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d29389de | 1 | /* |
ca632f55 | 2 | * SPI master driver using generic bitbanged GPIO |
d29389de DB |
3 | * |
4 | * Copyright (C) 2006,2008 David Brownell | |
9b00bc7b | 5 | * Copyright (C) 2017 Linus Walleij |
d29389de DB |
6 | * |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License as published by | |
9 | * the Free Software Foundation; either version 2 of the License, or | |
10 | * (at your option) any later version. | |
11 | * | |
12 | * This program is distributed in the hope that it will be useful, | |
13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | * GNU General Public License for more details. | |
d29389de DB |
16 | */ |
17 | #include <linux/kernel.h> | |
d7614de4 | 18 | #include <linux/module.h> |
d29389de | 19 | #include <linux/platform_device.h> |
9b00bc7b | 20 | #include <linux/gpio/consumer.h> |
ecc77773 | 21 | #include <linux/of.h> |
38ab18ca | 22 | #include <linux/of_device.h> |
d29389de DB |
23 | |
24 | #include <linux/spi/spi.h> | |
25 | #include <linux/spi/spi_bitbang.h> | |
26 | #include <linux/spi/spi_gpio.h> | |
27 | ||
28 | ||
29 | /* | |
30 | * This bitbanging SPI master driver should help make systems usable | |
31 | * when a native hardware SPI engine is not available, perhaps because | |
32 | * its driver isn't yet working or because the I/O pins it requires | |
33 | * are used for other purposes. | |
34 | * | |
35 | * platform_device->driver_data ... points to spi_gpio | |
36 | * | |
37 | * spi->controller_state ... reserved for bitbang framework code | |
38 | * spi->controller_data ... holds chipselect GPIO | |
39 | * | |
40 | * spi->master->dev.driver_data ... points to spi_gpio->bitbang | |
41 | */ | |
42 | ||
43 | struct spi_gpio { | |
44 | struct spi_bitbang bitbang; | |
45 | struct spi_gpio_platform_data pdata; | |
46 | struct platform_device *pdev; | |
9b00bc7b LW |
47 | struct gpio_desc *sck; |
48 | struct gpio_desc *miso; | |
49 | struct gpio_desc *mosi; | |
50 | struct gpio_desc **cs_gpios; | |
51 | bool has_cs; | |
d29389de DB |
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 | |
ca632f55 | 76 | * #include "spi-gpio.c" |
d29389de DB |
77 | */ |
78 | ||
79 | #ifndef DRIVER_NAME | |
80 | #define DRIVER_NAME "spi_gpio" | |
81 | ||
82 | #define GENERIC_BITBANG /* vs tight inlines */ | |
83 | ||
d29389de DB |
84 | #endif |
85 | ||
86 | /*----------------------------------------------------------------------*/ | |
87 | ||
650705cf | 88 | static inline struct spi_gpio *__pure |
161c2dd3 | 89 | spi_to_spi_gpio(const struct spi_device *spi) |
d29389de DB |
90 | { |
91 | const struct spi_bitbang *bang; | |
161c2dd3 | 92 | struct spi_gpio *spi_gpio; |
d29389de DB |
93 | |
94 | bang = spi_master_get_devdata(spi->master); | |
95 | spi_gpio = container_of(bang, struct spi_gpio, bitbang); | |
161c2dd3 DM |
96 | return spi_gpio; |
97 | } | |
98 | ||
650705cf | 99 | static inline struct spi_gpio_platform_data *__pure |
161c2dd3 DM |
100 | spi_to_pdata(const struct spi_device *spi) |
101 | { | |
102 | return &spi_to_spi_gpio(spi)->pdata; | |
d29389de DB |
103 | } |
104 | ||
9b00bc7b | 105 | /* These helpers are in turn called by the bitbang inlines */ |
d29389de DB |
106 | static inline void setsck(const struct spi_device *spi, int is_on) |
107 | { | |
9b00bc7b LW |
108 | struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
109 | ||
110 | gpiod_set_value_cansleep(spi_gpio->sck, is_on); | |
d29389de DB |
111 | } |
112 | ||
113 | static inline void setmosi(const struct spi_device *spi, int is_on) | |
114 | { | |
9b00bc7b LW |
115 | struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
116 | ||
117 | gpiod_set_value_cansleep(spi_gpio->mosi, is_on); | |
d29389de DB |
118 | } |
119 | ||
120 | static inline int getmiso(const struct spi_device *spi) | |
121 | { | |
9b00bc7b | 122 | struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
d29389de | 123 | |
9b00bc7b LW |
124 | return !!gpiod_get_value_cansleep(spi_gpio->miso); |
125 | } | |
d29389de DB |
126 | |
127 | /* | |
128 | * NOTE: this clocks "as fast as we can". It "should" be a function of the | |
129 | * requested device clock. Software overhead means we usually have trouble | |
130 | * reaching even one Mbit/sec (except when we can inline bitops), so for now | |
131 | * we'll just assume we never need additional per-bit slowdowns. | |
132 | */ | |
133 | #define spidelay(nsecs) do {} while (0) | |
134 | ||
ca632f55 | 135 | #include "spi-bitbang-txrx.h" |
d29389de DB |
136 | |
137 | /* | |
138 | * These functions can leverage inline expansion of GPIO calls to shrink | |
139 | * costs for a txrx bit, often by factors of around ten (by instruction | |
140 | * count). That is particularly visible for larger word sizes, but helps | |
141 | * even with default 8-bit words. | |
142 | * | |
143 | * REVISIT overheads calling these functions for each word also have | |
144 | * significant performance costs. Having txrx_bufs() calls that inline | |
145 | * the txrx_word() logic would help performance, e.g. on larger blocks | |
146 | * used with flash storage or MMC/SD. There should also be ways to make | |
147 | * GCC be less stupid about reloading registers inside the I/O loops, | |
148 | * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3? | |
149 | */ | |
150 | ||
151 | static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi, | |
152 | unsigned nsecs, u32 word, u8 bits) | |
153 | { | |
04bb2a03 | 154 | return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits); |
d29389de DB |
155 | } |
156 | ||
157 | static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi, | |
158 | unsigned nsecs, u32 word, u8 bits) | |
159 | { | |
04bb2a03 | 160 | return bitbang_txrx_be_cpha1(spi, nsecs, 0, 0, word, bits); |
d29389de DB |
161 | } |
162 | ||
163 | static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi, | |
164 | unsigned nsecs, u32 word, u8 bits) | |
165 | { | |
04bb2a03 | 166 | return bitbang_txrx_be_cpha0(spi, nsecs, 1, 0, word, bits); |
d29389de DB |
167 | } |
168 | ||
169 | static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi, | |
170 | unsigned nsecs, u32 word, u8 bits) | |
171 | { | |
04bb2a03 | 172 | return bitbang_txrx_be_cpha1(spi, nsecs, 1, 0, word, bits); |
d29389de DB |
173 | } |
174 | ||
3c8e1a84 MS |
175 | /* |
176 | * These functions do not call setmosi or getmiso if respective flag | |
177 | * (SPI_MASTER_NO_RX or SPI_MASTER_NO_TX) is set, so they are safe to | |
178 | * call when such pin is not present or defined in the controller. | |
179 | * A separate set of callbacks is defined to get highest possible | |
180 | * speed in the generic case (when both MISO and MOSI lines are | |
181 | * available), as optimiser will remove the checks when argument is | |
182 | * constant. | |
183 | */ | |
184 | ||
185 | static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi, | |
186 | unsigned nsecs, u32 word, u8 bits) | |
187 | { | |
188 | unsigned flags = spi->master->flags; | |
189 | return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); | |
190 | } | |
191 | ||
192 | static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi, | |
193 | unsigned nsecs, u32 word, u8 bits) | |
194 | { | |
195 | unsigned flags = spi->master->flags; | |
196 | return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits); | |
197 | } | |
198 | ||
199 | static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi, | |
200 | unsigned nsecs, u32 word, u8 bits) | |
201 | { | |
202 | unsigned flags = spi->master->flags; | |
203 | return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits); | |
204 | } | |
205 | ||
206 | static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi, | |
207 | unsigned nsecs, u32 word, u8 bits) | |
208 | { | |
209 | unsigned flags = spi->master->flags; | |
210 | return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits); | |
211 | } | |
212 | ||
d29389de DB |
213 | /*----------------------------------------------------------------------*/ |
214 | ||
215 | static void spi_gpio_chipselect(struct spi_device *spi, int is_active) | |
216 | { | |
161c2dd3 | 217 | struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); |
d29389de | 218 | |
9b00bc7b | 219 | /* set initial clock line level */ |
d29389de | 220 | if (is_active) |
9b00bc7b LW |
221 | gpiod_set_value_cansleep(spi_gpio->sck, spi->mode & SPI_CPOL); |
222 | ||
223 | /* Drive chip select line, if we have one */ | |
224 | if (spi_gpio->has_cs) { | |
225 | struct gpio_desc *cs = spi_gpio->cs_gpios[spi->chip_select]; | |
d29389de | 226 | |
9b00bc7b LW |
227 | /* SPI chip selects are normally active-low */ |
228 | gpiod_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active); | |
bfb9bcdb | 229 | } |
d29389de DB |
230 | } |
231 | ||
232 | static int spi_gpio_setup(struct spi_device *spi) | |
233 | { | |
9b00bc7b | 234 | struct gpio_desc *cs; |
161c2dd3 DM |
235 | int status = 0; |
236 | struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); | |
38ab18ca | 237 | |
9b00bc7b LW |
238 | /* |
239 | * The CS GPIOs have already been | |
240 | * initialized from the descriptor lookup. | |
241 | */ | |
242 | cs = spi_gpio->cs_gpios[spi->chip_select]; | |
243 | if (!spi->controller_state && cs) | |
244 | status = gpiod_direction_output(cs, | |
245 | !(spi->mode & SPI_CS_HIGH)); | |
246 | ||
247 | if (!status) | |
6b8cc330 | 248 | status = spi_bitbang_setup(spi); |
161c2dd3 | 249 | |
d29389de DB |
250 | return status; |
251 | } | |
252 | ||
253 | static void spi_gpio_cleanup(struct spi_device *spi) | |
254 | { | |
d29389de DB |
255 | spi_bitbang_cleanup(spi); |
256 | } | |
257 | ||
9b00bc7b LW |
258 | /* |
259 | * It can be convenient to use this driver with pins that have alternate | |
260 | * functions associated with a "native" SPI controller if a driver for that | |
261 | * controller is not available, or is missing important functionality. | |
262 | * | |
263 | * On platforms which can do so, configure MISO with a weak pullup unless | |
264 | * there's an external pullup on that signal. That saves power by avoiding | |
265 | * floating signals. (A weak pulldown would save power too, but many | |
266 | * drivers expect to see all-ones data as the no slave "response".) | |
267 | */ | |
268 | static int spi_gpio_request(struct device *dev, | |
269 | struct spi_gpio *spi_gpio, | |
270 | unsigned int num_chipselects, | |
271 | u16 *mflags) | |
d29389de | 272 | { |
9b00bc7b | 273 | int i; |
d29389de | 274 | |
9b00bc7b LW |
275 | spi_gpio->mosi = devm_gpiod_get_optional(dev, "mosi", GPIOD_OUT_LOW); |
276 | if (IS_ERR(spi_gpio->mosi)) | |
277 | return PTR_ERR(spi_gpio->mosi); | |
278 | if (!spi_gpio->mosi) | |
3c8e1a84 | 279 | /* HW configuration without MOSI pin */ |
9b00bc7b | 280 | *mflags |= SPI_MASTER_NO_TX; |
d29389de | 281 | |
9b00bc7b LW |
282 | spi_gpio->miso = devm_gpiod_get_optional(dev, "miso", GPIOD_IN); |
283 | if (IS_ERR(spi_gpio->miso)) | |
284 | return PTR_ERR(spi_gpio->miso); | |
285 | if (!spi_gpio->miso) | |
3c8e1a84 | 286 | /* HW configuration without MISO pin */ |
9b00bc7b | 287 | *mflags |= SPI_MASTER_NO_RX; |
d29389de | 288 | |
9b00bc7b LW |
289 | spi_gpio->sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW); |
290 | if (IS_ERR(spi_gpio->mosi)) | |
291 | return PTR_ERR(spi_gpio->mosi); | |
d29389de | 292 | |
9b00bc7b LW |
293 | for (i = 0; i < num_chipselects; i++) { |
294 | spi_gpio->cs_gpios[i] = devm_gpiod_get_index(dev, "cs", | |
295 | i, GPIOD_OUT_HIGH); | |
296 | if (IS_ERR(spi_gpio->cs_gpios[i])) | |
297 | return PTR_ERR(spi_gpio->cs_gpios[i]); | |
298 | } | |
d29389de | 299 | |
9b00bc7b | 300 | return 0; |
d29389de DB |
301 | } |
302 | ||
38ab18ca | 303 | #ifdef CONFIG_OF |
d9e15281 | 304 | static const struct of_device_id spi_gpio_dt_ids[] = { |
38ab18ca DM |
305 | { .compatible = "spi-gpio" }, |
306 | {} | |
307 | }; | |
308 | MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids); | |
309 | ||
310 | static int spi_gpio_probe_dt(struct platform_device *pdev) | |
311 | { | |
312 | int ret; | |
313 | u32 tmp; | |
314 | struct spi_gpio_platform_data *pdata; | |
315 | struct device_node *np = pdev->dev.of_node; | |
316 | const struct of_device_id *of_id = | |
317 | of_match_device(spi_gpio_dt_ids, &pdev->dev); | |
318 | ||
319 | if (!of_id) | |
320 | return 0; | |
321 | ||
322 | pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL); | |
323 | if (!pdata) | |
324 | return -ENOMEM; | |
325 | ||
38ab18ca DM |
326 | |
327 | ret = of_property_read_u32(np, "num-chipselects", &tmp); | |
328 | if (ret < 0) { | |
329 | dev_err(&pdev->dev, "num-chipselects property not found\n"); | |
330 | goto error_free; | |
331 | } | |
332 | ||
333 | pdata->num_chipselect = tmp; | |
334 | pdev->dev.platform_data = pdata; | |
335 | ||
336 | return 1; | |
337 | ||
338 | error_free: | |
339 | devm_kfree(&pdev->dev, pdata); | |
340 | return ret; | |
341 | } | |
342 | #else | |
ac2cb30b | 343 | static inline int spi_gpio_probe_dt(struct platform_device *pdev) |
38ab18ca DM |
344 | { |
345 | return 0; | |
346 | } | |
347 | #endif | |
348 | ||
fd4a319b | 349 | static int spi_gpio_probe(struct platform_device *pdev) |
d29389de DB |
350 | { |
351 | int status; | |
352 | struct spi_master *master; | |
353 | struct spi_gpio *spi_gpio; | |
354 | struct spi_gpio_platform_data *pdata; | |
3c8e1a84 | 355 | u16 master_flags = 0; |
38ab18ca DM |
356 | bool use_of = 0; |
357 | ||
358 | status = spi_gpio_probe_dt(pdev); | |
359 | if (status < 0) | |
360 | return status; | |
361 | if (status > 0) | |
362 | use_of = 1; | |
d29389de | 363 | |
8074cf06 | 364 | pdata = dev_get_platdata(&pdev->dev); |
d29389de | 365 | #ifdef GENERIC_BITBANG |
d1d81802 | 366 | if (!pdata || (!use_of && !pdata->num_chipselect)) |
d29389de DB |
367 | return -ENODEV; |
368 | #endif | |
369 | ||
9b00bc7b LW |
370 | master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio)); |
371 | if (!master) | |
372 | return -ENOMEM; | |
d29389de | 373 | |
d29389de | 374 | spi_gpio = spi_master_get_devdata(master); |
9b00bc7b | 375 | |
a86854d0 KC |
376 | spi_gpio->cs_gpios = devm_kcalloc(&pdev->dev, |
377 | pdata->num_chipselect, | |
378 | sizeof(*spi_gpio->cs_gpios), | |
9b00bc7b LW |
379 | GFP_KERNEL); |
380 | if (!spi_gpio->cs_gpios) | |
381 | return -ENOMEM; | |
382 | ||
d29389de DB |
383 | platform_set_drvdata(pdev, spi_gpio); |
384 | ||
9b00bc7b LW |
385 | /* Determine if we have chip selects connected */ |
386 | spi_gpio->has_cs = !!pdata->num_chipselect; | |
387 | ||
d29389de DB |
388 | spi_gpio->pdev = pdev; |
389 | if (pdata) | |
390 | spi_gpio->pdata = *pdata; | |
391 | ||
9b00bc7b LW |
392 | status = spi_gpio_request(&pdev->dev, spi_gpio, |
393 | pdata->num_chipselect, &master_flags); | |
394 | if (status) | |
395 | return status; | |
396 | ||
24778be2 | 397 | master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32); |
3c8e1a84 | 398 | master->flags = master_flags; |
d29389de | 399 | master->bus_num = pdev->id; |
9b00bc7b LW |
400 | /* The master needs to think there is a chipselect even if not connected */ |
401 | master->num_chipselect = spi_gpio->has_cs ? pdata->num_chipselect : 1; | |
d29389de DB |
402 | master->setup = spi_gpio_setup; |
403 | master->cleanup = spi_gpio_cleanup; | |
38ab18ca DM |
404 | #ifdef CONFIG_OF |
405 | master->dev.of_node = pdev->dev.of_node; | |
38ab18ca | 406 | #endif |
d29389de | 407 | |
94c69f76 | 408 | spi_gpio->bitbang.master = master; |
d29389de | 409 | spi_gpio->bitbang.chipselect = spi_gpio_chipselect; |
3c8e1a84 | 410 | |
23699f98 | 411 | if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) { |
3c8e1a84 MS |
412 | spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0; |
413 | spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1; | |
414 | spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2; | |
415 | spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3; | |
416 | } else { | |
417 | spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0; | |
418 | spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1; | |
419 | spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2; | |
420 | spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3; | |
421 | } | |
d29389de DB |
422 | spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer; |
423 | spi_gpio->bitbang.flags = SPI_CS_HIGH; | |
424 | ||
425 | status = spi_bitbang_start(&spi_gpio->bitbang); | |
9b00bc7b | 426 | if (status) |
d29389de | 427 | spi_master_put(master); |
d29389de DB |
428 | |
429 | return status; | |
430 | } | |
431 | ||
fd4a319b | 432 | static int spi_gpio_remove(struct platform_device *pdev) |
d29389de DB |
433 | { |
434 | struct spi_gpio *spi_gpio; | |
435 | struct spi_gpio_platform_data *pdata; | |
d29389de DB |
436 | |
437 | spi_gpio = platform_get_drvdata(pdev); | |
8074cf06 | 438 | pdata = dev_get_platdata(&pdev->dev); |
d29389de DB |
439 | |
440 | /* stop() unregisters child devices too */ | |
d9721ae1 | 441 | spi_bitbang_stop(&spi_gpio->bitbang); |
d29389de | 442 | |
94c69f76 | 443 | spi_master_put(spi_gpio->bitbang.master); |
d29389de | 444 | |
d9721ae1 | 445 | return 0; |
d29389de DB |
446 | } |
447 | ||
448 | MODULE_ALIAS("platform:" DRIVER_NAME); | |
449 | ||
450 | static struct platform_driver spi_gpio_driver = { | |
38ab18ca DM |
451 | .driver = { |
452 | .name = DRIVER_NAME, | |
38ab18ca DM |
453 | .of_match_table = of_match_ptr(spi_gpio_dt_ids), |
454 | }, | |
940ab889 | 455 | .probe = spi_gpio_probe, |
fd4a319b | 456 | .remove = spi_gpio_remove, |
d29389de | 457 | }; |
940ab889 | 458 | module_platform_driver(spi_gpio_driver); |
d29389de DB |
459 | |
460 | MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO "); | |
461 | MODULE_AUTHOR("David Brownell"); | |
462 | MODULE_LICENSE("GPL"); |