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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.
David Brownell9904f222006-01-08 13:34:26 -080013 */
14
David Brownell9904f222006-01-08 13:34:26 -080015#include <linux/spinlock.h>
16#include <linux/workqueue.h>
17#include <linux/interrupt.h>
Paul Gortmakerd7614de2011-07-03 15:44:29 -040018#include <linux/module.h>
David Brownell9904f222006-01-08 13:34:26 -080019#include <linux/delay.h>
20#include <linux/errno.h>
21#include <linux/platform_device.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090022#include <linux/slab.h>
David Brownell9904f222006-01-08 13:34:26 -080023
24#include <linux/spi/spi.h>
25#include <linux/spi/spi_bitbang.h>
26
Heiner Kallweit00376862015-09-29 23:15:53 +020027#define SPI_BITBANG_CS_DELAY 100
28
David Brownell9904f222006-01-08 13:34:26 -080029
30/*----------------------------------------------------------------------*/
31
32/*
33 * FIRST PART (OPTIONAL): word-at-a-time spi_transfer support.
34 * Use this for GPIO or shift-register level hardware APIs.
35 *
36 * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
37 * to glue code. These bitbang setup() and cleanup() routines are always
38 * used, though maybe they're called from controller-aware code.
39 *
Uwe Kleine-König03ddcbc2013-08-07 21:22:20 +020040 * chipselect() and friends may use spi_device->controller_data and
David Brownell9904f222006-01-08 13:34:26 -080041 * controller registers as appropriate.
42 *
43 *
44 * NOTE: SPI controller pins can often be used as GPIO pins instead,
45 * which means you could use a bitbang driver either to get hardware
46 * working quickly, or testing for differences that aren't speed related.
47 */
48
49struct spi_bitbang_cs {
50 unsigned nsecs; /* (clock cycle time)/2 */
51 u32 (*txrx_word)(struct spi_device *spi, unsigned nsecs,
52 u32 word, u8 bits);
53 unsigned (*txrx_bufs)(struct spi_device *,
54 u32 (*txrx_word)(
55 struct spi_device *spi,
56 unsigned nsecs,
57 u32 word, u8 bits),
58 unsigned, struct spi_transfer *);
59};
60
61static unsigned bitbang_txrx_8(
62 struct spi_device *spi,
63 u32 (*txrx_word)(struct spi_device *spi,
64 unsigned nsecs,
65 u32 word, u8 bits),
66 unsigned ns,
67 struct spi_transfer *t
68) {
Laxman Dewangan766ed702012-12-18 14:25:43 +053069 unsigned bits = t->bits_per_word;
David Brownell9904f222006-01-08 13:34:26 -080070 unsigned count = t->len;
71 const u8 *tx = t->tx_buf;
72 u8 *rx = t->rx_buf;
73
74 while (likely(count > 0)) {
75 u8 word = 0;
76
77 if (tx)
78 word = *tx++;
79 word = txrx_word(spi, ns, word, bits);
80 if (rx)
81 *rx++ = word;
82 count -= 1;
83 }
84 return t->len - count;
85}
86
87static unsigned bitbang_txrx_16(
88 struct spi_device *spi,
89 u32 (*txrx_word)(struct spi_device *spi,
90 unsigned nsecs,
91 u32 word, u8 bits),
92 unsigned ns,
93 struct spi_transfer *t
94) {
Laxman Dewangan766ed702012-12-18 14:25:43 +053095 unsigned bits = t->bits_per_word;
David Brownell9904f222006-01-08 13:34:26 -080096 unsigned count = t->len;
97 const u16 *tx = t->tx_buf;
98 u16 *rx = t->rx_buf;
99
100 while (likely(count > 1)) {
101 u16 word = 0;
102
103 if (tx)
104 word = *tx++;
105 word = txrx_word(spi, ns, word, bits);
106 if (rx)
107 *rx++ = word;
108 count -= 2;
109 }
110 return t->len - count;
111}
112
113static unsigned bitbang_txrx_32(
114 struct spi_device *spi,
115 u32 (*txrx_word)(struct spi_device *spi,
116 unsigned nsecs,
117 u32 word, u8 bits),
118 unsigned ns,
119 struct spi_transfer *t
120) {
Laxman Dewangan766ed702012-12-18 14:25:43 +0530121 unsigned bits = t->bits_per_word;
David Brownell9904f222006-01-08 13:34:26 -0800122 unsigned count = t->len;
123 const u32 *tx = t->tx_buf;
124 u32 *rx = t->rx_buf;
125
126 while (likely(count > 3)) {
127 u32 word = 0;
128
129 if (tx)
130 word = *tx++;
131 word = txrx_word(spi, ns, word, bits);
132 if (rx)
133 *rx++ = word;
134 count -= 4;
135 }
136 return t->len - count;
137}
138
Kumar Galaff9f4772006-04-02 16:06:35 -0500139int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
Imre Deak4cff33f2006-02-17 10:02:18 -0800140{
141 struct spi_bitbang_cs *cs = spi->controller_state;
142 u8 bits_per_word;
143 u32 hz;
144
145 if (t) {
146 bits_per_word = t->bits_per_word;
147 hz = t->speed_hz;
148 } else {
149 bits_per_word = 0;
150 hz = 0;
151 }
152
153 /* spi_transfer level calls that work per-word */
154 if (!bits_per_word)
155 bits_per_word = spi->bits_per_word;
156 if (bits_per_word <= 8)
157 cs->txrx_bufs = bitbang_txrx_8;
158 else if (bits_per_word <= 16)
159 cs->txrx_bufs = bitbang_txrx_16;
160 else if (bits_per_word <= 32)
161 cs->txrx_bufs = bitbang_txrx_32;
162 else
163 return -EINVAL;
164
165 /* nsecs = (clock period)/2 */
166 if (!hz)
167 hz = spi->max_speed_hz;
David Brownell1e316d72006-04-06 22:25:56 -0700168 if (hz) {
169 cs->nsecs = (1000000000/2) / hz;
170 if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
171 return -EINVAL;
172 }
Imre Deak4cff33f2006-02-17 10:02:18 -0800173
174 return 0;
175}
Kumar Galaff9f4772006-04-02 16:06:35 -0500176EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
Imre Deak4cff33f2006-02-17 10:02:18 -0800177
David Brownell9904f222006-01-08 13:34:26 -0800178/**
179 * spi_bitbang_setup - default setup for per-word I/O loops
180 */
181int spi_bitbang_setup(struct spi_device *spi)
182{
183 struct spi_bitbang_cs *cs = spi->controller_state;
184 struct spi_bitbang *bitbang;
185
David Brownellccf77cc2006-04-03 15:46:22 -0700186 bitbang = spi_master_get_devdata(spi->master);
187
David Brownell9904f222006-01-08 13:34:26 -0800188 if (!cs) {
Jingoo Hancff93c52013-10-14 10:33:38 +0900189 cs = kzalloc(sizeof(*cs), GFP_KERNEL);
David Brownell9904f222006-01-08 13:34:26 -0800190 if (!cs)
191 return -ENOMEM;
192 spi->controller_state = cs;
193 }
David Brownell9904f222006-01-08 13:34:26 -0800194
David Brownell9904f222006-01-08 13:34:26 -0800195 /* per-word shift register access, in hardware or bitbanging */
196 cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
197 if (!cs->txrx_word)
198 return -EINVAL;
199
Pelle Nilsson7d0ec8b2015-04-14 15:40:17 +0200200 if (bitbang->setup_transfer) {
201 int retval = bitbang->setup_transfer(spi, NULL);
202 if (retval < 0)
203 return retval;
204 }
David Brownell9904f222006-01-08 13:34:26 -0800205
David Brownell7d077192009-06-17 16:26:03 -0700206 dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
David Brownell9904f222006-01-08 13:34:26 -0800207
208 /* NOTE we _need_ to call chipselect() early, ideally with adapter
209 * setup, unless the hardware defaults cooperate to avoid confusion
210 * between normal (active low) and inverted chipselects.
211 */
212
213 /* deselect chip (low or high) */
Nicolas Boichatc15f6ed2015-08-17 11:52:54 +0800214 mutex_lock(&bitbang->lock);
David Brownell9904f222006-01-08 13:34:26 -0800215 if (!bitbang->busy) {
Vitaly Wool8275c642006-01-08 13:34:28 -0800216 bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
David Brownell9904f222006-01-08 13:34:26 -0800217 ndelay(cs->nsecs);
218 }
Nicolas Boichatc15f6ed2015-08-17 11:52:54 +0800219 mutex_unlock(&bitbang->lock);
David Brownell9904f222006-01-08 13:34:26 -0800220
221 return 0;
222}
223EXPORT_SYMBOL_GPL(spi_bitbang_setup);
224
225/**
226 * spi_bitbang_cleanup - default cleanup for per-word I/O loops
227 */
Hans-Peter Nilsson0ffa0282007-02-12 00:52:45 -0800228void spi_bitbang_cleanup(struct spi_device *spi)
David Brownell9904f222006-01-08 13:34:26 -0800229{
230 kfree(spi->controller_state);
231}
232EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
233
234static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
235{
236 struct spi_bitbang_cs *cs = spi->controller_state;
237 unsigned nsecs = cs->nsecs;
238
239 return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t);
240}
241
242/*----------------------------------------------------------------------*/
243
244/*
245 * SECOND PART ... simple transfer queue runner.
246 *
247 * This costs a task context per controller, running the queue by
248 * performing each transfer in sequence. Smarter hardware can queue
249 * several DMA transfers at once, and process several controller queues
250 * in parallel; this driver doesn't match such hardware very well.
251 *
252 * Drivers can provide word-at-a-time i/o primitives, or provide
253 * transfer-at-a-time ones to leverage dma or fifo hardware.
254 */
Mark Brown20251722013-07-05 20:07:27 +0100255
256static int spi_bitbang_prepare_hardware(struct spi_master *spi)
257{
Jingoo Hancff93c52013-10-14 10:33:38 +0900258 struct spi_bitbang *bitbang;
Mark Brown20251722013-07-05 20:07:27 +0100259
260 bitbang = spi_master_get_devdata(spi);
261
Nicolas Boichatc15f6ed2015-08-17 11:52:54 +0800262 mutex_lock(&bitbang->lock);
Mark Brown20251722013-07-05 20:07:27 +0100263 bitbang->busy = 1;
Nicolas Boichatc15f6ed2015-08-17 11:52:54 +0800264 mutex_unlock(&bitbang->lock);
Mark Brown20251722013-07-05 20:07:27 +0100265
266 return 0;
267}
268
Fabio Estevamd60990d52013-07-17 15:49:54 -0300269static int spi_bitbang_transfer_one(struct spi_master *master,
Heiner Kallweit00376862015-09-29 23:15:53 +0200270 struct spi_device *spi,
271 struct spi_transfer *transfer)
Mark Brown91b30852013-07-05 12:06:44 +0100272{
Heiner Kallweit00376862015-09-29 23:15:53 +0200273 struct spi_bitbang *bitbang = spi_master_get_devdata(master);
274 int status = 0;
Mark Brown91b30852013-07-05 12:06:44 +0100275
Heiner Kallweit00376862015-09-29 23:15:53 +0200276 if (bitbang->setup_transfer) {
277 status = bitbang->setup_transfer(spi, transfer);
278 if (status < 0)
279 goto out;
280 }
Mark Brown91b30852013-07-05 12:06:44 +0100281
Heiner Kallweit00376862015-09-29 23:15:53 +0200282 if (transfer->len)
283 status = bitbang->txrx_bufs(spi, transfer);
Mark Brown91b30852013-07-05 12:06:44 +0100284
Heiner Kallweit00376862015-09-29 23:15:53 +0200285 if (status == transfer->len)
Mark Brown91b30852013-07-05 12:06:44 +0100286 status = 0;
Heiner Kallweit00376862015-09-29 23:15:53 +0200287 else if (status >= 0)
288 status = -EREMOTEIO;
Mark Brown91b30852013-07-05 12:06:44 +0100289
Heiner Kallweit00376862015-09-29 23:15:53 +0200290out:
291 spi_finalize_current_transfer(master);
Mark Brown20251722013-07-05 20:07:27 +0100292
Mark Brown91b30852013-07-05 12:06:44 +0100293 return status;
294}
295
Mark Brown20251722013-07-05 20:07:27 +0100296static int spi_bitbang_unprepare_hardware(struct spi_master *spi)
David Brownell9904f222006-01-08 13:34:26 -0800297{
Jingoo Hancff93c52013-10-14 10:33:38 +0900298 struct spi_bitbang *bitbang;
Mark Brown20251722013-07-05 20:07:27 +0100299
300 bitbang = spi_master_get_devdata(spi);
David Brownell9904f222006-01-08 13:34:26 -0800301
Nicolas Boichatc15f6ed2015-08-17 11:52:54 +0800302 mutex_lock(&bitbang->lock);
David Brownell9904f222006-01-08 13:34:26 -0800303 bitbang->busy = 0;
Nicolas Boichatc15f6ed2015-08-17 11:52:54 +0800304 mutex_unlock(&bitbang->lock);
David Brownell9904f222006-01-08 13:34:26 -0800305
Mark Brown20251722013-07-05 20:07:27 +0100306 return 0;
David Brownell9904f222006-01-08 13:34:26 -0800307}
David Brownell9904f222006-01-08 13:34:26 -0800308
Heiner Kallweit00376862015-09-29 23:15:53 +0200309static void spi_bitbang_set_cs(struct spi_device *spi, bool enable)
310{
311 struct spi_bitbang *bitbang = spi_master_get_devdata(spi->master);
312
313 /* SPI core provides CS high / low, but bitbang driver
314 * expects CS active
315 * spi device driver takes care of handling SPI_CS_HIGH
316 */
317 enable = (!!(spi->mode & SPI_CS_HIGH) == enable);
318
319 ndelay(SPI_BITBANG_CS_DELAY);
320 bitbang->chipselect(spi, enable ? BITBANG_CS_ACTIVE :
321 BITBANG_CS_INACTIVE);
322 ndelay(SPI_BITBANG_CS_DELAY);
323}
324
David Brownell9904f222006-01-08 13:34:26 -0800325/*----------------------------------------------------------------------*/
326
327/**
328 * spi_bitbang_start - start up a polled/bitbanging SPI master driver
329 * @bitbang: driver handle
330 *
331 * Caller should have zero-initialized all parts of the structure, and then
332 * provided callbacks for chip selection and I/O loops. If the master has
333 * a transfer method, its final step should call spi_bitbang_transfer; or,
334 * that's the default if the transfer routine is not initialized. It should
335 * also set up the bus number and number of chipselects.
336 *
337 * For i/o loops, provide callbacks either per-word (for bitbanging, or for
338 * hardware that basically exposes a shift register) or per-spi_transfer
339 * (which takes better advantage of hardware like fifos or DMA engines).
340 *
Hans-Peter Nilsson7f8c7612007-02-12 00:52:44 -0800341 * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
342 * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
343 * master methods. Those methods are the defaults if the bitbang->txrx_bufs
344 * routine isn't initialized.
David Brownell9904f222006-01-08 13:34:26 -0800345 *
346 * This routine registers the spi_master, which will process requests in a
347 * dedicated task, keeping IRQs unblocked most of the time. To stop
348 * processing those requests, call spi_bitbang_stop().
Axel Lin702a4872013-09-10 15:43:41 +0800349 *
350 * On success, this routine will take a reference to master. The caller is
351 * responsible for calling spi_bitbang_stop() to decrement the reference and
352 * spi_master_put() as counterpart of spi_alloc_master() to prevent a memory
353 * leak.
David Brownell9904f222006-01-08 13:34:26 -0800354 */
355int spi_bitbang_start(struct spi_bitbang *bitbang)
356{
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100357 struct spi_master *master = bitbang->master;
Axel Lin702a4872013-09-10 15:43:41 +0800358 int ret;
David Brownell9904f222006-01-08 13:34:26 -0800359
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100360 if (!master || !bitbang->chipselect)
David Brownell9904f222006-01-08 13:34:26 -0800361 return -EINVAL;
362
Nicolas Boichatc15f6ed2015-08-17 11:52:54 +0800363 mutex_init(&bitbang->lock);
David Brownell9904f222006-01-08 13:34:26 -0800364
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100365 if (!master->mode_bits)
366 master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
David Brownelle7db06b2009-06-17 16:26:04 -0700367
Mark Brown20251722013-07-05 20:07:27 +0100368 if (master->transfer || master->transfer_one_message)
369 return -EINVAL;
370
371 master->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
372 master->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
Heiner Kallweit00376862015-09-29 23:15:53 +0200373 master->transfer_one = spi_bitbang_transfer_one;
374 master->set_cs = spi_bitbang_set_cs;
Mark Brown20251722013-07-05 20:07:27 +0100375
David Brownell9904f222006-01-08 13:34:26 -0800376 if (!bitbang->txrx_bufs) {
377 bitbang->use_dma = 0;
378 bitbang->txrx_bufs = spi_bitbang_bufs;
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100379 if (!master->setup) {
Kumar Galaff9f4772006-04-02 16:06:35 -0500380 if (!bitbang->setup_transfer)
381 bitbang->setup_transfer =
382 spi_bitbang_setup_transfer;
Guennadi Liakhovetski7a5d8ca2013-01-10 13:13:56 +0100383 master->setup = spi_bitbang_setup;
384 master->cleanup = spi_bitbang_cleanup;
David Brownell9904f222006-01-08 13:34:26 -0800385 }
Uwe Kleine-König52ade732013-08-08 16:09:49 +0200386 }
David Brownell9904f222006-01-08 13:34:26 -0800387
388 /* driver may get busy before register() returns, especially
389 * if someone registered boardinfo for devices
390 */
Axel Lin702a4872013-09-10 15:43:41 +0800391 ret = spi_register_master(spi_master_get(master));
392 if (ret)
393 spi_master_put(master);
394
395 return 0;
David Brownell9904f222006-01-08 13:34:26 -0800396}
397EXPORT_SYMBOL_GPL(spi_bitbang_start);
398
399/**
400 * spi_bitbang_stop - stops the task providing spi communication
401 */
Axel Lind9721ae2014-03-29 18:50:12 +0800402void spi_bitbang_stop(struct spi_bitbang *bitbang)
David Brownell9904f222006-01-08 13:34:26 -0800403{
Chris Lesiaka836f582007-03-16 13:38:13 -0800404 spi_unregister_master(bitbang->master);
David Brownell9904f222006-01-08 13:34:26 -0800405}
406EXPORT_SYMBOL_GPL(spi_bitbang_stop);
407
408MODULE_LICENSE("GPL");
409