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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/module.h> |
22 | #include <linux/init.h> |
23 | #include <linux/platform_device.h> |
24 | #include <linux/gpio.h> |
25 | #include <linux/of_device.h> |
26 | #include <linux/of_gpio.h> |
27 | |
28 | #include <linux/spi/spi.h> |
29 | #include <linux/spi/spi_bitbang.h> |
30 | #include <linux/spi/spi_gpio.h> |
31 | |
32 | |
33 | /* |
34 | * This bitbanging SPI master driver should help make systems usable |
35 | * when a native hardware SPI engine is not available, perhaps because |
36 | * its driver isn't yet working or because the I/O pins it requires |
37 | * are used for other purposes. |
38 | * |
39 | * platform_device->driver_data ... points to spi_gpio |
40 | * |
41 | * spi->controller_state ... reserved for bitbang framework code |
42 | * spi->controller_data ... holds chipselect GPIO |
43 | * |
44 | * spi->master->dev.driver_data ... points to spi_gpio->bitbang |
45 | */ |
46 | |
47 | struct spi_gpio { |
48 | struct spi_bitbang bitbang; |
49 | struct spi_gpio_platform_data pdata; |
50 | struct platform_device *pdev; |
51 | int cs_gpios[0]; |
52 | }; |
53 | |
54 | /*----------------------------------------------------------------------*/ |
55 | |
56 | /* |
57 | * Because the overhead of going through four GPIO procedure calls |
58 | * per transferred bit can make performance a problem, this code |
59 | * is set up so that you can use it in either of two ways: |
60 | * |
61 | * - The slow generic way: set up platform_data to hold the GPIO |
62 | * numbers used for MISO/MOSI/SCK, and issue procedure calls for |
63 | * each of them. This driver can handle several such busses. |
64 | * |
65 | * - The quicker inlined way: only helps with platform GPIO code |
66 | * that inlines operations for constant GPIOs. This can give |
67 | * you tight (fast!) inner loops, but each such bus needs a |
68 | * new driver. You'll define a new C file, with Makefile and |
69 | * Kconfig support; the C code can be a total of six lines: |
70 | * |
71 | * #define DRIVER_NAME "myboard_spi2" |
72 | * #define SPI_MISO_GPIO 119 |
73 | * #define SPI_MOSI_GPIO 120 |
74 | * #define SPI_SCK_GPIO 121 |
75 | * #define SPI_N_CHIPSEL 4 |
76 | * #include "spi-gpio.c" |
77 | */ |
78 | |
79 | #ifndef DRIVER_NAME |
80 | #define DRIVER_NAME "spi_gpio" |
81 | |
82 | #define GENERIC_BITBANG /* vs tight inlines */ |
83 | |
84 | /* all functions referencing these symbols must define pdata */ |
85 | #define SPI_MISO_GPIO ((pdata)->miso) |
86 | #define SPI_MOSI_GPIO ((pdata)->mosi) |
87 | #define SPI_SCK_GPIO ((pdata)->sck) |
88 | |
89 | #define SPI_N_CHIPSEL ((pdata)->num_chipselect) |
90 | |
91 | #endif |
92 | |
93 | /*----------------------------------------------------------------------*/ |
94 | |
95 | static inline struct spi_gpio * __pure |
96 | spi_to_spi_gpio(const struct spi_device *spi) |
97 | { |
98 | const struct spi_bitbang *bang; |
99 | struct spi_gpio *spi_gpio; |
100 | |
101 | bang = spi_master_get_devdata(spi->master); |
102 | spi_gpio = container_of(bang, struct spi_gpio, bitbang); |
103 | return spi_gpio; |
104 | } |
105 | |
106 | static inline struct spi_gpio_platform_data * __pure |
107 | spi_to_pdata(const struct spi_device *spi) |
108 | { |
109 | return &spi_to_spi_gpio(spi)->pdata; |
110 | } |
111 | |
112 | /* this is #defined to avoid unused-variable warnings when inlining */ |
113 | #define pdata spi_to_pdata(spi) |
114 | |
115 | static inline void setsck(const struct spi_device *spi, int is_on) |
116 | { |
117 | gpio_set_value(SPI_SCK_GPIO, is_on); |
118 | } |
119 | |
120 | static inline void setmosi(const struct spi_device *spi, int is_on) |
121 | { |
122 | gpio_set_value(SPI_MOSI_GPIO, is_on); |
123 | } |
124 | |
125 | static inline int getmiso(const struct spi_device *spi) |
126 | { |
127 | return !!gpio_get_value(SPI_MISO_GPIO); |
128 | } |
129 | |
130 | #undef pdata |
131 | |
132 | /* |
133 | * NOTE: this clocks "as fast as we can". It "should" be a function of the |
134 | * requested device clock. Software overhead means we usually have trouble |
135 | * reaching even one Mbit/sec (except when we can inline bitops), so for now |
136 | * we'll just assume we never need additional per-bit slowdowns. |
137 | */ |
138 | #define spidelay(nsecs) do {} while (0) |
139 | |
140 | #include "spi-bitbang-txrx.h" |
141 | |
142 | /* |
143 | * These functions can leverage inline expansion of GPIO calls to shrink |
144 | * costs for a txrx bit, often by factors of around ten (by instruction |
145 | * count). That is particularly visible for larger word sizes, but helps |
146 | * even with default 8-bit words. |
147 | * |
148 | * REVISIT overheads calling these functions for each word also have |
149 | * significant performance costs. Having txrx_bufs() calls that inline |
150 | * the txrx_word() logic would help performance, e.g. on larger blocks |
151 | * used with flash storage or MMC/SD. There should also be ways to make |
152 | * GCC be less stupid about reloading registers inside the I/O loops, |
153 | * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3? |
154 | */ |
155 | |
156 | static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi, |
157 | unsigned nsecs, u32 word, u8 bits) |
158 | { |
159 | return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits); |
160 | } |
161 | |
162 | static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi, |
163 | unsigned nsecs, u32 word, u8 bits) |
164 | { |
165 | return bitbang_txrx_be_cpha1(spi, nsecs, 0, 0, word, bits); |
166 | } |
167 | |
168 | static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi, |
169 | unsigned nsecs, u32 word, u8 bits) |
170 | { |
171 | return bitbang_txrx_be_cpha0(spi, nsecs, 1, 0, word, bits); |
172 | } |
173 | |
174 | static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi, |
175 | unsigned nsecs, u32 word, u8 bits) |
176 | { |
177 | return bitbang_txrx_be_cpha1(spi, nsecs, 1, 0, word, bits); |
178 | } |
179 | |
180 | /* |
181 | * These functions do not call setmosi or getmiso if respective flag |
182 | * (SPI_MASTER_NO_RX or SPI_MASTER_NO_TX) is set, so they are safe to |
183 | * call when such pin is not present or defined in the controller. |
184 | * A separate set of callbacks is defined to get highest possible |
185 | * speed in the generic case (when both MISO and MOSI lines are |
186 | * available), as optimiser will remove the checks when argument is |
187 | * constant. |
188 | */ |
189 | |
190 | static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi, |
191 | unsigned nsecs, u32 word, u8 bits) |
192 | { |
193 | unsigned flags = spi->master->flags; |
194 | return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); |
195 | } |
196 | |
197 | static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi, |
198 | unsigned nsecs, u32 word, u8 bits) |
199 | { |
200 | unsigned flags = spi->master->flags; |
201 | return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits); |
202 | } |
203 | |
204 | static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi, |
205 | unsigned nsecs, u32 word, u8 bits) |
206 | { |
207 | unsigned flags = spi->master->flags; |
208 | return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits); |
209 | } |
210 | |
211 | static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi, |
212 | unsigned nsecs, u32 word, u8 bits) |
213 | { |
214 | unsigned flags = spi->master->flags; |
215 | return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits); |
216 | } |
217 | |
218 | /*----------------------------------------------------------------------*/ |
219 | |
220 | static void spi_gpio_chipselect(struct spi_device *spi, int is_active) |
221 | { |
222 | struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
223 | unsigned int cs = spi_gpio->cs_gpios[spi->chip_select]; |
224 | |
225 | /* set initial clock polarity */ |
226 | if (is_active) |
227 | setsck(spi, spi->mode & SPI_CPOL); |
228 | |
229 | if (cs != SPI_GPIO_NO_CHIPSELECT) { |
230 | /* SPI is normally active-low */ |
231 | gpio_set_value(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active); |
232 | } |
233 | } |
234 | |
235 | static int spi_gpio_setup(struct spi_device *spi) |
236 | { |
237 | unsigned int cs; |
238 | int status = 0; |
239 | struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
240 | struct device_node *np = spi->master->dev.of_node; |
241 | |
242 | if (spi->bits_per_word > 32) |
243 | return -EINVAL; |
244 | |
245 | if (np) { |
246 | /* |
247 | * In DT environments, the CS GPIOs have already been |
248 | * initialized from the "cs-gpios" property of the node. |
249 | */ |
250 | cs = spi_gpio->cs_gpios[spi->chip_select]; |
251 | } else { |
252 | /* |
253 | * ... otherwise, take it from spi->controller_data |
254 | */ |
255 | cs = (unsigned int) spi->controller_data; |
256 | } |
257 | |
258 | if (!spi->controller_state) { |
259 | if (cs != SPI_GPIO_NO_CHIPSELECT) { |
260 | status = gpio_request(cs, dev_name(&spi->dev)); |
261 | if (status) |
262 | return status; |
263 | status = gpio_direction_output(cs, |
264 | !(spi->mode & SPI_CS_HIGH)); |
265 | } |
266 | } |
267 | if (!status) { |
268 | status = spi_bitbang_setup(spi); |
269 | /* in case it was initialized from static board data */ |
270 | spi_gpio->cs_gpios[spi->chip_select] = cs; |
271 | } |
272 | |
273 | if (status) { |
274 | if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT) |
275 | gpio_free(cs); |
276 | } |
277 | return status; |
278 | } |
279 | |
280 | static void spi_gpio_cleanup(struct spi_device *spi) |
281 | { |
282 | struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
283 | unsigned int cs = spi_gpio->cs_gpios[spi->chip_select]; |
284 | |
285 | if (cs != SPI_GPIO_NO_CHIPSELECT) |
286 | gpio_free(cs); |
287 | spi_bitbang_cleanup(spi); |
288 | } |
289 | |
290 | static int spi_gpio_alloc(unsigned pin, const char *label, bool is_in) |
291 | { |
292 | int value; |
293 | |
294 | value = gpio_request(pin, label); |
295 | if (value == 0) { |
296 | if (is_in) |
297 | value = gpio_direction_input(pin); |
298 | else |
299 | value = gpio_direction_output(pin, 0); |
300 | } |
301 | return value; |
302 | } |
303 | |
304 | static int spi_gpio_request(struct spi_gpio_platform_data *pdata, |
305 | const char *label, u16 *res_flags) |
306 | { |
307 | int value; |
308 | |
309 | /* NOTE: SPI_*_GPIO symbols may reference "pdata" */ |
310 | |
311 | if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) { |
312 | value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false); |
313 | if (value) |
314 | goto done; |
315 | } else { |
316 | /* HW configuration without MOSI pin */ |
317 | *res_flags |= SPI_MASTER_NO_TX; |
318 | } |
319 | |
320 | if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) { |
321 | value = spi_gpio_alloc(SPI_MISO_GPIO, label, true); |
322 | if (value) |
323 | goto free_mosi; |
324 | } else { |
325 | /* HW configuration without MISO pin */ |
326 | *res_flags |= SPI_MASTER_NO_RX; |
327 | } |
328 | |
329 | value = spi_gpio_alloc(SPI_SCK_GPIO, label, false); |
330 | if (value) |
331 | goto free_miso; |
332 | |
333 | goto done; |
334 | |
335 | free_miso: |
336 | if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) |
337 | gpio_free(SPI_MISO_GPIO); |
338 | free_mosi: |
339 | if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) |
340 | gpio_free(SPI_MOSI_GPIO); |
341 | done: |
342 | return value; |
343 | } |
344 | |
345 | #ifdef CONFIG_OF |
346 | static struct of_device_id spi_gpio_dt_ids[] = { |
347 | { .compatible = "spi-gpio" }, |
348 | {} |
349 | }; |
350 | MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids); |
351 | |
352 | static int spi_gpio_probe_dt(struct platform_device *pdev) |
353 | { |
354 | int ret; |
355 | u32 tmp; |
356 | struct spi_gpio_platform_data *pdata; |
357 | struct device_node *np = pdev->dev.of_node; |
358 | const struct of_device_id *of_id = |
359 | of_match_device(spi_gpio_dt_ids, &pdev->dev); |
360 | |
361 | if (!of_id) |
362 | return 0; |
363 | |
364 | pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL); |
365 | if (!pdata) |
366 | return -ENOMEM; |
367 | |
368 | ret = of_get_named_gpio(np, "gpio-sck", 0); |
369 | if (ret < 0) { |
370 | dev_err(&pdev->dev, "gpio-sck property not found\n"); |
371 | goto error_free; |
372 | } |
373 | pdata->sck = ret; |
374 | |
375 | ret = of_get_named_gpio(np, "gpio-miso", 0); |
376 | if (ret < 0) { |
377 | dev_info(&pdev->dev, "gpio-miso property not found, switching to no-rx mode\n"); |
378 | pdata->miso = SPI_GPIO_NO_MISO; |
379 | } else |
380 | pdata->miso = ret; |
381 | |
382 | ret = of_get_named_gpio(np, "gpio-mosi", 0); |
383 | if (ret < 0) { |
384 | dev_info(&pdev->dev, "gpio-mosi property not found, switching to no-tx mode\n"); |
385 | pdata->mosi = SPI_GPIO_NO_MOSI; |
386 | } else |
387 | pdata->mosi = ret; |
388 | |
389 | ret = of_property_read_u32(np, "num-chipselects", &tmp); |
390 | if (ret < 0) { |
391 | dev_err(&pdev->dev, "num-chipselects property not found\n"); |
392 | goto error_free; |
393 | } |
394 | |
395 | pdata->num_chipselect = tmp; |
396 | pdev->dev.platform_data = pdata; |
397 | |
398 | return 1; |
399 | |
400 | error_free: |
401 | devm_kfree(&pdev->dev, pdata); |
402 | return ret; |
403 | } |
404 | #else |
405 | static inline int spi_gpio_probe_dt(struct platform_device *pdev) |
406 | { |
407 | return 0; |
408 | } |
409 | #endif |
410 | |
411 | static int spi_gpio_probe(struct platform_device *pdev) |
412 | { |
413 | int status; |
414 | struct spi_master *master; |
415 | struct spi_gpio *spi_gpio; |
416 | struct spi_gpio_platform_data *pdata; |
417 | u16 master_flags = 0; |
418 | bool use_of = 0; |
419 | |
420 | status = spi_gpio_probe_dt(pdev); |
421 | if (status < 0) |
422 | return status; |
423 | if (status > 0) |
424 | use_of = 1; |
425 | |
426 | pdata = pdev->dev.platform_data; |
427 | #ifdef GENERIC_BITBANG |
428 | if (!pdata || !pdata->num_chipselect) |
429 | return -ENODEV; |
430 | #endif |
431 | |
432 | status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags); |
433 | if (status < 0) |
434 | return status; |
435 | |
436 | master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio) + |
437 | (sizeof(int) * SPI_N_CHIPSEL)); |
438 | if (!master) { |
439 | status = -ENOMEM; |
440 | goto gpio_free; |
441 | } |
442 | spi_gpio = spi_master_get_devdata(master); |
443 | platform_set_drvdata(pdev, spi_gpio); |
444 | |
445 | spi_gpio->pdev = pdev; |
446 | if (pdata) |
447 | spi_gpio->pdata = *pdata; |
448 | |
449 | master->flags = master_flags; |
450 | master->bus_num = pdev->id; |
451 | master->num_chipselect = SPI_N_CHIPSEL; |
452 | master->setup = spi_gpio_setup; |
453 | master->cleanup = spi_gpio_cleanup; |
454 | #ifdef CONFIG_OF |
455 | master->dev.of_node = pdev->dev.of_node; |
456 | |
457 | if (use_of) { |
458 | int i; |
459 | struct device_node *np = pdev->dev.of_node; |
460 | |
461 | /* |
462 | * In DT environments, take the CS GPIO from the "cs-gpios" |
463 | * property of the node. |
464 | */ |
465 | |
466 | for (i = 0; i < SPI_N_CHIPSEL; i++) |
467 | spi_gpio->cs_gpios[i] = |
468 | of_get_named_gpio(np, "cs-gpios", i); |
469 | } |
470 | #endif |
471 | |
472 | spi_gpio->bitbang.master = spi_master_get(master); |
473 | spi_gpio->bitbang.chipselect = spi_gpio_chipselect; |
474 | |
475 | if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) { |
476 | spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0; |
477 | spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1; |
478 | spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2; |
479 | spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3; |
480 | } else { |
481 | spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0; |
482 | spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1; |
483 | spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2; |
484 | spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3; |
485 | } |
486 | spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer; |
487 | spi_gpio->bitbang.flags = SPI_CS_HIGH; |
488 | |
489 | status = spi_bitbang_start(&spi_gpio->bitbang); |
490 | if (status < 0) { |
491 | spi_master_put(spi_gpio->bitbang.master); |
492 | gpio_free: |
493 | if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) |
494 | gpio_free(SPI_MISO_GPIO); |
495 | if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) |
496 | gpio_free(SPI_MOSI_GPIO); |
497 | gpio_free(SPI_SCK_GPIO); |
498 | spi_master_put(master); |
499 | } |
500 | |
501 | return status; |
502 | } |
503 | |
504 | static int spi_gpio_remove(struct platform_device *pdev) |
505 | { |
506 | struct spi_gpio *spi_gpio; |
507 | struct spi_gpio_platform_data *pdata; |
508 | int status; |
509 | |
510 | spi_gpio = platform_get_drvdata(pdev); |
511 | pdata = pdev->dev.platform_data; |
512 | |
513 | /* stop() unregisters child devices too */ |
514 | status = spi_bitbang_stop(&spi_gpio->bitbang); |
515 | spi_master_put(spi_gpio->bitbang.master); |
516 | |
517 | platform_set_drvdata(pdev, NULL); |
518 | |
519 | if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) |
520 | gpio_free(SPI_MISO_GPIO); |
521 | if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) |
522 | gpio_free(SPI_MOSI_GPIO); |
523 | gpio_free(SPI_SCK_GPIO); |
524 | |
525 | return status; |
526 | } |
527 | |
528 | MODULE_ALIAS("platform:" DRIVER_NAME); |
529 | |
530 | static struct platform_driver spi_gpio_driver = { |
531 | .driver = { |
532 | .name = DRIVER_NAME, |
533 | .owner = THIS_MODULE, |
534 | .of_match_table = of_match_ptr(spi_gpio_dt_ids), |
535 | }, |
536 | .probe = spi_gpio_probe, |
537 | .remove = spi_gpio_remove, |
538 | }; |
539 | module_platform_driver(spi_gpio_driver); |
540 | |
541 | MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO "); |
542 | MODULE_AUTHOR("David Brownell"); |
543 | MODULE_LICENSE("GPL"); |
544 |
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