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David Brownelld29389d2009-01-06 14:41:41 -08001/*
Grant Likelyca632f52011-06-06 01:16:30 -06002 * SPI master driver using generic bitbanged GPIO
David Brownelld29389d2009-01-06 14:41:41 -08003 *
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
Grant Likelyca632f52011-06-06 01:16:30 -060072 * #include "spi-gpio.c"
David Brownelld29389d2009-01-06 14:41:41 -080073 */
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{
Michael Bueschbe503442009-02-18 14:48:41 -0800117 return !!gpio_get_value(SPI_MISO_GPIO);
David Brownelld29389d2009-01-06 14:41:41 -0800118}
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
Grant Likelyca632f52011-06-06 01:16:30 -0600130#include "spi-bitbang-txrx.h"
David Brownelld29389d2009-01-06 14:41:41 -0800131
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{
Marek Szyprowski04bb2a02010-06-30 14:27:32 -0600149 return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
David Brownelld29389d2009-01-06 14:41:41 -0800150}
151
152static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
153 unsigned nsecs, u32 word, u8 bits)
154{
Marek Szyprowski04bb2a02010-06-30 14:27:32 -0600155 return bitbang_txrx_be_cpha1(spi, nsecs, 0, 0, word, bits);
David Brownelld29389d2009-01-06 14:41:41 -0800156}
157
158static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
159 unsigned nsecs, u32 word, u8 bits)
160{
Marek Szyprowski04bb2a02010-06-30 14:27:32 -0600161 return bitbang_txrx_be_cpha0(spi, nsecs, 1, 0, word, bits);
David Brownelld29389d2009-01-06 14:41:41 -0800162}
163
164static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
165 unsigned nsecs, u32 word, u8 bits)
166{
Marek Szyprowski04bb2a02010-06-30 14:27:32 -0600167 return bitbang_txrx_be_cpha1(spi, nsecs, 1, 0, word, bits);
David Brownelld29389d2009-01-06 14:41:41 -0800168}
169
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600170/*
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
David Brownelld29389d2009-01-06 14:41:41 -0800208/*----------------------------------------------------------------------*/
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
Michael Bueschbfb9bcd2009-04-02 16:57:07 -0700218 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 }
David Brownelld29389d2009-01-06 14:41:41 -0800222}
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) {
Michael Bueschbfb9bcd2009-04-02 16:57:07 -0700233 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 }
David Brownelld29389d2009-01-06 14:41:41 -0800239 }
240 if (!status)
241 status = spi_bitbang_setup(spi);
242 if (status) {
Michael Bueschbfb9bcd2009-04-02 16:57:07 -0700243 if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT)
David Brownelld29389d2009-01-06 14:41:41 -0800244 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
Michael Bueschbfb9bcd2009-04-02 16:57:07 -0700253 if (cs != SPI_GPIO_NO_CHIPSELECT)
254 gpio_free(cs);
David Brownelld29389d2009-01-06 14:41:41 -0800255 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
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600273spi_gpio_request(struct spi_gpio_platform_data *pdata, const char *label,
274 u16 *res_flags)
David Brownelld29389d2009-01-06 14:41:41 -0800275{
276 int value;
277
278 /* NOTE: SPI_*_GPIO symbols may reference "pdata" */
279
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600280 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 }
David Brownelld29389d2009-01-06 14:41:41 -0800288
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600289 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 }
David Brownelld29389d2009-01-06 14:41:41 -0800297
298 value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
299 if (value)
300 goto free_miso;
301
302 goto done;
303
304free_miso:
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600305 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
306 gpio_free(SPI_MISO_GPIO);
David Brownelld29389d2009-01-06 14:41:41 -0800307free_mosi:
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600308 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
309 gpio_free(SPI_MOSI_GPIO);
David Brownelld29389d2009-01-06 14:41:41 -0800310done:
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;
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600320 u16 master_flags = 0;
David Brownelld29389d2009-01-06 14:41:41 -0800321
322 pdata = pdev->dev.platform_data;
323#ifdef GENERIC_BITBANG
324 if (!pdata || !pdata->num_chipselect)
325 return -ENODEV;
326#endif
327
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600328 status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
David Brownelld29389d2009-01-06 14:41:41 -0800329 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
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600344 master->flags = master_flags;
David Brownelld29389d2009-01-06 14:41:41 -0800345 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;
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600352
Roel Kluin23699f92010-10-02 14:03:32 +0200353 if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) {
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600354 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 }
David Brownelld29389d2009-01-06 14:41:41 -0800364 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:
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600371 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);
David Brownelld29389d2009-01-06 14:41:41 -0800375 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
Marek Szyprowski3c8e1a82010-06-30 14:27:37 -0600397 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);
David Brownelld29389d2009-01-06 14:41:41 -0800401 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");