100_get_dma_pos(dma_regs_t *regs)
{
	int status;

	/*
	 * We must determine whether buffer A or B is active.
	 * Two possibilities: either we are in the middle of
	 * a buffer, or the DMA controller just switched to the
	 * next toggle but the interrupt hasn't been serviced yet.
	 * The former case is straight forward.  In the later case,
	 * we'll do like if DMA is just at the end of the previous
	 * toggle since all registers haven't been reset yet.
	 * This goes around the edge case and since we're always
	 * a little behind anyways it shouldn't make a big difference.
	 * If DMA has been stopped prior calling this then the
	 * position is exact.
	 */
	status = regs->RdDCSR;
	if ((!(status & DCSR_BIU) &&  (status & DCSR_STRTA)) ||
	    ( (status & DCSR_BIU) && !(status & DCSR_STRTB)))
		return regs->DBSA;
	else
		return regs->DBSB;
}


/**
 * 	sa1100_reset_dma - reset a DMA channel
 * 	@regs: identifier for the channel to use
 *
 * 	This function resets and reconfigure the given DMA channel. This is
 * 	particularly useful after a sleep/wakeup event.
 *
 * 	The @regs identifier is provided by a successful call to
 * 	sa1100_request_dma().
 **/

void sa1100_reset_dma(dma_regs_t *regs)
{
	int i;

	for (i = 0; i < SA1100_DMA_CHANNELS; i++)
		if (regs == (dma_regs_t *)&DDAR(i))
			break;
	if (i >= SA1100_DMA_CHANNELS) {
		printk(KERN_ERR "%s: bad DMA identifier\n", __func__);
		return;
	}

	regs->ClrDCSR =
		(DCSR_DONEA | DCSR_DONEB | DCSR_STRTA | DCSR_STRTB |
		 DCSR_IE | DCSR_ERROR | DCSR_RUN);
	regs->DDAR = dma_chan[i].device;
}


EXPORT_SYMBOL(sa1100_request_dma);
EXPORT_SYMBOL(sa1100_free_dma);
EXPORT_SYMBOL(sa1100_start_dma);
EXPORT_SYMBOL(sa1100_get_dma_pos);
EXPORT_SYMBOL(sa1100_reset_dma);

OpenPOWER on IntegriCloud