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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Polling/bitbanging SPI host controller 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#include <linux/time64.h>
15
16#include <linux/spi/spi.h>
17#include <linux/spi/spi_bitbang.h>
18
19#define SPI_BITBANG_CS_DELAY 100
20
21
22/*----------------------------------------------------------------------*/
23
24/*
25 * FIRST PART (OPTIONAL): word-at-a-time spi_transfer support.
26 * Use this for GPIO or shift-register level hardware APIs.
27 *
28 * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
29 * to glue code. These bitbang setup() and cleanup() routines are always
30 * used, though maybe they're called from controller-aware code.
31 *
32 * chipselect() and friends may use spi_device->controller_data and
33 * controller registers as appropriate.
34 *
35 *
36 * NOTE: SPI controller pins can often be used as GPIO pins instead,
37 * which means you could use a bitbang driver either to get hardware
38 * working quickly, or testing for differences that aren't speed related.
39 */
40
41typedef unsigned int (*spi_bb_txrx_bufs_fn)(struct spi_device *, spi_bb_txrx_word_fn,
42 unsigned int, struct spi_transfer *,
43 unsigned int);
44
45struct spi_bitbang_cs {
46 unsigned int nsecs; /* (clock cycle time) / 2 */
47 spi_bb_txrx_word_fn txrx_word;
48 spi_bb_txrx_bufs_fn txrx_bufs;
49};
50
51static unsigned int bitbang_txrx_8(struct spi_device *spi,
52 spi_bb_txrx_word_fn txrx_word,
53 unsigned int ns,
54 struct spi_transfer *t,
55 unsigned int flags)
56{
57 struct spi_bitbang *bitbang;
58 unsigned int bits = t->bits_per_word;
59 unsigned int count = t->len;
60 const u8 *tx = t->tx_buf;
61 u8 *rx = t->rx_buf;
62
63 bitbang = spi_controller_get_devdata(spi->controller);
64 while (likely(count > 0)) {
65 u8 word = 0;
66
67 if (tx)
68 word = *tx++;
69 else
70 word = spi->mode & SPI_MOSI_IDLE_HIGH ? 0xFF : 0;
71 word = txrx_word(spi, ns, word, bits, flags);
72 if (rx)
73 *rx++ = word;
74 count -= 1;
75 }
76 if (bitbang->set_mosi_idle)
77 bitbang->set_mosi_idle(spi);
78
79 return t->len - count;
80}
81
82static unsigned int bitbang_txrx_16(struct spi_device *spi,
83 spi_bb_txrx_word_fn txrx_word,
84 unsigned int ns,
85 struct spi_transfer *t,
86 unsigned int flags)
87{
88 struct spi_bitbang *bitbang;
89 unsigned int bits = t->bits_per_word;
90 unsigned int count = t->len;
91 const u16 *tx = t->tx_buf;
92 u16 *rx = t->rx_buf;
93
94 bitbang = spi_controller_get_devdata(spi->controller);
95 while (likely(count > 1)) {
96 u16 word = 0;
97
98 if (tx)
99 word = *tx++;
100 else
101 word = spi->mode & SPI_MOSI_IDLE_HIGH ? 0xFFFF : 0;
102 word = txrx_word(spi, ns, word, bits, flags);
103 if (rx)
104 *rx++ = word;
105 count -= 2;
106 }
107 if (bitbang->set_mosi_idle)
108 bitbang->set_mosi_idle(spi);
109
110 return t->len - count;
111}
112
113static unsigned int bitbang_txrx_32(struct spi_device *spi,
114 spi_bb_txrx_word_fn txrx_word,
115 unsigned int ns,
116 struct spi_transfer *t,
117 unsigned int flags)
118{
119 struct spi_bitbang *bitbang;
120 unsigned int bits = t->bits_per_word;
121 unsigned int count = t->len;
122 const u32 *tx = t->tx_buf;
123 u32 *rx = t->rx_buf;
124
125 bitbang = spi_controller_get_devdata(spi->controller);
126 while (likely(count > 3)) {
127 u32 word = 0;
128
129 if (tx)
130 word = *tx++;
131 else
132 word = spi->mode & SPI_MOSI_IDLE_HIGH ? 0xFFFFFFFF : 0;
133 word = txrx_word(spi, ns, word, bits, flags);
134 if (rx)
135 *rx++ = word;
136 count -= 4;
137 }
138 if (bitbang->set_mosi_idle)
139 bitbang->set_mosi_idle(spi);
140
141 return t->len - count;
142}
143
144int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
145{
146 struct spi_bitbang_cs *cs = spi->controller_state;
147 u8 bits_per_word;
148 u32 hz;
149
150 if (t) {
151 bits_per_word = t->bits_per_word;
152 hz = t->speed_hz;
153 } else {
154 bits_per_word = 0;
155 hz = 0;
156 }
157
158 /* spi_transfer level calls that work per-word */
159 if (!bits_per_word)
160 bits_per_word = spi->bits_per_word;
161 if (bits_per_word <= 8)
162 cs->txrx_bufs = bitbang_txrx_8;
163 else if (bits_per_word <= 16)
164 cs->txrx_bufs = bitbang_txrx_16;
165 else if (bits_per_word <= 32)
166 cs->txrx_bufs = bitbang_txrx_32;
167 else
168 return -EINVAL;
169
170 /* nsecs = (clock period)/2 */
171 if (!hz)
172 hz = spi->max_speed_hz;
173 if (hz) {
174 cs->nsecs = (NSEC_PER_SEC / 2) / hz;
175 if (cs->nsecs > (MAX_UDELAY_MS * NSEC_PER_MSEC))
176 return -EINVAL;
177 }
178
179 return 0;
180}
181EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
182
183/*
184 * spi_bitbang_setup - default setup for per-word I/O loops
185 */
186int spi_bitbang_setup(struct spi_device *spi)
187{
188 struct spi_bitbang_cs *cs = spi->controller_state;
189 struct spi_bitbang *bitbang;
190 bool initial_setup = false;
191 int retval;
192
193 bitbang = spi_controller_get_devdata(spi->controller);
194
195 if (!cs) {
196 cs = kzalloc(sizeof(*cs), GFP_KERNEL);
197 if (!cs)
198 return -ENOMEM;
199 spi->controller_state = cs;
200 initial_setup = true;
201 }
202
203 /* per-word shift register access, in hardware or bitbanging */
204 cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
205 if (!cs->txrx_word) {
206 retval = -EINVAL;
207 goto err_free;
208 }
209
210 if (bitbang->setup_transfer) {
211 retval = bitbang->setup_transfer(spi, NULL);
212 if (retval < 0)
213 goto err_free;
214 }
215
216 if (bitbang->set_mosi_idle)
217 bitbang->set_mosi_idle(spi);
218
219 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
220
221 return 0;
222
223err_free:
224 if (initial_setup)
225 kfree(cs);
226 return retval;
227}
228EXPORT_SYMBOL_GPL(spi_bitbang_setup);
229
230/*
231 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
232 */
233void spi_bitbang_cleanup(struct spi_device *spi)
234{
235 kfree(spi->controller_state);
236}
237EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
238
239static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
240{
241 struct spi_bitbang_cs *cs = spi->controller_state;
242 unsigned int nsecs = cs->nsecs;
243 struct spi_bitbang *bitbang;
244
245 bitbang = spi_controller_get_devdata(spi->controller);
246 if (bitbang->set_line_direction) {
247 int err;
248
249 err = bitbang->set_line_direction(spi, !!(t->tx_buf));
250 if (err < 0)
251 return err;
252 }
253
254 if (spi->mode & SPI_3WIRE) {
255 unsigned int flags;
256
257 flags = t->tx_buf ? SPI_CONTROLLER_NO_RX : SPI_CONTROLLER_NO_TX;
258 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, flags);
259 }
260 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, 0);
261}
262
263/*----------------------------------------------------------------------*/
264
265/*
266 * SECOND PART ... simple transfer queue runner.
267 *
268 * This costs a task context per controller, running the queue by
269 * performing each transfer in sequence. Smarter hardware can queue
270 * several DMA transfers at once, and process several controller queues
271 * in parallel; this driver doesn't match such hardware very well.
272 *
273 * Drivers can provide word-at-a-time i/o primitives, or provide
274 * transfer-at-a-time ones to leverage dma or fifo hardware.
275 */
276
277static int spi_bitbang_prepare_hardware(struct spi_controller *spi)
278{
279 struct spi_bitbang *bitbang;
280
281 bitbang = spi_controller_get_devdata(spi);
282
283 mutex_lock(&bitbang->lock);
284 bitbang->busy = 1;
285 mutex_unlock(&bitbang->lock);
286
287 return 0;
288}
289
290static int spi_bitbang_transfer_one(struct spi_controller *ctlr,
291 struct spi_device *spi,
292 struct spi_transfer *transfer)
293{
294 struct spi_bitbang *bitbang = spi_controller_get_devdata(ctlr);
295 int status = 0;
296
297 if (bitbang->setup_transfer) {
298 status = bitbang->setup_transfer(spi, transfer);
299 if (status < 0)
300 goto out;
301 }
302
303 if (transfer->len)
304 status = bitbang->txrx_bufs(spi, transfer);
305
306 if (status == transfer->len)
307 status = 0;
308 else if (status >= 0)
309 status = -EREMOTEIO;
310
311out:
312 spi_finalize_current_transfer(ctlr);
313
314 return status;
315}
316
317static int spi_bitbang_unprepare_hardware(struct spi_controller *spi)
318{
319 struct spi_bitbang *bitbang;
320
321 bitbang = spi_controller_get_devdata(spi);
322
323 mutex_lock(&bitbang->lock);
324 bitbang->busy = 0;
325 mutex_unlock(&bitbang->lock);
326
327 return 0;
328}
329
330static void spi_bitbang_set_cs(struct spi_device *spi, bool enable)
331{
332 struct spi_bitbang *bitbang = spi_controller_get_devdata(spi->controller);
333
334 /* SPI core provides CS high / low, but bitbang driver
335 * expects CS active
336 * spi device driver takes care of handling SPI_CS_HIGH
337 */
338 enable = (!!(spi->mode & SPI_CS_HIGH) == enable);
339
340 ndelay(SPI_BITBANG_CS_DELAY);
341 bitbang->chipselect(spi, enable ? BITBANG_CS_ACTIVE :
342 BITBANG_CS_INACTIVE);
343 ndelay(SPI_BITBANG_CS_DELAY);
344}
345
346/*----------------------------------------------------------------------*/
347
348int spi_bitbang_init(struct spi_bitbang *bitbang)
349{
350 struct spi_controller *ctlr = bitbang->ctlr;
351 bool custom_cs;
352
353 if (!ctlr)
354 return -EINVAL;
355 /*
356 * We only need the chipselect callback if we are actually using it.
357 * If we just use GPIO descriptors, it is surplus. If the
358 * SPI_CONTROLLER_GPIO_SS flag is set, we always need to call the
359 * driver-specific chipselect routine.
360 */
361 custom_cs = (!ctlr->use_gpio_descriptors ||
362 (ctlr->flags & SPI_CONTROLLER_GPIO_SS));
363
364 if (custom_cs && !bitbang->chipselect)
365 return -EINVAL;
366
367 mutex_init(&bitbang->lock);
368
369 if (!ctlr->mode_bits)
370 ctlr->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
371
372 if (ctlr->transfer || ctlr->transfer_one_message)
373 return -EINVAL;
374
375 ctlr->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
376 ctlr->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
377 ctlr->transfer_one = spi_bitbang_transfer_one;
378 /*
379 * When using GPIO descriptors, the ->set_cs() callback doesn't even
380 * get called unless SPI_CONTROLLER_GPIO_SS is set.
381 */
382 if (custom_cs)
383 ctlr->set_cs = spi_bitbang_set_cs;
384
385 if (!bitbang->txrx_bufs) {
386 bitbang->use_dma = 0;
387 bitbang->txrx_bufs = spi_bitbang_bufs;
388 if (!ctlr->setup) {
389 if (!bitbang->setup_transfer)
390 bitbang->setup_transfer =
391 spi_bitbang_setup_transfer;
392 ctlr->setup = spi_bitbang_setup;
393 ctlr->cleanup = spi_bitbang_cleanup;
394 }
395 }
396
397 return 0;
398}
399EXPORT_SYMBOL_GPL(spi_bitbang_init);
400
401/**
402 * spi_bitbang_start - start up a polled/bitbanging SPI host controller driver
403 * @bitbang: driver handle
404 *
405 * Caller should have zero-initialized all parts of the structure, and then
406 * provided callbacks for chip selection and I/O loops. If the host controller has
407 * a transfer method, its final step should call spi_bitbang_transfer(); or,
408 * that's the default if the transfer routine is not initialized. It should
409 * also set up the bus number and number of chipselects.
410 *
411 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
412 * hardware that basically exposes a shift register) or per-spi_transfer
413 * (which takes better advantage of hardware like fifos or DMA engines).
414 *
415 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup(),
416 * spi_bitbang_cleanup() and spi_bitbang_setup_transfer() to handle those SPI
417 * host controller methods. Those methods are the defaults if the bitbang->txrx_bufs
418 * routine isn't initialized.
419 *
420 * This routine registers the spi_controller, which will process requests in a
421 * dedicated task, keeping IRQs unblocked most of the time. To stop
422 * processing those requests, call spi_bitbang_stop().
423 *
424 * On success, this routine will take a reference to the controller. The caller
425 * is responsible for calling spi_bitbang_stop() to decrement the reference and
426 * spi_controller_put() as counterpart of spi_alloc_host() to prevent a memory
427 * leak.
428 */
429int spi_bitbang_start(struct spi_bitbang *bitbang)
430{
431 struct spi_controller *ctlr = bitbang->ctlr;
432 int ret;
433
434 ret = spi_bitbang_init(bitbang);
435 if (ret)
436 return ret;
437
438 /* driver may get busy before register() returns, especially
439 * if someone registered boardinfo for devices
440 */
441 ret = spi_register_controller(spi_controller_get(ctlr));
442 if (ret)
443 spi_controller_put(ctlr);
444
445 return ret;
446}
447EXPORT_SYMBOL_GPL(spi_bitbang_start);
448
449/*
450 * spi_bitbang_stop - stops the task providing spi communication
451 */
452void spi_bitbang_stop(struct spi_bitbang *bitbang)
453{
454 spi_unregister_controller(bitbang->ctlr);
455}
456EXPORT_SYMBOL_GPL(spi_bitbang_stop);
457
458MODULE_LICENSE("GPL");
459MODULE_DESCRIPTION("Utilities for Bitbanging SPI host controllers");
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