linux/drivers/spi/spi-gpio.c
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   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
  47struct 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
  95static inline struct spi_gpio * __pure
  96spi_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
 106static inline struct spi_gpio_platform_data * __pure
 107spi_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
 115static inline void setsck(const struct spi_device *spi, int is_on)
 116{
 117        gpio_set_value(SPI_SCK_GPIO, is_on);
 118}
 119
 120static inline void setmosi(const struct spi_device *spi, int is_on)
 121{
 122        gpio_set_value(SPI_MOSI_GPIO, is_on);
 123}
 124
 125static 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
 156static 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
 162static 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
 168static 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
 174static 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
 190static 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
 197static 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
 204static 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
 211static 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
 220static 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
 235static 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 (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 = (unsigned int) 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
 277static void spi_gpio_cleanup(struct spi_device *spi)
 278{
 279        struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
 280        unsigned int 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
 287static 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
 301static 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
 332free_miso:
 333        if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
 334                gpio_free(SPI_MISO_GPIO);
 335free_mosi:
 336        if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
 337                gpio_free(SPI_MOSI_GPIO);
 338done:
 339        return value;
 340}
 341
 342#ifdef CONFIG_OF
 343static struct of_device_id spi_gpio_dt_ids[] = {
 344        { .compatible = "spi-gpio" },
 345        {}
 346};
 347MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids);
 348
 349static 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
 397error_free:
 398        devm_kfree(&pdev->dev, pdata);
 399        return ret;
 400}
 401#else
 402static inline int spi_gpio_probe_dt(struct platform_device *pdev)
 403{
 404        return 0;
 405}
 406#endif
 407
 408static 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
 417        status = spi_gpio_probe_dt(pdev);
 418        if (status < 0)
 419                return status;
 420        if (status > 0)
 421                use_of = 1;
 422
 423        pdata = pdev->dev.platform_data;
 424#ifdef GENERIC_BITBANG
 425        if (!pdata || !pdata->num_chipselect)
 426                return -ENODEV;
 427#endif
 428
 429        status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
 430        if (status < 0)
 431                return status;
 432
 433        master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio) +
 434                                        (sizeof(int) * SPI_N_CHIPSEL));
 435        if (!master) {
 436                status = -ENOMEM;
 437                goto gpio_free;
 438        }
 439        spi_gpio = spi_master_get_devdata(master);
 440        platform_set_drvdata(pdev, spi_gpio);
 441
 442        spi_gpio->pdev = pdev;
 443        if (pdata)
 444                spi_gpio->pdata = *pdata;
 445
 446        master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
 447        master->flags = master_flags;
 448        master->bus_num = pdev->id;
 449        master->num_chipselect = SPI_N_CHIPSEL;
 450        master->setup = spi_gpio_setup;
 451        master->cleanup = spi_gpio_cleanup;
 452#ifdef CONFIG_OF
 453        master->dev.of_node = pdev->dev.of_node;
 454
 455        if (use_of) {
 456                int i;
 457                struct device_node *np = pdev->dev.of_node;
 458
 459                /*
 460                 * In DT environments, take the CS GPIO from the "cs-gpios"
 461                 * property of the node.
 462                 */
 463
 464                for (i = 0; i < SPI_N_CHIPSEL; i++)
 465                        spi_gpio->cs_gpios[i] =
 466                                of_get_named_gpio(np, "cs-gpios", i);
 467        }
 468#endif
 469
 470        spi_gpio->bitbang.master = spi_master_get(master);
 471        spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
 472
 473        if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) {
 474                spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
 475                spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
 476                spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
 477                spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
 478        } else {
 479                spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0;
 480                spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1;
 481                spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2;
 482                spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
 483        }
 484        spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
 485        spi_gpio->bitbang.flags = SPI_CS_HIGH;
 486
 487        status = spi_bitbang_start(&spi_gpio->bitbang);
 488        if (status < 0) {
 489                spi_master_put(spi_gpio->bitbang.master);
 490gpio_free:
 491                if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
 492                        gpio_free(SPI_MISO_GPIO);
 493                if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
 494                        gpio_free(SPI_MOSI_GPIO);
 495                gpio_free(SPI_SCK_GPIO);
 496                spi_master_put(master);
 497        }
 498
 499        return status;
 500}
 501
 502static int spi_gpio_remove(struct platform_device *pdev)
 503{
 504        struct spi_gpio                 *spi_gpio;
 505        struct spi_gpio_platform_data   *pdata;
 506        int                             status;
 507
 508        spi_gpio = platform_get_drvdata(pdev);
 509        pdata = pdev->dev.platform_data;
 510
 511        /* stop() unregisters child devices too */
 512        status = spi_bitbang_stop(&spi_gpio->bitbang);
 513        spi_master_put(spi_gpio->bitbang.master);
 514
 515        if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
 516                gpio_free(SPI_MISO_GPIO);
 517        if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
 518                gpio_free(SPI_MOSI_GPIO);
 519        gpio_free(SPI_SCK_GPIO);
 520
 521        return status;
 522}
 523
 524MODULE_ALIAS("platform:" DRIVER_NAME);
 525
 526static struct platform_driver spi_gpio_driver = {
 527        .driver = {
 528                .name   = DRIVER_NAME,
 529                .owner  = THIS_MODULE,
 530                .of_match_table = of_match_ptr(spi_gpio_dt_ids),
 531        },
 532        .probe          = spi_gpio_probe,
 533        .remove         = spi_gpio_remove,
 534};
 535module_platform_driver(spi_gpio_driver);
 536
 537MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
 538MODULE_AUTHOR("David Brownell");
 539MODULE_LICENSE("GPL");
 540
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