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/init.h>
  23 #include <linux/platform_device.h>
  24 #include <linux/gpio.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         int                             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(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(SPI_MOSI_GPIO, is_on);
 123 }
 124
 125 static inline int getmiso(const struct spi_device *spi)
 126 {
 127         return !!gpio_get_value(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 int 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(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 int            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 (spi->bits_per_word > 32)
 243                 return -EINVAL;
 244
 245         if (np) {
 246                 /*
 247                  * In DT environments, the CS GPIOs have already been
 248                  * initialized from the "cs-gpios" property of the node.
 249                  */
 250                 cs = spi_gpio->cs_gpios[spi->chip_select];
 251         } else {
 252                 /*
 253                  * ... otherwise, take it from spi->controller_data
 254                  */
 255                 cs = (unsigned int) spi->controller_data;
 256         }
 257
 258         if (!spi->controller_state) {
 259                 if (cs != SPI_GPIO_NO_CHIPSELECT) {
 260                         status = gpio_request(cs, dev_name(&spi->dev));
 261                         if (status)
 262                                 return status;
 263                         status = gpio_direction_output(cs,
 264                                         !(spi->mode & SPI_CS_HIGH));
 265                 }
 266         }
 267         if (!status) {
 268                 /* in case it was initialized from static board data */
 269                 spi_gpio->cs_gpios[spi->chip_select] = cs;
 270                 status = spi_bitbang_setup(spi);
 271         }
 272
 273         if (status) {
 274                 if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT)
 275                         gpio_free(cs);
 276         }
 277         return status;
 278 }
 279
 280 static void spi_gpio_cleanup(struct spi_device *spi)
 281 {
 282         struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
 283         unsigned int cs = spi_gpio->cs_gpios[spi->chip_select];
 284
 285         if (cs != SPI_GPIO_NO_CHIPSELECT)
 286                 gpio_free(cs);
 287         spi_bitbang_cleanup(spi);
 288 }
 289
 290 static int spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
 291 {
 292         int value;
 293
 294         value = gpio_request(pin, label);
 295         if (value == 0) {
 296                 if (is_in)
 297                         value = gpio_direction_input(pin);
 298                 else
 299                         value = gpio_direction_output(pin, 0);
 300         }
 301         return value;
 302 }
 303
 304 static int spi_gpio_request(struct spi_gpio_platform_data *pdata,
 305                             const char *label, u16 *res_flags)
 306 {
 307         int value;
 308
 309         /* NOTE:  SPI_*_GPIO symbols may reference "pdata" */
 310
 311         if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) {
 312                 value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false);
 313                 if (value)
 314                         goto done;
 315         } else {
 316                 /* HW configuration without MOSI pin */
 317                 *res_flags |= SPI_MASTER_NO_TX;
 318         }
 319
 320         if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) {
 321                 value = spi_gpio_alloc(SPI_MISO_GPIO, label, true);
 322                 if (value)
 323                         goto free_mosi;
 324         } else {
 325                 /* HW configuration without MISO pin */
 326                 *res_flags |= SPI_MASTER_NO_RX;
 327         }
 328
 329         value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
 330         if (value)
 331                 goto free_miso;
 332
 333         goto done;
 334
 335 free_miso:
 336         if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
 337                 gpio_free(SPI_MISO_GPIO);
 338 free_mosi:
 339         if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
 340                 gpio_free(SPI_MOSI_GPIO);
 341 done:
 342         return value;
 343 }
 344
 345 #ifdef CONFIG_OF
 346 static struct of_device_id spi_gpio_dt_ids[] = {
 347         { .compatible = "spi-gpio" },
 348         {}
 349 };
 350 MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids);
 351
 352 static int spi_gpio_probe_dt(struct platform_device *pdev)
 353 {
 354         int ret;
 355         u32 tmp;
 356         struct spi_gpio_platform_data   *pdata;
 357         struct device_node *np = pdev->dev.of_node;
 358         const struct of_device_id *of_id =
 359                         of_match_device(spi_gpio_dt_ids, &pdev->dev);
 360
 361         if (!of_id)
 362                 return 0;
 363
 364         pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
 365         if (!pdata)
 366                 return -ENOMEM;
 367
 368         ret = of_get_named_gpio(np, "gpio-sck", 0);
 369         if (ret < 0) {
 370                 dev_err(&pdev->dev, "gpio-sck property not found\n");
 371                 goto error_free;
 372         }
 373         pdata->sck = ret;
 374
 375         ret = of_get_named_gpio(np, "gpio-miso", 0);
 376         if (ret < 0) {
 377                 dev_info(&pdev->dev, "gpio-miso property not found, switching to no-rx mode\n");
 378                 pdata->miso = SPI_GPIO_NO_MISO;
 379         } else
 380                 pdata->miso = ret;
 381
 382         ret = of_get_named_gpio(np, "gpio-mosi", 0);
 383         if (ret < 0) {
 384                 dev_info(&pdev->dev, "gpio-mosi property not found, switching to no-tx mode\n");
 385                 pdata->mosi = SPI_GPIO_NO_MOSI;
 386         } else
 387                 pdata->mosi = ret;
 388
 389         ret = of_property_read_u32(np, "num-chipselects", &tmp);
 390         if (ret < 0) {
 391                 dev_err(&pdev->dev, "num-chipselects property not found\n");
 392                 goto error_free;
 393         }
 394
 395         pdata->num_chipselect = tmp;
 396         pdev->dev.platform_data = pdata;
 397
 398         return 1;
 399
 400 error_free:
 401         devm_kfree(&pdev->dev, pdata);
 402         return ret;
 403 }
 404 #else
 405 static inline int spi_gpio_probe_dt(struct platform_device *pdev)
 406 {
 407         return 0;
 408 }
 409 #endif
 410
 411 static int spi_gpio_probe(struct platform_device *pdev)
 412 {
 413         int                             status;
 414         struct spi_master               *master;
 415         struct spi_gpio                 *spi_gpio;
 416         struct spi_gpio_platform_data   *pdata;
 417         u16 master_flags = 0;
 418         bool use_of = 0;
 419
 420         status = spi_gpio_probe_dt(pdev);
 421         if (status < 0)
 422                 return status;
 423         if (status > 0)
 424                 use_of = 1;
 425
 426         pdata = pdev->dev.platform_data;
 427 #ifdef GENERIC_BITBANG
 428         if (!pdata || !pdata->num_chipselect)
 429                 return -ENODEV;
 430 #endif
 431
 432         status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
 433         if (status < 0)
 434                 return status;
 435
 436         master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio) +
 437                                         (sizeof(int) * SPI_N_CHIPSEL));
 438         if (!master) {
 439                 status = -ENOMEM;
 440                 goto gpio_free;
 441         }
 442         spi_gpio = spi_master_get_devdata(master);
 443         platform_set_drvdata(pdev, spi_gpio);
 444
 445         spi_gpio->pdev = pdev;
 446         if (pdata)
 447                 spi_gpio->pdata = *pdata;
 448
 449         master->flags = master_flags;
 450         master->bus_num = pdev->id;
 451         master->num_chipselect = SPI_N_CHIPSEL;
 452         master->setup = spi_gpio_setup;
 453         master->cleanup = spi_gpio_cleanup;
 454 #ifdef CONFIG_OF
 455         master->dev.of_node = pdev->dev.of_node;
 456
 457         if (use_of) {
 458                 int i;
 459                 struct device_node *np = pdev->dev.of_node;
 460
 461                 /*
 462                  * In DT environments, take the CS GPIO from the "cs-gpios"
 463                  * property of the node.
 464                  */
 465
 466                 for (i = 0; i < SPI_N_CHIPSEL; i++)
 467                         spi_gpio->cs_gpios[i] =
 468                                 of_get_named_gpio(np, "cs-gpios", i);
 469         }
 470 #endif
 471
 472         spi_gpio->bitbang.master = spi_master_get(master);
 473         spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
 474
 475         if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) {
 476                 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
 477                 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
 478                 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
 479                 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
 480         } else {
 481                 spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0;
 482                 spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1;
 483                 spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2;
 484                 spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
 485         }
 486         spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
 487         spi_gpio->bitbang.flags = SPI_CS_HIGH;
 488
 489         status = spi_bitbang_start(&spi_gpio->bitbang);
 490         if (status < 0) {
 491                 spi_master_put(spi_gpio->bitbang.master);
 492 gpio_free:
 493                 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
 494                         gpio_free(SPI_MISO_GPIO);
 495                 if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
 496                         gpio_free(SPI_MOSI_GPIO);
 497                 gpio_free(SPI_SCK_GPIO);
 498                 spi_master_put(master);
 499         }
 500
 501         return status;
 502 }
 503
 504 static int spi_gpio_remove(struct platform_device *pdev)
 505 {
 506         struct spi_gpio                 *spi_gpio;
 507         struct spi_gpio_platform_data   *pdata;
 508         int                             status;
 509
 510         spi_gpio = platform_get_drvdata(pdev);
 511         pdata = pdev->dev.platform_data;
 512
 513         /* stop() unregisters child devices too */
 514         status = spi_bitbang_stop(&spi_gpio->bitbang);
 515         spi_master_put(spi_gpio->bitbang.master);
 516
 517         platform_set_drvdata(pdev, NULL);
 518
 519         if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
 520                 gpio_free(SPI_MISO_GPIO);
 521         if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
 522                 gpio_free(SPI_MOSI_GPIO);
 523         gpio_free(SPI_SCK_GPIO);
 524
 525         return status;
 526 }
 527
 528 MODULE_ALIAS("platform:" DRIVER_NAME);
 529
 530 static struct platform_driver spi_gpio_driver = {
 531         .driver = {
 532                 .name   = DRIVER_NAME,
 533                 .owner  = THIS_MODULE,
 534                 .of_match_table = of_match_ptr(spi_gpio_dt_ids),
 535         },
 536         .probe          = spi_gpio_probe,
 537         .remove         = spi_gpio_remove,
 538 };
 539 module_platform_driver(spi_gpio_driver);
 540
 541 MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
 542 MODULE_AUTHOR("David Brownell");
 543 MODULE_LICENSE("GPL");