Loading...
1/*
2 * 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
19#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#include <linux/slab.h>
27
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 = t->bits_per_word ? : 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 = t->bits_per_word ? : 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 = t->bits_per_word ? : 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
141int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
142{
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;
170 if (hz) {
171 cs->nsecs = (1000000000/2) / hz;
172 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
173 return -EINVAL;
174 }
175
176 return 0;
177}
178EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
179
180/**
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;
187 int retval;
188 unsigned long flags;
189
190 bitbang = spi_master_get_devdata(spi->master);
191
192 if (!cs) {
193 cs = kzalloc(sizeof *cs, GFP_KERNEL);
194 if (!cs)
195 return -ENOMEM;
196 spi->controller_state = cs;
197 }
198
199 /* 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
204 retval = bitbang->setup_transfer(spi, NULL);
205 if (retval < 0)
206 return retval;
207
208 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
209
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) */
216 spin_lock_irqsave(&bitbang->lock, flags);
217 if (!bitbang->busy) {
218 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
219 ndelay(cs->nsecs);
220 }
221 spin_unlock_irqrestore(&bitbang->lock, flags);
222
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 */
230void spi_bitbang_cleanup(struct spi_device *spi)
231{
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 */
257static void bitbang_work(struct work_struct *work)
258{
259 struct spi_bitbang *bitbang =
260 container_of(work, struct spi_bitbang, work);
261 unsigned long flags;
262
263 spin_lock_irqsave(&bitbang->lock, flags);
264 bitbang->busy = 1;
265 while (!list_empty(&bitbang->queue)) {
266 struct spi_message *m;
267 struct spi_device *spi;
268 unsigned nsecs;
269 struct spi_transfer *t = NULL;
270 unsigned tmp;
271 unsigned cs_change;
272 int status;
273 int do_setup = -1;
274
275 m = container_of(bitbang->queue.next, struct spi_message,
276 queue);
277 list_del_init(&m->queue);
278 spin_unlock_irqrestore(&bitbang->lock, flags);
279
280 /* FIXME this is made-up ... the correct value is known to
281 * word-at-a-time bitbang code, and presumably chipselect()
282 * should enforce these requirements too?
283 */
284 nsecs = 100;
285
286 spi = m->spi;
287 tmp = 0;
288 cs_change = 1;
289 status = 0;
290
291 list_for_each_entry (t, &m->transfers, transfer_list) {
292
293 /* override speed or wordsize? */
294 if (t->speed_hz || t->bits_per_word)
295 do_setup = 1;
296
297 /* init (-1) or override (1) transfer params */
298 if (do_setup != 0) {
299 status = bitbang->setup_transfer(spi, t);
300 if (status < 0)
301 break;
302 if (do_setup == -1)
303 do_setup = 0;
304 }
305
306 /* set up default clock polarity, and activate chip;
307 * this implicitly updates clock and spi modes as
308 * previously recorded for this device via setup().
309 * (and also deselects any other chip that might be
310 * selected ...)
311 */
312 if (cs_change) {
313 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
314 ndelay(nsecs);
315 }
316 cs_change = t->cs_change;
317 if (!t->tx_buf && !t->rx_buf && t->len) {
318 status = -EINVAL;
319 break;
320 }
321
322 /* transfer data. the lower level code handles any
323 * new dma mappings it needs. our caller always gave
324 * us dma-safe buffers.
325 */
326 if (t->len) {
327 /* REVISIT dma API still needs a designated
328 * DMA_ADDR_INVALID; ~0 might be better.
329 */
330 if (!m->is_dma_mapped)
331 t->rx_dma = t->tx_dma = 0;
332 status = bitbang->txrx_bufs(spi, t);
333 }
334 if (status > 0)
335 m->actual_length += status;
336 if (status != t->len) {
337 /* always report some kind of error */
338 if (status >= 0)
339 status = -EREMOTEIO;
340 break;
341 }
342 status = 0;
343
344 /* protocol tweaks before next transfer */
345 if (t->delay_usecs)
346 udelay(t->delay_usecs);
347
348 if (!cs_change)
349 continue;
350 if (t->transfer_list.next == &m->transfers)
351 break;
352
353 /* sometimes a short mid-message deselect of the chip
354 * may be needed to terminate a mode or command
355 */
356 ndelay(nsecs);
357 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
358 ndelay(nsecs);
359 }
360
361 m->status = status;
362 m->complete(m->context);
363
364 /* normally deactivate chipselect ... unless no error and
365 * cs_change has hinted that the next message will probably
366 * be for this chip too.
367 */
368 if (!(status == 0 && cs_change)) {
369 ndelay(nsecs);
370 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
371 ndelay(nsecs);
372 }
373
374 spin_lock_irqsave(&bitbang->lock, flags);
375 }
376 bitbang->busy = 0;
377 spin_unlock_irqrestore(&bitbang->lock, flags);
378}
379
380/**
381 * spi_bitbang_transfer - default submit to transfer queue
382 */
383int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m)
384{
385 struct spi_bitbang *bitbang;
386 unsigned long flags;
387 int status = 0;
388
389 m->actual_length = 0;
390 m->status = -EINPROGRESS;
391
392 bitbang = spi_master_get_devdata(spi->master);
393
394 spin_lock_irqsave(&bitbang->lock, flags);
395 if (!spi->max_speed_hz)
396 status = -ENETDOWN;
397 else {
398 list_add_tail(&m->queue, &bitbang->queue);
399 queue_work(bitbang->workqueue, &bitbang->work);
400 }
401 spin_unlock_irqrestore(&bitbang->lock, flags);
402
403 return status;
404}
405EXPORT_SYMBOL_GPL(spi_bitbang_transfer);
406
407/*----------------------------------------------------------------------*/
408
409/**
410 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
411 * @bitbang: driver handle
412 *
413 * Caller should have zero-initialized all parts of the structure, and then
414 * provided callbacks for chip selection and I/O loops. If the master has
415 * a transfer method, its final step should call spi_bitbang_transfer; or,
416 * that's the default if the transfer routine is not initialized. It should
417 * also set up the bus number and number of chipselects.
418 *
419 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
420 * hardware that basically exposes a shift register) or per-spi_transfer
421 * (which takes better advantage of hardware like fifos or DMA engines).
422 *
423 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
424 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
425 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
426 * routine isn't initialized.
427 *
428 * This routine registers the spi_master, which will process requests in a
429 * dedicated task, keeping IRQs unblocked most of the time. To stop
430 * processing those requests, call spi_bitbang_stop().
431 */
432int spi_bitbang_start(struct spi_bitbang *bitbang)
433{
434 int status;
435
436 if (!bitbang->master || !bitbang->chipselect)
437 return -EINVAL;
438
439 INIT_WORK(&bitbang->work, bitbang_work);
440 spin_lock_init(&bitbang->lock);
441 INIT_LIST_HEAD(&bitbang->queue);
442
443 if (!bitbang->master->mode_bits)
444 bitbang->master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
445
446 if (!bitbang->master->transfer)
447 bitbang->master->transfer = spi_bitbang_transfer;
448 if (!bitbang->txrx_bufs) {
449 bitbang->use_dma = 0;
450 bitbang->txrx_bufs = spi_bitbang_bufs;
451 if (!bitbang->master->setup) {
452 if (!bitbang->setup_transfer)
453 bitbang->setup_transfer =
454 spi_bitbang_setup_transfer;
455 bitbang->master->setup = spi_bitbang_setup;
456 bitbang->master->cleanup = spi_bitbang_cleanup;
457 }
458 } else if (!bitbang->master->setup)
459 return -EINVAL;
460 if (bitbang->master->transfer == spi_bitbang_transfer &&
461 !bitbang->setup_transfer)
462 return -EINVAL;
463
464 /* this task is the only thing to touch the SPI bits */
465 bitbang->busy = 0;
466 bitbang->workqueue = create_singlethread_workqueue(
467 dev_name(bitbang->master->dev.parent));
468 if (bitbang->workqueue == NULL) {
469 status = -EBUSY;
470 goto err1;
471 }
472
473 /* driver may get busy before register() returns, especially
474 * if someone registered boardinfo for devices
475 */
476 status = spi_register_master(bitbang->master);
477 if (status < 0)
478 goto err2;
479
480 return status;
481
482err2:
483 destroy_workqueue(bitbang->workqueue);
484err1:
485 return status;
486}
487EXPORT_SYMBOL_GPL(spi_bitbang_start);
488
489/**
490 * spi_bitbang_stop - stops the task providing spi communication
491 */
492int spi_bitbang_stop(struct spi_bitbang *bitbang)
493{
494 spi_unregister_master(bitbang->master);
495
496 WARN_ON(!list_empty(&bitbang->queue));
497
498 destroy_workqueue(bitbang->workqueue);
499
500 return 0;
501}
502EXPORT_SYMBOL_GPL(spi_bitbang_stop);
503
504MODULE_LICENSE("GPL");
505
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * polling/bitbanging SPI master controller driver utilities
4 */
5
6#include <linux/spinlock.h>
7#include <linux/workqueue.h>
8#include <linux/interrupt.h>
9#include <linux/module.h>
10#include <linux/delay.h>
11#include <linux/errno.h>
12#include <linux/platform_device.h>
13#include <linux/slab.h>
14
15#include <linux/spi/spi.h>
16#include <linux/spi/spi_bitbang.h>
17
18#define SPI_BITBANG_CS_DELAY 100
19
20
21/*----------------------------------------------------------------------*/
22
23/*
24 * FIRST PART (OPTIONAL): word-at-a-time spi_transfer support.
25 * Use this for GPIO or shift-register level hardware APIs.
26 *
27 * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
28 * to glue code. These bitbang setup() and cleanup() routines are always
29 * used, though maybe they're called from controller-aware code.
30 *
31 * chipselect() and friends may use spi_device->controller_data and
32 * controller registers as appropriate.
33 *
34 *
35 * NOTE: SPI controller pins can often be used as GPIO pins instead,
36 * which means you could use a bitbang driver either to get hardware
37 * working quickly, or testing for differences that aren't speed related.
38 */
39
40struct spi_bitbang_cs {
41 unsigned nsecs; /* (clock cycle time)/2 */
42 u32 (*txrx_word)(struct spi_device *spi, unsigned nsecs,
43 u32 word, u8 bits, unsigned flags);
44 unsigned (*txrx_bufs)(struct spi_device *,
45 u32 (*txrx_word)(
46 struct spi_device *spi,
47 unsigned nsecs,
48 u32 word, u8 bits,
49 unsigned flags),
50 unsigned, struct spi_transfer *,
51 unsigned);
52};
53
54static unsigned bitbang_txrx_8(
55 struct spi_device *spi,
56 u32 (*txrx_word)(struct spi_device *spi,
57 unsigned nsecs,
58 u32 word, u8 bits,
59 unsigned flags),
60 unsigned ns,
61 struct spi_transfer *t,
62 unsigned flags
63)
64{
65 unsigned bits = t->bits_per_word;
66 unsigned count = t->len;
67 const u8 *tx = t->tx_buf;
68 u8 *rx = t->rx_buf;
69
70 while (likely(count > 0)) {
71 u8 word = 0;
72
73 if (tx)
74 word = *tx++;
75 word = txrx_word(spi, ns, word, bits, flags);
76 if (rx)
77 *rx++ = word;
78 count -= 1;
79 }
80 return t->len - count;
81}
82
83static unsigned bitbang_txrx_16(
84 struct spi_device *spi,
85 u32 (*txrx_word)(struct spi_device *spi,
86 unsigned nsecs,
87 u32 word, u8 bits,
88 unsigned flags),
89 unsigned ns,
90 struct spi_transfer *t,
91 unsigned flags
92)
93{
94 unsigned bits = t->bits_per_word;
95 unsigned count = t->len;
96 const u16 *tx = t->tx_buf;
97 u16 *rx = t->rx_buf;
98
99 while (likely(count > 1)) {
100 u16 word = 0;
101
102 if (tx)
103 word = *tx++;
104 word = txrx_word(spi, ns, word, bits, flags);
105 if (rx)
106 *rx++ = word;
107 count -= 2;
108 }
109 return t->len - count;
110}
111
112static unsigned bitbang_txrx_32(
113 struct spi_device *spi,
114 u32 (*txrx_word)(struct spi_device *spi,
115 unsigned nsecs,
116 u32 word, u8 bits,
117 unsigned flags),
118 unsigned ns,
119 struct spi_transfer *t,
120 unsigned flags
121)
122{
123 unsigned bits = t->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, flags);
134 if (rx)
135 *rx++ = word;
136 count -= 4;
137 }
138 return t->len - count;
139}
140
141int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
142{
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;
170 if (hz) {
171 cs->nsecs = (1000000000/2) / hz;
172 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
173 return -EINVAL;
174 }
175
176 return 0;
177}
178EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
179
180/*
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;
187 bool initial_setup = false;
188 int retval;
189
190 bitbang = spi_master_get_devdata(spi->master);
191
192 if (!cs) {
193 cs = kzalloc(sizeof(*cs), GFP_KERNEL);
194 if (!cs)
195 return -ENOMEM;
196 spi->controller_state = cs;
197 initial_setup = true;
198 }
199
200 /* per-word shift register access, in hardware or bitbanging */
201 cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
202 if (!cs->txrx_word) {
203 retval = -EINVAL;
204 goto err_free;
205 }
206
207 if (bitbang->setup_transfer) {
208 retval = bitbang->setup_transfer(spi, NULL);
209 if (retval < 0)
210 goto err_free;
211 }
212
213 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
214
215 return 0;
216
217err_free:
218 if (initial_setup)
219 kfree(cs);
220 return retval;
221}
222EXPORT_SYMBOL_GPL(spi_bitbang_setup);
223
224/*
225 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
226 */
227void spi_bitbang_cleanup(struct spi_device *spi)
228{
229 kfree(spi->controller_state);
230}
231EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
232
233static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
234{
235 struct spi_bitbang_cs *cs = spi->controller_state;
236 unsigned nsecs = cs->nsecs;
237 struct spi_bitbang *bitbang;
238
239 bitbang = spi_master_get_devdata(spi->master);
240 if (bitbang->set_line_direction) {
241 int err;
242
243 err = bitbang->set_line_direction(spi, !!(t->tx_buf));
244 if (err < 0)
245 return err;
246 }
247
248 if (spi->mode & SPI_3WIRE) {
249 unsigned flags;
250
251 flags = t->tx_buf ? SPI_MASTER_NO_RX : SPI_MASTER_NO_TX;
252 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, flags);
253 }
254 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, 0);
255}
256
257/*----------------------------------------------------------------------*/
258
259/*
260 * SECOND PART ... simple transfer queue runner.
261 *
262 * This costs a task context per controller, running the queue by
263 * performing each transfer in sequence. Smarter hardware can queue
264 * several DMA transfers at once, and process several controller queues
265 * in parallel; this driver doesn't match such hardware very well.
266 *
267 * Drivers can provide word-at-a-time i/o primitives, or provide
268 * transfer-at-a-time ones to leverage dma or fifo hardware.
269 */
270
271static int spi_bitbang_prepare_hardware(struct spi_master *spi)
272{
273 struct spi_bitbang *bitbang;
274
275 bitbang = spi_master_get_devdata(spi);
276
277 mutex_lock(&bitbang->lock);
278 bitbang->busy = 1;
279 mutex_unlock(&bitbang->lock);
280
281 return 0;
282}
283
284static int spi_bitbang_transfer_one(struct spi_master *master,
285 struct spi_device *spi,
286 struct spi_transfer *transfer)
287{
288 struct spi_bitbang *bitbang = spi_master_get_devdata(master);
289 int status = 0;
290
291 if (bitbang->setup_transfer) {
292 status = bitbang->setup_transfer(spi, transfer);
293 if (status < 0)
294 goto out;
295 }
296
297 if (transfer->len)
298 status = bitbang->txrx_bufs(spi, transfer);
299
300 if (status == transfer->len)
301 status = 0;
302 else if (status >= 0)
303 status = -EREMOTEIO;
304
305out:
306 spi_finalize_current_transfer(master);
307
308 return status;
309}
310
311static int spi_bitbang_unprepare_hardware(struct spi_master *spi)
312{
313 struct spi_bitbang *bitbang;
314
315 bitbang = spi_master_get_devdata(spi);
316
317 mutex_lock(&bitbang->lock);
318 bitbang->busy = 0;
319 mutex_unlock(&bitbang->lock);
320
321 return 0;
322}
323
324static void spi_bitbang_set_cs(struct spi_device *spi, bool enable)
325{
326 struct spi_bitbang *bitbang = spi_master_get_devdata(spi->master);
327
328 /* SPI core provides CS high / low, but bitbang driver
329 * expects CS active
330 * spi device driver takes care of handling SPI_CS_HIGH
331 */
332 enable = (!!(spi->mode & SPI_CS_HIGH) == enable);
333
334 ndelay(SPI_BITBANG_CS_DELAY);
335 bitbang->chipselect(spi, enable ? BITBANG_CS_ACTIVE :
336 BITBANG_CS_INACTIVE);
337 ndelay(SPI_BITBANG_CS_DELAY);
338}
339
340/*----------------------------------------------------------------------*/
341
342int spi_bitbang_init(struct spi_bitbang *bitbang)
343{
344 struct spi_master *master = bitbang->master;
345 bool custom_cs;
346
347 if (!master)
348 return -EINVAL;
349 /*
350 * We only need the chipselect callback if we are actually using it.
351 * If we just use GPIO descriptors, it is surplus. If the
352 * SPI_MASTER_GPIO_SS flag is set, we always need to call the
353 * driver-specific chipselect routine.
354 */
355 custom_cs = (!master->use_gpio_descriptors ||
356 (master->flags & SPI_MASTER_GPIO_SS));
357
358 if (custom_cs && !bitbang->chipselect)
359 return -EINVAL;
360
361 mutex_init(&bitbang->lock);
362
363 if (!master->mode_bits)
364 master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
365
366 if (master->transfer || master->transfer_one_message)
367 return -EINVAL;
368
369 master->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
370 master->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
371 master->transfer_one = spi_bitbang_transfer_one;
372 /*
373 * When using GPIO descriptors, the ->set_cs() callback doesn't even
374 * get called unless SPI_MASTER_GPIO_SS is set.
375 */
376 if (custom_cs)
377 master->set_cs = spi_bitbang_set_cs;
378
379 if (!bitbang->txrx_bufs) {
380 bitbang->use_dma = 0;
381 bitbang->txrx_bufs = spi_bitbang_bufs;
382 if (!master->setup) {
383 if (!bitbang->setup_transfer)
384 bitbang->setup_transfer =
385 spi_bitbang_setup_transfer;
386 master->setup = spi_bitbang_setup;
387 master->cleanup = spi_bitbang_cleanup;
388 }
389 }
390
391 return 0;
392}
393EXPORT_SYMBOL_GPL(spi_bitbang_init);
394
395/**
396 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
397 * @bitbang: driver handle
398 *
399 * Caller should have zero-initialized all parts of the structure, and then
400 * provided callbacks for chip selection and I/O loops. If the master has
401 * a transfer method, its final step should call spi_bitbang_transfer; or,
402 * that's the default if the transfer routine is not initialized. It should
403 * also set up the bus number and number of chipselects.
404 *
405 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
406 * hardware that basically exposes a shift register) or per-spi_transfer
407 * (which takes better advantage of hardware like fifos or DMA engines).
408 *
409 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
410 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
411 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
412 * routine isn't initialized.
413 *
414 * This routine registers the spi_master, which will process requests in a
415 * dedicated task, keeping IRQs unblocked most of the time. To stop
416 * processing those requests, call spi_bitbang_stop().
417 *
418 * On success, this routine will take a reference to master. The caller is
419 * responsible for calling spi_bitbang_stop() to decrement the reference and
420 * spi_master_put() as counterpart of spi_alloc_master() to prevent a memory
421 * leak.
422 */
423int spi_bitbang_start(struct spi_bitbang *bitbang)
424{
425 struct spi_master *master = bitbang->master;
426 int ret;
427
428 ret = spi_bitbang_init(bitbang);
429 if (ret)
430 return ret;
431
432 /* driver may get busy before register() returns, especially
433 * if someone registered boardinfo for devices
434 */
435 ret = spi_register_master(spi_master_get(master));
436 if (ret)
437 spi_master_put(master);
438
439 return ret;
440}
441EXPORT_SYMBOL_GPL(spi_bitbang_start);
442
443/*
444 * spi_bitbang_stop - stops the task providing spi communication
445 */
446void spi_bitbang_stop(struct spi_bitbang *bitbang)
447{
448 spi_unregister_master(bitbang->master);
449}
450EXPORT_SYMBOL_GPL(spi_bitbang_stop);
451
452MODULE_LICENSE("GPL");
453