summaryrefslogtreecommitdiffstats
path: root/drivers/spi/spi.c
blob: 5e5d29bb2dd56aa2b44efa6d2c854327a0c95701 (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
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
/*
 * spi.c - SPI init/core code
 *
 * Copyright (C) 2005 David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/cache.h>
#include <linux/mutex.h>
#include <linux/spi/spi.h>


/* SPI bustype and spi_master class are registered after board init code
 * provides the SPI device tables, ensuring that both are present by the
 * time controller driver registration causes spi_devices to "enumerate".
 */
static void spidev_release(struct device *dev)
{
	struct spi_device	*spi = to_spi_device(dev);

	/* spi masters may cleanup for released devices */
	if (spi->master->cleanup)
		spi->master->cleanup(spi);

	spi_master_put(spi->master);
	kfree(dev);
}

static ssize_t
modalias_show(struct device *dev, struct device_attribute *a, char *buf)
{
	const struct spi_device	*spi = to_spi_device(dev);

	return snprintf(buf, BUS_ID_SIZE + 1, "%s\n", spi->modalias);
}

static struct device_attribute spi_dev_attrs[] = {
	__ATTR_RO(modalias),
	__ATTR_NULL,
};

/* modalias support makes "modprobe $MODALIAS" new-style hotplug work,
 * and the sysfs version makes coldplug work too.
 */

static int spi_match_device(struct device *dev, struct device_driver *drv)
{
	const struct spi_device	*spi = to_spi_device(dev);

	return strncmp(spi->modalias, drv->name, BUS_ID_SIZE) == 0;
}

static int spi_uevent(struct device *dev, struct kobj_uevent_env *env)
{
	const struct spi_device		*spi = to_spi_device(dev);

	add_uevent_var(env, "MODALIAS=%s", spi->modalias);
	return 0;
}

#ifdef	CONFIG_PM

/*
 * NOTE:  the suspend() method for an spi_master controller driver
 * should verify that all its child devices are marked as suspended;
 * suspend requests delivered through sysfs power/state files don't
 * enforce such constraints.
 */
static int spi_suspend(struct device *dev, pm_message_t message)
{
	int			value;
	struct spi_driver	*drv = to_spi_driver(dev->driver);

	if (!drv || !drv->suspend)
		return 0;

	/* suspend will stop irqs and dma; no more i/o */
	value = drv->suspend(to_spi_device(dev), message);
	if (value == 0)
		dev->power.power_state = message;
	return value;
}

static int spi_resume(struct device *dev)
{
	int			value;
	struct spi_driver	*drv = to_spi_driver(dev->driver);

	if (!drv || !drv->resume)
		return 0;

	/* resume may restart the i/o queue */
	value = drv->resume(to_spi_device(dev));
	if (value == 0)
		dev->power.power_state = PMSG_ON;
	return value;
}

#else
#define spi_suspend	NULL
#define spi_resume	NULL
#endif

struct bus_type spi_bus_type = {
	.name		= "spi",
	.dev_attrs	= spi_dev_attrs,
	.match		= spi_match_device,
	.uevent		= spi_uevent,
	.suspend	= spi_suspend,
	.resume		= spi_resume,
};
EXPORT_SYMBOL_GPL(spi_bus_type);


static int spi_drv_probe(struct device *dev)
{
	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);

	return sdrv->probe(to_spi_device(dev));
}

static int spi_drv_remove(struct device *dev)
{
	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);

	return sdrv->remove(to_spi_device(dev));
}

static void spi_drv_shutdown(struct device *dev)
{
	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);

	sdrv->shutdown(to_spi_device(dev));
}

/**
 * spi_register_driver - register a SPI driver
 * @sdrv: the driver to register
 * Context: can sleep
 */
int spi_register_driver(struct spi_driver *sdrv)
{
	sdrv->driver.bus = &spi_bus_type;
	if (sdrv->probe)
		sdrv->driver.probe = spi_drv_probe;
	if (sdrv->remove)
		sdrv->driver.remove = spi_drv_remove;
	if (sdrv->shutdown)
		sdrv->driver.shutdown = spi_drv_shutdown;
	return driver_register(&sdrv->driver);
}
EXPORT_SYMBOL_GPL(spi_register_driver);

/*-------------------------------------------------------------------------*/

/* SPI devices should normally not be created by SPI device drivers; that
 * would make them board-specific.  Similarly with SPI master drivers.
 * Device registration normally goes into like arch/.../mach.../board-YYY.c
 * with other readonly (flashable) information about mainboard devices.
 */

struct boardinfo {
	struct list_head	list;
	unsigned		n_board_info;
	struct spi_board_info	board_info[0];
};

static LIST_HEAD(board_list);
static DEFINE_MUTEX(board_lock);


/**
 * spi_new_device - instantiate one new SPI device
 * @master: Controller to which device is connected
 * @chip: Describes the SPI device
 * Context: can sleep
 *
 * On typical mainboards, this is purely internal; and it's not needed
 * after board init creates the hard-wired devices.  Some development
 * platforms may not be able to use spi_register_board_info though, and
 * this is exported so that for example a USB or parport based adapter
 * driver could add devices (which it would learn about out-of-band).
 *
 * Returns the new device, or NULL.
 */
struct spi_device *spi_new_device(struct spi_master *master,
				  struct spi_board_info *chip)
{
	struct spi_device	*proxy;
	struct device		*dev = master->dev.parent;
	int			status;

	/* NOTE:  caller did any chip->bus_num checks necessary.
	 *
	 * Also, unless we change the return value convention to use
	 * error-or-pointer (not NULL-or-pointer), troubleshootability
	 * suggests syslogged diagnostics are best here (ugh).
	 */

	/* Chipselects are numbered 0..max; validate. */
	if (chip->chip_select >= master->num_chipselect) {
		dev_err(dev, "cs%d > max %d\n",
			chip->chip_select,
			master->num_chipselect);
		return NULL;
	}

	if (!spi_master_get(master))
		return NULL;

	proxy = kzalloc(sizeof *proxy, GFP_KERNEL);
	if (!proxy) {
		dev_err(dev, "can't alloc dev for cs%d\n",
			chip->chip_select);
		goto fail;
	}
	proxy->master = master;
	proxy->chip_select = chip->chip_select;
	proxy->max_speed_hz = chip->max_speed_hz;
	proxy->mode = chip->mode;
	proxy->irq = chip->irq;
	proxy->modalias = chip->modalias;

	snprintf(proxy->dev.bus_id, sizeof proxy->dev.bus_id,
			"%s.%u", master->dev.bus_id,
			chip->chip_select);
	proxy->dev.parent = dev;
	proxy->dev.bus = &spi_bus_type;
	proxy->dev.platform_data = (void *) chip->platform_data;
	proxy->controller_data = chip->controller_data;
	proxy->controller_state = NULL;
	proxy->dev.release = spidev_release;

	/* drivers may modify this initial i/o setup */
	status = master->setup(proxy);
	if (status < 0) {
		dev_err(dev, "can't %s %s, status %d\n",
				"setup", proxy->dev.bus_id, status);
		goto fail;
	}

	/* driver core catches callers that misbehave by defining
	 * devices that already exist.
	 */
	status = device_register(&proxy->dev);
	if (status < 0) {
		dev_err(dev, "can't %s %s, status %d\n",
				"add", proxy->dev.bus_id, status);
		goto fail;
	}
	dev_dbg(dev, "registered child %s\n", proxy->dev.bus_id);
	return proxy;

fail:
	spi_master_put(master);
	kfree(proxy);
	return NULL;
}
EXPORT_SYMBOL_GPL(spi_new_device);

/**
 * spi_register_board_info - register SPI devices for a given board
 * @info: array of chip descriptors
 * @n: how many descriptors are provided
 * Context: can sleep
 *
 * Board-specific early init code calls this (probably during arch_initcall)
 * with segments of the SPI device table.  Any device nodes are created later,
 * after the relevant parent SPI controller (bus_num) is defined.  We keep
 * this table of devices forever, so that reloading a controller driver will
 * not make Linux forget about these hard-wired devices.
 *
 * Other code can also call this, e.g. a particular add-on board might provide
 * SPI devices through its expansion connector, so code initializing that board
 * would naturally declare its SPI devices.
 *
 * The board info passed can safely be __initdata ... but be careful of
 * any embedded pointers (platform_data, etc), they're copied as-is.
 */
int __init
spi_register_board_info(struct spi_board_info const *info, unsigned n)
{
	struct boardinfo	*bi;

	bi = kmalloc(sizeof(*bi) + n * sizeof *info, GFP_KERNEL);
	if (!bi)
		return -ENOMEM;
	bi->n_board_info = n;
	memcpy(bi->board_info, info, n * sizeof *info);

	mutex_lock(&board_lock);
	list_add_tail(&bi->list, &board_list);
	mutex_unlock(&board_lock);
	return 0;
}

/* FIXME someone should add support for a __setup("spi", ...) that
 * creates board info from kernel command lines
 */

static void scan_boardinfo(struct spi_master *master)
{
	struct boardinfo	*bi;

	mutex_lock(&board_lock);
	list_for_each_entry(bi, &board_list, list) {
		struct spi_board_info	*chip = bi->board_info;
		unsigned		n;

		for (n = bi->n_board_info; n > 0; n--, chip++) {
			if (chip->bus_num != master->bus_num)
				continue;
			/* NOTE: this relies on spi_new_device to
			 * issue diagnostics when given bogus inputs
			 */
			(void) spi_new_device(master, chip);
		}
	}
	mutex_unlock(&board_lock);
}

/*-------------------------------------------------------------------------*/

static void spi_master_release(struct device *dev)
{
	struct spi_master *master;

	master = container_of(dev, struct spi_master, dev);
	kfree(master);
}

static struct class spi_master_class = {
	.name		= "spi_master",
	.owner		= THIS_MODULE,
	.dev_release	= spi_master_release,
};


/**
 * spi_alloc_master - allocate SPI master controller
 * @dev: the controller, possibly using the platform_bus
 * @size: how much zeroed driver-private data to allocate; the pointer to this
 *	memory is in the driver_data field of the returned device,
 *	accessible with spi_master_get_devdata().
 * Context: can sleep
 *
 * This call is used only by SPI master controller drivers, which are the
 * only ones directly touching chip registers.  It's how they allocate
 * an spi_master structure, prior to calling spi_register_master().
 *
 * This must be called from context that can sleep.  It returns the SPI
 * master structure on success, else NULL.
 *
 * The caller is responsible for assigning the bus number and initializing
 * the master's methods before calling spi_register_master(); and (after errors
 * adding the device) calling spi_master_put() to prevent a memory leak.
 */
struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
{
	struct spi_master	*master;

	if (!dev)
		return NULL;

	master = kzalloc(size + sizeof *master, GFP_KERNEL);
	if (!master)
		return NULL;

	device_initialize(&master->dev);
	master->dev.class = &spi_master_class;
	master->dev.parent = get_device(dev);
	spi_master_set_devdata(master, &master[1]);

	return master;
}
EXPORT_SYMBOL_GPL(spi_alloc_master);

/**
 * spi_register_master - register SPI master controller
 * @master: initialized master, originally from spi_alloc_master()
 * Context: can sleep
 *
 * SPI master controllers connect to their drivers using some non-SPI bus,
 * such as the platform bus.  The final stage of probe() in that code
 * includes calling spi_register_master() to hook up to this SPI bus glue.
 *
 * SPI controllers use board specific (often SOC specific) bus numbers,
 * and board-specific addressing for SPI devices combines those numbers
 * with chip select numbers.  Since SPI does not directly support dynamic
 * device identification, boards need configuration tables telling which
 * chip is at which address.
 *
 * This must be called from context that can sleep.  It returns zero on
 * success, else a negative error code (dropping the master's refcount).
 * After a successful return, the caller is responsible for calling
 * spi_unregister_master().
 */
int spi_register_master(struct spi_master *master)
{
	static atomic_t		dyn_bus_id = ATOMIC_INIT((1<<15) - 1);
	struct device		*dev = master->dev.parent;
	int			status = -ENODEV;
	int			dynamic = 0;

	if (!dev)
		return -ENODEV;

	/* even if it's just one always-selected device, there must
	 * be at least one chipselect
	 */
	if (master->num_chipselect == 0)
		return -EINVAL;

	/* convention:  dynamically assigned bus IDs count down from the max */
	if (master->bus_num < 0) {
		/* FIXME switch to an IDR based scheme, something like
		 * I2C now uses, so we can't run out of "dynamic" IDs
		 */
		master->bus_num = atomic_dec_return(&dyn_bus_id);
		dynamic = 1;
	}

	/* register the device, then userspace will see it.
	 * registration fails if the bus ID is in use.
	 */
	snprintf(master->dev.bus_id, sizeof master->dev.bus_id,
		"spi%u", master->bus_num);
	status = device_add(&master->dev);
	if (status < 0)
		goto done;
	dev_dbg(dev, "registered master %s%s\n", master->dev.bus_id,
			dynamic ? " (dynamic)" : "");

	/* populate children from any spi device tables */
	scan_boardinfo(master);
	status = 0;
done:
	return status;
}
EXPORT_SYMBOL_GPL(spi_register_master);


static int __unregister(struct device *dev, void *master_dev)
{
	/* note: before about 2.6.14-rc1 this would corrupt memory: */
	if (dev != master_dev)
		spi_unregister_device(to_spi_device(dev));
	return 0;
}

/**
 * spi_unregister_master - unregister SPI master controller
 * @master: the master being unregistered
 * Context: can sleep
 *
 * This call is used only by SPI master controller drivers, which are the
 * only ones directly touching chip registers.
 *
 * This must be called from context that can sleep.
 */
void spi_unregister_master(struct spi_master *master)
{
	int dummy;

	dummy = device_for_each_child(master->dev.parent, &master->dev,
					__unregister);
	device_unregister(&master->dev);
}
EXPORT_SYMBOL_GPL(spi_unregister_master);

static int __spi_master_match(struct device *dev, void *data)
{
	struct spi_master *m;
	u16 *bus_num = data;

	m = container_of(dev, struct spi_master, dev);
	return m->bus_num == *bus_num;
}

/**
 * spi_busnum_to_master - look up master associated with bus_num
 * @bus_num: the master's bus number
 * Context: can sleep
 *
 * This call may be used with devices that are registered after
 * arch init time.  It returns a refcounted pointer to the relevant
 * spi_master (which the caller must release), or NULL if there is
 * no such master registered.
 */
struct spi_master *spi_busnum_to_master(u16 bus_num)
{
	struct device		*dev;
	struct spi_master	*master = NULL;

	dev = class_find_device(&spi_master_class, &bus_num,
				__spi_master_match);
	if (dev)
		master = container_of(dev, struct spi_master, dev);
	/* reference got in class_find_device */
	return master;
}
EXPORT_SYMBOL_GPL(spi_busnum_to_master);


/*-------------------------------------------------------------------------*/

static void spi_complete(void *arg)
{
	complete(arg);
}

/**
 * spi_sync - blocking/synchronous SPI data transfers
 * @spi: device with which data will be exchanged
 * @message: describes the data transfers
 * Context: can sleep
 *
 * This call may only be used from a context that may sleep.  The sleep
 * is non-interruptible, and has no timeout.  Low-overhead controller
 * drivers may DMA directly into and out of the message buffers.
 *
 * Note that the SPI device's chip select is active during the message,
 * and then is normally disabled between messages.  Drivers for some
 * frequently-used devices may want to minimize costs of selecting a chip,
 * by leaving it selected in anticipation that the next message will go
 * to the same chip.  (That may increase power usage.)
 *
 * Also, the caller is guaranteeing that the memory associated with the
 * message will not be freed before this call returns.
 *
 * It returns zero on success, else a negative error code.
 */
int spi_sync(struct spi_device *spi, struct spi_message *message)
{
	DECLARE_COMPLETION_ONSTACK(done);
	int status;

	message->complete = spi_complete;
	message->context = &done;
	status = spi_async(spi, message);
	if (status == 0) {
		wait_for_completion(&done);
		status = message->status;
	}
	message->context = NULL;
	return status;
}
EXPORT_SYMBOL_GPL(spi_sync);

/* portable code must never pass more than 32 bytes */
#define	SPI_BUFSIZ	max(32,SMP_CACHE_BYTES)

static u8	*buf;

/**
 * spi_write_then_read - SPI synchronous write followed by read
 * @spi: device with which data will be exchanged
 * @txbuf: data to be written (need not be dma-safe)
 * @n_tx: size of txbuf, in bytes
 * @rxbuf: buffer into which data will be read
 * @n_rx: size of rxbuf, in bytes (need not be dma-safe)
 * Context: can sleep
 *
 * This performs a half duplex MicroWire style transaction with the
 * device, sending txbuf and then reading rxbuf.  The return value
 * is zero for success, else a negative errno status code.
 * This call may only be used from a context that may sleep.
 *
 * Parameters to this routine are always copied using a small buffer;
 * portable code should never use this for more than 32 bytes.
 * Performance-sensitive or bulk transfer code should instead use
 * spi_{async,sync}() calls with dma-safe buffers.
 */
int spi_write_then_read(struct spi_device *spi,
		const u8 *txbuf, unsigned n_tx,
		u8 *rxbuf, unsigned n_rx)
{
	static DEFINE_MUTEX(lock);

	int			status;
	struct spi_message	message;
	struct spi_transfer	x[2];
	u8			*local_buf;

	/* Use preallocated DMA-safe buffer.  We can't avoid copying here,
	 * (as a pure convenience thing), but we can keep heap costs
	 * out of the hot path ...
	 */
	if ((n_tx + n_rx) > SPI_BUFSIZ)
		return -EINVAL;

	spi_message_init(&message);
	memset(x, 0, sizeof x);
	if (n_tx) {
		x[0].len = n_tx;
		spi_message_add_tail(&x[0], &message);
	}
	if (n_rx) {
		x[1].len = n_rx;
		spi_message_add_tail(&x[1], &message);
	}

	/* ... unless someone else is using the pre-allocated buffer */
	if (!mutex_trylock(&lock)) {
		local_buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
		if (!local_buf)
			return -ENOMEM;
	} else
		local_buf = buf;

	memcpy(local_buf, txbuf, n_tx);
	x[0].tx_buf = local_buf;
	x[1].rx_buf = local_buf + n_tx;

	/* do the i/o */
	status = spi_sync(spi, &message);
	if (status == 0)
		memcpy(rxbuf, x[1].rx_buf, n_rx);

	if (x[0].tx_buf == buf)
		mutex_unlock(&lock);
	else
		kfree(local_buf);

	return status;
}
EXPORT_SYMBOL_GPL(spi_write_then_read);

/*-------------------------------------------------------------------------*/

static int __init spi_init(void)
{
	int	status;

	buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
	if (!buf) {
		status = -ENOMEM;
		goto err0;
	}

	status = bus_register(&spi_bus_type);
	if (status < 0)
		goto err1;

	status = class_register(&spi_master_class);
	if (status < 0)
		goto err2;
	return 0;

err2:
	bus_unregister(&spi_bus_type);
err1:
	kfree(buf);
	buf = NULL;
err0:
	return status;
}

/* board_info is normally registered in arch_initcall(),
 * but even essential drivers wait till later
 *
 * REVISIT only boardinfo really needs static linking. the rest (device and
 * driver registration) _could_ be dynamically linked (modular) ... costs
 * include needing to have boardinfo data structures be much more public.
 */
subsys_initcall(spi_init);

OpenPOWER on IntegriCloud