drivers/spi/spi-gpio.c

   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  * 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/module.h>
  22 #include <linux/platform_device.h>
  23 #include <linux/gpio.h>
  24 #include <linux/of.h>
  25 #include <linux/of_device.h>
  26 #include <linux/of_gpio.h>
  27
  28 #include <linux/spi/spi.h>
  29 #include <linux/spi/spi_bitbang.h>
  30 #include <linux/spi/spi_gpio.h>
  31
  32
  33 /*
  34  * This bitbanging SPI master driver should help make systems usable
  35  * when a native hardware SPI engine is not available, perhaps because
  36  * its driver isn't yet working or because the I/O pins it requires
  37  * are used for other purposes.
  38  *
  39  * platform_device->driver_data ... points to spi_gpio
  40  *
  41  * spi->controller_state ... reserved for bitbang framework code
  42  * spi->controller_data ... holds chipselect GPIO
  43  *
  44  * spi->master->dev.driver_data ... points to spi_gpio->bitbang
  45  */
  46
  47 struct spi_gpio {
  48         struct spi_bitbang              bitbang;
  49         struct spi_gpio_platform_data   pdata;
  50         struct platform_device          *pdev;
  51         unsigned long                   cs_gpios[0];
  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 /* all functions referencing these symbols must define pdata */
  85 #define SPI_MISO_GPIO   ((pdata)->miso)
  86 #define SPI_MOSI_GPIO   ((pdata)->mosi)
  87 #define SPI_SCK_GPIO    ((pdata)->sck)
  88
  89 #define SPI_N_CHIPSEL   ((pdata)->num_chipselect)
  90
  91 #endif
  92
  93 /*----------------------------------------------------------------------*/
  94
  95 static inline struct spi_gpio * __pure
  96 spi_to_spi_gpio(const struct spi_device *spi)
  97 {
  98         const struct spi_bitbang        *bang;
  99         struct spi_gpio                 *spi_gpio;
 100
 101         bang = spi_master_get_devdata(spi->master);
 102         spi_gpio = container_of(bang, struct spi_gpio, bitbang);
 103         return spi_gpio;
 104 }
 105
 106 static inline struct spi_gpio_platform_data * __pure
 107 spi_to_pdata(const struct spi_device *spi)
 108 {
 109         return &spi_to_spi_gpio(spi)->pdata;
 110 }
 111
 112 /* this is #defined to avoid unused-variable warnings when inlining */
 113 #define pdata           spi_to_pdata(spi)
 114
 115 static inline void setsck(const struct spi_device *spi, int is_on)
 116 {
 117         gpio_set_value_cansleep(SPI_SCK_GPIO, is_on);
 118 }
 119
 120 static inline void setmosi(const struct spi_device *spi, int is_on)
 121 {
 122         gpio_set_value_cansleep(SPI_MOSI_GPIO, is_on);
 123 }
 124
 125 static inline int getmiso(const struct spi_device *spi)
 126 {
 127         return !!gpio_get_value_cansleep(SPI_MISO_GPIO);
 128 }
 129
 130 #undef pdata
 131
 132 /*
 133  * NOTE:  this clocks "as fast as we can".  It "should" be a function of the
 134  * requested device clock.  Software overhead means we usually have trouble
 135  * reaching even one Mbit/sec (except when we can inline bitops), so for now
 136  * we'll just assume we never need additional per-bit slowdowns.
 137  */
 138 #define spidelay(nsecs) do {} while (0)
 139
 140 #include "spi-bitbang-txrx.h"
 141
 142 /*
 143  * These functions can leverage inline expansion of GPIO calls to shrink
 144  * costs for a txrx bit, often by factors of around ten (by instruction
 145  * count).  That is particularly visible for larger word sizes, but helps
 146  * even with default 8-bit words.
 147  *
 148  * REVISIT overheads calling these functions for each word also have
 149  * significant performance costs.  Having txrx_bufs() calls that inline
 150  * the txrx_word() logic would help performance, e.g. on larger blocks
 151  * used with flash storage or MMC/SD.  There should also be ways to make
 152  * GCC be less stupid about reloading registers inside the I/O loops,
 153  * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3?
 154  */
 155
 156 static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi,
 157                 unsigned nsecs, u32 word, u8 bits)
 158 {
 159         return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
 160 }
 161
 162 static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
 163                 unsigned nsecs, u32 word, u8 bits)
 164 {
 165         return bitbang_txrx_be_cpha1(spi, nsecs, 0, 0, word, bits);
 166 }
 167
 168 static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
 169                 unsigned nsecs, u32 word, u8 bits)
 170 {
 171         return bitbang_txrx_be_cpha0(spi, nsecs, 1, 0, word, bits);
 172 }
 173
 174 static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
 175                 unsigned nsecs, u32 word, u8 bits)
 176 {
 177         return bitbang_txrx_be_cpha1(spi, nsecs, 1, 0, word, bits);
 178 }
 179
 180 /*
 181  * These functions do not call setmosi or getmiso if respective flag
 182  * (SPI_MASTER_NO_RX or SPI_MASTER_NO_TX) is set, so they are safe to
 183  * call when such pin is not present or defined in the controller.
 184  * A separate set of callbacks is defined to get highest possible
 185  * speed in the generic case (when both MISO and MOSI lines are
 186  * available), as optimiser will remove the checks when argument is
 187  * constant.
 188  */
 189
 190 static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi,
 191                 unsigned nsecs, u32 word, u8 bits)
 192 {
 193         unsigned flags = spi->master->flags;
 194         return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
 195 }
 196
 197 static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi,
 198                 unsigned nsecs, u32 word, u8 bits)
 199 {
 200         unsigned flags = spi->master->flags;
 201         return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits);
 202 }
 203
 204 static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi,
 205                 unsigned nsecs, u32 word, u8 bits)
 206 {
 207         unsigned flags = spi->master->flags;
 208         return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits);
 209 }
 210
 211 static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi,
 212                 unsigned nsecs, u32 word, u8 bits)
 213 {
 214         unsigned flags = spi->master->flags;
 215         return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits);
 216 }
 217
 218 /*----------------------------------------------------------------------*/
 219
 220 static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
 221 {
 222         struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
 223         unsigned long cs = spi_gpio->cs_gpios[spi->chip_select];
 224
 225         /* set initial clock polarity */
 226         if (is_active)
 227                 setsck(spi, spi->mode & SPI_CPOL);
 228
 229         if (cs != SPI_GPIO_NO_CHIPSELECT) {
 230                 /* SPI is normally active-low */
 231                 gpio_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
 232         }
 233 }
 234
 235 static int spi_gpio_setup(struct spi_device *spi)
 236 {
 237         unsigned long           cs;
 238         int                     status = 0;
 239         struct spi_gpio         *spi_gpio = spi_to_spi_gpio(spi);
 240         struct device_node      *np = spi->master->dev.of_node;
 241
 242         if (np) {
 243                 /*
 244                  * In DT environments, the CS GPIOs have already been
 245                  * initialized from the "cs-gpios" property of the node.
 246                  */
 247                 cs = spi_gpio->cs_gpios[spi->chip_select];
 248         } else {
 249                 /*
 250                  * ... otherwise, take it from spi->controller_data
 251                  */
 252                 cs = (uintptr_t) spi->controller_data;
 253         }
 254
 255         if (!spi->controller_state) {
 256                 if (cs != SPI_GPIO_NO_CHIPSELECT) {
 257                         status = gpio_request(cs, dev_name(&spi->dev));
 258                         if (status)
 259                                 return status;
 260                         status = gpio_direction_output(cs,
 261                                         !(spi->mode & SPI_CS_HIGH));
 262                 }
 263         }
 264         if (!status) {
 265                 /* in case it was initialized from static board data */
 266                 spi_gpio->cs_gpios[spi->chip_select] = cs;
 267                 status = spi_bitbang_setup(spi);
 268         }
 269
 270         if (status) {
 271                 if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT)
 272                         gpio_free(cs);
 273         }
 274         return status;
 275 }
 276
 277 static void spi_gpio_cleanup(struct spi_device *spi)
 278 {
 279         struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
 280         unsigned long cs = spi_gpio->cs_gpios[spi->chip_select];
 281
 282         if (cs != SPI_GPIO_NO_CHIPSELECT)
 283                 gpio_free(cs);
 284         spi_bitbang_cleanup(spi);
 285 }
 286
 287 static int spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
 288 {
 289         int value;
 290
 291         value = gpio_request(pin, label);
 292         if (value == 0) {
 293                 if (is_in)
 294                         value = gpio_direction_input(pin);
 295                 else
 296                         value = gpio_direction_output(pin, 0);
 297         }
 298         return value;
 299 }
 300
 301 static int spi_gpio_request(struct spi_gpio_platform_data *pdata,
 302                             const char *label, u16 *res_flags)
 303 {
 304         int value;
 305
 306         /* NOTE:  SPI_*_GPIO symbols may reference "pdata" */
 307
 308         if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) {
 309                 value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false);
 310                 if (value)
 311                         goto done;
 312         } else {
 313                 /* HW configuration without MOSI pin */
 314                 *res_flags |= SPI_MASTER_NO_TX;
 315         }
 316
 317         if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) {
 318                 value = spi_gpio_alloc(SPI_MISO_GPIO, label, true);
 319                 if (value)
 320                         goto free_mosi;
 321         } else {
 322                 /* HW configuration without MISO pin */
 323                 *res_flags |= SPI_MASTER_NO_RX;
 324         }
 325
 326         value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
 327         if (value)
 328                 goto free_miso;
 329
 330         goto done;
 331
 332 free_miso:
 333         if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
 334                 gpio_free(SPI_MISO_GPIO);
 335 free_mosi:
 336         if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
 337                 gpio_free(SPI_MOSI_GPIO);
 338 done:
 339         return value;
 340 }
 341
 342 #ifdef CONFIG_OF
 343 static const struct of_device_id spi_gpio_dt_ids[] = {
 344         { .compatible = "spi-gpio" },
 345         {}
 346 };
 347 MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids);
 348
 349 static int spi_gpio_probe_dt(struct platform_device *pdev)
 350 {
 351         int ret;
 352         u32 tmp;
 353         struct spi_gpio_platform_data   *pdata;
 354         struct device_node *np = pdev->dev.of_node;
 355         const struct of_device_id *of_id =
 356                         of_match_device(spi_gpio_dt_ids, &pdev->dev);
 357
 358         if (!of_id)
 359                 return 0;
 360
 361         pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
 362         if (!pdata)
 363                 return -ENOMEM;
 364
 365         ret = of_get_named_gpio(np, "gpio-sck", 0);
 366         if (ret < 0) {
 367                 dev_err(&pdev->dev, "gpio-sck property not found\n");
 368                 goto error_free;
 369         }
 370         pdata->sck = ret;
 371
 372         ret = of_get_named_gpio(np, "gpio-miso", 0);
 373         if (ret < 0) {
 374                 dev_info(&pdev->dev, "gpio-miso property not found, switching to no-rx mode\n");
 375                 pdata->miso = SPI_GPIO_NO_MISO;
 376         } else
 377                 pdata->miso = ret;
 378
 379         ret = of_get_named_gpio(np, "gpio-mosi", 0);
 380         if (ret < 0) {
 381                 dev_info(&pdev->dev, "gpio-mosi property not found, switching to no-tx mode\n");
 382                 pdata->mosi = SPI_GPIO_NO_MOSI;
 383         } else
 384                 pdata->mosi = ret;
 385
 386         ret = of_property_read_u32(np, "num-chipselects", &tmp);
 387         if (ret < 0) {
 388                 dev_err(&pdev->dev, "num-chipselects property not found\n");
 389                 goto error_free;
 390         }
 391
 392         pdata->num_chipselect = tmp;
 393         pdev->dev.platform_data = pdata;
 394
 395         return 1;
 396
 397 error_free:
 398         devm_kfree(&pdev->dev, pdata);
 399         return ret;
 400 }
 401 #else
 402 static inline int spi_gpio_probe_dt(struct platform_device *pdev)
 403 {
 404         return 0;
 405 }
 406 #endif
 407
 408 static int spi_gpio_probe(struct platform_device *pdev)
 409 {
 410         int                             status;
 411         struct spi_master               *master;
 412         struct spi_gpio                 *spi_gpio;
 413         struct spi_gpio_platform_data   *pdata;
 414         u16 master_flags = 0;
 415         bool use_of = 0;
 416         int num_devices;
 417
 418         status = spi_gpio_probe_dt(pdev);
 419         if (status < 0)
 420                 return status;
 421         if (status > 0)
 422                 use_of = 1;
 423
 424         pdata = dev_get_platdata(&pdev->dev);
 425 #ifdef GENERIC_BITBANG
 426         if (!pdata || (!use_of && !pdata->num_chipselect))
 427                 return -ENODEV;
 428 #endif
 429
 430         if (use_of && !SPI_N_CHIPSEL)
 431                 num_devices = 1;
 432         else
 433                 num_devices = SPI_N_CHIPSEL;
 434
 435         status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
 436         if (status < 0)
 437                 return status;
 438
 439         master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio) +
 440                                         (sizeof(unsigned long) * num_devices));
 441         if (!master) {
 442                 status = -ENOMEM;
 443                 goto gpio_free;
 444         }
 445         spi_gpio = spi_master_get_devdata(master);
 446         platform_set_drvdata(pdev, spi_gpio);
 447
 448         spi_gpio->pdev = pdev;
 449         if (pdata)
 450                 spi_gpio->pdata = *pdata;
 451
 452         master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
 453         master->flags = master_flags;
 454         master->bus_num = pdev->id;
 455         master->num_chipselect = num_devices;
 456         master->setup = spi_gpio_setup;
 457         master->cleanup = spi_gpio_cleanup;
 458 #ifdef CONFIG_OF
 459         master->dev.of_node = pdev->dev.of_node;
 460
 461         if (use_of) {
 462                 int i;
 463                 struct device_node *np = pdev->dev.of_node;
 464
 465                 /*
 466                  * In DT environments, take the CS GPIO from the "cs-gpios"
 467                  * property of the node.
 468                  */
 469
 470                 if (!SPI_N_CHIPSEL)
 471                         spi_gpio->cs_gpios[0] = SPI_GPIO_NO_CHIPSELECT;
 472                 else
 473                         for (i = 0; i < SPI_N_CHIPSEL; i++) {
 474                                 status = of_get_named_gpio(np, "cs-gpios", i);
 475                                 if (status < 0) {
 476                                         dev_err(&pdev->dev,
 477                                                 "invalid cs-gpios property\n");
 478                                         goto gpio_free;
 479                                 }
 480                                 spi_gpio->cs_gpios[i] = status;
 481                         }
 482         }
 483 #endif
 484
 485         spi_gpio->bitbang.master = master;
 486         spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
 487
 488         if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) {
 489                 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
 490                 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
 491                 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
 492                 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
 493         } else {
 494                 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0;
 495                 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1;
 496                 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2;
 497                 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
 498         }
 499         spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
 500         spi_gpio->bitbang.flags = SPI_CS_HIGH;
 501
 502         status = spi_bitbang_start(&spi_gpio->bitbang);
 503         if (status < 0) {
 504 gpio_free:
 505                 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
 506                         gpio_free(SPI_MISO_GPIO);
 507                 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
 508                         gpio_free(SPI_MOSI_GPIO);
 509                 gpio_free(SPI_SCK_GPIO);
 510                 spi_master_put(master);
 511         }
 512
 513         return status;
 514 }
 515
 516 static int spi_gpio_remove(struct platform_device *pdev)
 517 {
 518         struct spi_gpio                 *spi_gpio;
 519         struct spi_gpio_platform_data   *pdata;
 520
 521         spi_gpio = platform_get_drvdata(pdev);
 522         pdata = dev_get_platdata(&pdev->dev);
 523
 524         /* stop() unregisters child devices too */
 525         spi_bitbang_stop(&spi_gpio->bitbang);
 526
 527         if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
 528                 gpio_free(SPI_MISO_GPIO);
 529         if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
 530                 gpio_free(SPI_MOSI_GPIO);
 531         gpio_free(SPI_SCK_GPIO);
 532         spi_master_put(spi_gpio->bitbang.master);
 533
 534         return 0;
 535 }
 536
 537 MODULE_ALIAS("platform:" DRIVER_NAME);
 538
 539 static struct platform_driver spi_gpio_driver = {
 540         .driver = {
 541                 .name   = DRIVER_NAME,
 542                 .of_match_table = of_match_ptr(spi_gpio_dt_ids),
 543         },
 544         .probe          = spi_gpio_probe,
 545         .remove         = spi_gpio_remove,
 546 };
 547 module_platform_driver(spi_gpio_driver);
 548
 549 MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
 550 MODULE_AUTHOR("David Brownell");
 551 MODULE_LICENSE("GPL");