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/module.h>
24#include <linux/delay.h>
25#include <linux/errno.h>
26#include <linux/platform_device.h>
27#include <linux/slab.h>
28
29#include <linux/spi/spi.h>
30#include <linux/spi/spi_bitbang.h>
31
32
33/*----------------------------------------------------------------------*/
34
35/*
36 * FIRST PART (OPTIONAL): word-at-a-time spi_transfer support.
37 * Use this for GPIO or shift-register level hardware APIs.
38 *
39 * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
40 * to glue code. These bitbang setup() and cleanup() routines are always
41 * used, though maybe they're called from controller-aware code.
42 *
43 * chipselect() and friends may use use spi_device->controller_data and
44 * controller registers as appropriate.
45 *
46 *
47 * NOTE: SPI controller pins can often be used as GPIO pins instead,
48 * which means you could use a bitbang driver either to get hardware
49 * working quickly, or testing for differences that aren't speed related.
50 */
51
52struct spi_bitbang_cs {
53 unsigned nsecs; /* (clock cycle time)/2 */
54 u32 (*txrx_word)(struct spi_device *spi, unsigned nsecs,
55 u32 word, u8 bits);
56 unsigned (*txrx_bufs)(struct spi_device *,
57 u32 (*txrx_word)(
58 struct spi_device *spi,
59 unsigned nsecs,
60 u32 word, u8 bits),
61 unsigned, struct spi_transfer *);
62};
63
64static unsigned bitbang_txrx_8(
65 struct spi_device *spi,
66 u32 (*txrx_word)(struct spi_device *spi,
67 unsigned nsecs,
68 u32 word, u8 bits),
69 unsigned ns,
70 struct spi_transfer *t
71) {
72 unsigned bits = t->bits_per_word ? : spi->bits_per_word;
73 unsigned count = t->len;
74 const u8 *tx = t->tx_buf;
75 u8 *rx = t->rx_buf;
76
77 while (likely(count > 0)) {
78 u8 word = 0;
79
80 if (tx)
81 word = *tx++;
82 word = txrx_word(spi, ns, word, bits);
83 if (rx)
84 *rx++ = word;
85 count -= 1;
86 }
87 return t->len - count;
88}
89
90static unsigned bitbang_txrx_16(
91 struct spi_device *spi,
92 u32 (*txrx_word)(struct spi_device *spi,
93 unsigned nsecs,
94 u32 word, u8 bits),
95 unsigned ns,
96 struct spi_transfer *t
97) {
98 unsigned bits = t->bits_per_word ? : spi->bits_per_word;
99 unsigned count = t->len;
100 const u16 *tx = t->tx_buf;
101 u16 *rx = t->rx_buf;
102
103 while (likely(count > 1)) {
104 u16 word = 0;
105
106 if (tx)
107 word = *tx++;
108 word = txrx_word(spi, ns, word, bits);
109 if (rx)
110 *rx++ = word;
111 count -= 2;
112 }
113 return t->len - count;
114}
115
116static unsigned bitbang_txrx_32(
117 struct spi_device *spi,
118 u32 (*txrx_word)(struct spi_device *spi,
119 unsigned nsecs,
120 u32 word, u8 bits),
121 unsigned ns,
122 struct spi_transfer *t
123) {
124 unsigned bits = t->bits_per_word ? : spi->bits_per_word;
125 unsigned count = t->len;
126 const u32 *tx = t->tx_buf;
127 u32 *rx = t->rx_buf;
128
129 while (likely(count > 3)) {
130 u32 word = 0;
131
132 if (tx)
133 word = *tx++;
134 word = txrx_word(spi, ns, word, bits);
135 if (rx)
136 *rx++ = word;
137 count -= 4;
138 }
139 return t->len - count;
140}
141
142int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
143{
144 struct spi_bitbang_cs *cs = spi->controller_state;
145 u8 bits_per_word;
146 u32 hz;
147
148 if (t) {
149 bits_per_word = t->bits_per_word;
150 hz = t->speed_hz;
151 } else {
152 bits_per_word = 0;
153 hz = 0;
154 }
155
156 /* spi_transfer level calls that work per-word */
157 if (!bits_per_word)
158 bits_per_word = spi->bits_per_word;
159 if (bits_per_word <= 8)
160 cs->txrx_bufs = bitbang_txrx_8;
161 else if (bits_per_word <= 16)
162 cs->txrx_bufs = bitbang_txrx_16;
163 else if (bits_per_word <= 32)
164 cs->txrx_bufs = bitbang_txrx_32;
165 else
166 return -EINVAL;
167
168 /* nsecs = (clock period)/2 */
169 if (!hz)
170 hz = spi->max_speed_hz;
171 if (hz) {
172 cs->nsecs = (1000000000/2) / hz;
173 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
174 return -EINVAL;
175 }
176
177 return 0;
178}
179EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
180
181/**
182 * spi_bitbang_setup - default setup for per-word I/O loops
183 */
184int spi_bitbang_setup(struct spi_device *spi)
185{
186 struct spi_bitbang_cs *cs = spi->controller_state;
187 struct spi_bitbang *bitbang;
188 int retval;
189 unsigned long flags;
190
191 bitbang = spi_master_get_devdata(spi->master);
192
193 if (!cs) {
194 cs = kzalloc(sizeof *cs, GFP_KERNEL);
195 if (!cs)
196 return -ENOMEM;
197 spi->controller_state = cs;
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 return -EINVAL;
204
205 retval = bitbang->setup_transfer(spi, NULL);
206 if (retval < 0)
207 return retval;
208
209 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
210
211 /* NOTE we _need_ to call chipselect() early, ideally with adapter
212 * setup, unless the hardware defaults cooperate to avoid confusion
213 * between normal (active low) and inverted chipselects.
214 */
215
216 /* deselect chip (low or high) */
217 spin_lock_irqsave(&bitbang->lock, flags);
218 if (!bitbang->busy) {
219 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
220 ndelay(cs->nsecs);
221 }
222 spin_unlock_irqrestore(&bitbang->lock, flags);
223
224 return 0;
225}
226EXPORT_SYMBOL_GPL(spi_bitbang_setup);
227
228/**
229 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
230 */
231void spi_bitbang_cleanup(struct spi_device *spi)
232{
233 kfree(spi->controller_state);
234}
235EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
236
237static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
238{
239 struct spi_bitbang_cs *cs = spi->controller_state;
240 unsigned nsecs = cs->nsecs;
241
242 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t);
243}
244
245/*----------------------------------------------------------------------*/
246
247/*
248 * SECOND PART ... simple transfer queue runner.
249 *
250 * This costs a task context per controller, running the queue by
251 * performing each transfer in sequence. Smarter hardware can queue
252 * several DMA transfers at once, and process several controller queues
253 * in parallel; this driver doesn't match such hardware very well.
254 *
255 * Drivers can provide word-at-a-time i/o primitives, or provide
256 * transfer-at-a-time ones to leverage dma or fifo hardware.
257 */
258static void bitbang_work(struct work_struct *work)
259{
260 struct spi_bitbang *bitbang =
261 container_of(work, struct spi_bitbang, work);
262 unsigned long flags;
263
264 spin_lock_irqsave(&bitbang->lock, flags);
265 bitbang->busy = 1;
266 while (!list_empty(&bitbang->queue)) {
267 struct spi_message *m;
268 struct spi_device *spi;
269 unsigned nsecs;
270 struct spi_transfer *t = NULL;
271 unsigned tmp;
272 unsigned cs_change;
273 int status;
274 int do_setup = -1;
275
276 m = container_of(bitbang->queue.next, struct spi_message,
277 queue);
278 list_del_init(&m->queue);
279 spin_unlock_irqrestore(&bitbang->lock, flags);
280
281 /* FIXME this is made-up ... the correct value is known to
282 * word-at-a-time bitbang code, and presumably chipselect()
283 * should enforce these requirements too?
284 */
285 nsecs = 100;
286
287 spi = m->spi;
288 tmp = 0;
289 cs_change = 1;
290 status = 0;
291
292 list_for_each_entry (t, &m->transfers, transfer_list) {
293
294 /* override speed or wordsize? */
295 if (t->speed_hz || t->bits_per_word)
296 do_setup = 1;
297
298 /* init (-1) or override (1) transfer params */
299 if (do_setup != 0) {
300 status = bitbang->setup_transfer(spi, t);
301 if (status < 0)
302 break;
303 if (do_setup == -1)
304 do_setup = 0;
305 }
306
307 /* set up default clock polarity, and activate chip;
308 * this implicitly updates clock and spi modes as
309 * previously recorded for this device via setup().
310 * (and also deselects any other chip that might be
311 * selected ...)
312 */
313 if (cs_change) {
314 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
315 ndelay(nsecs);
316 }
317 cs_change = t->cs_change;
318 if (!t->tx_buf && !t->rx_buf && t->len) {
319 status = -EINVAL;
320 break;
321 }
322
323 /* transfer data. the lower level code handles any
324 * new dma mappings it needs. our caller always gave
325 * us dma-safe buffers.
326 */
327 if (t->len) {
328 /* REVISIT dma API still needs a designated
329 * DMA_ADDR_INVALID; ~0 might be better.
330 */
331 if (!m->is_dma_mapped)
332 t->rx_dma = t->tx_dma = 0;
333 status = bitbang->txrx_bufs(spi, t);
334 }
335 if (status > 0)
336 m->actual_length += status;
337 if (status != t->len) {
338 /* always report some kind of error */
339 if (status >= 0)
340 status = -EREMOTEIO;
341 break;
342 }
343 status = 0;
344
345 /* protocol tweaks before next transfer */
346 if (t->delay_usecs)
347 udelay(t->delay_usecs);
348
349 if (!cs_change)
350 continue;
351 if (t->transfer_list.next == &m->transfers)
352 break;
353
354 /* sometimes a short mid-message deselect of the chip
355 * may be needed to terminate a mode or command
356 */
357 ndelay(nsecs);
358 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
359 ndelay(nsecs);
360 }
361
362 m->status = status;
363 m->complete(m->context);
364
365 /* normally deactivate chipselect ... unless no error and
366 * cs_change has hinted that the next message will probably
367 * be for this chip too.
368 */
369 if (!(status == 0 && cs_change)) {
370 ndelay(nsecs);
371 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
372 ndelay(nsecs);
373 }
374
375 spin_lock_irqsave(&bitbang->lock, flags);
376 }
377 bitbang->busy = 0;
378 spin_unlock_irqrestore(&bitbang->lock, flags);
379}
380
381/**
382 * spi_bitbang_transfer - default submit to transfer queue
383 */
384int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m)
385{
386 struct spi_bitbang *bitbang;
387 unsigned long flags;
388 int status = 0;
389
390 m->actual_length = 0;
391 m->status = -EINPROGRESS;
392
393 bitbang = spi_master_get_devdata(spi->master);
394
395 spin_lock_irqsave(&bitbang->lock, flags);
396 if (!spi->max_speed_hz)
397 status = -ENETDOWN;
398 else {
399 list_add_tail(&m->queue, &bitbang->queue);
400 queue_work(bitbang->workqueue, &bitbang->work);
401 }
402 spin_unlock_irqrestore(&bitbang->lock, flags);
403
404 return status;
405}
406EXPORT_SYMBOL_GPL(spi_bitbang_transfer);
407
408/*----------------------------------------------------------------------*/
409
410/**
411 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
412 * @bitbang: driver handle
413 *
414 * Caller should have zero-initialized all parts of the structure, and then
415 * provided callbacks for chip selection and I/O loops. If the master has
416 * a transfer method, its final step should call spi_bitbang_transfer; or,
417 * that's the default if the transfer routine is not initialized. It should
418 * also set up the bus number and number of chipselects.
419 *
420 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
421 * hardware that basically exposes a shift register) or per-spi_transfer
422 * (which takes better advantage of hardware like fifos or DMA engines).
423 *
424 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
425 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
426 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
427 * routine isn't initialized.
428 *
429 * This routine registers the spi_master, which will process requests in a
430 * dedicated task, keeping IRQs unblocked most of the time. To stop
431 * processing those requests, call spi_bitbang_stop().
432 */
433int spi_bitbang_start(struct spi_bitbang *bitbang)
434{
435 int status;
436
437 if (!bitbang->master || !bitbang->chipselect)
438 return -EINVAL;
439
440 INIT_WORK(&bitbang->work, bitbang_work);
441 spin_lock_init(&bitbang->lock);
442 INIT_LIST_HEAD(&bitbang->queue);
443
444 if (!bitbang->master->mode_bits)
445 bitbang->master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
446
447 if (!bitbang->master->transfer)
448 bitbang->master->transfer = spi_bitbang_transfer;
449 if (!bitbang->txrx_bufs) {
450 bitbang->use_dma = 0;
451 bitbang->txrx_bufs = spi_bitbang_bufs;
452 if (!bitbang->master->setup) {
453 if (!bitbang->setup_transfer)
454 bitbang->setup_transfer =
455 spi_bitbang_setup_transfer;
456 bitbang->master->setup = spi_bitbang_setup;
457 bitbang->master->cleanup = spi_bitbang_cleanup;
458 }
459 } else if (!bitbang->master->setup)
460 return -EINVAL;
461 if (bitbang->master->transfer == spi_bitbang_transfer &&
462 !bitbang->setup_transfer)
463 return -EINVAL;
464
465 /* this task is the only thing to touch the SPI bits */
466 bitbang->busy = 0;
467 bitbang->workqueue = create_singlethread_workqueue(
468 dev_name(bitbang->master->dev.parent));
469 if (bitbang->workqueue == NULL) {
470 status = -EBUSY;
471 goto err1;
472 }
473
474 /* driver may get busy before register() returns, especially
475 * if someone registered boardinfo for devices
476 */
477 status = spi_register_master(bitbang->master);
478 if (status < 0)
479 goto err2;
480
481 return status;
482
483err2:
484 destroy_workqueue(bitbang->workqueue);
485err1:
486 return status;
487}
488EXPORT_SYMBOL_GPL(spi_bitbang_start);
489
490/**
491 * spi_bitbang_stop - stops the task providing spi communication
492 */
493int spi_bitbang_stop(struct spi_bitbang *bitbang)
494{
495 spi_unregister_master(bitbang->master);
496
497 WARN_ON(!list_empty(&bitbang->queue));
498
499 destroy_workqueue(bitbang->workqueue);
500
501 return 0;
502}
503EXPORT_SYMBOL_GPL(spi_bitbang_stop);
504
505MODULE_LICENSE("GPL");
506
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 unsigned bits = t->bits_per_word;
65 unsigned count = t->len;
66 const u8 *tx = t->tx_buf;
67 u8 *rx = t->rx_buf;
68
69 while (likely(count > 0)) {
70 u8 word = 0;
71
72 if (tx)
73 word = *tx++;
74 word = txrx_word(spi, ns, word, bits, flags);
75 if (rx)
76 *rx++ = word;
77 count -= 1;
78 }
79 return t->len - count;
80}
81
82static unsigned bitbang_txrx_16(
83 struct spi_device *spi,
84 u32 (*txrx_word)(struct spi_device *spi,
85 unsigned nsecs,
86 u32 word, u8 bits,
87 unsigned flags),
88 unsigned ns,
89 struct spi_transfer *t,
90 unsigned flags
91) {
92 unsigned bits = t->bits_per_word;
93 unsigned count = t->len;
94 const u16 *tx = t->tx_buf;
95 u16 *rx = t->rx_buf;
96
97 while (likely(count > 1)) {
98 u16 word = 0;
99
100 if (tx)
101 word = *tx++;
102 word = txrx_word(spi, ns, word, bits, flags);
103 if (rx)
104 *rx++ = word;
105 count -= 2;
106 }
107 return t->len - count;
108}
109
110static unsigned bitbang_txrx_32(
111 struct spi_device *spi,
112 u32 (*txrx_word)(struct spi_device *spi,
113 unsigned nsecs,
114 u32 word, u8 bits,
115 unsigned flags),
116 unsigned ns,
117 struct spi_transfer *t,
118 unsigned flags
119) {
120 unsigned bits = t->bits_per_word;
121 unsigned count = t->len;
122 const u32 *tx = t->tx_buf;
123 u32 *rx = t->rx_buf;
124
125 while (likely(count > 3)) {
126 u32 word = 0;
127
128 if (tx)
129 word = *tx++;
130 word = txrx_word(spi, ns, word, bits, flags);
131 if (rx)
132 *rx++ = word;
133 count -= 4;
134 }
135 return t->len - count;
136}
137
138int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
139{
140 struct spi_bitbang_cs *cs = spi->controller_state;
141 u8 bits_per_word;
142 u32 hz;
143
144 if (t) {
145 bits_per_word = t->bits_per_word;
146 hz = t->speed_hz;
147 } else {
148 bits_per_word = 0;
149 hz = 0;
150 }
151
152 /* spi_transfer level calls that work per-word */
153 if (!bits_per_word)
154 bits_per_word = spi->bits_per_word;
155 if (bits_per_word <= 8)
156 cs->txrx_bufs = bitbang_txrx_8;
157 else if (bits_per_word <= 16)
158 cs->txrx_bufs = bitbang_txrx_16;
159 else if (bits_per_word <= 32)
160 cs->txrx_bufs = bitbang_txrx_32;
161 else
162 return -EINVAL;
163
164 /* nsecs = (clock period)/2 */
165 if (!hz)
166 hz = spi->max_speed_hz;
167 if (hz) {
168 cs->nsecs = (1000000000/2) / hz;
169 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
170 return -EINVAL;
171 }
172
173 return 0;
174}
175EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
176
177/*
178 * spi_bitbang_setup - default setup for per-word I/O loops
179 */
180int spi_bitbang_setup(struct spi_device *spi)
181{
182 struct spi_bitbang_cs *cs = spi->controller_state;
183 struct spi_bitbang *bitbang;
184
185 bitbang = spi_master_get_devdata(spi->master);
186
187 if (!cs) {
188 cs = kzalloc(sizeof(*cs), GFP_KERNEL);
189 if (!cs)
190 return -ENOMEM;
191 spi->controller_state = cs;
192 }
193
194 /* per-word shift register access, in hardware or bitbanging */
195 cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
196 if (!cs->txrx_word)
197 return -EINVAL;
198
199 if (bitbang->setup_transfer) {
200 int retval = bitbang->setup_transfer(spi, NULL);
201 if (retval < 0)
202 return retval;
203 }
204
205 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
206
207 return 0;
208}
209EXPORT_SYMBOL_GPL(spi_bitbang_setup);
210
211/*
212 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
213 */
214void spi_bitbang_cleanup(struct spi_device *spi)
215{
216 kfree(spi->controller_state);
217}
218EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
219
220static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
221{
222 struct spi_bitbang_cs *cs = spi->controller_state;
223 unsigned nsecs = cs->nsecs;
224 struct spi_bitbang *bitbang;
225
226 bitbang = spi_master_get_devdata(spi->master);
227 if (bitbang->set_line_direction) {
228 int err;
229
230 err = bitbang->set_line_direction(spi, !!(t->tx_buf));
231 if (err < 0)
232 return err;
233 }
234
235 if (spi->mode & SPI_3WIRE) {
236 unsigned flags;
237
238 flags = t->tx_buf ? SPI_MASTER_NO_RX : SPI_MASTER_NO_TX;
239 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, flags);
240 }
241 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, 0);
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 */
257
258static int spi_bitbang_prepare_hardware(struct spi_master *spi)
259{
260 struct spi_bitbang *bitbang;
261
262 bitbang = spi_master_get_devdata(spi);
263
264 mutex_lock(&bitbang->lock);
265 bitbang->busy = 1;
266 mutex_unlock(&bitbang->lock);
267
268 return 0;
269}
270
271static int spi_bitbang_transfer_one(struct spi_master *master,
272 struct spi_device *spi,
273 struct spi_transfer *transfer)
274{
275 struct spi_bitbang *bitbang = spi_master_get_devdata(master);
276 int status = 0;
277
278 if (bitbang->setup_transfer) {
279 status = bitbang->setup_transfer(spi, transfer);
280 if (status < 0)
281 goto out;
282 }
283
284 if (transfer->len)
285 status = bitbang->txrx_bufs(spi, transfer);
286
287 if (status == transfer->len)
288 status = 0;
289 else if (status >= 0)
290 status = -EREMOTEIO;
291
292out:
293 spi_finalize_current_transfer(master);
294
295 return status;
296}
297
298static int spi_bitbang_unprepare_hardware(struct spi_master *spi)
299{
300 struct spi_bitbang *bitbang;
301
302 bitbang = spi_master_get_devdata(spi);
303
304 mutex_lock(&bitbang->lock);
305 bitbang->busy = 0;
306 mutex_unlock(&bitbang->lock);
307
308 return 0;
309}
310
311static void spi_bitbang_set_cs(struct spi_device *spi, bool enable)
312{
313 struct spi_bitbang *bitbang = spi_master_get_devdata(spi->master);
314
315 /* SPI core provides CS high / low, but bitbang driver
316 * expects CS active
317 * spi device driver takes care of handling SPI_CS_HIGH
318 */
319 enable = (!!(spi->mode & SPI_CS_HIGH) == enable);
320
321 ndelay(SPI_BITBANG_CS_DELAY);
322 bitbang->chipselect(spi, enable ? BITBANG_CS_ACTIVE :
323 BITBANG_CS_INACTIVE);
324 ndelay(SPI_BITBANG_CS_DELAY);
325}
326
327/*----------------------------------------------------------------------*/
328
329int spi_bitbang_init(struct spi_bitbang *bitbang)
330{
331 struct spi_master *master = bitbang->master;
332 bool custom_cs;
333
334 if (!master)
335 return -EINVAL;
336 /*
337 * We only need the chipselect callback if we are actually using it.
338 * If we just use GPIO descriptors, it is surplus. If the
339 * SPI_MASTER_GPIO_SS flag is set, we always need to call the
340 * driver-specific chipselect routine.
341 */
342 custom_cs = (!master->use_gpio_descriptors ||
343 (master->flags & SPI_MASTER_GPIO_SS));
344
345 if (custom_cs && !bitbang->chipselect)
346 return -EINVAL;
347
348 mutex_init(&bitbang->lock);
349
350 if (!master->mode_bits)
351 master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
352
353 if (master->transfer || master->transfer_one_message)
354 return -EINVAL;
355
356 master->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
357 master->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
358 master->transfer_one = spi_bitbang_transfer_one;
359 /*
360 * When using GPIO descriptors, the ->set_cs() callback doesn't even
361 * get called unless SPI_MASTER_GPIO_SS is set.
362 */
363 if (custom_cs)
364 master->set_cs = spi_bitbang_set_cs;
365
366 if (!bitbang->txrx_bufs) {
367 bitbang->use_dma = 0;
368 bitbang->txrx_bufs = spi_bitbang_bufs;
369 if (!master->setup) {
370 if (!bitbang->setup_transfer)
371 bitbang->setup_transfer =
372 spi_bitbang_setup_transfer;
373 master->setup = spi_bitbang_setup;
374 master->cleanup = spi_bitbang_cleanup;
375 }
376 }
377
378 return 0;
379}
380EXPORT_SYMBOL_GPL(spi_bitbang_init);
381
382/**
383 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
384 * @bitbang: driver handle
385 *
386 * Caller should have zero-initialized all parts of the structure, and then
387 * provided callbacks for chip selection and I/O loops. If the master has
388 * a transfer method, its final step should call spi_bitbang_transfer; or,
389 * that's the default if the transfer routine is not initialized. It should
390 * also set up the bus number and number of chipselects.
391 *
392 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
393 * hardware that basically exposes a shift register) or per-spi_transfer
394 * (which takes better advantage of hardware like fifos or DMA engines).
395 *
396 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
397 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
398 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
399 * routine isn't initialized.
400 *
401 * This routine registers the spi_master, which will process requests in a
402 * dedicated task, keeping IRQs unblocked most of the time. To stop
403 * processing those requests, call spi_bitbang_stop().
404 *
405 * On success, this routine will take a reference to master. The caller is
406 * responsible for calling spi_bitbang_stop() to decrement the reference and
407 * spi_master_put() as counterpart of spi_alloc_master() to prevent a memory
408 * leak.
409 */
410int spi_bitbang_start(struct spi_bitbang *bitbang)
411{
412 struct spi_master *master = bitbang->master;
413 int ret;
414
415 ret = spi_bitbang_init(bitbang);
416 if (ret)
417 return ret;
418
419 /* driver may get busy before register() returns, especially
420 * if someone registered boardinfo for devices
421 */
422 ret = spi_register_master(spi_master_get(master));
423 if (ret)
424 spi_master_put(master);
425
426 return ret;
427}
428EXPORT_SYMBOL_GPL(spi_bitbang_start);
429
430/*
431 * spi_bitbang_stop - stops the task providing spi communication
432 */
433void spi_bitbang_stop(struct spi_bitbang *bitbang)
434{
435 spi_unregister_master(bitbang->master);
436}
437EXPORT_SYMBOL_GPL(spi_bitbang_stop);
438
439MODULE_LICENSE("GPL");
440