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1/*
2 * SPI master driver using generic bitbanged GPIO
3 *
4 * Copyright (C) 2006,2008 David Brownell
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 */
20#include <linux/kernel.h>
21#include <linux/init.h>
22#include <linux/platform_device.h>
23#include <linux/gpio.h>
24
25#include <linux/spi/spi.h>
26#include <linux/spi/spi_bitbang.h>
27#include <linux/spi/spi_gpio.h>
28
29
30/*
31 * This bitbanging SPI master driver should help make systems usable
32 * when a native hardware SPI engine is not available, perhaps because
33 * its driver isn't yet working or because the I/O pins it requires
34 * are used for other purposes.
35 *
36 * platform_device->driver_data ... points to spi_gpio
37 *
38 * spi->controller_state ... reserved for bitbang framework code
39 * spi->controller_data ... holds chipselect GPIO
40 *
41 * spi->master->dev.driver_data ... points to spi_gpio->bitbang
42 */
43
44struct spi_gpio {
45 struct spi_bitbang bitbang;
46 struct spi_gpio_platform_data pdata;
47 struct platform_device *pdev;
48};
49
50/*----------------------------------------------------------------------*/
51
52/*
53 * Because the overhead of going through four GPIO procedure calls
54 * per transferred bit can make performance a problem, this code
55 * is set up so that you can use it in either of two ways:
56 *
57 * - The slow generic way: set up platform_data to hold the GPIO
58 * numbers used for MISO/MOSI/SCK, and issue procedure calls for
59 * each of them. This driver can handle several such busses.
60 *
61 * - The quicker inlined way: only helps with platform GPIO code
62 * that inlines operations for constant GPIOs. This can give
63 * you tight (fast!) inner loops, but each such bus needs a
64 * new driver. You'll define a new C file, with Makefile and
65 * Kconfig support; the C code can be a total of six lines:
66 *
67 * #define DRIVER_NAME "myboard_spi2"
68 * #define SPI_MISO_GPIO 119
69 * #define SPI_MOSI_GPIO 120
70 * #define SPI_SCK_GPIO 121
71 * #define SPI_N_CHIPSEL 4
72 * #include "spi-gpio.c"
73 */
74
75#ifndef DRIVER_NAME
76#define DRIVER_NAME "spi_gpio"
77
78#define GENERIC_BITBANG /* vs tight inlines */
79
80/* all functions referencing these symbols must define pdata */
81#define SPI_MISO_GPIO ((pdata)->miso)
82#define SPI_MOSI_GPIO ((pdata)->mosi)
83#define SPI_SCK_GPIO ((pdata)->sck)
84
85#define SPI_N_CHIPSEL ((pdata)->num_chipselect)
86
87#endif
88
89/*----------------------------------------------------------------------*/
90
91static inline const struct spi_gpio_platform_data * __pure
92spi_to_pdata(const struct spi_device *spi)
93{
94 const struct spi_bitbang *bang;
95 const struct spi_gpio *spi_gpio;
96
97 bang = spi_master_get_devdata(spi->master);
98 spi_gpio = container_of(bang, struct spi_gpio, bitbang);
99 return &spi_gpio->pdata;
100}
101
102/* this is #defined to avoid unused-variable warnings when inlining */
103#define pdata spi_to_pdata(spi)
104
105static inline void setsck(const struct spi_device *spi, int is_on)
106{
107 gpio_set_value(SPI_SCK_GPIO, is_on);
108}
109
110static inline void setmosi(const struct spi_device *spi, int is_on)
111{
112 gpio_set_value(SPI_MOSI_GPIO, is_on);
113}
114
115static inline int getmiso(const struct spi_device *spi)
116{
117 return !!gpio_get_value(SPI_MISO_GPIO);
118}
119
120#undef pdata
121
122/*
123 * NOTE: this clocks "as fast as we can". It "should" be a function of the
124 * requested device clock. Software overhead means we usually have trouble
125 * reaching even one Mbit/sec (except when we can inline bitops), so for now
126 * we'll just assume we never need additional per-bit slowdowns.
127 */
128#define spidelay(nsecs) do {} while (0)
129
130#include "spi-bitbang-txrx.h"
131
132/*
133 * These functions can leverage inline expansion of GPIO calls to shrink
134 * costs for a txrx bit, often by factors of around ten (by instruction
135 * count). That is particularly visible for larger word sizes, but helps
136 * even with default 8-bit words.
137 *
138 * REVISIT overheads calling these functions for each word also have
139 * significant performance costs. Having txrx_bufs() calls that inline
140 * the txrx_word() logic would help performance, e.g. on larger blocks
141 * used with flash storage or MMC/SD. There should also be ways to make
142 * GCC be less stupid about reloading registers inside the I/O loops,
143 * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3?
144 */
145
146static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi,
147 unsigned nsecs, u32 word, u8 bits)
148{
149 return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
150}
151
152static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
153 unsigned nsecs, u32 word, u8 bits)
154{
155 return bitbang_txrx_be_cpha1(spi, nsecs, 0, 0, word, bits);
156}
157
158static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
159 unsigned nsecs, u32 word, u8 bits)
160{
161 return bitbang_txrx_be_cpha0(spi, nsecs, 1, 0, word, bits);
162}
163
164static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
165 unsigned nsecs, u32 word, u8 bits)
166{
167 return bitbang_txrx_be_cpha1(spi, nsecs, 1, 0, word, bits);
168}
169
170/*
171 * These functions do not call setmosi or getmiso if respective flag
172 * (SPI_MASTER_NO_RX or SPI_MASTER_NO_TX) is set, so they are safe to
173 * call when such pin is not present or defined in the controller.
174 * A separate set of callbacks is defined to get highest possible
175 * speed in the generic case (when both MISO and MOSI lines are
176 * available), as optimiser will remove the checks when argument is
177 * constant.
178 */
179
180static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi,
181 unsigned nsecs, u32 word, u8 bits)
182{
183 unsigned flags = spi->master->flags;
184 return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
185}
186
187static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi,
188 unsigned nsecs, u32 word, u8 bits)
189{
190 unsigned flags = spi->master->flags;
191 return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits);
192}
193
194static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi,
195 unsigned nsecs, u32 word, u8 bits)
196{
197 unsigned flags = spi->master->flags;
198 return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits);
199}
200
201static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi,
202 unsigned nsecs, u32 word, u8 bits)
203{
204 unsigned flags = spi->master->flags;
205 return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits);
206}
207
208/*----------------------------------------------------------------------*/
209
210static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
211{
212 unsigned long cs = (unsigned long) spi->controller_data;
213
214 /* set initial clock polarity */
215 if (is_active)
216 setsck(spi, spi->mode & SPI_CPOL);
217
218 if (cs != SPI_GPIO_NO_CHIPSELECT) {
219 /* SPI is normally active-low */
220 gpio_set_value(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
221 }
222}
223
224static int spi_gpio_setup(struct spi_device *spi)
225{
226 unsigned long cs = (unsigned long) spi->controller_data;
227 int status = 0;
228
229 if (spi->bits_per_word > 32)
230 return -EINVAL;
231
232 if (!spi->controller_state) {
233 if (cs != SPI_GPIO_NO_CHIPSELECT) {
234 status = gpio_request(cs, dev_name(&spi->dev));
235 if (status)
236 return status;
237 status = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
238 }
239 }
240 if (!status)
241 status = spi_bitbang_setup(spi);
242 if (status) {
243 if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT)
244 gpio_free(cs);
245 }
246 return status;
247}
248
249static void spi_gpio_cleanup(struct spi_device *spi)
250{
251 unsigned long cs = (unsigned long) spi->controller_data;
252
253 if (cs != SPI_GPIO_NO_CHIPSELECT)
254 gpio_free(cs);
255 spi_bitbang_cleanup(spi);
256}
257
258static int __init spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
259{
260 int value;
261
262 value = gpio_request(pin, label);
263 if (value == 0) {
264 if (is_in)
265 value = gpio_direction_input(pin);
266 else
267 value = gpio_direction_output(pin, 0);
268 }
269 return value;
270}
271
272static int __init
273spi_gpio_request(struct spi_gpio_platform_data *pdata, const char *label,
274 u16 *res_flags)
275{
276 int value;
277
278 /* NOTE: SPI_*_GPIO symbols may reference "pdata" */
279
280 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) {
281 value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false);
282 if (value)
283 goto done;
284 } else {
285 /* HW configuration without MOSI pin */
286 *res_flags |= SPI_MASTER_NO_TX;
287 }
288
289 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) {
290 value = spi_gpio_alloc(SPI_MISO_GPIO, label, true);
291 if (value)
292 goto free_mosi;
293 } else {
294 /* HW configuration without MISO pin */
295 *res_flags |= SPI_MASTER_NO_RX;
296 }
297
298 value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
299 if (value)
300 goto free_miso;
301
302 goto done;
303
304free_miso:
305 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
306 gpio_free(SPI_MISO_GPIO);
307free_mosi:
308 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
309 gpio_free(SPI_MOSI_GPIO);
310done:
311 return value;
312}
313
314static int __init spi_gpio_probe(struct platform_device *pdev)
315{
316 int status;
317 struct spi_master *master;
318 struct spi_gpio *spi_gpio;
319 struct spi_gpio_platform_data *pdata;
320 u16 master_flags = 0;
321
322 pdata = pdev->dev.platform_data;
323#ifdef GENERIC_BITBANG
324 if (!pdata || !pdata->num_chipselect)
325 return -ENODEV;
326#endif
327
328 status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
329 if (status < 0)
330 return status;
331
332 master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio);
333 if (!master) {
334 status = -ENOMEM;
335 goto gpio_free;
336 }
337 spi_gpio = spi_master_get_devdata(master);
338 platform_set_drvdata(pdev, spi_gpio);
339
340 spi_gpio->pdev = pdev;
341 if (pdata)
342 spi_gpio->pdata = *pdata;
343
344 master->flags = master_flags;
345 master->bus_num = pdev->id;
346 master->num_chipselect = SPI_N_CHIPSEL;
347 master->setup = spi_gpio_setup;
348 master->cleanup = spi_gpio_cleanup;
349
350 spi_gpio->bitbang.master = spi_master_get(master);
351 spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
352
353 if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) {
354 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
355 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
356 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
357 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
358 } else {
359 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0;
360 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1;
361 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2;
362 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
363 }
364 spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
365 spi_gpio->bitbang.flags = SPI_CS_HIGH;
366
367 status = spi_bitbang_start(&spi_gpio->bitbang);
368 if (status < 0) {
369 spi_master_put(spi_gpio->bitbang.master);
370gpio_free:
371 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
372 gpio_free(SPI_MISO_GPIO);
373 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
374 gpio_free(SPI_MOSI_GPIO);
375 gpio_free(SPI_SCK_GPIO);
376 spi_master_put(master);
377 }
378
379 return status;
380}
381
382static int __exit spi_gpio_remove(struct platform_device *pdev)
383{
384 struct spi_gpio *spi_gpio;
385 struct spi_gpio_platform_data *pdata;
386 int status;
387
388 spi_gpio = platform_get_drvdata(pdev);
389 pdata = pdev->dev.platform_data;
390
391 /* stop() unregisters child devices too */
392 status = spi_bitbang_stop(&spi_gpio->bitbang);
393 spi_master_put(spi_gpio->bitbang.master);
394
395 platform_set_drvdata(pdev, NULL);
396
397 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
398 gpio_free(SPI_MISO_GPIO);
399 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
400 gpio_free(SPI_MOSI_GPIO);
401 gpio_free(SPI_SCK_GPIO);
402
403 return status;
404}
405
406MODULE_ALIAS("platform:" DRIVER_NAME);
407
408static struct platform_driver spi_gpio_driver = {
409 .driver.name = DRIVER_NAME,
410 .driver.owner = THIS_MODULE,
411 .remove = __exit_p(spi_gpio_remove),
412};
413
414static int __init spi_gpio_init(void)
415{
416 return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe);
417}
418module_init(spi_gpio_init);
419
420static void __exit spi_gpio_exit(void)
421{
422 platform_driver_unregister(&spi_gpio_driver);
423}
424module_exit(spi_gpio_exit);
425
426
427MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
428MODULE_AUTHOR("David Brownell");
429MODULE_LICENSE("GPL");
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * SPI master driver using generic bitbanged GPIO
4 *
5 * Copyright (C) 2006,2008 David Brownell
6 * Copyright (C) 2017 Linus Walleij
7 */
8#include <linux/kernel.h>
9#include <linux/module.h>
10#include <linux/platform_device.h>
11#include <linux/gpio/consumer.h>
12#include <linux/of.h>
13#include <linux/of_device.h>
14
15#include <linux/spi/spi.h>
16#include <linux/spi/spi_bitbang.h>
17#include <linux/spi/spi_gpio.h>
18
19
20/*
21 * This bitbanging SPI master driver should help make systems usable
22 * when a native hardware SPI engine is not available, perhaps because
23 * its driver isn't yet working or because the I/O pins it requires
24 * are used for other purposes.
25 *
26 * platform_device->driver_data ... points to spi_gpio
27 *
28 * spi->controller_state ... reserved for bitbang framework code
29 *
30 * spi->master->dev.driver_data ... points to spi_gpio->bitbang
31 */
32
33struct spi_gpio {
34 struct spi_bitbang bitbang;
35 struct gpio_desc *sck;
36 struct gpio_desc *miso;
37 struct gpio_desc *mosi;
38 struct gpio_desc **cs_gpios;
39};
40
41/*----------------------------------------------------------------------*/
42
43/*
44 * Because the overhead of going through four GPIO procedure calls
45 * per transferred bit can make performance a problem, this code
46 * is set up so that you can use it in either of two ways:
47 *
48 * - The slow generic way: set up platform_data to hold the GPIO
49 * numbers used for MISO/MOSI/SCK, and issue procedure calls for
50 * each of them. This driver can handle several such busses.
51 *
52 * - The quicker inlined way: only helps with platform GPIO code
53 * that inlines operations for constant GPIOs. This can give
54 * you tight (fast!) inner loops, but each such bus needs a
55 * new driver. You'll define a new C file, with Makefile and
56 * Kconfig support; the C code can be a total of six lines:
57 *
58 * #define DRIVER_NAME "myboard_spi2"
59 * #define SPI_MISO_GPIO 119
60 * #define SPI_MOSI_GPIO 120
61 * #define SPI_SCK_GPIO 121
62 * #define SPI_N_CHIPSEL 4
63 * #include "spi-gpio.c"
64 */
65
66#ifndef DRIVER_NAME
67#define DRIVER_NAME "spi_gpio"
68
69#define GENERIC_BITBANG /* vs tight inlines */
70
71#endif
72
73/*----------------------------------------------------------------------*/
74
75static inline struct spi_gpio *__pure
76spi_to_spi_gpio(const struct spi_device *spi)
77{
78 const struct spi_bitbang *bang;
79 struct spi_gpio *spi_gpio;
80
81 bang = spi_master_get_devdata(spi->master);
82 spi_gpio = container_of(bang, struct spi_gpio, bitbang);
83 return spi_gpio;
84}
85
86/* These helpers are in turn called by the bitbang inlines */
87static inline void setsck(const struct spi_device *spi, int is_on)
88{
89 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
90
91 gpiod_set_value_cansleep(spi_gpio->sck, is_on);
92}
93
94static inline void setmosi(const struct spi_device *spi, int is_on)
95{
96 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
97
98 gpiod_set_value_cansleep(spi_gpio->mosi, is_on);
99}
100
101static inline int getmiso(const struct spi_device *spi)
102{
103 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
104
105 if (spi->mode & SPI_3WIRE)
106 return !!gpiod_get_value_cansleep(spi_gpio->mosi);
107 else
108 return !!gpiod_get_value_cansleep(spi_gpio->miso);
109}
110
111/*
112 * NOTE: this clocks "as fast as we can". It "should" be a function of the
113 * requested device clock. Software overhead means we usually have trouble
114 * reaching even one Mbit/sec (except when we can inline bitops), so for now
115 * we'll just assume we never need additional per-bit slowdowns.
116 */
117#define spidelay(nsecs) do {} while (0)
118
119#include "spi-bitbang-txrx.h"
120
121/*
122 * These functions can leverage inline expansion of GPIO calls to shrink
123 * costs for a txrx bit, often by factors of around ten (by instruction
124 * count). That is particularly visible for larger word sizes, but helps
125 * even with default 8-bit words.
126 *
127 * REVISIT overheads calling these functions for each word also have
128 * significant performance costs. Having txrx_bufs() calls that inline
129 * the txrx_word() logic would help performance, e.g. on larger blocks
130 * used with flash storage or MMC/SD. There should also be ways to make
131 * GCC be less stupid about reloading registers inside the I/O loops,
132 * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3?
133 */
134
135static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi,
136 unsigned nsecs, u32 word, u8 bits, unsigned flags)
137{
138 if (unlikely(spi->mode & SPI_LSB_FIRST))
139 return bitbang_txrx_le_cpha0(spi, nsecs, 0, flags, word, bits);
140 else
141 return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
142}
143
144static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
145 unsigned nsecs, u32 word, u8 bits, unsigned flags)
146{
147 if (unlikely(spi->mode & SPI_LSB_FIRST))
148 return bitbang_txrx_le_cpha1(spi, nsecs, 0, flags, word, bits);
149 else
150 return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits);
151}
152
153static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
154 unsigned nsecs, u32 word, u8 bits, unsigned flags)
155{
156 if (unlikely(spi->mode & SPI_LSB_FIRST))
157 return bitbang_txrx_le_cpha0(spi, nsecs, 1, flags, word, bits);
158 else
159 return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits);
160}
161
162static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
163 unsigned nsecs, u32 word, u8 bits, unsigned flags)
164{
165 if (unlikely(spi->mode & SPI_LSB_FIRST))
166 return bitbang_txrx_le_cpha1(spi, nsecs, 1, flags, word, bits);
167 else
168 return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits);
169}
170
171/*
172 * These functions do not call setmosi or getmiso if respective flag
173 * (SPI_MASTER_NO_RX or SPI_MASTER_NO_TX) is set, so they are safe to
174 * call when such pin is not present or defined in the controller.
175 * A separate set of callbacks is defined to get highest possible
176 * speed in the generic case (when both MISO and MOSI lines are
177 * available), as optimiser will remove the checks when argument is
178 * constant.
179 */
180
181static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi,
182 unsigned nsecs, u32 word, u8 bits, unsigned flags)
183{
184 flags = spi->master->flags;
185 if (unlikely(spi->mode & SPI_LSB_FIRST))
186 return bitbang_txrx_le_cpha0(spi, nsecs, 0, flags, word, bits);
187 else
188 return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
189}
190
191static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi,
192 unsigned nsecs, u32 word, u8 bits, unsigned flags)
193{
194 flags = spi->master->flags;
195 if (unlikely(spi->mode & SPI_LSB_FIRST))
196 return bitbang_txrx_le_cpha1(spi, nsecs, 0, flags, word, bits);
197 else
198 return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits);
199}
200
201static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi,
202 unsigned nsecs, u32 word, u8 bits, unsigned flags)
203{
204 flags = spi->master->flags;
205 if (unlikely(spi->mode & SPI_LSB_FIRST))
206 return bitbang_txrx_le_cpha0(spi, nsecs, 1, flags, word, bits);
207 else
208 return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits);
209}
210
211static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi,
212 unsigned nsecs, u32 word, u8 bits, unsigned flags)
213{
214 flags = spi->master->flags;
215 if (unlikely(spi->mode & SPI_LSB_FIRST))
216 return bitbang_txrx_le_cpha1(spi, nsecs, 1, flags, word, bits);
217 else
218 return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits);
219}
220
221/*----------------------------------------------------------------------*/
222
223static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
224{
225 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
226
227 /* set initial clock line level */
228 if (is_active)
229 gpiod_set_value_cansleep(spi_gpio->sck, spi->mode & SPI_CPOL);
230
231 /* Drive chip select line, if we have one */
232 if (spi_gpio->cs_gpios) {
233 struct gpio_desc *cs = spi_gpio->cs_gpios[spi->chip_select];
234
235 /* SPI chip selects are normally active-low */
236 gpiod_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
237 }
238}
239
240static int spi_gpio_setup(struct spi_device *spi)
241{
242 struct gpio_desc *cs;
243 int status = 0;
244 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
245
246 /*
247 * The CS GPIOs have already been
248 * initialized from the descriptor lookup.
249 */
250 if (spi_gpio->cs_gpios) {
251 cs = spi_gpio->cs_gpios[spi->chip_select];
252 if (!spi->controller_state && cs)
253 status = gpiod_direction_output(cs,
254 !(spi->mode & SPI_CS_HIGH));
255 }
256
257 if (!status)
258 status = spi_bitbang_setup(spi);
259
260 return status;
261}
262
263static int spi_gpio_set_direction(struct spi_device *spi, bool output)
264{
265 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
266 int ret;
267
268 if (output)
269 return gpiod_direction_output(spi_gpio->mosi, 1);
270
271 /*
272 * Only change MOSI to an input if using 3WIRE mode.
273 * Otherwise, MOSI could be left floating if there is
274 * no pull resistor connected to the I/O pin, or could
275 * be left logic high if there is a pull-up. Transmitting
276 * logic high when only clocking MISO data in can put some
277 * SPI devices in to a bad state.
278 */
279 if (spi->mode & SPI_3WIRE) {
280 ret = gpiod_direction_input(spi_gpio->mosi);
281 if (ret)
282 return ret;
283 }
284 /*
285 * Send a turnaround high impedance cycle when switching
286 * from output to input. Theoretically there should be
287 * a clock delay here, but as has been noted above, the
288 * nsec delay function for bit-banged GPIO is simply
289 * {} because bit-banging just doesn't get fast enough
290 * anyway.
291 */
292 if (spi->mode & SPI_3WIRE_HIZ) {
293 gpiod_set_value_cansleep(spi_gpio->sck,
294 !(spi->mode & SPI_CPOL));
295 gpiod_set_value_cansleep(spi_gpio->sck,
296 !!(spi->mode & SPI_CPOL));
297 }
298 return 0;
299}
300
301static void spi_gpio_cleanup(struct spi_device *spi)
302{
303 spi_bitbang_cleanup(spi);
304}
305
306/*
307 * It can be convenient to use this driver with pins that have alternate
308 * functions associated with a "native" SPI controller if a driver for that
309 * controller is not available, or is missing important functionality.
310 *
311 * On platforms which can do so, configure MISO with a weak pullup unless
312 * there's an external pullup on that signal. That saves power by avoiding
313 * floating signals. (A weak pulldown would save power too, but many
314 * drivers expect to see all-ones data as the no slave "response".)
315 */
316static int spi_gpio_request(struct device *dev, struct spi_gpio *spi_gpio)
317{
318 spi_gpio->mosi = devm_gpiod_get_optional(dev, "mosi", GPIOD_OUT_LOW);
319 if (IS_ERR(spi_gpio->mosi))
320 return PTR_ERR(spi_gpio->mosi);
321
322 spi_gpio->miso = devm_gpiod_get_optional(dev, "miso", GPIOD_IN);
323 if (IS_ERR(spi_gpio->miso))
324 return PTR_ERR(spi_gpio->miso);
325
326 spi_gpio->sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW);
327 return PTR_ERR_OR_ZERO(spi_gpio->sck);
328}
329
330#ifdef CONFIG_OF
331static const struct of_device_id spi_gpio_dt_ids[] = {
332 { .compatible = "spi-gpio" },
333 {}
334};
335MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids);
336
337static int spi_gpio_probe_dt(struct platform_device *pdev,
338 struct spi_master *master)
339{
340 master->dev.of_node = pdev->dev.of_node;
341 master->use_gpio_descriptors = true;
342
343 return 0;
344}
345#else
346static inline int spi_gpio_probe_dt(struct platform_device *pdev,
347 struct spi_master *master)
348{
349 return 0;
350}
351#endif
352
353static int spi_gpio_probe_pdata(struct platform_device *pdev,
354 struct spi_master *master)
355{
356 struct device *dev = &pdev->dev;
357 struct spi_gpio_platform_data *pdata = dev_get_platdata(dev);
358 struct spi_gpio *spi_gpio = spi_master_get_devdata(master);
359 int i;
360
361#ifdef GENERIC_BITBANG
362 if (!pdata || !pdata->num_chipselect)
363 return -ENODEV;
364#endif
365 /*
366 * The master needs to think there is a chipselect even if not
367 * connected
368 */
369 master->num_chipselect = pdata->num_chipselect ?: 1;
370
371 spi_gpio->cs_gpios = devm_kcalloc(dev, master->num_chipselect,
372 sizeof(*spi_gpio->cs_gpios),
373 GFP_KERNEL);
374 if (!spi_gpio->cs_gpios)
375 return -ENOMEM;
376
377 for (i = 0; i < master->num_chipselect; i++) {
378 spi_gpio->cs_gpios[i] = devm_gpiod_get_index(dev, "cs", i,
379 GPIOD_OUT_HIGH);
380 if (IS_ERR(spi_gpio->cs_gpios[i]))
381 return PTR_ERR(spi_gpio->cs_gpios[i]);
382 }
383
384 return 0;
385}
386
387static int spi_gpio_probe(struct platform_device *pdev)
388{
389 int status;
390 struct spi_master *master;
391 struct spi_gpio *spi_gpio;
392 struct device *dev = &pdev->dev;
393 struct spi_bitbang *bb;
394
395 master = devm_spi_alloc_master(dev, sizeof(*spi_gpio));
396 if (!master)
397 return -ENOMEM;
398
399 if (pdev->dev.of_node)
400 status = spi_gpio_probe_dt(pdev, master);
401 else
402 status = spi_gpio_probe_pdata(pdev, master);
403
404 if (status)
405 return status;
406
407 spi_gpio = spi_master_get_devdata(master);
408
409 status = spi_gpio_request(dev, spi_gpio);
410 if (status)
411 return status;
412
413 master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
414 master->mode_bits = SPI_3WIRE | SPI_3WIRE_HIZ | SPI_CPHA | SPI_CPOL |
415 SPI_CS_HIGH | SPI_LSB_FIRST;
416 if (!spi_gpio->mosi) {
417 /* HW configuration without MOSI pin
418 *
419 * No setting SPI_MASTER_NO_RX here - if there is only
420 * a MOSI pin connected the host can still do RX by
421 * changing the direction of the line.
422 */
423 master->flags = SPI_MASTER_NO_TX;
424 }
425
426 master->bus_num = pdev->id;
427 master->setup = spi_gpio_setup;
428 master->cleanup = spi_gpio_cleanup;
429
430 bb = &spi_gpio->bitbang;
431 bb->master = master;
432 /*
433 * There is some additional business, apart from driving the CS GPIO
434 * line, that we need to do on selection. This makes the local
435 * callback for chipselect always get called.
436 */
437 master->flags |= SPI_MASTER_GPIO_SS;
438 bb->chipselect = spi_gpio_chipselect;
439 bb->set_line_direction = spi_gpio_set_direction;
440
441 if (master->flags & SPI_MASTER_NO_TX) {
442 bb->txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0;
443 bb->txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1;
444 bb->txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2;
445 bb->txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
446 } else {
447 bb->txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
448 bb->txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
449 bb->txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
450 bb->txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
451 }
452 bb->setup_transfer = spi_bitbang_setup_transfer;
453
454 status = spi_bitbang_init(&spi_gpio->bitbang);
455 if (status)
456 return status;
457
458 return devm_spi_register_master(&pdev->dev, master);
459}
460
461MODULE_ALIAS("platform:" DRIVER_NAME);
462
463static struct platform_driver spi_gpio_driver = {
464 .driver = {
465 .name = DRIVER_NAME,
466 .of_match_table = of_match_ptr(spi_gpio_dt_ids),
467 },
468 .probe = spi_gpio_probe,
469};
470module_platform_driver(spi_gpio_driver);
471
472MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
473MODULE_AUTHOR("David Brownell");
474MODULE_LICENSE("GPL");