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David Brownell9904f222006-01-08 13:34:26 -08001/*
Grant Likelyca632f52011-06-06 01:16:30 -06002 * polling/bitbanging SPI master controller driver utilities
David Brownell9904f222006-01-08 13:34:26 -08003 *
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>
Paul Gortmakerd7614de2011-07-03 15:44:29 -040023#include <linux/module.h>
David Brownell9904f222006-01-08 13:34:26 -080024#include <linux/delay.h>
25#include <linux/errno.h>
26#include <linux/platform_device.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090027#include <linux/slab.h>
David Brownell9904f222006-01-08 13:34:26 -080028
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 *
Uwe Kleine-König03ddcbc2013-08-07 21:22:20 +020043 * chipselect() and friends may use spi_device->controller_data and
David Brownell9904f222006-01-08 13:34:26 -080044 * 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) {
Laxman Dewangan766ed702012-12-18 14:25:43 +053072 unsigned bits = t->bits_per_word;
David Brownell9904f222006-01-08 13:34:26 -080073 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) {
Laxman Dewangan766ed702012-12-18 14:25:43 +053098 unsigned bits = t->bits_per_word;
David Brownell9904f222006-01-08 13:34:26 -080099 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) {
Laxman Dewangan766ed702012-12-18 14:25:43 +0530124 unsigned bits = t->bits_per_word;
David Brownell9904f222006-01-08 13:34:26 -0800125 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
Kumar Galaff9f4772006-04-02 16:06:35 -0500142int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
Imre Deak4cff33f2006-02-17 10:02:18 -0800143{
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;
David Brownell1e316d72006-04-06 22:25:56 -0700171 if (hz) {
172 cs->nsecs = (1000000000/2) / hz;
173 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
174 return -EINVAL;
175 }
Imre Deak4cff33f2006-02-17 10:02:18 -0800176
177 return 0;
178}
Kumar Galaff9f4772006-04-02 16:06:35 -0500179EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
Imre Deak4cff33f2006-02-17 10:02:18 -0800180
David Brownell9904f222006-01-08 13:34:26 -0800181/**
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;
Imre Deak4cff33f2006-02-17 10:02:18 -0800188 int retval;
David Brownelld52df2e2008-01-08 15:32:40 -0800189 unsigned long flags;
David Brownell9904f222006-01-08 13:34:26 -0800190
David Brownellccf77cc2006-04-03 15:46:22 -0700191 bitbang = spi_master_get_devdata(spi->master);
192
David Brownell9904f222006-01-08 13:34:26 -0800193 if (!cs) {
Christoph Lametere94b1762006-12-06 20:33:17 -0800194 cs = kzalloc(sizeof *cs, GFP_KERNEL);
David Brownell9904f222006-01-08 13:34:26 -0800195 if (!cs)
196 return -ENOMEM;
197 spi->controller_state = cs;
198 }
David Brownell9904f222006-01-08 13:34:26 -0800199
David Brownell9904f222006-01-08 13:34:26 -0800200 /* 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
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800205 retval = bitbang->setup_transfer(spi, NULL);
Imre Deak4cff33f2006-02-17 10:02:18 -0800206 if (retval < 0)
207 return retval;
David Brownell9904f222006-01-08 13:34:26 -0800208
David Brownell7d077192009-06-17 16:26:03 -0700209 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
David Brownell9904f222006-01-08 13:34:26 -0800210
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) */
David Brownelld52df2e2008-01-08 15:32:40 -0800217 spin_lock_irqsave(&bitbang->lock, flags);
David Brownell9904f222006-01-08 13:34:26 -0800218 if (!bitbang->busy) {
Vitaly Wool8275c642006-01-08 13:34:28 -0800219 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
David Brownell9904f222006-01-08 13:34:26 -0800220 ndelay(cs->nsecs);
221 }
David Brownelld52df2e2008-01-08 15:32:40 -0800222 spin_unlock_irqrestore(&bitbang->lock, flags);
David Brownell9904f222006-01-08 13:34:26 -0800223
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 */
Hans-Peter Nilsson0ffa0282007-02-12 00:52:45 -0800231void spi_bitbang_cleanup(struct spi_device *spi)
David Brownell9904f222006-01-08 13:34:26 -0800232{
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 */
Mark Brown20251722013-07-05 20:07:27 +0100258
259static int spi_bitbang_prepare_hardware(struct spi_master *spi)
260{
261 struct spi_bitbang *bitbang;
262 unsigned long flags;
263
264 bitbang = spi_master_get_devdata(spi);
265
266 spin_lock_irqsave(&bitbang->lock, flags);
267 bitbang->busy = 1;
268 spin_unlock_irqrestore(&bitbang->lock, flags);
269
270 return 0;
271}
272
Fabio Estevamd60990d52013-07-17 15:49:54 -0300273static int spi_bitbang_transfer_one(struct spi_master *master,
Mark Brown91b30852013-07-05 12:06:44 +0100274 struct spi_message *m)
275{
276 struct spi_bitbang *bitbang;
277 unsigned nsecs;
278 struct spi_transfer *t = NULL;
Mark Brown91b30852013-07-05 12:06:44 +0100279 unsigned cs_change;
280 int status;
281 int do_setup = -1;
Fabio Estevamd60990d52013-07-17 15:49:54 -0300282 struct spi_device *spi = m->spi;
Mark Brown91b30852013-07-05 12:06:44 +0100283
Fabio Estevamd60990d52013-07-17 15:49:54 -0300284 bitbang = spi_master_get_devdata(master);
Mark Brown91b30852013-07-05 12:06:44 +0100285
286 /* FIXME this is made-up ... the correct value is known to
287 * word-at-a-time bitbang code, and presumably chipselect()
288 * should enforce these requirements too?
289 */
290 nsecs = 100;
291
Mark Brown91b30852013-07-05 12:06:44 +0100292 cs_change = 1;
293 status = 0;
294
295 list_for_each_entry (t, &m->transfers, transfer_list) {
296
297 /* 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) {
303 status = bitbang->setup_transfer(spi, t);
304 if (status < 0)
305 break;
306 if (do_setup == -1)
307 do_setup = 0;
308 }
309
310 /* set up default clock polarity, and activate chip;
311 * this implicitly updates clock and spi modes as
312 * previously recorded for this device via setup().
313 * (and also deselects any other chip that might be
314 * selected ...)
315 */
316 if (cs_change) {
317 bitbang->chipselect(spi, BITBANG_CS_ACTIVE);
318 ndelay(nsecs);
319 }
320 cs_change = t->cs_change;
321 if (!t->tx_buf && !t->rx_buf && t->len) {
322 status = -EINVAL;
323 break;
324 }
325
326 /* transfer data. the lower level code handles any
327 * new dma mappings it needs. our caller always gave
328 * us dma-safe buffers.
329 */
330 if (t->len) {
331 /* REVISIT dma API still needs a designated
332 * DMA_ADDR_INVALID; ~0 might be better.
333 */
334 if (!m->is_dma_mapped)
335 t->rx_dma = t->tx_dma = 0;
336 status = bitbang->txrx_bufs(spi, t);
337 }
338 if (status > 0)
339 m->actual_length += status;
340 if (status != t->len) {
341 /* always report some kind of error */
342 if (status >= 0)
343 status = -EREMOTEIO;
344 break;
345 }
346 status = 0;
347
348 /* protocol tweaks before next transfer */
349 if (t->delay_usecs)
350 udelay(t->delay_usecs);
351
352 if (cs_change && !list_is_last(&t->transfer_list, &m->transfers)) {
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
362 m->status = status;
Mark Brown91b30852013-07-05 12:06:44 +0100363
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
Fabio Estevamd60990d52013-07-17 15:49:54 -0300374 spi_finalize_current_message(master);
Mark Brown20251722013-07-05 20:07:27 +0100375
Mark Brown91b30852013-07-05 12:06:44 +0100376 return status;
377}
378
Mark Brown20251722013-07-05 20:07:27 +0100379static int spi_bitbang_unprepare_hardware(struct spi_master *spi)
David Brownell9904f222006-01-08 13:34:26 -0800380{
Mark Brown20251722013-07-05 20:07:27 +0100381 struct spi_bitbang *bitbang;
David Brownell9904f222006-01-08 13:34:26 -0800382 unsigned long flags;
Mark Brown20251722013-07-05 20:07:27 +0100383
384 bitbang = spi_master_get_devdata(spi);
David Brownell9904f222006-01-08 13:34:26 -0800385
386 spin_lock_irqsave(&bitbang->lock, flags);
David Brownell9904f222006-01-08 13:34:26 -0800387 bitbang->busy = 0;
388 spin_unlock_irqrestore(&bitbang->lock, flags);
David Brownell9904f222006-01-08 13:34:26 -0800389
Mark Brown20251722013-07-05 20:07:27 +0100390 return 0;
David Brownell9904f222006-01-08 13:34:26 -0800391}
David Brownell9904f222006-01-08 13:34:26 -0800392
393/*----------------------------------------------------------------------*/
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 *
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800409 * 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.
David Brownell9904f222006-01-08 13:34:26 -0800413 *
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 */
418int spi_bitbang_start(struct spi_bitbang *bitbang)
419{
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100420 struct spi_master *master = bitbang->master;
David Brownell9904f222006-01-08 13:34:26 -0800421
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100422 if (!master || !bitbang->chipselect)
David Brownell9904f222006-01-08 13:34:26 -0800423 return -EINVAL;
424
David Brownell9904f222006-01-08 13:34:26 -0800425 spin_lock_init(&bitbang->lock);
David Brownell9904f222006-01-08 13:34:26 -0800426
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100427 if (!master->mode_bits)
428 master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
David Brownelle7db06b2009-06-17 16:26:04 -0700429
Mark Brown20251722013-07-05 20:07:27 +0100430 if (master->transfer || master->transfer_one_message)
431 return -EINVAL;
432
433 master->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
434 master->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
435 master->transfer_one_message = spi_bitbang_transfer_one;
436
David Brownell9904f222006-01-08 13:34:26 -0800437 if (!bitbang->txrx_bufs) {
438 bitbang->use_dma = 0;
439 bitbang->txrx_bufs = spi_bitbang_bufs;
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100440 if (!master->setup) {
Kumar Galaff9f4772006-04-02 16:06:35 -0500441 if (!bitbang->setup_transfer)
442 bitbang->setup_transfer =
443 spi_bitbang_setup_transfer;
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100444 master->setup = spi_bitbang_setup;
445 master->cleanup = spi_bitbang_cleanup;
David Brownell9904f222006-01-08 13:34:26 -0800446 }
Uwe Kleine-König52ade732013-08-08 16:09:49 +0200447 }
David Brownell9904f222006-01-08 13:34:26 -0800448
449 /* driver may get busy before register() returns, especially
450 * if someone registered boardinfo for devices
451 */
Mark Brown20251722013-07-05 20:07:27 +0100452 return spi_register_master(master);
David Brownell9904f222006-01-08 13:34:26 -0800453}
454EXPORT_SYMBOL_GPL(spi_bitbang_start);
455
456/**
457 * spi_bitbang_stop - stops the task providing spi communication
458 */
459int spi_bitbang_stop(struct spi_bitbang *bitbang)
460{
Chris Lesiaka836f582007-03-16 13:38:13 -0800461 spi_unregister_master(bitbang->master);
David Brownell9904f222006-01-08 13:34:26 -0800462
David Brownell9904f222006-01-08 13:34:26 -0800463 return 0;
464}
465EXPORT_SYMBOL_GPL(spi_bitbang_stop);
466
467MODULE_LICENSE("GPL");
468