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");
548