blob: 85e61f451218418849eb35376aeccc7f09094c9d [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 Brownelld52df2e2008-01-08 15:32:40 -0800187 unsigned long flags;
David Brownell9904f222006-01-08 13:34:26 -0800188
David Brownellccf77cc2006-04-03 15:46:22 -0700189 bitbang = spi_master_get_devdata(spi->master);
190
David Brownelldccd5732007-07-17 04:04:02 -0700191 /* Bitbangers can support SPI_CS_HIGH, SPI_3WIRE, and so on;
192 * add those to master->flags, and provide the other support.
David Brownellccf77cc2006-04-03 15:46:22 -0700193 */
David Brownelldccd5732007-07-17 04:04:02 -0700194 if ((spi->mode & ~(SPI_CPOL|SPI_CPHA|bitbang->flags)) != 0)
David Brownellccf77cc2006-04-03 15:46:22 -0700195 return -EINVAL;
196
David Brownell9904f222006-01-08 13:34:26 -0800197 if (!cs) {
Christoph Lametere94b1762006-12-06 20:33:17 -0800198 cs = kzalloc(sizeof *cs, GFP_KERNEL);
David Brownell9904f222006-01-08 13:34:26 -0800199 if (!cs)
200 return -ENOMEM;
201 spi->controller_state = cs;
202 }
David Brownell9904f222006-01-08 13:34:26 -0800203
204 if (!spi->bits_per_word)
205 spi->bits_per_word = 8;
206
David Brownell9904f222006-01-08 13:34:26 -0800207 /* per-word shift register access, in hardware or bitbanging */
208 cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
209 if (!cs->txrx_word)
210 return -EINVAL;
211
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800212 retval = bitbang->setup_transfer(spi, NULL);
Imre Deak4cff33f2006-02-17 10:02:18 -0800213 if (retval < 0)
214 return retval;
David Brownell9904f222006-01-08 13:34:26 -0800215
David Brownell1e316d72006-04-06 22:25:56 -0700216 dev_dbg(&spi->dev, "%s, mode %d, %u bits/w, %u nsec/bit\n",
Harvey Harrisonb687d2a2008-04-28 02:14:19 -0700217 __func__, spi->mode & (SPI_CPOL | SPI_CPHA),
David Brownell9904f222006-01-08 13:34:26 -0800218 spi->bits_per_word, 2 * cs->nsecs);
219
220 /* NOTE we _need_ to call chipselect() early, ideally with adapter
221 * setup, unless the hardware defaults cooperate to avoid confusion
222 * between normal (active low) and inverted chipselects.
223 */
224
225 /* deselect chip (low or high) */
David Brownelld52df2e2008-01-08 15:32:40 -0800226 spin_lock_irqsave(&bitbang->lock, flags);
David Brownell9904f222006-01-08 13:34:26 -0800227 if (!bitbang->busy) {
Vitaly Wool8275c642006-01-08 13:34:28 -0800228 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
David Brownell9904f222006-01-08 13:34:26 -0800229 ndelay(cs->nsecs);
230 }
David Brownelld52df2e2008-01-08 15:32:40 -0800231 spin_unlock_irqrestore(&bitbang->lock, flags);
David Brownell9904f222006-01-08 13:34:26 -0800232
233 return 0;
234}
235EXPORT_SYMBOL_GPL(spi_bitbang_setup);
236
237/**
238 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
239 */
Hans-Peter Nilsson0ffa0282007-02-12 00:52:45 -0800240void spi_bitbang_cleanup(struct spi_device *spi)
David Brownell9904f222006-01-08 13:34:26 -0800241{
242 kfree(spi->controller_state);
243}
244EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
245
246static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
247{
248 struct spi_bitbang_cs *cs = spi->controller_state;
249 unsigned nsecs = cs->nsecs;
250
251 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t);
252}
253
254/*----------------------------------------------------------------------*/
255
256/*
257 * SECOND PART ... simple transfer queue runner.
258 *
259 * This costs a task context per controller, running the queue by
260 * performing each transfer in sequence. Smarter hardware can queue
261 * several DMA transfers at once, and process several controller queues
262 * in parallel; this driver doesn't match such hardware very well.
263 *
264 * Drivers can provide word-at-a-time i/o primitives, or provide
265 * transfer-at-a-time ones to leverage dma or fifo hardware.
266 */
David Howellsc4028952006-11-22 14:57:56 +0000267static void bitbang_work(struct work_struct *work)
David Brownell9904f222006-01-08 13:34:26 -0800268{
David Howellsc4028952006-11-22 14:57:56 +0000269 struct spi_bitbang *bitbang =
270 container_of(work, struct spi_bitbang, work);
David Brownell9904f222006-01-08 13:34:26 -0800271 unsigned long flags;
272
273 spin_lock_irqsave(&bitbang->lock, flags);
274 bitbang->busy = 1;
275 while (!list_empty(&bitbang->queue)) {
276 struct spi_message *m;
277 struct spi_device *spi;
278 unsigned nsecs;
Vitaly Wool8275c642006-01-08 13:34:28 -0800279 struct spi_transfer *t = NULL;
David Brownell9904f222006-01-08 13:34:26 -0800280 unsigned tmp;
Vitaly Wool8275c642006-01-08 13:34:28 -0800281 unsigned cs_change;
David Brownell9904f222006-01-08 13:34:26 -0800282 int status;
Imre Deak4cff33f2006-02-17 10:02:18 -0800283 int (*setup_transfer)(struct spi_device *,
284 struct spi_transfer *);
David Brownell9904f222006-01-08 13:34:26 -0800285
286 m = container_of(bitbang->queue.next, struct spi_message,
287 queue);
288 list_del_init(&m->queue);
289 spin_unlock_irqrestore(&bitbang->lock, flags);
290
Vitaly Wool8275c642006-01-08 13:34:28 -0800291 /* FIXME this is made-up ... the correct value is known to
292 * word-at-a-time bitbang code, and presumably chipselect()
293 * should enforce these requirements too?
294 */
295 nsecs = 100;
David Brownell9904f222006-01-08 13:34:26 -0800296
297 spi = m->spi;
David Brownell9904f222006-01-08 13:34:26 -0800298 tmp = 0;
Vitaly Wool8275c642006-01-08 13:34:28 -0800299 cs_change = 1;
David Brownell9904f222006-01-08 13:34:26 -0800300 status = 0;
Imre Deak4cff33f2006-02-17 10:02:18 -0800301 setup_transfer = NULL;
David Brownell9904f222006-01-08 13:34:26 -0800302
Vitaly Wool8275c642006-01-08 13:34:28 -0800303 list_for_each_entry (t, &m->transfers, transfer_list) {
David Brownell9904f222006-01-08 13:34:26 -0800304
Imre Deak4cff33f2006-02-17 10:02:18 -0800305 /* override or restore speed and wordsize */
306 if (t->speed_hz || t->bits_per_word) {
307 setup_transfer = bitbang->setup_transfer;
308 if (!setup_transfer) {
309 status = -ENOPROTOOPT;
310 break;
311 }
312 }
313 if (setup_transfer) {
314 status = setup_transfer(spi, t);
315 if (status < 0)
316 break;
317 }
318
Vitaly Wool8275c642006-01-08 13:34:28 -0800319 /* set up default clock polarity, and activate chip;
320 * this implicitly updates clock and spi modes as
321 * previously recorded for this device via setup().
322 * (and also deselects any other chip that might be
323 * selected ...)
324 */
325 if (cs_change) {
326 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
David Brownell9904f222006-01-08 13:34:26 -0800327 ndelay(nsecs);
328 }
Vitaly Wool8275c642006-01-08 13:34:28 -0800329 cs_change = t->cs_change;
David Brownell9904f222006-01-08 13:34:26 -0800330 if (!t->tx_buf && !t->rx_buf && t->len) {
331 status = -EINVAL;
332 break;
333 }
334
Vitaly Wool8275c642006-01-08 13:34:28 -0800335 /* transfer data. the lower level code handles any
336 * new dma mappings it needs. our caller always gave
337 * us dma-safe buffers.
338 */
David Brownell9904f222006-01-08 13:34:26 -0800339 if (t->len) {
Vitaly Wool8275c642006-01-08 13:34:28 -0800340 /* REVISIT dma API still needs a designated
341 * DMA_ADDR_INVALID; ~0 might be better.
David Brownell9904f222006-01-08 13:34:26 -0800342 */
Vitaly Wool8275c642006-01-08 13:34:28 -0800343 if (!m->is_dma_mapped)
344 t->rx_dma = t->tx_dma = 0;
David Brownell9904f222006-01-08 13:34:26 -0800345 status = bitbang->txrx_bufs(spi, t);
346 }
Jan Nikitenko2cfb8ce2008-03-13 12:32:39 -0700347 if (status > 0)
348 m->actual_length += status;
David Brownell9904f222006-01-08 13:34:26 -0800349 if (status != t->len) {
Jan Nikitenko2cfb8ce2008-03-13 12:32:39 -0700350 /* always report some kind of error */
351 if (status >= 0)
352 status = -EREMOTEIO;
David Brownell9904f222006-01-08 13:34:26 -0800353 break;
354 }
David Brownell9904f222006-01-08 13:34:26 -0800355 status = 0;
356
357 /* protocol tweaks before next transfer */
358 if (t->delay_usecs)
359 udelay(t->delay_usecs);
360
Vitaly Wool8275c642006-01-08 13:34:28 -0800361 if (!cs_change)
362 continue;
363 if (t->transfer_list.next == &m->transfers)
David Brownell9904f222006-01-08 13:34:26 -0800364 break;
365
Vitaly Wool8275c642006-01-08 13:34:28 -0800366 /* sometimes a short mid-message deselect of the chip
367 * may be needed to terminate a mode or command
368 */
369 ndelay(nsecs);
370 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
371 ndelay(nsecs);
David Brownell9904f222006-01-08 13:34:26 -0800372 }
373
David Brownell9904f222006-01-08 13:34:26 -0800374 m->status = status;
375 m->complete(m->context);
376
Imre Deak4cff33f2006-02-17 10:02:18 -0800377 /* restore speed and wordsize */
378 if (setup_transfer)
379 setup_transfer(spi, NULL);
380
Vitaly Wool8275c642006-01-08 13:34:28 -0800381 /* normally deactivate chipselect ... unless no error and
382 * cs_change has hinted that the next message will probably
383 * be for this chip too.
384 */
385 if (!(status == 0 && cs_change)) {
386 ndelay(nsecs);
387 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
388 ndelay(nsecs);
389 }
David Brownell9904f222006-01-08 13:34:26 -0800390
391 spin_lock_irqsave(&bitbang->lock, flags);
392 }
393 bitbang->busy = 0;
394 spin_unlock_irqrestore(&bitbang->lock, flags);
395}
396
397/**
398 * spi_bitbang_transfer - default submit to transfer queue
399 */
400int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m)
401{
402 struct spi_bitbang *bitbang;
403 unsigned long flags;
David Brownell1e316d72006-04-06 22:25:56 -0700404 int status = 0;
David Brownell9904f222006-01-08 13:34:26 -0800405
406 m->actual_length = 0;
407 m->status = -EINPROGRESS;
408
409 bitbang = spi_master_get_devdata(spi->master);
David Brownell9904f222006-01-08 13:34:26 -0800410
411 spin_lock_irqsave(&bitbang->lock, flags);
David Brownell1e316d72006-04-06 22:25:56 -0700412 if (!spi->max_speed_hz)
413 status = -ENETDOWN;
414 else {
415 list_add_tail(&m->queue, &bitbang->queue);
416 queue_work(bitbang->workqueue, &bitbang->work);
417 }
David Brownell9904f222006-01-08 13:34:26 -0800418 spin_unlock_irqrestore(&bitbang->lock, flags);
419
David Brownell1e316d72006-04-06 22:25:56 -0700420 return status;
David Brownell9904f222006-01-08 13:34:26 -0800421}
422EXPORT_SYMBOL_GPL(spi_bitbang_transfer);
423
424/*----------------------------------------------------------------------*/
425
426/**
427 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
428 * @bitbang: driver handle
429 *
430 * Caller should have zero-initialized all parts of the structure, and then
431 * provided callbacks for chip selection and I/O loops. If the master has
432 * a transfer method, its final step should call spi_bitbang_transfer; or,
433 * that's the default if the transfer routine is not initialized. It should
434 * also set up the bus number and number of chipselects.
435 *
436 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
437 * hardware that basically exposes a shift register) or per-spi_transfer
438 * (which takes better advantage of hardware like fifos or DMA engines).
439 *
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800440 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
441 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
442 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
443 * routine isn't initialized.
David Brownell9904f222006-01-08 13:34:26 -0800444 *
445 * This routine registers the spi_master, which will process requests in a
446 * dedicated task, keeping IRQs unblocked most of the time. To stop
447 * processing those requests, call spi_bitbang_stop().
448 */
449int spi_bitbang_start(struct spi_bitbang *bitbang)
450{
451 int status;
452
453 if (!bitbang->master || !bitbang->chipselect)
454 return -EINVAL;
455
David Howellsc4028952006-11-22 14:57:56 +0000456 INIT_WORK(&bitbang->work, bitbang_work);
David Brownell9904f222006-01-08 13:34:26 -0800457 spin_lock_init(&bitbang->lock);
458 INIT_LIST_HEAD(&bitbang->queue);
459
460 if (!bitbang->master->transfer)
461 bitbang->master->transfer = spi_bitbang_transfer;
462 if (!bitbang->txrx_bufs) {
463 bitbang->use_dma = 0;
464 bitbang->txrx_bufs = spi_bitbang_bufs;
465 if (!bitbang->master->setup) {
Kumar Galaff9f4772006-04-02 16:06:35 -0500466 if (!bitbang->setup_transfer)
467 bitbang->setup_transfer =
468 spi_bitbang_setup_transfer;
David Brownell9904f222006-01-08 13:34:26 -0800469 bitbang->master->setup = spi_bitbang_setup;
470 bitbang->master->cleanup = spi_bitbang_cleanup;
471 }
472 } else if (!bitbang->master->setup)
473 return -EINVAL;
474
475 /* this task is the only thing to touch the SPI bits */
476 bitbang->busy = 0;
477 bitbang->workqueue = create_singlethread_workqueue(
Kay Sievers35f74fc2009-01-06 10:44:37 -0800478 dev_name(bitbang->master->dev.parent));
David Brownell9904f222006-01-08 13:34:26 -0800479 if (bitbang->workqueue == NULL) {
480 status = -EBUSY;
481 goto err1;
482 }
483
484 /* driver may get busy before register() returns, especially
485 * if someone registered boardinfo for devices
486 */
487 status = spi_register_master(bitbang->master);
488 if (status < 0)
489 goto err2;
490
491 return status;
492
493err2:
494 destroy_workqueue(bitbang->workqueue);
495err1:
496 return status;
497}
498EXPORT_SYMBOL_GPL(spi_bitbang_start);
499
500/**
501 * spi_bitbang_stop - stops the task providing spi communication
502 */
503int spi_bitbang_stop(struct spi_bitbang *bitbang)
504{
Chris Lesiaka836f582007-03-16 13:38:13 -0800505 spi_unregister_master(bitbang->master);
David Brownell9904f222006-01-08 13:34:26 -0800506
Chris Lesiaka836f582007-03-16 13:38:13 -0800507 WARN_ON(!list_empty(&bitbang->queue));
David Brownell9904f222006-01-08 13:34:26 -0800508
509 destroy_workqueue(bitbang->workqueue);
510
David Brownell9904f222006-01-08 13:34:26 -0800511 return 0;
512}
513EXPORT_SYMBOL_GPL(spi_bitbang_stop);
514
515MODULE_LICENSE("GPL");
516