blob: 5265330a528fb2a367f164465fefb0b496e25c31 [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>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090026#include <linux/slab.h>
David Brownell9904f222006-01-08 13:34:26 -080027
28#include <linux/spi/spi.h>
29#include <linux/spi/spi_bitbang.h>
30
31
32/*----------------------------------------------------------------------*/
33
34/*
35 * FIRST PART (OPTIONAL): word-at-a-time spi_transfer support.
36 * Use this for GPIO or shift-register level hardware APIs.
37 *
38 * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
39 * to glue code. These bitbang setup() and cleanup() routines are always
40 * used, though maybe they're called from controller-aware code.
41 *
42 * chipselect() and friends may use use spi_device->controller_data and
43 * controller registers as appropriate.
44 *
45 *
46 * NOTE: SPI controller pins can often be used as GPIO pins instead,
47 * which means you could use a bitbang driver either to get hardware
48 * working quickly, or testing for differences that aren't speed related.
49 */
50
51struct spi_bitbang_cs {
52 unsigned nsecs; /* (clock cycle time)/2 */
53 u32 (*txrx_word)(struct spi_device *spi, unsigned nsecs,
54 u32 word, u8 bits);
55 unsigned (*txrx_bufs)(struct spi_device *,
56 u32 (*txrx_word)(
57 struct spi_device *spi,
58 unsigned nsecs,
59 u32 word, u8 bits),
60 unsigned, struct spi_transfer *);
61};
62
63static unsigned bitbang_txrx_8(
64 struct spi_device *spi,
65 u32 (*txrx_word)(struct spi_device *spi,
66 unsigned nsecs,
67 u32 word, u8 bits),
68 unsigned ns,
69 struct spi_transfer *t
70) {
71 unsigned bits = spi->bits_per_word;
72 unsigned count = t->len;
73 const u8 *tx = t->tx_buf;
74 u8 *rx = t->rx_buf;
75
76 while (likely(count > 0)) {
77 u8 word = 0;
78
79 if (tx)
80 word = *tx++;
81 word = txrx_word(spi, ns, word, bits);
82 if (rx)
83 *rx++ = word;
84 count -= 1;
85 }
86 return t->len - count;
87}
88
89static unsigned bitbang_txrx_16(
90 struct spi_device *spi,
91 u32 (*txrx_word)(struct spi_device *spi,
92 unsigned nsecs,
93 u32 word, u8 bits),
94 unsigned ns,
95 struct spi_transfer *t
96) {
97 unsigned bits = spi->bits_per_word;
98 unsigned count = t->len;
99 const u16 *tx = t->tx_buf;
100 u16 *rx = t->rx_buf;
101
102 while (likely(count > 1)) {
103 u16 word = 0;
104
105 if (tx)
106 word = *tx++;
107 word = txrx_word(spi, ns, word, bits);
108 if (rx)
109 *rx++ = word;
110 count -= 2;
111 }
112 return t->len - count;
113}
114
115static unsigned bitbang_txrx_32(
116 struct spi_device *spi,
117 u32 (*txrx_word)(struct spi_device *spi,
118 unsigned nsecs,
119 u32 word, u8 bits),
120 unsigned ns,
121 struct spi_transfer *t
122) {
123 unsigned bits = spi->bits_per_word;
124 unsigned count = t->len;
125 const u32 *tx = t->tx_buf;
126 u32 *rx = t->rx_buf;
127
128 while (likely(count > 3)) {
129 u32 word = 0;
130
131 if (tx)
132 word = *tx++;
133 word = txrx_word(spi, ns, word, bits);
134 if (rx)
135 *rx++ = word;
136 count -= 4;
137 }
138 return t->len - count;
139}
140
Kumar Galaff9f4772006-04-02 16:06:35 -0500141int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
Imre Deak4cff33f2006-02-17 10:02:18 -0800142{
143 struct spi_bitbang_cs *cs = spi->controller_state;
144 u8 bits_per_word;
145 u32 hz;
146
147 if (t) {
148 bits_per_word = t->bits_per_word;
149 hz = t->speed_hz;
150 } else {
151 bits_per_word = 0;
152 hz = 0;
153 }
154
155 /* spi_transfer level calls that work per-word */
156 if (!bits_per_word)
157 bits_per_word = spi->bits_per_word;
158 if (bits_per_word <= 8)
159 cs->txrx_bufs = bitbang_txrx_8;
160 else if (bits_per_word <= 16)
161 cs->txrx_bufs = bitbang_txrx_16;
162 else if (bits_per_word <= 32)
163 cs->txrx_bufs = bitbang_txrx_32;
164 else
165 return -EINVAL;
166
167 /* nsecs = (clock period)/2 */
168 if (!hz)
169 hz = spi->max_speed_hz;
David Brownell1e316d72006-04-06 22:25:56 -0700170 if (hz) {
171 cs->nsecs = (1000000000/2) / hz;
172 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
173 return -EINVAL;
174 }
Imre Deak4cff33f2006-02-17 10:02:18 -0800175
176 return 0;
177}
Kumar Galaff9f4772006-04-02 16:06:35 -0500178EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
Imre Deak4cff33f2006-02-17 10:02:18 -0800179
David Brownell9904f222006-01-08 13:34:26 -0800180/**
181 * spi_bitbang_setup - default setup for per-word I/O loops
182 */
183int spi_bitbang_setup(struct spi_device *spi)
184{
185 struct spi_bitbang_cs *cs = spi->controller_state;
186 struct spi_bitbang *bitbang;
Imre Deak4cff33f2006-02-17 10:02:18 -0800187 int retval;
David Brownelld52df2e2008-01-08 15:32:40 -0800188 unsigned long flags;
David Brownell9904f222006-01-08 13:34:26 -0800189
David Brownellccf77cc2006-04-03 15:46:22 -0700190 bitbang = spi_master_get_devdata(spi->master);
191
David Brownell9904f222006-01-08 13:34:26 -0800192 if (!cs) {
Christoph Lametere94b1762006-12-06 20:33:17 -0800193 cs = kzalloc(sizeof *cs, GFP_KERNEL);
David Brownell9904f222006-01-08 13:34:26 -0800194 if (!cs)
195 return -ENOMEM;
196 spi->controller_state = cs;
197 }
David Brownell9904f222006-01-08 13:34:26 -0800198
David Brownell9904f222006-01-08 13:34:26 -0800199 /* per-word shift register access, in hardware or bitbanging */
200 cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
201 if (!cs->txrx_word)
202 return -EINVAL;
203
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800204 retval = bitbang->setup_transfer(spi, NULL);
Imre Deak4cff33f2006-02-17 10:02:18 -0800205 if (retval < 0)
206 return retval;
David Brownell9904f222006-01-08 13:34:26 -0800207
David Brownell7d077192009-06-17 16:26:03 -0700208 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
David Brownell9904f222006-01-08 13:34:26 -0800209
210 /* NOTE we _need_ to call chipselect() early, ideally with adapter
211 * setup, unless the hardware defaults cooperate to avoid confusion
212 * between normal (active low) and inverted chipselects.
213 */
214
215 /* deselect chip (low or high) */
David Brownelld52df2e2008-01-08 15:32:40 -0800216 spin_lock_irqsave(&bitbang->lock, flags);
David Brownell9904f222006-01-08 13:34:26 -0800217 if (!bitbang->busy) {
Vitaly Wool8275c642006-01-08 13:34:28 -0800218 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
David Brownell9904f222006-01-08 13:34:26 -0800219 ndelay(cs->nsecs);
220 }
David Brownelld52df2e2008-01-08 15:32:40 -0800221 spin_unlock_irqrestore(&bitbang->lock, flags);
David Brownell9904f222006-01-08 13:34:26 -0800222
223 return 0;
224}
225EXPORT_SYMBOL_GPL(spi_bitbang_setup);
226
227/**
228 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
229 */
Hans-Peter Nilsson0ffa0282007-02-12 00:52:45 -0800230void spi_bitbang_cleanup(struct spi_device *spi)
David Brownell9904f222006-01-08 13:34:26 -0800231{
232 kfree(spi->controller_state);
233}
234EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
235
236static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
237{
238 struct spi_bitbang_cs *cs = spi->controller_state;
239 unsigned nsecs = cs->nsecs;
240
241 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t);
242}
243
244/*----------------------------------------------------------------------*/
245
246/*
247 * SECOND PART ... simple transfer queue runner.
248 *
249 * This costs a task context per controller, running the queue by
250 * performing each transfer in sequence. Smarter hardware can queue
251 * several DMA transfers at once, and process several controller queues
252 * in parallel; this driver doesn't match such hardware very well.
253 *
254 * Drivers can provide word-at-a-time i/o primitives, or provide
255 * transfer-at-a-time ones to leverage dma or fifo hardware.
256 */
David Howellsc4028952006-11-22 14:57:56 +0000257static void bitbang_work(struct work_struct *work)
David Brownell9904f222006-01-08 13:34:26 -0800258{
David Howellsc4028952006-11-22 14:57:56 +0000259 struct spi_bitbang *bitbang =
260 container_of(work, struct spi_bitbang, work);
David Brownell9904f222006-01-08 13:34:26 -0800261 unsigned long flags;
David Brownell529ba0d2009-06-30 11:41:30 -0700262 int do_setup = -1;
263 int (*setup_transfer)(struct spi_device *,
264 struct spi_transfer *);
265
266 setup_transfer = bitbang->setup_transfer;
David Brownell9904f222006-01-08 13:34:26 -0800267
268 spin_lock_irqsave(&bitbang->lock, flags);
269 bitbang->busy = 1;
270 while (!list_empty(&bitbang->queue)) {
271 struct spi_message *m;
272 struct spi_device *spi;
273 unsigned nsecs;
Vitaly Wool8275c642006-01-08 13:34:28 -0800274 struct spi_transfer *t = NULL;
David Brownell9904f222006-01-08 13:34:26 -0800275 unsigned tmp;
Vitaly Wool8275c642006-01-08 13:34:28 -0800276 unsigned cs_change;
David Brownell9904f222006-01-08 13:34:26 -0800277 int status;
278
279 m = container_of(bitbang->queue.next, struct spi_message,
280 queue);
281 list_del_init(&m->queue);
282 spin_unlock_irqrestore(&bitbang->lock, flags);
283
Vitaly Wool8275c642006-01-08 13:34:28 -0800284 /* FIXME this is made-up ... the correct value is known to
285 * word-at-a-time bitbang code, and presumably chipselect()
286 * should enforce these requirements too?
287 */
288 nsecs = 100;
David Brownell9904f222006-01-08 13:34:26 -0800289
290 spi = m->spi;
David Brownell9904f222006-01-08 13:34:26 -0800291 tmp = 0;
Vitaly Wool8275c642006-01-08 13:34:28 -0800292 cs_change = 1;
David Brownell9904f222006-01-08 13:34:26 -0800293 status = 0;
294
Vitaly Wool8275c642006-01-08 13:34:28 -0800295 list_for_each_entry (t, &m->transfers, transfer_list) {
David Brownell9904f222006-01-08 13:34:26 -0800296
David Brownell529ba0d2009-06-30 11:41:30 -0700297 /* override speed or wordsize? */
298 if (t->speed_hz || t->bits_per_word)
299 do_setup = 1;
300
301 /* init (-1) or override (1) transfer params */
302 if (do_setup != 0) {
Imre Deak4cff33f2006-02-17 10:02:18 -0800303 if (!setup_transfer) {
304 status = -ENOPROTOOPT;
305 break;
306 }
Imre Deak4cff33f2006-02-17 10:02:18 -0800307 status = setup_transfer(spi, t);
308 if (status < 0)
309 break;
310 }
311
Vitaly Wool8275c642006-01-08 13:34:28 -0800312 /* set up default clock polarity, and activate chip;
313 * this implicitly updates clock and spi modes as
314 * previously recorded for this device via setup().
315 * (and also deselects any other chip that might be
316 * selected ...)
317 */
318 if (cs_change) {
319 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
David Brownell9904f222006-01-08 13:34:26 -0800320 ndelay(nsecs);
321 }
Vitaly Wool8275c642006-01-08 13:34:28 -0800322 cs_change = t->cs_change;
David Brownell9904f222006-01-08 13:34:26 -0800323 if (!t->tx_buf && !t->rx_buf && t->len) {
324 status = -EINVAL;
325 break;
326 }
327
Vitaly Wool8275c642006-01-08 13:34:28 -0800328 /* transfer data. the lower level code handles any
329 * new dma mappings it needs. our caller always gave
330 * us dma-safe buffers.
331 */
David Brownell9904f222006-01-08 13:34:26 -0800332 if (t->len) {
Vitaly Wool8275c642006-01-08 13:34:28 -0800333 /* REVISIT dma API still needs a designated
334 * DMA_ADDR_INVALID; ~0 might be better.
David Brownell9904f222006-01-08 13:34:26 -0800335 */
Vitaly Wool8275c642006-01-08 13:34:28 -0800336 if (!m->is_dma_mapped)
337 t->rx_dma = t->tx_dma = 0;
David Brownell9904f222006-01-08 13:34:26 -0800338 status = bitbang->txrx_bufs(spi, t);
339 }
Jan Nikitenko2cfb8ce2008-03-13 12:32:39 -0700340 if (status > 0)
341 m->actual_length += status;
David Brownell9904f222006-01-08 13:34:26 -0800342 if (status != t->len) {
Jan Nikitenko2cfb8ce2008-03-13 12:32:39 -0700343 /* always report some kind of error */
344 if (status >= 0)
345 status = -EREMOTEIO;
David Brownell9904f222006-01-08 13:34:26 -0800346 break;
347 }
David Brownell9904f222006-01-08 13:34:26 -0800348 status = 0;
349
350 /* protocol tweaks before next transfer */
351 if (t->delay_usecs)
352 udelay(t->delay_usecs);
353
Vitaly Wool8275c642006-01-08 13:34:28 -0800354 if (!cs_change)
355 continue;
356 if (t->transfer_list.next == &m->transfers)
David Brownell9904f222006-01-08 13:34:26 -0800357 break;
358
Vitaly Wool8275c642006-01-08 13:34:28 -0800359 /* sometimes a short mid-message deselect of the chip
360 * may be needed to terminate a mode or command
361 */
362 ndelay(nsecs);
363 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
364 ndelay(nsecs);
David Brownell9904f222006-01-08 13:34:26 -0800365 }
366
David Brownell9904f222006-01-08 13:34:26 -0800367 m->status = status;
368 m->complete(m->context);
369
David Brownell529ba0d2009-06-30 11:41:30 -0700370 /* restore speed and wordsize if it was overridden */
371 if (do_setup == 1)
Imre Deak4cff33f2006-02-17 10:02:18 -0800372 setup_transfer(spi, NULL);
David Brownell529ba0d2009-06-30 11:41:30 -0700373 do_setup = 0;
Imre Deak4cff33f2006-02-17 10:02:18 -0800374
Vitaly Wool8275c642006-01-08 13:34:28 -0800375 /* normally deactivate chipselect ... unless no error and
376 * cs_change has hinted that the next message will probably
377 * be for this chip too.
378 */
379 if (!(status == 0 && cs_change)) {
380 ndelay(nsecs);
381 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
382 ndelay(nsecs);
383 }
David Brownell9904f222006-01-08 13:34:26 -0800384
385 spin_lock_irqsave(&bitbang->lock, flags);
386 }
387 bitbang->busy = 0;
388 spin_unlock_irqrestore(&bitbang->lock, flags);
389}
390
391/**
392 * spi_bitbang_transfer - default submit to transfer queue
393 */
394int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m)
395{
396 struct spi_bitbang *bitbang;
397 unsigned long flags;
David Brownell1e316d72006-04-06 22:25:56 -0700398 int status = 0;
David Brownell9904f222006-01-08 13:34:26 -0800399
400 m->actual_length = 0;
401 m->status = -EINPROGRESS;
402
403 bitbang = spi_master_get_devdata(spi->master);
David Brownell9904f222006-01-08 13:34:26 -0800404
405 spin_lock_irqsave(&bitbang->lock, flags);
David Brownell1e316d72006-04-06 22:25:56 -0700406 if (!spi->max_speed_hz)
407 status = -ENETDOWN;
408 else {
409 list_add_tail(&m->queue, &bitbang->queue);
410 queue_work(bitbang->workqueue, &bitbang->work);
411 }
David Brownell9904f222006-01-08 13:34:26 -0800412 spin_unlock_irqrestore(&bitbang->lock, flags);
413
David Brownell1e316d72006-04-06 22:25:56 -0700414 return status;
David Brownell9904f222006-01-08 13:34:26 -0800415}
416EXPORT_SYMBOL_GPL(spi_bitbang_transfer);
417
418/*----------------------------------------------------------------------*/
419
420/**
421 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
422 * @bitbang: driver handle
423 *
424 * Caller should have zero-initialized all parts of the structure, and then
425 * provided callbacks for chip selection and I/O loops. If the master has
426 * a transfer method, its final step should call spi_bitbang_transfer; or,
427 * that's the default if the transfer routine is not initialized. It should
428 * also set up the bus number and number of chipselects.
429 *
430 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
431 * hardware that basically exposes a shift register) or per-spi_transfer
432 * (which takes better advantage of hardware like fifos or DMA engines).
433 *
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800434 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
435 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
436 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
437 * routine isn't initialized.
David Brownell9904f222006-01-08 13:34:26 -0800438 *
439 * This routine registers the spi_master, which will process requests in a
440 * dedicated task, keeping IRQs unblocked most of the time. To stop
441 * processing those requests, call spi_bitbang_stop().
442 */
443int spi_bitbang_start(struct spi_bitbang *bitbang)
444{
445 int status;
446
447 if (!bitbang->master || !bitbang->chipselect)
448 return -EINVAL;
449
David Howellsc4028952006-11-22 14:57:56 +0000450 INIT_WORK(&bitbang->work, bitbang_work);
David Brownell9904f222006-01-08 13:34:26 -0800451 spin_lock_init(&bitbang->lock);
452 INIT_LIST_HEAD(&bitbang->queue);
453
David Brownelle7db06b2009-06-17 16:26:04 -0700454 if (!bitbang->master->mode_bits)
455 bitbang->master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
456
David Brownell9904f222006-01-08 13:34:26 -0800457 if (!bitbang->master->transfer)
458 bitbang->master->transfer = spi_bitbang_transfer;
459 if (!bitbang->txrx_bufs) {
460 bitbang->use_dma = 0;
461 bitbang->txrx_bufs = spi_bitbang_bufs;
462 if (!bitbang->master->setup) {
Kumar Galaff9f4772006-04-02 16:06:35 -0500463 if (!bitbang->setup_transfer)
464 bitbang->setup_transfer =
465 spi_bitbang_setup_transfer;
David Brownell9904f222006-01-08 13:34:26 -0800466 bitbang->master->setup = spi_bitbang_setup;
467 bitbang->master->cleanup = spi_bitbang_cleanup;
468 }
469 } else if (!bitbang->master->setup)
470 return -EINVAL;
471
472 /* this task is the only thing to touch the SPI bits */
473 bitbang->busy = 0;
474 bitbang->workqueue = create_singlethread_workqueue(
Kay Sievers35f74fc2009-01-06 10:44:37 -0800475 dev_name(bitbang->master->dev.parent));
David Brownell9904f222006-01-08 13:34:26 -0800476 if (bitbang->workqueue == NULL) {
477 status = -EBUSY;
478 goto err1;
479 }
480
481 /* driver may get busy before register() returns, especially
482 * if someone registered boardinfo for devices
483 */
484 status = spi_register_master(bitbang->master);
485 if (status < 0)
486 goto err2;
487
488 return status;
489
490err2:
491 destroy_workqueue(bitbang->workqueue);
492err1:
493 return status;
494}
495EXPORT_SYMBOL_GPL(spi_bitbang_start);
496
497/**
498 * spi_bitbang_stop - stops the task providing spi communication
499 */
500int spi_bitbang_stop(struct spi_bitbang *bitbang)
501{
Chris Lesiaka836f582007-03-16 13:38:13 -0800502 spi_unregister_master(bitbang->master);
David Brownell9904f222006-01-08 13:34:26 -0800503
Chris Lesiaka836f582007-03-16 13:38:13 -0800504 WARN_ON(!list_empty(&bitbang->queue));
David Brownell9904f222006-01-08 13:34:26 -0800505
506 destroy_workqueue(bitbang->workqueue);
507
David Brownell9904f222006-01-08 13:34:26 -0800508 return 0;
509}
510EXPORT_SYMBOL_GPL(spi_bitbang_stop);
511
512MODULE_LICENSE("GPL");
513