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1 | /* |
2 | * spi_gpio.c - 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 | ||
44 | struct 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 | ||
91 | static inline const struct spi_gpio_platform_data * __pure | |
92 | spi_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 | ||
105 | static inline void setsck(const struct spi_device *spi, int is_on) | |
106 | { | |
107 | gpio_set_value(SPI_SCK_GPIO, is_on); | |
108 | } | |
109 | ||
110 | static inline void setmosi(const struct spi_device *spi, int is_on) | |
111 | { | |
112 | gpio_set_value(SPI_MOSI_GPIO, is_on); | |
113 | } | |
114 | ||
115 | static 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 | #define EXPAND_BITBANG_TXRX | |
131 | #include <linux/spi/spi_bitbang.h> | |
132 | ||
133 | /* | |
134 | * These functions can leverage inline expansion of GPIO calls to shrink | |
135 | * costs for a txrx bit, often by factors of around ten (by instruction | |
136 | * count). That is particularly visible for larger word sizes, but helps | |
137 | * even with default 8-bit words. | |
138 | * | |
139 | * REVISIT overheads calling these functions for each word also have | |
140 | * significant performance costs. Having txrx_bufs() calls that inline | |
141 | * the txrx_word() logic would help performance, e.g. on larger blocks | |
142 | * used with flash storage or MMC/SD. There should also be ways to make | |
143 | * GCC be less stupid about reloading registers inside the I/O loops, | |
144 | * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3? | |
145 | */ | |
146 | ||
147 | static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi, | |
148 | unsigned nsecs, u32 word, u8 bits) | |
149 | { | |
150 | return bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits); | |
151 | } | |
152 | ||
153 | static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi, | |
154 | unsigned nsecs, u32 word, u8 bits) | |
155 | { | |
156 | return bitbang_txrx_be_cpha1(spi, nsecs, 0, word, bits); | |
157 | } | |
158 | ||
159 | static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi, | |
160 | unsigned nsecs, u32 word, u8 bits) | |
161 | { | |
162 | return bitbang_txrx_be_cpha0(spi, nsecs, 1, word, bits); | |
163 | } | |
164 | ||
165 | static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi, | |
166 | unsigned nsecs, u32 word, u8 bits) | |
167 | { | |
168 | return bitbang_txrx_be_cpha1(spi, nsecs, 1, word, bits); | |
169 | } | |
170 | ||
171 | /*----------------------------------------------------------------------*/ | |
172 | ||
173 | static void spi_gpio_chipselect(struct spi_device *spi, int is_active) | |
174 | { | |
175 | unsigned long cs = (unsigned long) spi->controller_data; | |
176 | ||
177 | /* set initial clock polarity */ | |
178 | if (is_active) | |
179 | setsck(spi, spi->mode & SPI_CPOL); | |
180 | ||
181 | /* SPI is normally active-low */ | |
182 | gpio_set_value(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active); | |
183 | } | |
184 | ||
185 | static int spi_gpio_setup(struct spi_device *spi) | |
186 | { | |
187 | unsigned long cs = (unsigned long) spi->controller_data; | |
188 | int status = 0; | |
189 | ||
190 | if (spi->bits_per_word > 32) | |
191 | return -EINVAL; | |
192 | ||
193 | if (!spi->controller_state) { | |
194 | status = gpio_request(cs, spi->dev.bus_id); | |
195 | if (status) | |
196 | return status; | |
197 | status = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH); | |
198 | } | |
199 | if (!status) | |
200 | status = spi_bitbang_setup(spi); | |
201 | if (status) { | |
202 | if (!spi->controller_state) | |
203 | gpio_free(cs); | |
204 | } | |
205 | return status; | |
206 | } | |
207 | ||
208 | static void spi_gpio_cleanup(struct spi_device *spi) | |
209 | { | |
210 | unsigned long cs = (unsigned long) spi->controller_data; | |
211 | ||
212 | gpio_free(cs); | |
213 | spi_bitbang_cleanup(spi); | |
214 | } | |
215 | ||
216 | static int __init spi_gpio_alloc(unsigned pin, const char *label, bool is_in) | |
217 | { | |
218 | int value; | |
219 | ||
220 | value = gpio_request(pin, label); | |
221 | if (value == 0) { | |
222 | if (is_in) | |
223 | value = gpio_direction_input(pin); | |
224 | else | |
225 | value = gpio_direction_output(pin, 0); | |
226 | } | |
227 | return value; | |
228 | } | |
229 | ||
230 | static int __init | |
231 | spi_gpio_request(struct spi_gpio_platform_data *pdata, const char *label) | |
232 | { | |
233 | int value; | |
234 | ||
235 | /* NOTE: SPI_*_GPIO symbols may reference "pdata" */ | |
236 | ||
237 | value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false); | |
238 | if (value) | |
239 | goto done; | |
240 | ||
241 | value = spi_gpio_alloc(SPI_MISO_GPIO, label, true); | |
242 | if (value) | |
243 | goto free_mosi; | |
244 | ||
245 | value = spi_gpio_alloc(SPI_SCK_GPIO, label, false); | |
246 | if (value) | |
247 | goto free_miso; | |
248 | ||
249 | goto done; | |
250 | ||
251 | free_miso: | |
252 | gpio_free(SPI_MISO_GPIO); | |
253 | free_mosi: | |
254 | gpio_free(SPI_MOSI_GPIO); | |
255 | done: | |
256 | return value; | |
257 | } | |
258 | ||
259 | static int __init spi_gpio_probe(struct platform_device *pdev) | |
260 | { | |
261 | int status; | |
262 | struct spi_master *master; | |
263 | struct spi_gpio *spi_gpio; | |
264 | struct spi_gpio_platform_data *pdata; | |
265 | ||
266 | pdata = pdev->dev.platform_data; | |
267 | #ifdef GENERIC_BITBANG | |
268 | if (!pdata || !pdata->num_chipselect) | |
269 | return -ENODEV; | |
270 | #endif | |
271 | ||
272 | status = spi_gpio_request(pdata, dev_name(&pdev->dev)); | |
273 | if (status < 0) | |
274 | return status; | |
275 | ||
276 | master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio); | |
277 | if (!master) { | |
278 | status = -ENOMEM; | |
279 | goto gpio_free; | |
280 | } | |
281 | spi_gpio = spi_master_get_devdata(master); | |
282 | platform_set_drvdata(pdev, spi_gpio); | |
283 | ||
284 | spi_gpio->pdev = pdev; | |
285 | if (pdata) | |
286 | spi_gpio->pdata = *pdata; | |
287 | ||
288 | master->bus_num = pdev->id; | |
289 | master->num_chipselect = SPI_N_CHIPSEL; | |
290 | master->setup = spi_gpio_setup; | |
291 | master->cleanup = spi_gpio_cleanup; | |
292 | ||
293 | spi_gpio->bitbang.master = spi_master_get(master); | |
294 | spi_gpio->bitbang.chipselect = spi_gpio_chipselect; | |
295 | spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0; | |
296 | spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1; | |
297 | spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2; | |
298 | spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3; | |
299 | spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer; | |
300 | spi_gpio->bitbang.flags = SPI_CS_HIGH; | |
301 | ||
302 | status = spi_bitbang_start(&spi_gpio->bitbang); | |
303 | if (status < 0) { | |
304 | spi_master_put(spi_gpio->bitbang.master); | |
305 | gpio_free: | |
306 | gpio_free(SPI_MISO_GPIO); | |
307 | gpio_free(SPI_MOSI_GPIO); | |
308 | gpio_free(SPI_SCK_GPIO); | |
309 | spi_master_put(master); | |
310 | } | |
311 | ||
312 | return status; | |
313 | } | |
314 | ||
315 | static int __exit spi_gpio_remove(struct platform_device *pdev) | |
316 | { | |
317 | struct spi_gpio *spi_gpio; | |
318 | struct spi_gpio_platform_data *pdata; | |
319 | int status; | |
320 | ||
321 | spi_gpio = platform_get_drvdata(pdev); | |
322 | pdata = pdev->dev.platform_data; | |
323 | ||
324 | /* stop() unregisters child devices too */ | |
325 | status = spi_bitbang_stop(&spi_gpio->bitbang); | |
326 | spi_master_put(spi_gpio->bitbang.master); | |
327 | ||
328 | platform_set_drvdata(pdev, NULL); | |
329 | ||
330 | gpio_free(SPI_MISO_GPIO); | |
331 | gpio_free(SPI_MOSI_GPIO); | |
332 | gpio_free(SPI_SCK_GPIO); | |
333 | ||
334 | return status; | |
335 | } | |
336 | ||
337 | MODULE_ALIAS("platform:" DRIVER_NAME); | |
338 | ||
339 | static struct platform_driver spi_gpio_driver = { | |
340 | .driver.name = DRIVER_NAME, | |
341 | .driver.owner = THIS_MODULE, | |
342 | .remove = __exit_p(spi_gpio_remove), | |
343 | }; | |
344 | ||
345 | static int __init spi_gpio_init(void) | |
346 | { | |
347 | return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe); | |
348 | } | |
349 | module_init(spi_gpio_init); | |
350 | ||
351 | static void __exit spi_gpio_exit(void) | |
352 | { | |
353 | platform_driver_unregister(&spi_gpio_driver); | |
354 | } | |
355 | module_exit(spi_gpio_exit); | |
356 | ||
357 | ||
358 | MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO "); | |
359 | MODULE_AUTHOR("David Brownell"); | |
360 | MODULE_LICENSE("GPL"); |