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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 (*setup_transfer)(struct spi_device *,
263 struct spi_transfer *);
264
265 setup_transfer = bitbang->setup_transfer;
David Brownell9904f222006-01-08 13:34:26 -0800266
267 spin_lock_irqsave(&bitbang->lock, flags);
268 bitbang->busy = 1;
269 while (!list_empty(&bitbang->queue)) {
270 struct spi_message *m;
271 struct spi_device *spi;
272 unsigned nsecs;
Vitaly Wool8275c642006-01-08 13:34:28 -0800273 struct spi_transfer *t = NULL;
David Brownell9904f222006-01-08 13:34:26 -0800274 unsigned tmp;
Vitaly Wool8275c642006-01-08 13:34:28 -0800275 unsigned cs_change;
David Brownell9904f222006-01-08 13:34:26 -0800276 int status;
Brian Niebuhrb8f2e7b2010-07-02 15:30:17 +0000277 int do_setup = -1;
David Brownell9904f222006-01-08 13:34:26 -0800278
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;
Brian Niebuhrb8f2e7b2010-07-02 15:30:17 +0000310 if (do_setup == -1)
311 do_setup = 0;
Imre Deak4cff33f2006-02-17 10:02:18 -0800312 }
313
Vitaly Wool8275c642006-01-08 13:34:28 -0800314 /* set up default clock polarity, and activate chip;
315 * this implicitly updates clock and spi modes as
316 * previously recorded for this device via setup().
317 * (and also deselects any other chip that might be
318 * selected ...)
319 */
320 if (cs_change) {
321 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
David Brownell9904f222006-01-08 13:34:26 -0800322 ndelay(nsecs);
323 }
Vitaly Wool8275c642006-01-08 13:34:28 -0800324 cs_change = t->cs_change;
David Brownell9904f222006-01-08 13:34:26 -0800325 if (!t->tx_buf && !t->rx_buf && t->len) {
326 status = -EINVAL;
327 break;
328 }
329
Vitaly Wool8275c642006-01-08 13:34:28 -0800330 /* transfer data. the lower level code handles any
331 * new dma mappings it needs. our caller always gave
332 * us dma-safe buffers.
333 */
David Brownell9904f222006-01-08 13:34:26 -0800334 if (t->len) {
Vitaly Wool8275c642006-01-08 13:34:28 -0800335 /* REVISIT dma API still needs a designated
336 * DMA_ADDR_INVALID; ~0 might be better.
David Brownell9904f222006-01-08 13:34:26 -0800337 */
Vitaly Wool8275c642006-01-08 13:34:28 -0800338 if (!m->is_dma_mapped)
339 t->rx_dma = t->tx_dma = 0;
David Brownell9904f222006-01-08 13:34:26 -0800340 status = bitbang->txrx_bufs(spi, t);
341 }
Jan Nikitenko2cfb8ce2008-03-13 12:32:39 -0700342 if (status > 0)
343 m->actual_length += status;
David Brownell9904f222006-01-08 13:34:26 -0800344 if (status != t->len) {
Jan Nikitenko2cfb8ce2008-03-13 12:32:39 -0700345 /* always report some kind of error */
346 if (status >= 0)
347 status = -EREMOTEIO;
David Brownell9904f222006-01-08 13:34:26 -0800348 break;
349 }
David Brownell9904f222006-01-08 13:34:26 -0800350 status = 0;
351
352 /* protocol tweaks before next transfer */
353 if (t->delay_usecs)
354 udelay(t->delay_usecs);
355
Vitaly Wool8275c642006-01-08 13:34:28 -0800356 if (!cs_change)
357 continue;
358 if (t->transfer_list.next == &m->transfers)
David Brownell9904f222006-01-08 13:34:26 -0800359 break;
360
Vitaly Wool8275c642006-01-08 13:34:28 -0800361 /* sometimes a short mid-message deselect of the chip
362 * may be needed to terminate a mode or command
363 */
364 ndelay(nsecs);
365 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
366 ndelay(nsecs);
David Brownell9904f222006-01-08 13:34:26 -0800367 }
368
David Brownell9904f222006-01-08 13:34:26 -0800369 m->status = status;
370 m->complete(m->context);
371
Vitaly Wool8275c642006-01-08 13:34:28 -0800372 /* normally deactivate chipselect ... unless no error and
373 * cs_change has hinted that the next message will probably
374 * be for this chip too.
375 */
376 if (!(status == 0 && cs_change)) {
377 ndelay(nsecs);
378 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
379 ndelay(nsecs);
380 }
David Brownell9904f222006-01-08 13:34:26 -0800381
382 spin_lock_irqsave(&bitbang->lock, flags);
383 }
384 bitbang->busy = 0;
385 spin_unlock_irqrestore(&bitbang->lock, flags);
386}
387
388/**
389 * spi_bitbang_transfer - default submit to transfer queue
390 */
391int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m)
392{
393 struct spi_bitbang *bitbang;
394 unsigned long flags;
David Brownell1e316d72006-04-06 22:25:56 -0700395 int status = 0;
David Brownell9904f222006-01-08 13:34:26 -0800396
397 m->actual_length = 0;
398 m->status = -EINPROGRESS;
399
400 bitbang = spi_master_get_devdata(spi->master);
David Brownell9904f222006-01-08 13:34:26 -0800401
402 spin_lock_irqsave(&bitbang->lock, flags);
David Brownell1e316d72006-04-06 22:25:56 -0700403 if (!spi->max_speed_hz)
404 status = -ENETDOWN;
405 else {
406 list_add_tail(&m->queue, &bitbang->queue);
407 queue_work(bitbang->workqueue, &bitbang->work);
408 }
David Brownell9904f222006-01-08 13:34:26 -0800409 spin_unlock_irqrestore(&bitbang->lock, flags);
410
David Brownell1e316d72006-04-06 22:25:56 -0700411 return status;
David Brownell9904f222006-01-08 13:34:26 -0800412}
413EXPORT_SYMBOL_GPL(spi_bitbang_transfer);
414
415/*----------------------------------------------------------------------*/
416
417/**
418 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
419 * @bitbang: driver handle
420 *
421 * Caller should have zero-initialized all parts of the structure, and then
422 * provided callbacks for chip selection and I/O loops. If the master has
423 * a transfer method, its final step should call spi_bitbang_transfer; or,
424 * that's the default if the transfer routine is not initialized. It should
425 * also set up the bus number and number of chipselects.
426 *
427 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
428 * hardware that basically exposes a shift register) or per-spi_transfer
429 * (which takes better advantage of hardware like fifos or DMA engines).
430 *
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800431 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
432 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
433 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
434 * routine isn't initialized.
David Brownell9904f222006-01-08 13:34:26 -0800435 *
436 * This routine registers the spi_master, which will process requests in a
437 * dedicated task, keeping IRQs unblocked most of the time. To stop
438 * processing those requests, call spi_bitbang_stop().
439 */
440int spi_bitbang_start(struct spi_bitbang *bitbang)
441{
442 int status;
443
444 if (!bitbang->master || !bitbang->chipselect)
445 return -EINVAL;
446
David Howellsc4028952006-11-22 14:57:56 +0000447 INIT_WORK(&bitbang->work, bitbang_work);
David Brownell9904f222006-01-08 13:34:26 -0800448 spin_lock_init(&bitbang->lock);
449 INIT_LIST_HEAD(&bitbang->queue);
450
David Brownelle7db06b2009-06-17 16:26:04 -0700451 if (!bitbang->master->mode_bits)
452 bitbang->master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
453
David Brownell9904f222006-01-08 13:34:26 -0800454 if (!bitbang->master->transfer)
455 bitbang->master->transfer = spi_bitbang_transfer;
456 if (!bitbang->txrx_bufs) {
457 bitbang->use_dma = 0;
458 bitbang->txrx_bufs = spi_bitbang_bufs;
459 if (!bitbang->master->setup) {
Kumar Galaff9f4772006-04-02 16:06:35 -0500460 if (!bitbang->setup_transfer)
461 bitbang->setup_transfer =
462 spi_bitbang_setup_transfer;
David Brownell9904f222006-01-08 13:34:26 -0800463 bitbang->master->setup = spi_bitbang_setup;
464 bitbang->master->cleanup = spi_bitbang_cleanup;
465 }
466 } else if (!bitbang->master->setup)
467 return -EINVAL;
468
469 /* this task is the only thing to touch the SPI bits */
470 bitbang->busy = 0;
471 bitbang->workqueue = create_singlethread_workqueue(
Kay Sievers35f74fc2009-01-06 10:44:37 -0800472 dev_name(bitbang->master->dev.parent));
David Brownell9904f222006-01-08 13:34:26 -0800473 if (bitbang->workqueue == NULL) {
474 status = -EBUSY;
475 goto err1;
476 }
477
478 /* driver may get busy before register() returns, especially
479 * if someone registered boardinfo for devices
480 */
481 status = spi_register_master(bitbang->master);
482 if (status < 0)
483 goto err2;
484
485 return status;
486
487err2:
488 destroy_workqueue(bitbang->workqueue);
489err1:
490 return status;
491}
492EXPORT_SYMBOL_GPL(spi_bitbang_start);
493
494/**
495 * spi_bitbang_stop - stops the task providing spi communication
496 */
497int spi_bitbang_stop(struct spi_bitbang *bitbang)
498{
Chris Lesiaka836f582007-03-16 13:38:13 -0800499 spi_unregister_master(bitbang->master);
David Brownell9904f222006-01-08 13:34:26 -0800500
Chris Lesiaka836f582007-03-16 13:38:13 -0800501 WARN_ON(!list_empty(&bitbang->queue));
David Brownell9904f222006-01-08 13:34:26 -0800502
503 destroy_workqueue(bitbang->workqueue);
504
David Brownell9904f222006-01-08 13:34:26 -0800505 return 0;
506}
507EXPORT_SYMBOL_GPL(spi_bitbang_stop);
508
509MODULE_LICENSE("GPL");
510