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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#include <linux/kernel.h>
17#include <linux/module.h>
18#include <linux/platform_device.h>
19#include <linux/gpio.h>
20#include <linux/of.h>
21#include <linux/of_device.h>
22#include <linux/of_gpio.h>
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
43struct spi_gpio {
44 struct spi_bitbang bitbang;
45 struct spi_gpio_platform_data pdata;
46 struct platform_device *pdev;
47 unsigned long cs_gpios[0];
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
91static inline struct spi_gpio *__pure
92spi_to_spi_gpio(const struct spi_device *spi)
93{
94 const struct spi_bitbang *bang;
95 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;
100}
101
102static inline struct spi_gpio_platform_data *__pure
103spi_to_pdata(const struct spi_device *spi)
104{
105 return &spi_to_spi_gpio(spi)->pdata;
106}
107
108/* this is #defined to avoid unused-variable warnings when inlining */
109#define pdata spi_to_pdata(spi)
110
111static inline void setsck(const struct spi_device *spi, int is_on)
112{
113 gpio_set_value_cansleep(SPI_SCK_GPIO, is_on);
114}
115
116static inline void setmosi(const struct spi_device *spi, int is_on)
117{
118 gpio_set_value_cansleep(SPI_MOSI_GPIO, is_on);
119}
120
121static inline int getmiso(const struct spi_device *spi)
122{
123 return !!gpio_get_value_cansleep(SPI_MISO_GPIO);
124}
125
126#undef pdata
127
128/*
129 * NOTE: this clocks "as fast as we can". It "should" be a function of the
130 * requested device clock. Software overhead means we usually have trouble
131 * reaching even one Mbit/sec (except when we can inline bitops), so for now
132 * we'll just assume we never need additional per-bit slowdowns.
133 */
134#define spidelay(nsecs) do {} while (0)
135
136#include "spi-bitbang-txrx.h"
137
138/*
139 * These functions can leverage inline expansion of GPIO calls to shrink
140 * costs for a txrx bit, often by factors of around ten (by instruction
141 * count). That is particularly visible for larger word sizes, but helps
142 * even with default 8-bit words.
143 *
144 * REVISIT overheads calling these functions for each word also have
145 * significant performance costs. Having txrx_bufs() calls that inline
146 * the txrx_word() logic would help performance, e.g. on larger blocks
147 * used with flash storage or MMC/SD. There should also be ways to make
148 * GCC be less stupid about reloading registers inside the I/O loops,
149 * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3?
150 */
151
152static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi,
153 unsigned nsecs, u32 word, u8 bits)
154{
155 return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
156}
157
158static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
159 unsigned nsecs, u32 word, u8 bits)
160{
161 return bitbang_txrx_be_cpha1(spi, nsecs, 0, 0, word, bits);
162}
163
164static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
165 unsigned nsecs, u32 word, u8 bits)
166{
167 return bitbang_txrx_be_cpha0(spi, nsecs, 1, 0, word, bits);
168}
169
170static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
171 unsigned nsecs, u32 word, u8 bits)
172{
173 return bitbang_txrx_be_cpha1(spi, nsecs, 1, 0, word, bits);
174}
175
176/*
177 * These functions do not call setmosi or getmiso if respective flag
178 * (SPI_MASTER_NO_RX or SPI_MASTER_NO_TX) is set, so they are safe to
179 * call when such pin is not present or defined in the controller.
180 * A separate set of callbacks is defined to get highest possible
181 * speed in the generic case (when both MISO and MOSI lines are
182 * available), as optimiser will remove the checks when argument is
183 * constant.
184 */
185
186static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi,
187 unsigned nsecs, u32 word, u8 bits)
188{
189 unsigned flags = spi->master->flags;
190 return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
191}
192
193static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi,
194 unsigned nsecs, u32 word, u8 bits)
195{
196 unsigned flags = spi->master->flags;
197 return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits);
198}
199
200static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi,
201 unsigned nsecs, u32 word, u8 bits)
202{
203 unsigned flags = spi->master->flags;
204 return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits);
205}
206
207static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi,
208 unsigned nsecs, u32 word, u8 bits)
209{
210 unsigned flags = spi->master->flags;
211 return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits);
212}
213
214/*----------------------------------------------------------------------*/
215
216static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
217{
218 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
219 unsigned long cs = spi_gpio->cs_gpios[spi->chip_select];
220
221 /* set initial clock polarity */
222 if (is_active)
223 setsck(spi, spi->mode & SPI_CPOL);
224
225 if (cs != SPI_GPIO_NO_CHIPSELECT) {
226 /* SPI is normally active-low */
227 gpio_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
228 }
229}
230
231static int spi_gpio_setup(struct spi_device *spi)
232{
233 unsigned long cs;
234 int status = 0;
235 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
236 struct device_node *np = spi->master->dev.of_node;
237
238 if (np) {
239 /*
240 * In DT environments, the CS GPIOs have already been
241 * initialized from the "cs-gpios" property of the node.
242 */
243 cs = spi_gpio->cs_gpios[spi->chip_select];
244 } else {
245 /*
246 * ... otherwise, take it from spi->controller_data
247 */
248 cs = (uintptr_t) spi->controller_data;
249 }
250
251 if (!spi->controller_state) {
252 if (cs != SPI_GPIO_NO_CHIPSELECT) {
253 status = gpio_request(cs, dev_name(&spi->dev));
254 if (status)
255 return status;
256 status = gpio_direction_output(cs,
257 !(spi->mode & SPI_CS_HIGH));
258 }
259 }
260 if (!status) {
261 /* in case it was initialized from static board data */
262 spi_gpio->cs_gpios[spi->chip_select] = cs;
263 status = spi_bitbang_setup(spi);
264 }
265
266 if (status) {
267 if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT)
268 gpio_free(cs);
269 }
270 return status;
271}
272
273static void spi_gpio_cleanup(struct spi_device *spi)
274{
275 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
276 unsigned long cs = spi_gpio->cs_gpios[spi->chip_select];
277
278 if (cs != SPI_GPIO_NO_CHIPSELECT)
279 gpio_free(cs);
280 spi_bitbang_cleanup(spi);
281}
282
283static int spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
284{
285 int value;
286
287 value = gpio_request(pin, label);
288 if (value == 0) {
289 if (is_in)
290 value = gpio_direction_input(pin);
291 else
292 value = gpio_direction_output(pin, 0);
293 }
294 return value;
295}
296
297static int spi_gpio_request(struct spi_gpio_platform_data *pdata,
298 const char *label, u16 *res_flags)
299{
300 int value;
301
302 /* NOTE: SPI_*_GPIO symbols may reference "pdata" */
303
304 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) {
305 value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false);
306 if (value)
307 goto done;
308 } else {
309 /* HW configuration without MOSI pin */
310 *res_flags |= SPI_MASTER_NO_TX;
311 }
312
313 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) {
314 value = spi_gpio_alloc(SPI_MISO_GPIO, label, true);
315 if (value)
316 goto free_mosi;
317 } else {
318 /* HW configuration without MISO pin */
319 *res_flags |= SPI_MASTER_NO_RX;
320 }
321
322 value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
323 if (value)
324 goto free_miso;
325
326 goto done;
327
328free_miso:
329 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
330 gpio_free(SPI_MISO_GPIO);
331free_mosi:
332 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
333 gpio_free(SPI_MOSI_GPIO);
334done:
335 return value;
336}
337
338#ifdef CONFIG_OF
339static const struct of_device_id spi_gpio_dt_ids[] = {
340 { .compatible = "spi-gpio" },
341 {}
342};
343MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids);
344
345static int spi_gpio_probe_dt(struct platform_device *pdev)
346{
347 int ret;
348 u32 tmp;
349 struct spi_gpio_platform_data *pdata;
350 struct device_node *np = pdev->dev.of_node;
351 const struct of_device_id *of_id =
352 of_match_device(spi_gpio_dt_ids, &pdev->dev);
353
354 if (!of_id)
355 return 0;
356
357 pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
358 if (!pdata)
359 return -ENOMEM;
360
361 ret = of_get_named_gpio(np, "gpio-sck", 0);
362 if (ret < 0) {
363 dev_err(&pdev->dev, "gpio-sck property not found\n");
364 goto error_free;
365 }
366 pdata->sck = ret;
367
368 ret = of_get_named_gpio(np, "gpio-miso", 0);
369 if (ret < 0) {
370 dev_info(&pdev->dev, "gpio-miso property not found, switching to no-rx mode\n");
371 pdata->miso = SPI_GPIO_NO_MISO;
372 } else
373 pdata->miso = ret;
374
375 ret = of_get_named_gpio(np, "gpio-mosi", 0);
376 if (ret < 0) {
377 dev_info(&pdev->dev, "gpio-mosi property not found, switching to no-tx mode\n");
378 pdata->mosi = SPI_GPIO_NO_MOSI;
379 } else
380 pdata->mosi = ret;
381
382 ret = of_property_read_u32(np, "num-chipselects", &tmp);
383 if (ret < 0) {
384 dev_err(&pdev->dev, "num-chipselects property not found\n");
385 goto error_free;
386 }
387
388 pdata->num_chipselect = tmp;
389 pdev->dev.platform_data = pdata;
390
391 return 1;
392
393error_free:
394 devm_kfree(&pdev->dev, pdata);
395 return ret;
396}
397#else
398static inline int spi_gpio_probe_dt(struct platform_device *pdev)
399{
400 return 0;
401}
402#endif
403
404static int spi_gpio_probe(struct platform_device *pdev)
405{
406 int status;
407 struct spi_master *master;
408 struct spi_gpio *spi_gpio;
409 struct spi_gpio_platform_data *pdata;
410 u16 master_flags = 0;
411 bool use_of = 0;
412 int num_devices;
413
414 status = spi_gpio_probe_dt(pdev);
415 if (status < 0)
416 return status;
417 if (status > 0)
418 use_of = 1;
419
420 pdata = dev_get_platdata(&pdev->dev);
421#ifdef GENERIC_BITBANG
422 if (!pdata || (!use_of && !pdata->num_chipselect))
423 return -ENODEV;
424#endif
425
426 if (use_of && !SPI_N_CHIPSEL)
427 num_devices = 1;
428 else
429 num_devices = SPI_N_CHIPSEL;
430
431 status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
432 if (status < 0)
433 return status;
434
435 master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio) +
436 (sizeof(unsigned long) * num_devices));
437 if (!master) {
438 status = -ENOMEM;
439 goto gpio_free;
440 }
441 spi_gpio = spi_master_get_devdata(master);
442 platform_set_drvdata(pdev, spi_gpio);
443
444 spi_gpio->pdev = pdev;
445 if (pdata)
446 spi_gpio->pdata = *pdata;
447
448 master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
449 master->flags = master_flags;
450 master->bus_num = pdev->id;
451 master->num_chipselect = num_devices;
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 if (!SPI_N_CHIPSEL)
467 spi_gpio->cs_gpios[0] = SPI_GPIO_NO_CHIPSELECT;
468 else
469 for (i = 0; i < SPI_N_CHIPSEL; i++) {
470 status = of_get_named_gpio(np, "cs-gpios", i);
471 if (status < 0) {
472 dev_err(&pdev->dev,
473 "invalid cs-gpios property\n");
474 goto gpio_free;
475 }
476 spi_gpio->cs_gpios[i] = status;
477 }
478 }
479#endif
480
481 spi_gpio->bitbang.master = master;
482 spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
483
484 if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) {
485 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
486 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
487 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
488 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
489 } else {
490 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0;
491 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1;
492 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2;
493 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
494 }
495 spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
496 spi_gpio->bitbang.flags = SPI_CS_HIGH;
497
498 status = spi_bitbang_start(&spi_gpio->bitbang);
499 if (status < 0) {
500gpio_free:
501 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
502 gpio_free(SPI_MISO_GPIO);
503 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
504 gpio_free(SPI_MOSI_GPIO);
505 gpio_free(SPI_SCK_GPIO);
506 spi_master_put(master);
507 }
508
509 return status;
510}
511
512static int spi_gpio_remove(struct platform_device *pdev)
513{
514 struct spi_gpio *spi_gpio;
515 struct spi_gpio_platform_data *pdata;
516
517 spi_gpio = platform_get_drvdata(pdev);
518 pdata = dev_get_platdata(&pdev->dev);
519
520 /* stop() unregisters child devices too */
521 spi_bitbang_stop(&spi_gpio->bitbang);
522
523 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
524 gpio_free(SPI_MISO_GPIO);
525 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
526 gpio_free(SPI_MOSI_GPIO);
527 gpio_free(SPI_SCK_GPIO);
528 spi_master_put(spi_gpio->bitbang.master);
529
530 return 0;
531}
532
533MODULE_ALIAS("platform:" DRIVER_NAME);
534
535static struct platform_driver spi_gpio_driver = {
536 .driver = {
537 .name = DRIVER_NAME,
538 .of_match_table = of_match_ptr(spi_gpio_dt_ids),
539 },
540 .probe = spi_gpio_probe,
541 .remove = spi_gpio_remove,
542};
543module_platform_driver(spi_gpio_driver);
544
545MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
546MODULE_AUTHOR("David Brownell");
547MODULE_LICENSE("GPL");
1/*
2 * SPI master driver using generic bitbanged GPIO
3 *
4 * Copyright (C) 2006,2008 David Brownell
5 * Copyright (C) 2017 Linus Walleij
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.
16 */
17#include <linux/kernel.h>
18#include <linux/module.h>
19#include <linux/platform_device.h>
20#include <linux/gpio/consumer.h>
21#include <linux/of.h>
22#include <linux/of_device.h>
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
43struct spi_gpio {
44 struct spi_bitbang bitbang;
45 struct spi_gpio_platform_data pdata;
46 struct platform_device *pdev;
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;
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#endif
85
86/*----------------------------------------------------------------------*/
87
88static inline struct spi_gpio *__pure
89spi_to_spi_gpio(const struct spi_device *spi)
90{
91 const struct spi_bitbang *bang;
92 struct spi_gpio *spi_gpio;
93
94 bang = spi_master_get_devdata(spi->master);
95 spi_gpio = container_of(bang, struct spi_gpio, bitbang);
96 return spi_gpio;
97}
98
99static inline struct spi_gpio_platform_data *__pure
100spi_to_pdata(const struct spi_device *spi)
101{
102 return &spi_to_spi_gpio(spi)->pdata;
103}
104
105/* These helpers are in turn called by the bitbang inlines */
106static inline void setsck(const struct spi_device *spi, int is_on)
107{
108 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
109
110 gpiod_set_value_cansleep(spi_gpio->sck, is_on);
111}
112
113static inline void setmosi(const struct spi_device *spi, int is_on)
114{
115 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
116
117 gpiod_set_value_cansleep(spi_gpio->mosi, is_on);
118}
119
120static inline int getmiso(const struct spi_device *spi)
121{
122 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
123
124 return !!gpiod_get_value_cansleep(spi_gpio->miso);
125}
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
135#include "spi-bitbang-txrx.h"
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
151static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi,
152 unsigned nsecs, u32 word, u8 bits)
153{
154 return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
155}
156
157static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
158 unsigned nsecs, u32 word, u8 bits)
159{
160 return bitbang_txrx_be_cpha1(spi, nsecs, 0, 0, word, bits);
161}
162
163static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
164 unsigned nsecs, u32 word, u8 bits)
165{
166 return bitbang_txrx_be_cpha0(spi, nsecs, 1, 0, word, bits);
167}
168
169static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
170 unsigned nsecs, u32 word, u8 bits)
171{
172 return bitbang_txrx_be_cpha1(spi, nsecs, 1, 0, word, bits);
173}
174
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
185static 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
192static 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
199static 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
206static 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
213/*----------------------------------------------------------------------*/
214
215static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
216{
217 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
218
219 /* set initial clock line level */
220 if (is_active)
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];
226
227 /* SPI chip selects are normally active-low */
228 gpiod_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
229 }
230}
231
232static int spi_gpio_setup(struct spi_device *spi)
233{
234 struct gpio_desc *cs;
235 int status = 0;
236 struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
237
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)
248 status = spi_bitbang_setup(spi);
249
250 return status;
251}
252
253static void spi_gpio_cleanup(struct spi_device *spi)
254{
255 spi_bitbang_cleanup(spi);
256}
257
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 */
268static int spi_gpio_request(struct device *dev,
269 struct spi_gpio *spi_gpio,
270 unsigned int num_chipselects,
271 u16 *mflags)
272{
273 int i;
274
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)
279 /* HW configuration without MOSI pin */
280 *mflags |= SPI_MASTER_NO_TX;
281
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)
286 /* HW configuration without MISO pin */
287 *mflags |= SPI_MASTER_NO_RX;
288
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);
292
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 }
299
300 return 0;
301}
302
303#ifdef CONFIG_OF
304static const struct of_device_id spi_gpio_dt_ids[] = {
305 { .compatible = "spi-gpio" },
306 {}
307};
308MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids);
309
310static 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
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
338error_free:
339 devm_kfree(&pdev->dev, pdata);
340 return ret;
341}
342#else
343static inline int spi_gpio_probe_dt(struct platform_device *pdev)
344{
345 return 0;
346}
347#endif
348
349static int spi_gpio_probe(struct platform_device *pdev)
350{
351 int status;
352 struct spi_master *master;
353 struct spi_gpio *spi_gpio;
354 struct spi_gpio_platform_data *pdata;
355 u16 master_flags = 0;
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;
363
364 pdata = dev_get_platdata(&pdev->dev);
365#ifdef GENERIC_BITBANG
366 if (!pdata || (!use_of && !pdata->num_chipselect))
367 return -ENODEV;
368#endif
369
370 master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio));
371 if (!master)
372 return -ENOMEM;
373
374 spi_gpio = spi_master_get_devdata(master);
375
376 spi_gpio->cs_gpios = devm_kzalloc(&pdev->dev,
377 pdata->num_chipselect * sizeof(*spi_gpio->cs_gpios),
378 GFP_KERNEL);
379 if (!spi_gpio->cs_gpios)
380 return -ENOMEM;
381
382 platform_set_drvdata(pdev, spi_gpio);
383
384 /* Determine if we have chip selects connected */
385 spi_gpio->has_cs = !!pdata->num_chipselect;
386
387 spi_gpio->pdev = pdev;
388 if (pdata)
389 spi_gpio->pdata = *pdata;
390
391 status = spi_gpio_request(&pdev->dev, spi_gpio,
392 pdata->num_chipselect, &master_flags);
393 if (status)
394 return status;
395
396 master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
397 master->flags = master_flags;
398 master->bus_num = pdev->id;
399 /* The master needs to think there is a chipselect even if not connected */
400 master->num_chipselect = spi_gpio->has_cs ? pdata->num_chipselect : 1;
401 master->setup = spi_gpio_setup;
402 master->cleanup = spi_gpio_cleanup;
403#ifdef CONFIG_OF
404 master->dev.of_node = pdev->dev.of_node;
405#endif
406
407 spi_gpio->bitbang.master = master;
408 spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
409
410 if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) {
411 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
412 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
413 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
414 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
415 } else {
416 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0;
417 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1;
418 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2;
419 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
420 }
421 spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
422 spi_gpio->bitbang.flags = SPI_CS_HIGH;
423
424 status = spi_bitbang_start(&spi_gpio->bitbang);
425 if (status)
426 spi_master_put(master);
427
428 return status;
429}
430
431static int spi_gpio_remove(struct platform_device *pdev)
432{
433 struct spi_gpio *spi_gpio;
434 struct spi_gpio_platform_data *pdata;
435
436 spi_gpio = platform_get_drvdata(pdev);
437 pdata = dev_get_platdata(&pdev->dev);
438
439 /* stop() unregisters child devices too */
440 spi_bitbang_stop(&spi_gpio->bitbang);
441
442 spi_master_put(spi_gpio->bitbang.master);
443
444 return 0;
445}
446
447MODULE_ALIAS("platform:" DRIVER_NAME);
448
449static struct platform_driver spi_gpio_driver = {
450 .driver = {
451 .name = DRIVER_NAME,
452 .of_match_table = of_match_ptr(spi_gpio_dt_ids),
453 },
454 .probe = spi_gpio_probe,
455 .remove = spi_gpio_remove,
456};
457module_platform_driver(spi_gpio_driver);
458
459MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
460MODULE_AUTHOR("David Brownell");
461MODULE_LICENSE("GPL");