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Source at commit 6c17a31f1fc515425221067cb3ece599c09dbc5d created 12 years 8 months ago. By Werner Almesberger, atusb, atben: moved from spi/ to ieee802154/; renamed atusb to spi_atusb | |
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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 | #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 | |
146 | static 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 | |
152 | static 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 | |
158 | static 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 | |
164 | static 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 | |
180 | static 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 | |
187 | static 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 | |
194 | static 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 | |
201 | static 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 | |
210 | static 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 | |
224 | static 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 | |
249 | static 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 | |
258 | static 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 | |
272 | static int __init |
273 | spi_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 | |
304 | free_miso: |
305 | if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) |
306 | gpio_free(SPI_MISO_GPIO); |
307 | free_mosi: |
308 | if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) |
309 | gpio_free(SPI_MOSI_GPIO); |
310 | done: |
311 | return value; |
312 | } |
313 | |
314 | static 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); |
370 | gpio_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 | |
382 | static 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 | |
406 | MODULE_ALIAS("platform:" DRIVER_NAME); |
407 | |
408 | static 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 | |
414 | static int __init spi_gpio_init(void) |
415 | { |
416 | return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe); |
417 | } |
418 | module_init(spi_gpio_init); |
419 | |
420 | static void __exit spi_gpio_exit(void) |
421 | { |
422 | platform_driver_unregister(&spi_gpio_driver); |
423 | } |
424 | module_exit(spi_gpio_exit); |
425 | |
426 | |
427 | MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO "); |
428 | MODULE_AUTHOR("David Brownell"); |
429 | MODULE_LICENSE("GPL"); |
430 |
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