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 43 struct 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 88 static inline struct spi_gpio *__pure 89 spi_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 99 static inline struct spi_gpio_platform_data *__pure 100 spi_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 */ 106 static 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 } 112 113 static 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 } 119 120 static 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 */ 150 151 static 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 } 156 157 static 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 } 162 163 static 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 } 168 169 static 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 */ 184 185 static 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 } 191 192 static 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 } 198 199 static 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 } 205 206 static 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 /*----------------------------------------------------------------------*/ 214 215 static 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 } 231 232 static 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 } 252 253 static 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 */ 268 static 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 304 static const struct of_device_id spi_gpio_dt_ids[] = { 305 { .compatible = "spi-gpio" }, 306 {} 307 }; 308 MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids); 309 310 static 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; 337 338 error_free: 339 devm_kfree(&pdev->dev, pdata); 340 return ret; 341 } 342 #else 343 static inline int spi_gpio_probe_dt(struct platform_device *pdev) 344 { 345 return 0; 346 } 347 #endif 348 349 static 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_kcalloc(&pdev->dev, 377 pdata->num_chipselect, 378 sizeof(*spi_gpio->cs_gpios), 379 GFP_KERNEL); 380 if (!spi_gpio->cs_gpios) 381 return -ENOMEM; 382 383 platform_set_drvdata(pdev, spi_gpio); 384 385 /* Determine if we have chip selects connected */ 386 spi_gpio->has_cs = !!pdata->num_chipselect; 387 388 spi_gpio->pdev = pdev; 389 if (pdata) 390 spi_gpio->pdata = *pdata; 391 392 status = spi_gpio_request(&pdev->dev, spi_gpio, 393 pdata->num_chipselect, &master_flags); 394 if (status) 395 return status; 396 397 master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32); 398 master->flags = master_flags; 399 master->bus_num = pdev->id; 400 /* The master needs to think there is a chipselect even if not connected */ 401 master->num_chipselect = spi_gpio->has_cs ? pdata->num_chipselect : 1; 402 master->setup = spi_gpio_setup; 403 master->cleanup = spi_gpio_cleanup; 404 #ifdef CONFIG_OF 405 master->dev.of_node = pdev->dev.of_node; 406 #endif 407 408 spi_gpio->bitbang.master = master; 409 spi_gpio->bitbang.chipselect = spi_gpio_chipselect; 410 411 if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) { 412 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0; 413 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1; 414 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2; 415 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3; 416 } else { 417 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0; 418 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1; 419 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2; 420 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3; 421 } 422 spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer; 423 spi_gpio->bitbang.flags = SPI_CS_HIGH; 424 425 status = spi_bitbang_start(&spi_gpio->bitbang); 426 if (status) 427 spi_master_put(master); 428 429 return status; 430 } 431 432 static int spi_gpio_remove(struct platform_device *pdev) 433 { 434 struct spi_gpio *spi_gpio; 435 struct spi_gpio_platform_data *pdata; 436 437 spi_gpio = platform_get_drvdata(pdev); 438 pdata = dev_get_platdata(&pdev->dev); 439 440 /* stop() unregisters child devices too */ 441 spi_bitbang_stop(&spi_gpio->bitbang); 442 443 spi_master_put(spi_gpio->bitbang.master); 444 445 return 0; 446 } 447 448 MODULE_ALIAS("platform:" DRIVER_NAME); 449 450 static struct platform_driver spi_gpio_driver = { 451 .driver = { 452 .name = DRIVER_NAME, 453 .of_match_table = of_match_ptr(spi_gpio_dt_ids), 454 }, 455 .probe = spi_gpio_probe, 456 .remove = spi_gpio_remove, 457 }; 458 module_platform_driver(spi_gpio_driver); 459 460 MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO "); 461 MODULE_AUTHOR("David Brownell"); 462 MODULE_LICENSE("GPL"); 463