Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input
[linux-btrfs-devel.git] / drivers / spi / spi-gpio.c
blob0e88ab7454906ddb5dce94997dc51e84965559ea
1 /*
2 * SPI master driver using generic bitbanged GPIO
4 * Copyright (C) 2006,2008 David Brownell
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.
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.
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.
20 #include <linux/kernel.h>
21 #include <linux/init.h>
22 #include <linux/platform_device.h>
23 #include <linux/gpio.h>
25 #include <linux/spi/spi.h>
26 #include <linux/spi/spi_bitbang.h>
27 #include <linux/spi/spi_gpio.h>
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.
36 * platform_device->driver_data ... points to spi_gpio
38 * spi->controller_state ... reserved for bitbang framework code
39 * spi->controller_data ... holds chipselect GPIO
41 * spi->master->dev.driver_data ... points to spi_gpio->bitbang
44 struct spi_gpio {
45 struct spi_bitbang bitbang;
46 struct spi_gpio_platform_data pdata;
47 struct platform_device *pdev;
50 /*----------------------------------------------------------------------*/
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:
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.
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:
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"
75 #ifndef DRIVER_NAME
76 #define DRIVER_NAME "spi_gpio"
78 #define GENERIC_BITBANG /* vs tight inlines */
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)
85 #define SPI_N_CHIPSEL ((pdata)->num_chipselect)
87 #endif
89 /*----------------------------------------------------------------------*/
91 static inline const struct spi_gpio_platform_data * __pure
92 spi_to_pdata(const struct spi_device *spi)
94 const struct spi_bitbang *bang;
95 const struct spi_gpio *spi_gpio;
97 bang = spi_master_get_devdata(spi->master);
98 spi_gpio = container_of(bang, struct spi_gpio, bitbang);
99 return &spi_gpio->pdata;
102 /* this is #defined to avoid unused-variable warnings when inlining */
103 #define pdata spi_to_pdata(spi)
105 static inline void setsck(const struct spi_device *spi, int is_on)
107 gpio_set_value(SPI_SCK_GPIO, is_on);
110 static inline void setmosi(const struct spi_device *spi, int is_on)
112 gpio_set_value(SPI_MOSI_GPIO, is_on);
115 static inline int getmiso(const struct spi_device *spi)
117 return !!gpio_get_value(SPI_MISO_GPIO);
120 #undef pdata
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.
128 #define spidelay(nsecs) do {} while (0)
130 #include "spi-bitbang-txrx.h"
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.
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?
146 static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi,
147 unsigned nsecs, u32 word, u8 bits)
149 return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
152 static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
153 unsigned nsecs, u32 word, u8 bits)
155 return bitbang_txrx_be_cpha1(spi, nsecs, 0, 0, word, bits);
158 static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
159 unsigned nsecs, u32 word, u8 bits)
161 return bitbang_txrx_be_cpha0(spi, nsecs, 1, 0, word, bits);
164 static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
165 unsigned nsecs, u32 word, u8 bits)
167 return bitbang_txrx_be_cpha1(spi, nsecs, 1, 0, word, bits);
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.
180 static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi,
181 unsigned nsecs, u32 word, u8 bits)
183 unsigned flags = spi->master->flags;
184 return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
187 static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi,
188 unsigned nsecs, u32 word, u8 bits)
190 unsigned flags = spi->master->flags;
191 return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits);
194 static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi,
195 unsigned nsecs, u32 word, u8 bits)
197 unsigned flags = spi->master->flags;
198 return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits);
201 static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi,
202 unsigned nsecs, u32 word, u8 bits)
204 unsigned flags = spi->master->flags;
205 return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits);
208 /*----------------------------------------------------------------------*/
210 static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
212 unsigned long cs = (unsigned long) spi->controller_data;
214 /* set initial clock polarity */
215 if (is_active)
216 setsck(spi, spi->mode & SPI_CPOL);
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);
224 static int spi_gpio_setup(struct spi_device *spi)
226 unsigned long cs = (unsigned long) spi->controller_data;
227 int status = 0;
229 if (spi->bits_per_word > 32)
230 return -EINVAL;
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);
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);
246 return status;
249 static void spi_gpio_cleanup(struct spi_device *spi)
251 unsigned long cs = (unsigned long) spi->controller_data;
253 if (cs != SPI_GPIO_NO_CHIPSELECT)
254 gpio_free(cs);
255 spi_bitbang_cleanup(spi);
258 static int __init spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
260 int value;
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);
269 return value;
272 static int __init
273 spi_gpio_request(struct spi_gpio_platform_data *pdata, const char *label,
274 u16 *res_flags)
276 int value;
278 /* NOTE: SPI_*_GPIO symbols may reference "pdata" */
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;
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;
298 value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
299 if (value)
300 goto free_miso;
302 goto done;
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;
314 static int __init spi_gpio_probe(struct platform_device *pdev)
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;
322 pdata = pdev->dev.platform_data;
323 #ifdef GENERIC_BITBANG
324 if (!pdata || !pdata->num_chipselect)
325 return -ENODEV;
326 #endif
328 status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
329 if (status < 0)
330 return status;
332 master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio);
333 if (!master) {
334 status = -ENOMEM;
335 goto gpio_free;
337 spi_gpio = spi_master_get_devdata(master);
338 platform_set_drvdata(pdev, spi_gpio);
340 spi_gpio->pdev = pdev;
341 if (pdata)
342 spi_gpio->pdata = *pdata;
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;
350 spi_gpio->bitbang.master = spi_master_get(master);
351 spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
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;
364 spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
365 spi_gpio->bitbang.flags = SPI_CS_HIGH;
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);
379 return status;
382 static int __exit spi_gpio_remove(struct platform_device *pdev)
384 struct spi_gpio *spi_gpio;
385 struct spi_gpio_platform_data *pdata;
386 int status;
388 spi_gpio = platform_get_drvdata(pdev);
389 pdata = pdev->dev.platform_data;
391 /* stop() unregisters child devices too */
392 status = spi_bitbang_stop(&spi_gpio->bitbang);
393 spi_master_put(spi_gpio->bitbang.master);
395 platform_set_drvdata(pdev, NULL);
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);
403 return status;
406 MODULE_ALIAS("platform:" DRIVER_NAME);
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),
414 static int __init spi_gpio_init(void)
416 return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe);
418 module_init(spi_gpio_init);
420 static void __exit spi_gpio_exit(void)
422 platform_driver_unregister(&spi_gpio_driver);
424 module_exit(spi_gpio_exit);
427 MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
428 MODULE_AUTHOR("David Brownell");
429 MODULE_LICENSE("GPL");