blob: 88425e1af4d353fcc0ce14c0dd29c130c770f7f1 [file] [log] [blame]
David Brownell9904f222006-01-08 13:34:26 -08001/*
2 * spi_bitbang.c - polling/bitbanging SPI master controller driver utilities
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17 */
18
David Brownell9904f222006-01-08 13:34:26 -080019#include <linux/init.h>
20#include <linux/spinlock.h>
21#include <linux/workqueue.h>
22#include <linux/interrupt.h>
23#include <linux/delay.h>
24#include <linux/errno.h>
25#include <linux/platform_device.h>
26
27#include <linux/spi/spi.h>
28#include <linux/spi/spi_bitbang.h>
29
30
31/*----------------------------------------------------------------------*/
32
33/*
34 * FIRST PART (OPTIONAL): word-at-a-time spi_transfer support.
35 * Use this for GPIO or shift-register level hardware APIs.
36 *
37 * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
38 * to glue code. These bitbang setup() and cleanup() routines are always
39 * used, though maybe they're called from controller-aware code.
40 *
41 * chipselect() and friends may use use spi_device->controller_data and
42 * controller registers as appropriate.
43 *
44 *
45 * NOTE: SPI controller pins can often be used as GPIO pins instead,
46 * which means you could use a bitbang driver either to get hardware
47 * working quickly, or testing for differences that aren't speed related.
48 */
49
50struct spi_bitbang_cs {
51 unsigned nsecs; /* (clock cycle time)/2 */
52 u32 (*txrx_word)(struct spi_device *spi, unsigned nsecs,
53 u32 word, u8 bits);
54 unsigned (*txrx_bufs)(struct spi_device *,
55 u32 (*txrx_word)(
56 struct spi_device *spi,
57 unsigned nsecs,
58 u32 word, u8 bits),
59 unsigned, struct spi_transfer *);
60};
61
62static unsigned bitbang_txrx_8(
63 struct spi_device *spi,
64 u32 (*txrx_word)(struct spi_device *spi,
65 unsigned nsecs,
66 u32 word, u8 bits),
67 unsigned ns,
68 struct spi_transfer *t
69) {
70 unsigned bits = spi->bits_per_word;
71 unsigned count = t->len;
72 const u8 *tx = t->tx_buf;
73 u8 *rx = t->rx_buf;
74
75 while (likely(count > 0)) {
76 u8 word = 0;
77
78 if (tx)
79 word = *tx++;
80 word = txrx_word(spi, ns, word, bits);
81 if (rx)
82 *rx++ = word;
83 count -= 1;
84 }
85 return t->len - count;
86}
87
88static unsigned bitbang_txrx_16(
89 struct spi_device *spi,
90 u32 (*txrx_word)(struct spi_device *spi,
91 unsigned nsecs,
92 u32 word, u8 bits),
93 unsigned ns,
94 struct spi_transfer *t
95) {
96 unsigned bits = spi->bits_per_word;
97 unsigned count = t->len;
98 const u16 *tx = t->tx_buf;
99 u16 *rx = t->rx_buf;
100
101 while (likely(count > 1)) {
102 u16 word = 0;
103
104 if (tx)
105 word = *tx++;
106 word = txrx_word(spi, ns, word, bits);
107 if (rx)
108 *rx++ = word;
109 count -= 2;
110 }
111 return t->len - count;
112}
113
114static unsigned bitbang_txrx_32(
115 struct spi_device *spi,
116 u32 (*txrx_word)(struct spi_device *spi,
117 unsigned nsecs,
118 u32 word, u8 bits),
119 unsigned ns,
120 struct spi_transfer *t
121) {
122 unsigned bits = spi->bits_per_word;
123 unsigned count = t->len;
124 const u32 *tx = t->tx_buf;
125 u32 *rx = t->rx_buf;
126
127 while (likely(count > 3)) {
128 u32 word = 0;
129
130 if (tx)
131 word = *tx++;
132 word = txrx_word(spi, ns, word, bits);
133 if (rx)
134 *rx++ = word;
135 count -= 4;
136 }
137 return t->len - count;
138}
139
Kumar Galaff9f4772006-04-02 16:06:35 -0500140int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
Imre Deak4cff33f2006-02-17 10:02:18 -0800141{
142 struct spi_bitbang_cs *cs = spi->controller_state;
143 u8 bits_per_word;
144 u32 hz;
145
146 if (t) {
147 bits_per_word = t->bits_per_word;
148 hz = t->speed_hz;
149 } else {
150 bits_per_word = 0;
151 hz = 0;
152 }
153
154 /* spi_transfer level calls that work per-word */
155 if (!bits_per_word)
156 bits_per_word = spi->bits_per_word;
157 if (bits_per_word <= 8)
158 cs->txrx_bufs = bitbang_txrx_8;
159 else if (bits_per_word <= 16)
160 cs->txrx_bufs = bitbang_txrx_16;
161 else if (bits_per_word <= 32)
162 cs->txrx_bufs = bitbang_txrx_32;
163 else
164 return -EINVAL;
165
166 /* nsecs = (clock period)/2 */
167 if (!hz)
168 hz = spi->max_speed_hz;
David Brownell1e316d72006-04-06 22:25:56 -0700169 if (hz) {
170 cs->nsecs = (1000000000/2) / hz;
171 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
172 return -EINVAL;
173 }
Imre Deak4cff33f2006-02-17 10:02:18 -0800174
175 return 0;
176}
Kumar Galaff9f4772006-04-02 16:06:35 -0500177EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
Imre Deak4cff33f2006-02-17 10:02:18 -0800178
David Brownell9904f222006-01-08 13:34:26 -0800179/**
180 * spi_bitbang_setup - default setup for per-word I/O loops
181 */
182int spi_bitbang_setup(struct spi_device *spi)
183{
184 struct spi_bitbang_cs *cs = spi->controller_state;
185 struct spi_bitbang *bitbang;
Imre Deak4cff33f2006-02-17 10:02:18 -0800186 int retval;
David Brownell9904f222006-01-08 13:34:26 -0800187
David Brownellccf77cc2006-04-03 15:46:22 -0700188 bitbang = spi_master_get_devdata(spi->master);
189
190 /* REVISIT: some systems will want to support devices using lsb-first
191 * bit encodings on the wire. In pure software that would be trivial,
192 * just bitbang_txrx_le_cphaX() routines shifting the other way, and
193 * some hardware controllers also have this support.
194 */
195 if ((spi->mode & SPI_LSB_FIRST) != 0)
196 return -EINVAL;
197
David Brownell9904f222006-01-08 13:34:26 -0800198 if (!cs) {
Christoph Lametere94b1762006-12-06 20:33:17 -0800199 cs = kzalloc(sizeof *cs, GFP_KERNEL);
David Brownell9904f222006-01-08 13:34:26 -0800200 if (!cs)
201 return -ENOMEM;
202 spi->controller_state = cs;
203 }
David Brownell9904f222006-01-08 13:34:26 -0800204
205 if (!spi->bits_per_word)
206 spi->bits_per_word = 8;
207
David Brownell9904f222006-01-08 13:34:26 -0800208 /* per-word shift register access, in hardware or bitbanging */
209 cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
210 if (!cs->txrx_word)
211 return -EINVAL;
212
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800213 retval = bitbang->setup_transfer(spi, NULL);
Imre Deak4cff33f2006-02-17 10:02:18 -0800214 if (retval < 0)
215 return retval;
David Brownell9904f222006-01-08 13:34:26 -0800216
David Brownell1e316d72006-04-06 22:25:56 -0700217 dev_dbg(&spi->dev, "%s, mode %d, %u bits/w, %u nsec/bit\n",
David Brownell9904f222006-01-08 13:34:26 -0800218 __FUNCTION__, spi->mode & (SPI_CPOL | SPI_CPHA),
219 spi->bits_per_word, 2 * cs->nsecs);
220
221 /* NOTE we _need_ to call chipselect() early, ideally with adapter
222 * setup, unless the hardware defaults cooperate to avoid confusion
223 * between normal (active low) and inverted chipselects.
224 */
225
226 /* deselect chip (low or high) */
227 spin_lock(&bitbang->lock);
228 if (!bitbang->busy) {
Vitaly Wool8275c642006-01-08 13:34:28 -0800229 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
David Brownell9904f222006-01-08 13:34:26 -0800230 ndelay(cs->nsecs);
231 }
232 spin_unlock(&bitbang->lock);
233
234 return 0;
235}
236EXPORT_SYMBOL_GPL(spi_bitbang_setup);
237
238/**
239 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
240 */
Hans-Peter Nilsson0ffa0282007-02-12 00:52:45 -0800241void spi_bitbang_cleanup(struct spi_device *spi)
David Brownell9904f222006-01-08 13:34:26 -0800242{
243 kfree(spi->controller_state);
244}
245EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
246
247static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
248{
249 struct spi_bitbang_cs *cs = spi->controller_state;
250 unsigned nsecs = cs->nsecs;
251
252 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t);
253}
254
255/*----------------------------------------------------------------------*/
256
257/*
258 * SECOND PART ... simple transfer queue runner.
259 *
260 * This costs a task context per controller, running the queue by
261 * performing each transfer in sequence. Smarter hardware can queue
262 * several DMA transfers at once, and process several controller queues
263 * in parallel; this driver doesn't match such hardware very well.
264 *
265 * Drivers can provide word-at-a-time i/o primitives, or provide
266 * transfer-at-a-time ones to leverage dma or fifo hardware.
267 */
David Howellsc4028952006-11-22 14:57:56 +0000268static void bitbang_work(struct work_struct *work)
David Brownell9904f222006-01-08 13:34:26 -0800269{
David Howellsc4028952006-11-22 14:57:56 +0000270 struct spi_bitbang *bitbang =
271 container_of(work, struct spi_bitbang, work);
David Brownell9904f222006-01-08 13:34:26 -0800272 unsigned long flags;
273
274 spin_lock_irqsave(&bitbang->lock, flags);
275 bitbang->busy = 1;
276 while (!list_empty(&bitbang->queue)) {
277 struct spi_message *m;
278 struct spi_device *spi;
279 unsigned nsecs;
Vitaly Wool8275c642006-01-08 13:34:28 -0800280 struct spi_transfer *t = NULL;
David Brownell9904f222006-01-08 13:34:26 -0800281 unsigned tmp;
Vitaly Wool8275c642006-01-08 13:34:28 -0800282 unsigned cs_change;
David Brownell9904f222006-01-08 13:34:26 -0800283 int status;
Imre Deak4cff33f2006-02-17 10:02:18 -0800284 int (*setup_transfer)(struct spi_device *,
285 struct spi_transfer *);
David Brownell9904f222006-01-08 13:34:26 -0800286
287 m = container_of(bitbang->queue.next, struct spi_message,
288 queue);
289 list_del_init(&m->queue);
290 spin_unlock_irqrestore(&bitbang->lock, flags);
291
Vitaly Wool8275c642006-01-08 13:34:28 -0800292 /* FIXME this is made-up ... the correct value is known to
293 * word-at-a-time bitbang code, and presumably chipselect()
294 * should enforce these requirements too?
295 */
296 nsecs = 100;
David Brownell9904f222006-01-08 13:34:26 -0800297
298 spi = m->spi;
David Brownell9904f222006-01-08 13:34:26 -0800299 tmp = 0;
Vitaly Wool8275c642006-01-08 13:34:28 -0800300 cs_change = 1;
David Brownell9904f222006-01-08 13:34:26 -0800301 status = 0;
Imre Deak4cff33f2006-02-17 10:02:18 -0800302 setup_transfer = NULL;
David Brownell9904f222006-01-08 13:34:26 -0800303
Vitaly Wool8275c642006-01-08 13:34:28 -0800304 list_for_each_entry (t, &m->transfers, transfer_list) {
David Brownell9904f222006-01-08 13:34:26 -0800305
Imre Deak4cff33f2006-02-17 10:02:18 -0800306 /* override or restore speed and wordsize */
307 if (t->speed_hz || t->bits_per_word) {
308 setup_transfer = bitbang->setup_transfer;
309 if (!setup_transfer) {
310 status = -ENOPROTOOPT;
311 break;
312 }
313 }
314 if (setup_transfer) {
315 status = setup_transfer(spi, t);
316 if (status < 0)
317 break;
318 }
319
Vitaly Wool8275c642006-01-08 13:34:28 -0800320 /* set up default clock polarity, and activate chip;
321 * this implicitly updates clock and spi modes as
322 * previously recorded for this device via setup().
323 * (and also deselects any other chip that might be
324 * selected ...)
325 */
326 if (cs_change) {
327 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
David Brownell9904f222006-01-08 13:34:26 -0800328 ndelay(nsecs);
329 }
Vitaly Wool8275c642006-01-08 13:34:28 -0800330 cs_change = t->cs_change;
David Brownell9904f222006-01-08 13:34:26 -0800331 if (!t->tx_buf && !t->rx_buf && t->len) {
332 status = -EINVAL;
333 break;
334 }
335
Vitaly Wool8275c642006-01-08 13:34:28 -0800336 /* transfer data. the lower level code handles any
337 * new dma mappings it needs. our caller always gave
338 * us dma-safe buffers.
339 */
David Brownell9904f222006-01-08 13:34:26 -0800340 if (t->len) {
Vitaly Wool8275c642006-01-08 13:34:28 -0800341 /* REVISIT dma API still needs a designated
342 * DMA_ADDR_INVALID; ~0 might be better.
David Brownell9904f222006-01-08 13:34:26 -0800343 */
Vitaly Wool8275c642006-01-08 13:34:28 -0800344 if (!m->is_dma_mapped)
345 t->rx_dma = t->tx_dma = 0;
David Brownell9904f222006-01-08 13:34:26 -0800346 status = bitbang->txrx_bufs(spi, t);
347 }
348 if (status != t->len) {
349 if (status > 0)
350 status = -EMSGSIZE;
351 break;
352 }
353 m->actual_length += status;
354 status = 0;
355
356 /* protocol tweaks before next transfer */
357 if (t->delay_usecs)
358 udelay(t->delay_usecs);
359
Vitaly Wool8275c642006-01-08 13:34:28 -0800360 if (!cs_change)
361 continue;
362 if (t->transfer_list.next == &m->transfers)
David Brownell9904f222006-01-08 13:34:26 -0800363 break;
364
Vitaly Wool8275c642006-01-08 13:34:28 -0800365 /* sometimes a short mid-message deselect of the chip
366 * may be needed to terminate a mode or command
367 */
368 ndelay(nsecs);
369 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
370 ndelay(nsecs);
David Brownell9904f222006-01-08 13:34:26 -0800371 }
372
David Brownell9904f222006-01-08 13:34:26 -0800373 m->status = status;
374 m->complete(m->context);
375
Imre Deak4cff33f2006-02-17 10:02:18 -0800376 /* restore speed and wordsize */
377 if (setup_transfer)
378 setup_transfer(spi, NULL);
379
Vitaly Wool8275c642006-01-08 13:34:28 -0800380 /* normally deactivate chipselect ... unless no error and
381 * cs_change has hinted that the next message will probably
382 * be for this chip too.
383 */
384 if (!(status == 0 && cs_change)) {
385 ndelay(nsecs);
386 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
387 ndelay(nsecs);
388 }
David Brownell9904f222006-01-08 13:34:26 -0800389
390 spin_lock_irqsave(&bitbang->lock, flags);
391 }
392 bitbang->busy = 0;
393 spin_unlock_irqrestore(&bitbang->lock, flags);
394}
395
396/**
397 * spi_bitbang_transfer - default submit to transfer queue
398 */
399int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m)
400{
401 struct spi_bitbang *bitbang;
402 unsigned long flags;
David Brownell1e316d72006-04-06 22:25:56 -0700403 int status = 0;
David Brownell9904f222006-01-08 13:34:26 -0800404
405 m->actual_length = 0;
406 m->status = -EINPROGRESS;
407
408 bitbang = spi_master_get_devdata(spi->master);
David Brownell9904f222006-01-08 13:34:26 -0800409
410 spin_lock_irqsave(&bitbang->lock, flags);
David Brownell1e316d72006-04-06 22:25:56 -0700411 if (!spi->max_speed_hz)
412 status = -ENETDOWN;
413 else {
414 list_add_tail(&m->queue, &bitbang->queue);
415 queue_work(bitbang->workqueue, &bitbang->work);
416 }
David Brownell9904f222006-01-08 13:34:26 -0800417 spin_unlock_irqrestore(&bitbang->lock, flags);
418
David Brownell1e316d72006-04-06 22:25:56 -0700419 return status;
David Brownell9904f222006-01-08 13:34:26 -0800420}
421EXPORT_SYMBOL_GPL(spi_bitbang_transfer);
422
423/*----------------------------------------------------------------------*/
424
425/**
426 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
427 * @bitbang: driver handle
428 *
429 * Caller should have zero-initialized all parts of the structure, and then
430 * provided callbacks for chip selection and I/O loops. If the master has
431 * a transfer method, its final step should call spi_bitbang_transfer; or,
432 * that's the default if the transfer routine is not initialized. It should
433 * also set up the bus number and number of chipselects.
434 *
435 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
436 * hardware that basically exposes a shift register) or per-spi_transfer
437 * (which takes better advantage of hardware like fifos or DMA engines).
438 *
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800439 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
440 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
441 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
442 * routine isn't initialized.
David Brownell9904f222006-01-08 13:34:26 -0800443 *
444 * This routine registers the spi_master, which will process requests in a
445 * dedicated task, keeping IRQs unblocked most of the time. To stop
446 * processing those requests, call spi_bitbang_stop().
447 */
448int spi_bitbang_start(struct spi_bitbang *bitbang)
449{
450 int status;
451
452 if (!bitbang->master || !bitbang->chipselect)
453 return -EINVAL;
454
David Howellsc4028952006-11-22 14:57:56 +0000455 INIT_WORK(&bitbang->work, bitbang_work);
David Brownell9904f222006-01-08 13:34:26 -0800456 spin_lock_init(&bitbang->lock);
457 INIT_LIST_HEAD(&bitbang->queue);
458
459 if (!bitbang->master->transfer)
460 bitbang->master->transfer = spi_bitbang_transfer;
461 if (!bitbang->txrx_bufs) {
462 bitbang->use_dma = 0;
463 bitbang->txrx_bufs = spi_bitbang_bufs;
464 if (!bitbang->master->setup) {
Kumar Galaff9f4772006-04-02 16:06:35 -0500465 if (!bitbang->setup_transfer)
466 bitbang->setup_transfer =
467 spi_bitbang_setup_transfer;
David Brownell9904f222006-01-08 13:34:26 -0800468 bitbang->master->setup = spi_bitbang_setup;
469 bitbang->master->cleanup = spi_bitbang_cleanup;
470 }
471 } else if (!bitbang->master->setup)
472 return -EINVAL;
473
474 /* this task is the only thing to touch the SPI bits */
475 bitbang->busy = 0;
476 bitbang->workqueue = create_singlethread_workqueue(
Greg Kroah-Hartman07b24632007-02-07 21:34:08 -0800477 bitbang->master->cdev.dev->bus_id);
David Brownell9904f222006-01-08 13:34:26 -0800478 if (bitbang->workqueue == NULL) {
479 status = -EBUSY;
480 goto err1;
481 }
482
483 /* driver may get busy before register() returns, especially
484 * if someone registered boardinfo for devices
485 */
486 status = spi_register_master(bitbang->master);
487 if (status < 0)
488 goto err2;
489
490 return status;
491
492err2:
493 destroy_workqueue(bitbang->workqueue);
494err1:
495 return status;
496}
497EXPORT_SYMBOL_GPL(spi_bitbang_start);
498
499/**
500 * spi_bitbang_stop - stops the task providing spi communication
501 */
502int spi_bitbang_stop(struct spi_bitbang *bitbang)
503{
Chris Lesiaka836f582007-03-16 13:38:13 -0800504 spi_unregister_master(bitbang->master);
David Brownell9904f222006-01-08 13:34:26 -0800505
Chris Lesiaka836f582007-03-16 13:38:13 -0800506 WARN_ON(!list_empty(&bitbang->queue));
David Brownell9904f222006-01-08 13:34:26 -0800507
508 destroy_workqueue(bitbang->workqueue);
509
David Brownell9904f222006-01-08 13:34:26 -0800510 return 0;
511}
512EXPORT_SYMBOL_GPL(spi_bitbang_stop);
513
514MODULE_LICENSE("GPL");
515