xref: /openbmc/linux/drivers/spi/spi.c (revision f42b3800)
1 /*
2  * spi.c - SPI init/core code
3  *
4  * Copyright (C) 2005 David Brownell
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  * GNU General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program; if not, write to the Free Software
18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19  */
20 
21 #include <linux/kernel.h>
22 #include <linux/device.h>
23 #include <linux/init.h>
24 #include <linux/cache.h>
25 #include <linux/mutex.h>
26 #include <linux/spi/spi.h>
27 
28 
29 /* SPI bustype and spi_master class are registered after board init code
30  * provides the SPI device tables, ensuring that both are present by the
31  * time controller driver registration causes spi_devices to "enumerate".
32  */
33 static void spidev_release(struct device *dev)
34 {
35 	struct spi_device	*spi = to_spi_device(dev);
36 
37 	/* spi masters may cleanup for released devices */
38 	if (spi->master->cleanup)
39 		spi->master->cleanup(spi);
40 
41 	spi_master_put(spi->master);
42 	kfree(dev);
43 }
44 
45 static ssize_t
46 modalias_show(struct device *dev, struct device_attribute *a, char *buf)
47 {
48 	const struct spi_device	*spi = to_spi_device(dev);
49 
50 	return snprintf(buf, BUS_ID_SIZE + 1, "%s\n", spi->modalias);
51 }
52 
53 static struct device_attribute spi_dev_attrs[] = {
54 	__ATTR_RO(modalias),
55 	__ATTR_NULL,
56 };
57 
58 /* modalias support makes "modprobe $MODALIAS" new-style hotplug work,
59  * and the sysfs version makes coldplug work too.
60  */
61 
62 static int spi_match_device(struct device *dev, struct device_driver *drv)
63 {
64 	const struct spi_device	*spi = to_spi_device(dev);
65 
66 	return strncmp(spi->modalias, drv->name, BUS_ID_SIZE) == 0;
67 }
68 
69 static int spi_uevent(struct device *dev, struct kobj_uevent_env *env)
70 {
71 	const struct spi_device		*spi = to_spi_device(dev);
72 
73 	add_uevent_var(env, "MODALIAS=%s", spi->modalias);
74 	return 0;
75 }
76 
77 #ifdef	CONFIG_PM
78 
79 static int spi_suspend(struct device *dev, pm_message_t message)
80 {
81 	int			value = 0;
82 	struct spi_driver	*drv = to_spi_driver(dev->driver);
83 
84 	/* suspend will stop irqs and dma; no more i/o */
85 	if (drv) {
86 		if (drv->suspend)
87 			value = drv->suspend(to_spi_device(dev), message);
88 		else
89 			dev_dbg(dev, "... can't suspend\n");
90 	}
91 	return value;
92 }
93 
94 static int spi_resume(struct device *dev)
95 {
96 	int			value = 0;
97 	struct spi_driver	*drv = to_spi_driver(dev->driver);
98 
99 	/* resume may restart the i/o queue */
100 	if (drv) {
101 		if (drv->resume)
102 			value = drv->resume(to_spi_device(dev));
103 		else
104 			dev_dbg(dev, "... can't resume\n");
105 	}
106 	return value;
107 }
108 
109 #else
110 #define spi_suspend	NULL
111 #define spi_resume	NULL
112 #endif
113 
114 struct bus_type spi_bus_type = {
115 	.name		= "spi",
116 	.dev_attrs	= spi_dev_attrs,
117 	.match		= spi_match_device,
118 	.uevent		= spi_uevent,
119 	.suspend	= spi_suspend,
120 	.resume		= spi_resume,
121 };
122 EXPORT_SYMBOL_GPL(spi_bus_type);
123 
124 
125 static int spi_drv_probe(struct device *dev)
126 {
127 	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
128 
129 	return sdrv->probe(to_spi_device(dev));
130 }
131 
132 static int spi_drv_remove(struct device *dev)
133 {
134 	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
135 
136 	return sdrv->remove(to_spi_device(dev));
137 }
138 
139 static void spi_drv_shutdown(struct device *dev)
140 {
141 	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
142 
143 	sdrv->shutdown(to_spi_device(dev));
144 }
145 
146 /**
147  * spi_register_driver - register a SPI driver
148  * @sdrv: the driver to register
149  * Context: can sleep
150  */
151 int spi_register_driver(struct spi_driver *sdrv)
152 {
153 	sdrv->driver.bus = &spi_bus_type;
154 	if (sdrv->probe)
155 		sdrv->driver.probe = spi_drv_probe;
156 	if (sdrv->remove)
157 		sdrv->driver.remove = spi_drv_remove;
158 	if (sdrv->shutdown)
159 		sdrv->driver.shutdown = spi_drv_shutdown;
160 	return driver_register(&sdrv->driver);
161 }
162 EXPORT_SYMBOL_GPL(spi_register_driver);
163 
164 /*-------------------------------------------------------------------------*/
165 
166 /* SPI devices should normally not be created by SPI device drivers; that
167  * would make them board-specific.  Similarly with SPI master drivers.
168  * Device registration normally goes into like arch/.../mach.../board-YYY.c
169  * with other readonly (flashable) information about mainboard devices.
170  */
171 
172 struct boardinfo {
173 	struct list_head	list;
174 	unsigned		n_board_info;
175 	struct spi_board_info	board_info[0];
176 };
177 
178 static LIST_HEAD(board_list);
179 static DEFINE_MUTEX(board_lock);
180 
181 
182 /**
183  * spi_new_device - instantiate one new SPI device
184  * @master: Controller to which device is connected
185  * @chip: Describes the SPI device
186  * Context: can sleep
187  *
188  * On typical mainboards, this is purely internal; and it's not needed
189  * after board init creates the hard-wired devices.  Some development
190  * platforms may not be able to use spi_register_board_info though, and
191  * this is exported so that for example a USB or parport based adapter
192  * driver could add devices (which it would learn about out-of-band).
193  *
194  * Returns the new device, or NULL.
195  */
196 struct spi_device *spi_new_device(struct spi_master *master,
197 				  struct spi_board_info *chip)
198 {
199 	struct spi_device	*proxy;
200 	struct device		*dev = master->dev.parent;
201 	int			status;
202 
203 	/* NOTE:  caller did any chip->bus_num checks necessary.
204 	 *
205 	 * Also, unless we change the return value convention to use
206 	 * error-or-pointer (not NULL-or-pointer), troubleshootability
207 	 * suggests syslogged diagnostics are best here (ugh).
208 	 */
209 
210 	/* Chipselects are numbered 0..max; validate. */
211 	if (chip->chip_select >= master->num_chipselect) {
212 		dev_err(dev, "cs%d > max %d\n",
213 			chip->chip_select,
214 			master->num_chipselect);
215 		return NULL;
216 	}
217 
218 	if (!spi_master_get(master))
219 		return NULL;
220 
221 	proxy = kzalloc(sizeof *proxy, GFP_KERNEL);
222 	if (!proxy) {
223 		dev_err(dev, "can't alloc dev for cs%d\n",
224 			chip->chip_select);
225 		goto fail;
226 	}
227 	proxy->master = master;
228 	proxy->chip_select = chip->chip_select;
229 	proxy->max_speed_hz = chip->max_speed_hz;
230 	proxy->mode = chip->mode;
231 	proxy->irq = chip->irq;
232 	proxy->modalias = chip->modalias;
233 
234 	snprintf(proxy->dev.bus_id, sizeof proxy->dev.bus_id,
235 			"%s.%u", master->dev.bus_id,
236 			chip->chip_select);
237 	proxy->dev.parent = dev;
238 	proxy->dev.bus = &spi_bus_type;
239 	proxy->dev.platform_data = (void *) chip->platform_data;
240 	proxy->controller_data = chip->controller_data;
241 	proxy->controller_state = NULL;
242 	proxy->dev.release = spidev_release;
243 
244 	/* drivers may modify this initial i/o setup */
245 	status = master->setup(proxy);
246 	if (status < 0) {
247 		dev_err(dev, "can't %s %s, status %d\n",
248 				"setup", proxy->dev.bus_id, status);
249 		goto fail;
250 	}
251 
252 	/* driver core catches callers that misbehave by defining
253 	 * devices that already exist.
254 	 */
255 	status = device_register(&proxy->dev);
256 	if (status < 0) {
257 		dev_err(dev, "can't %s %s, status %d\n",
258 				"add", proxy->dev.bus_id, status);
259 		goto fail;
260 	}
261 	dev_dbg(dev, "registered child %s\n", proxy->dev.bus_id);
262 	return proxy;
263 
264 fail:
265 	spi_master_put(master);
266 	kfree(proxy);
267 	return NULL;
268 }
269 EXPORT_SYMBOL_GPL(spi_new_device);
270 
271 /**
272  * spi_register_board_info - register SPI devices for a given board
273  * @info: array of chip descriptors
274  * @n: how many descriptors are provided
275  * Context: can sleep
276  *
277  * Board-specific early init code calls this (probably during arch_initcall)
278  * with segments of the SPI device table.  Any device nodes are created later,
279  * after the relevant parent SPI controller (bus_num) is defined.  We keep
280  * this table of devices forever, so that reloading a controller driver will
281  * not make Linux forget about these hard-wired devices.
282  *
283  * Other code can also call this, e.g. a particular add-on board might provide
284  * SPI devices through its expansion connector, so code initializing that board
285  * would naturally declare its SPI devices.
286  *
287  * The board info passed can safely be __initdata ... but be careful of
288  * any embedded pointers (platform_data, etc), they're copied as-is.
289  */
290 int __init
291 spi_register_board_info(struct spi_board_info const *info, unsigned n)
292 {
293 	struct boardinfo	*bi;
294 
295 	bi = kmalloc(sizeof(*bi) + n * sizeof *info, GFP_KERNEL);
296 	if (!bi)
297 		return -ENOMEM;
298 	bi->n_board_info = n;
299 	memcpy(bi->board_info, info, n * sizeof *info);
300 
301 	mutex_lock(&board_lock);
302 	list_add_tail(&bi->list, &board_list);
303 	mutex_unlock(&board_lock);
304 	return 0;
305 }
306 
307 /* FIXME someone should add support for a __setup("spi", ...) that
308  * creates board info from kernel command lines
309  */
310 
311 static void scan_boardinfo(struct spi_master *master)
312 {
313 	struct boardinfo	*bi;
314 
315 	mutex_lock(&board_lock);
316 	list_for_each_entry(bi, &board_list, list) {
317 		struct spi_board_info	*chip = bi->board_info;
318 		unsigned		n;
319 
320 		for (n = bi->n_board_info; n > 0; n--, chip++) {
321 			if (chip->bus_num != master->bus_num)
322 				continue;
323 			/* NOTE: this relies on spi_new_device to
324 			 * issue diagnostics when given bogus inputs
325 			 */
326 			(void) spi_new_device(master, chip);
327 		}
328 	}
329 	mutex_unlock(&board_lock);
330 }
331 
332 /*-------------------------------------------------------------------------*/
333 
334 static void spi_master_release(struct device *dev)
335 {
336 	struct spi_master *master;
337 
338 	master = container_of(dev, struct spi_master, dev);
339 	kfree(master);
340 }
341 
342 static struct class spi_master_class = {
343 	.name		= "spi_master",
344 	.owner		= THIS_MODULE,
345 	.dev_release	= spi_master_release,
346 };
347 
348 
349 /**
350  * spi_alloc_master - allocate SPI master controller
351  * @dev: the controller, possibly using the platform_bus
352  * @size: how much zeroed driver-private data to allocate; the pointer to this
353  *	memory is in the driver_data field of the returned device,
354  *	accessible with spi_master_get_devdata().
355  * Context: can sleep
356  *
357  * This call is used only by SPI master controller drivers, which are the
358  * only ones directly touching chip registers.  It's how they allocate
359  * an spi_master structure, prior to calling spi_register_master().
360  *
361  * This must be called from context that can sleep.  It returns the SPI
362  * master structure on success, else NULL.
363  *
364  * The caller is responsible for assigning the bus number and initializing
365  * the master's methods before calling spi_register_master(); and (after errors
366  * adding the device) calling spi_master_put() to prevent a memory leak.
367  */
368 struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
369 {
370 	struct spi_master	*master;
371 
372 	if (!dev)
373 		return NULL;
374 
375 	master = kzalloc(size + sizeof *master, GFP_KERNEL);
376 	if (!master)
377 		return NULL;
378 
379 	device_initialize(&master->dev);
380 	master->dev.class = &spi_master_class;
381 	master->dev.parent = get_device(dev);
382 	spi_master_set_devdata(master, &master[1]);
383 
384 	return master;
385 }
386 EXPORT_SYMBOL_GPL(spi_alloc_master);
387 
388 /**
389  * spi_register_master - register SPI master controller
390  * @master: initialized master, originally from spi_alloc_master()
391  * Context: can sleep
392  *
393  * SPI master controllers connect to their drivers using some non-SPI bus,
394  * such as the platform bus.  The final stage of probe() in that code
395  * includes calling spi_register_master() to hook up to this SPI bus glue.
396  *
397  * SPI controllers use board specific (often SOC specific) bus numbers,
398  * and board-specific addressing for SPI devices combines those numbers
399  * with chip select numbers.  Since SPI does not directly support dynamic
400  * device identification, boards need configuration tables telling which
401  * chip is at which address.
402  *
403  * This must be called from context that can sleep.  It returns zero on
404  * success, else a negative error code (dropping the master's refcount).
405  * After a successful return, the caller is responsible for calling
406  * spi_unregister_master().
407  */
408 int spi_register_master(struct spi_master *master)
409 {
410 	static atomic_t		dyn_bus_id = ATOMIC_INIT((1<<15) - 1);
411 	struct device		*dev = master->dev.parent;
412 	int			status = -ENODEV;
413 	int			dynamic = 0;
414 
415 	if (!dev)
416 		return -ENODEV;
417 
418 	/* even if it's just one always-selected device, there must
419 	 * be at least one chipselect
420 	 */
421 	if (master->num_chipselect == 0)
422 		return -EINVAL;
423 
424 	/* convention:  dynamically assigned bus IDs count down from the max */
425 	if (master->bus_num < 0) {
426 		/* FIXME switch to an IDR based scheme, something like
427 		 * I2C now uses, so we can't run out of "dynamic" IDs
428 		 */
429 		master->bus_num = atomic_dec_return(&dyn_bus_id);
430 		dynamic = 1;
431 	}
432 
433 	/* register the device, then userspace will see it.
434 	 * registration fails if the bus ID is in use.
435 	 */
436 	snprintf(master->dev.bus_id, sizeof master->dev.bus_id,
437 		"spi%u", master->bus_num);
438 	status = device_add(&master->dev);
439 	if (status < 0)
440 		goto done;
441 	dev_dbg(dev, "registered master %s%s\n", master->dev.bus_id,
442 			dynamic ? " (dynamic)" : "");
443 
444 	/* populate children from any spi device tables */
445 	scan_boardinfo(master);
446 	status = 0;
447 done:
448 	return status;
449 }
450 EXPORT_SYMBOL_GPL(spi_register_master);
451 
452 
453 static int __unregister(struct device *dev, void *master_dev)
454 {
455 	/* note: before about 2.6.14-rc1 this would corrupt memory: */
456 	if (dev != master_dev)
457 		spi_unregister_device(to_spi_device(dev));
458 	return 0;
459 }
460 
461 /**
462  * spi_unregister_master - unregister SPI master controller
463  * @master: the master being unregistered
464  * Context: can sleep
465  *
466  * This call is used only by SPI master controller drivers, which are the
467  * only ones directly touching chip registers.
468  *
469  * This must be called from context that can sleep.
470  */
471 void spi_unregister_master(struct spi_master *master)
472 {
473 	int dummy;
474 
475 	dummy = device_for_each_child(master->dev.parent, &master->dev,
476 					__unregister);
477 	device_unregister(&master->dev);
478 }
479 EXPORT_SYMBOL_GPL(spi_unregister_master);
480 
481 static int __spi_master_match(struct device *dev, void *data)
482 {
483 	struct spi_master *m;
484 	u16 *bus_num = data;
485 
486 	m = container_of(dev, struct spi_master, dev);
487 	return m->bus_num == *bus_num;
488 }
489 
490 /**
491  * spi_busnum_to_master - look up master associated with bus_num
492  * @bus_num: the master's bus number
493  * Context: can sleep
494  *
495  * This call may be used with devices that are registered after
496  * arch init time.  It returns a refcounted pointer to the relevant
497  * spi_master (which the caller must release), or NULL if there is
498  * no such master registered.
499  */
500 struct spi_master *spi_busnum_to_master(u16 bus_num)
501 {
502 	struct device		*dev;
503 	struct spi_master	*master = NULL;
504 
505 	dev = class_find_device(&spi_master_class, &bus_num,
506 				__spi_master_match);
507 	if (dev)
508 		master = container_of(dev, struct spi_master, dev);
509 	/* reference got in class_find_device */
510 	return master;
511 }
512 EXPORT_SYMBOL_GPL(spi_busnum_to_master);
513 
514 
515 /*-------------------------------------------------------------------------*/
516 
517 static void spi_complete(void *arg)
518 {
519 	complete(arg);
520 }
521 
522 /**
523  * spi_sync - blocking/synchronous SPI data transfers
524  * @spi: device with which data will be exchanged
525  * @message: describes the data transfers
526  * Context: can sleep
527  *
528  * This call may only be used from a context that may sleep.  The sleep
529  * is non-interruptible, and has no timeout.  Low-overhead controller
530  * drivers may DMA directly into and out of the message buffers.
531  *
532  * Note that the SPI device's chip select is active during the message,
533  * and then is normally disabled between messages.  Drivers for some
534  * frequently-used devices may want to minimize costs of selecting a chip,
535  * by leaving it selected in anticipation that the next message will go
536  * to the same chip.  (That may increase power usage.)
537  *
538  * Also, the caller is guaranteeing that the memory associated with the
539  * message will not be freed before this call returns.
540  *
541  * It returns zero on success, else a negative error code.
542  */
543 int spi_sync(struct spi_device *spi, struct spi_message *message)
544 {
545 	DECLARE_COMPLETION_ONSTACK(done);
546 	int status;
547 
548 	message->complete = spi_complete;
549 	message->context = &done;
550 	status = spi_async(spi, message);
551 	if (status == 0) {
552 		wait_for_completion(&done);
553 		status = message->status;
554 	}
555 	message->context = NULL;
556 	return status;
557 }
558 EXPORT_SYMBOL_GPL(spi_sync);
559 
560 /* portable code must never pass more than 32 bytes */
561 #define	SPI_BUFSIZ	max(32,SMP_CACHE_BYTES)
562 
563 static u8	*buf;
564 
565 /**
566  * spi_write_then_read - SPI synchronous write followed by read
567  * @spi: device with which data will be exchanged
568  * @txbuf: data to be written (need not be dma-safe)
569  * @n_tx: size of txbuf, in bytes
570  * @rxbuf: buffer into which data will be read
571  * @n_rx: size of rxbuf, in bytes (need not be dma-safe)
572  * Context: can sleep
573  *
574  * This performs a half duplex MicroWire style transaction with the
575  * device, sending txbuf and then reading rxbuf.  The return value
576  * is zero for success, else a negative errno status code.
577  * This call may only be used from a context that may sleep.
578  *
579  * Parameters to this routine are always copied using a small buffer;
580  * portable code should never use this for more than 32 bytes.
581  * Performance-sensitive or bulk transfer code should instead use
582  * spi_{async,sync}() calls with dma-safe buffers.
583  */
584 int spi_write_then_read(struct spi_device *spi,
585 		const u8 *txbuf, unsigned n_tx,
586 		u8 *rxbuf, unsigned n_rx)
587 {
588 	static DEFINE_MUTEX(lock);
589 
590 	int			status;
591 	struct spi_message	message;
592 	struct spi_transfer	x[2];
593 	u8			*local_buf;
594 
595 	/* Use preallocated DMA-safe buffer.  We can't avoid copying here,
596 	 * (as a pure convenience thing), but we can keep heap costs
597 	 * out of the hot path ...
598 	 */
599 	if ((n_tx + n_rx) > SPI_BUFSIZ)
600 		return -EINVAL;
601 
602 	spi_message_init(&message);
603 	memset(x, 0, sizeof x);
604 	if (n_tx) {
605 		x[0].len = n_tx;
606 		spi_message_add_tail(&x[0], &message);
607 	}
608 	if (n_rx) {
609 		x[1].len = n_rx;
610 		spi_message_add_tail(&x[1], &message);
611 	}
612 
613 	/* ... unless someone else is using the pre-allocated buffer */
614 	if (!mutex_trylock(&lock)) {
615 		local_buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
616 		if (!local_buf)
617 			return -ENOMEM;
618 	} else
619 		local_buf = buf;
620 
621 	memcpy(local_buf, txbuf, n_tx);
622 	x[0].tx_buf = local_buf;
623 	x[1].rx_buf = local_buf + n_tx;
624 
625 	/* do the i/o */
626 	status = spi_sync(spi, &message);
627 	if (status == 0)
628 		memcpy(rxbuf, x[1].rx_buf, n_rx);
629 
630 	if (x[0].tx_buf == buf)
631 		mutex_unlock(&lock);
632 	else
633 		kfree(local_buf);
634 
635 	return status;
636 }
637 EXPORT_SYMBOL_GPL(spi_write_then_read);
638 
639 /*-------------------------------------------------------------------------*/
640 
641 static int __init spi_init(void)
642 {
643 	int	status;
644 
645 	buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
646 	if (!buf) {
647 		status = -ENOMEM;
648 		goto err0;
649 	}
650 
651 	status = bus_register(&spi_bus_type);
652 	if (status < 0)
653 		goto err1;
654 
655 	status = class_register(&spi_master_class);
656 	if (status < 0)
657 		goto err2;
658 	return 0;
659 
660 err2:
661 	bus_unregister(&spi_bus_type);
662 err1:
663 	kfree(buf);
664 	buf = NULL;
665 err0:
666 	return status;
667 }
668 
669 /* board_info is normally registered in arch_initcall(),
670  * but even essential drivers wait till later
671  *
672  * REVISIT only boardinfo really needs static linking. the rest (device and
673  * driver registration) _could_ be dynamically linked (modular) ... costs
674  * include needing to have boardinfo data structures be much more public.
675  */
676 subsys_initcall(spi_init);
677 
678