perf_counter: Check task on counter read IPI
[linux-2.6/mini2440.git] / drivers / spi / spi_gpio.c
blob26bd03e61855fba412726f23b638066a90abcaa9
1 /*
2 * spi_gpio.c - 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 #define EXPAND_BITBANG_TXRX
131 #include <linux/spi/spi_bitbang.h>
134 * These functions can leverage inline expansion of GPIO calls to shrink
135 * costs for a txrx bit, often by factors of around ten (by instruction
136 * count). That is particularly visible for larger word sizes, but helps
137 * even with default 8-bit words.
139 * REVISIT overheads calling these functions for each word also have
140 * significant performance costs. Having txrx_bufs() calls that inline
141 * the txrx_word() logic would help performance, e.g. on larger blocks
142 * used with flash storage or MMC/SD. There should also be ways to make
143 * GCC be less stupid about reloading registers inside the I/O loops,
144 * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3?
147 static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi,
148 unsigned nsecs, u32 word, u8 bits)
150 return bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);
153 static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
154 unsigned nsecs, u32 word, u8 bits)
156 return bitbang_txrx_be_cpha1(spi, nsecs, 0, word, bits);
159 static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
160 unsigned nsecs, u32 word, u8 bits)
162 return bitbang_txrx_be_cpha0(spi, nsecs, 1, word, bits);
165 static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
166 unsigned nsecs, u32 word, u8 bits)
168 return bitbang_txrx_be_cpha1(spi, nsecs, 1, word, bits);
171 /*----------------------------------------------------------------------*/
173 static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
175 unsigned long cs = (unsigned long) spi->controller_data;
177 /* set initial clock polarity */
178 if (is_active)
179 setsck(spi, spi->mode & SPI_CPOL);
181 if (cs != SPI_GPIO_NO_CHIPSELECT) {
182 /* SPI is normally active-low */
183 gpio_set_value(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
187 static int spi_gpio_setup(struct spi_device *spi)
189 unsigned long cs = (unsigned long) spi->controller_data;
190 int status = 0;
192 if (spi->bits_per_word > 32)
193 return -EINVAL;
195 if (!spi->controller_state) {
196 if (cs != SPI_GPIO_NO_CHIPSELECT) {
197 status = gpio_request(cs, dev_name(&spi->dev));
198 if (status)
199 return status;
200 status = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
203 if (!status)
204 status = spi_bitbang_setup(spi);
205 if (status) {
206 if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT)
207 gpio_free(cs);
209 return status;
212 static void spi_gpio_cleanup(struct spi_device *spi)
214 unsigned long cs = (unsigned long) spi->controller_data;
216 if (cs != SPI_GPIO_NO_CHIPSELECT)
217 gpio_free(cs);
218 spi_bitbang_cleanup(spi);
221 static int __init spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
223 int value;
225 value = gpio_request(pin, label);
226 if (value == 0) {
227 if (is_in)
228 value = gpio_direction_input(pin);
229 else
230 value = gpio_direction_output(pin, 0);
232 return value;
235 static int __init
236 spi_gpio_request(struct spi_gpio_platform_data *pdata, const char *label)
238 int value;
240 /* NOTE: SPI_*_GPIO symbols may reference "pdata" */
242 value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false);
243 if (value)
244 goto done;
246 value = spi_gpio_alloc(SPI_MISO_GPIO, label, true);
247 if (value)
248 goto free_mosi;
250 value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
251 if (value)
252 goto free_miso;
254 goto done;
256 free_miso:
257 gpio_free(SPI_MISO_GPIO);
258 free_mosi:
259 gpio_free(SPI_MOSI_GPIO);
260 done:
261 return value;
264 static int __init spi_gpio_probe(struct platform_device *pdev)
266 int status;
267 struct spi_master *master;
268 struct spi_gpio *spi_gpio;
269 struct spi_gpio_platform_data *pdata;
271 pdata = pdev->dev.platform_data;
272 #ifdef GENERIC_BITBANG
273 if (!pdata || !pdata->num_chipselect)
274 return -ENODEV;
275 #endif
277 status = spi_gpio_request(pdata, dev_name(&pdev->dev));
278 if (status < 0)
279 return status;
281 master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio);
282 if (!master) {
283 status = -ENOMEM;
284 goto gpio_free;
286 spi_gpio = spi_master_get_devdata(master);
287 platform_set_drvdata(pdev, spi_gpio);
289 spi_gpio->pdev = pdev;
290 if (pdata)
291 spi_gpio->pdata = *pdata;
293 master->bus_num = pdev->id;
294 master->num_chipselect = SPI_N_CHIPSEL;
295 master->setup = spi_gpio_setup;
296 master->cleanup = spi_gpio_cleanup;
298 spi_gpio->bitbang.master = spi_master_get(master);
299 spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
300 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
301 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
302 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
303 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
304 spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
305 spi_gpio->bitbang.flags = SPI_CS_HIGH;
307 status = spi_bitbang_start(&spi_gpio->bitbang);
308 if (status < 0) {
309 spi_master_put(spi_gpio->bitbang.master);
310 gpio_free:
311 gpio_free(SPI_MISO_GPIO);
312 gpio_free(SPI_MOSI_GPIO);
313 gpio_free(SPI_SCK_GPIO);
314 spi_master_put(master);
317 return status;
320 static int __exit spi_gpio_remove(struct platform_device *pdev)
322 struct spi_gpio *spi_gpio;
323 struct spi_gpio_platform_data *pdata;
324 int status;
326 spi_gpio = platform_get_drvdata(pdev);
327 pdata = pdev->dev.platform_data;
329 /* stop() unregisters child devices too */
330 status = spi_bitbang_stop(&spi_gpio->bitbang);
331 spi_master_put(spi_gpio->bitbang.master);
333 platform_set_drvdata(pdev, NULL);
335 gpio_free(SPI_MISO_GPIO);
336 gpio_free(SPI_MOSI_GPIO);
337 gpio_free(SPI_SCK_GPIO);
339 return status;
342 MODULE_ALIAS("platform:" DRIVER_NAME);
344 static struct platform_driver spi_gpio_driver = {
345 .driver.name = DRIVER_NAME,
346 .driver.owner = THIS_MODULE,
347 .remove = __exit_p(spi_gpio_remove),
350 static int __init spi_gpio_init(void)
352 return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe);
354 module_init(spi_gpio_init);
356 static void __exit spi_gpio_exit(void)
358 platform_driver_unregister(&spi_gpio_driver);
360 module_exit(spi_gpio_exit);
363 MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
364 MODULE_AUTHOR("David Brownell");
365 MODULE_LICENSE("GPL");