| 1 | /* |
| 2 | * spi_gpio.c - 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 | * 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. |
| 19 | */ |
| 20 | #include <linux/kernel.h> |
| 21 | #include <linux/init.h> |
| 22 | #include <linux/platform_device.h> |
| 23 | #include <linux/gpio.h> |
| 24 | |
| 25 | #include <linux/spi/spi.h> |
| 26 | #include <linux/spi/spi_bitbang.h> |
| 27 | #include <linux/spi/spi_gpio.h> |
| 28 | |
| 29 | |
| 30 | /* |
| 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. |
| 35 | * |
| 36 | * platform_device->driver_data ... points to spi_gpio |
| 37 | * |
| 38 | * spi->controller_state ... reserved for bitbang framework code |
| 39 | * spi->controller_data ... holds chipselect GPIO |
| 40 | * |
| 41 | * spi->master->dev.driver_data ... points to spi_gpio->bitbang |
| 42 | */ |
| 43 | |
| 44 | struct spi_gpio { |
| 45 | struct spi_bitbang bitbang; |
| 46 | struct spi_gpio_platform_data pdata; |
| 47 | struct platform_device *pdev; |
| 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 | |
| 91 | static inline const struct spi_gpio_platform_data * __pure |
| 92 | spi_to_pdata(const struct spi_device *spi) |
| 93 | { |
| 94 | const struct spi_bitbang *bang; |
| 95 | const 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->pdata; |
| 100 | } |
| 101 | |
| 102 | /* this is #defined to avoid unused-variable warnings when inlining */ |
| 103 | #define pdata spi_to_pdata(spi) |
| 104 | |
| 105 | static inline void setsck(const struct spi_device *spi, int is_on) |
| 106 | { |
| 107 | gpio_set_value(SPI_SCK_GPIO, is_on); |
| 108 | } |
| 109 | |
| 110 | static inline void setmosi(const struct spi_device *spi, int is_on) |
| 111 | { |
| 112 | gpio_set_value(SPI_MOSI_GPIO, is_on); |
| 113 | } |
| 114 | |
| 115 | static inline int getmiso(const struct spi_device *spi) |
| 116 | { |
| 117 | return !!gpio_get_value(SPI_MISO_GPIO); |
| 118 | } |
| 119 | |
| 120 | #undef pdata |
| 121 | |
| 122 | /* |
| 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. |
| 127 | */ |
| 128 | #define spidelay(nsecs) do {} while (0) |
| 129 | |
| 130 | #define EXPAND_BITBANG_TXRX |
| 131 | #include <linux/spi/spi_bitbang.h> |
| 132 | |
| 133 | /* |
| 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. |
| 138 | * |
| 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? |
| 145 | */ |
| 146 | |
| 147 | static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi, |
| 148 | unsigned nsecs, u32 word, u8 bits) |
| 149 | { |
| 150 | return bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits); |
| 151 | } |
| 152 | |
| 153 | static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi, |
| 154 | unsigned nsecs, u32 word, u8 bits) |
| 155 | { |
| 156 | return bitbang_txrx_be_cpha1(spi, nsecs, 0, word, bits); |
| 157 | } |
| 158 | |
| 159 | static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi, |
| 160 | unsigned nsecs, u32 word, u8 bits) |
| 161 | { |
| 162 | return bitbang_txrx_be_cpha0(spi, nsecs, 1, word, bits); |
| 163 | } |
| 164 | |
| 165 | static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi, |
| 166 | unsigned nsecs, u32 word, u8 bits) |
| 167 | { |
| 168 | return bitbang_txrx_be_cpha1(spi, nsecs, 1, word, bits); |
| 169 | } |
| 170 | |
| 171 | /*----------------------------------------------------------------------*/ |
| 172 | |
| 173 | static void spi_gpio_chipselect(struct spi_device *spi, int is_active) |
| 174 | { |
| 175 | unsigned long cs = (unsigned long) spi->controller_data; |
| 176 | |
| 177 | /* set initial clock polarity */ |
| 178 | if (is_active) |
| 179 | setsck(spi, spi->mode & SPI_CPOL); |
| 180 | |
| 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); |
| 184 | } |
| 185 | } |
| 186 | |
| 187 | static int spi_gpio_setup(struct spi_device *spi) |
| 188 | { |
| 189 | unsigned long cs = (unsigned long) spi->controller_data; |
| 190 | int status = 0; |
| 191 | |
| 192 | if (spi->bits_per_word > 32) |
| 193 | return -EINVAL; |
| 194 | |
| 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); |
| 201 | } |
| 202 | } |
| 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); |
| 208 | } |
| 209 | return status; |
| 210 | } |
| 211 | |
| 212 | static void spi_gpio_cleanup(struct spi_device *spi) |
| 213 | { |
| 214 | unsigned long cs = (unsigned long) spi->controller_data; |
| 215 | |
| 216 | if (cs != SPI_GPIO_NO_CHIPSELECT) |
| 217 | gpio_free(cs); |
| 218 | spi_bitbang_cleanup(spi); |
| 219 | } |
| 220 | |
| 221 | static int __init spi_gpio_alloc(unsigned pin, const char *label, bool is_in) |
| 222 | { |
| 223 | int value; |
| 224 | |
| 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); |
| 231 | } |
| 232 | return value; |
| 233 | } |
| 234 | |
| 235 | static int __init |
| 236 | spi_gpio_request(struct spi_gpio_platform_data *pdata, const char *label) |
| 237 | { |
| 238 | int value; |
| 239 | |
| 240 | /* NOTE: SPI_*_GPIO symbols may reference "pdata" */ |
| 241 | |
| 242 | value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false); |
| 243 | if (value) |
| 244 | goto done; |
| 245 | |
| 246 | value = spi_gpio_alloc(SPI_MISO_GPIO, label, true); |
| 247 | if (value) |
| 248 | goto free_mosi; |
| 249 | |
| 250 | value = spi_gpio_alloc(SPI_SCK_GPIO, label, false); |
| 251 | if (value) |
| 252 | goto free_miso; |
| 253 | |
| 254 | goto done; |
| 255 | |
| 256 | free_miso: |
| 257 | gpio_free(SPI_MISO_GPIO); |
| 258 | free_mosi: |
| 259 | gpio_free(SPI_MOSI_GPIO); |
| 260 | done: |
| 261 | return value; |
| 262 | } |
| 263 | |
| 264 | static int __init spi_gpio_probe(struct platform_device *pdev) |
| 265 | { |
| 266 | int status; |
| 267 | struct spi_master *master; |
| 268 | struct spi_gpio *spi_gpio; |
| 269 | struct spi_gpio_platform_data *pdata; |
| 270 | |
| 271 | pdata = pdev->dev.platform_data; |
| 272 | #ifdef GENERIC_BITBANG |
| 273 | if (!pdata || !pdata->num_chipselect) |
| 274 | return -ENODEV; |
| 275 | #endif |
| 276 | |
| 277 | status = spi_gpio_request(pdata, dev_name(&pdev->dev)); |
| 278 | if (status < 0) |
| 279 | return status; |
| 280 | |
| 281 | master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio); |
| 282 | if (!master) { |
| 283 | status = -ENOMEM; |
| 284 | goto gpio_free; |
| 285 | } |
| 286 | spi_gpio = spi_master_get_devdata(master); |
| 287 | platform_set_drvdata(pdev, spi_gpio); |
| 288 | |
| 289 | spi_gpio->pdev = pdev; |
| 290 | if (pdata) |
| 291 | spi_gpio->pdata = *pdata; |
| 292 | |
| 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; |
| 297 | |
| 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; |
| 306 | |
| 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); |
| 315 | } |
| 316 | |
| 317 | return status; |
| 318 | } |
| 319 | |
| 320 | static int __exit spi_gpio_remove(struct platform_device *pdev) |
| 321 | { |
| 322 | struct spi_gpio *spi_gpio; |
| 323 | struct spi_gpio_platform_data *pdata; |
| 324 | int status; |
| 325 | |
| 326 | spi_gpio = platform_get_drvdata(pdev); |
| 327 | pdata = pdev->dev.platform_data; |
| 328 | |
| 329 | /* stop() unregisters child devices too */ |
| 330 | status = spi_bitbang_stop(&spi_gpio->bitbang); |
| 331 | spi_master_put(spi_gpio->bitbang.master); |
| 332 | |
| 333 | platform_set_drvdata(pdev, NULL); |
| 334 | |
| 335 | gpio_free(SPI_MISO_GPIO); |
| 336 | gpio_free(SPI_MOSI_GPIO); |
| 337 | gpio_free(SPI_SCK_GPIO); |
| 338 | |
| 339 | return status; |
| 340 | } |
| 341 | |
| 342 | MODULE_ALIAS("platform:" DRIVER_NAME); |
| 343 | |
| 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), |
| 348 | }; |
| 349 | |
| 350 | static int __init spi_gpio_init(void) |
| 351 | { |
| 352 | return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe); |
| 353 | } |
| 354 | module_init(spi_gpio_init); |
| 355 | |
| 356 | static void __exit spi_gpio_exit(void) |
| 357 | { |
| 358 | platform_driver_unregister(&spi_gpio_driver); |
| 359 | } |
| 360 | module_exit(spi_gpio_exit); |
| 361 | |
| 362 | |
| 363 | MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO "); |
| 364 | MODULE_AUTHOR("David Brownell"); |
| 365 | MODULE_LICENSE("GPL"); |