target/linux/generic-2.6/patches-2.6.28/920-00-spi-gpio.patch

   1 Port of the SPI-GPIO driver from 2.6.29-rc4.
   2
   3 --mb
   4
   5
   6
   7 --- /dev/null
   8 +++ b/drivers/spi/spi_gpio.c
   9 @@ -0,0 +1,360 @@
  10 +/*
  11 + * spi_gpio.c - SPI master driver using generic bitbanged GPIO
  12 + *
  13 + * Copyright (C) 2006,2008 David Brownell
  14 + *
  15 + * This program is free software; you can redistribute it and/or modify
  16 + * it under the terms of the GNU General Public License as published by
  17 + * the Free Software Foundation; either version 2 of the License, or
  18 + * (at your option) any later version.
  19 + *
  20 + * This program is distributed in the hope that it will be useful,
  21 + * but WITHOUT ANY WARRANTY; without even the implied warranty of
  22 + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23 + * GNU General Public License for more details.
  24 + *
  25 + * You should have received a copy of the GNU General Public License
  26 + * along with this program; if not, write to the Free Software
  27 + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  28 + */
  29 +#include <linux/kernel.h>
  30 +#include <linux/init.h>
  31 +#include <linux/platform_device.h>
  32 +#include <linux/gpio.h>
  33 +
  34 +#include <linux/spi/spi.h>
  35 +#include <linux/spi/spi_bitbang.h>
  36 +#include <linux/spi/spi_gpio.h>
  37 +
  38 +
  39 +/*
  40 + * This bitbanging SPI master driver should help make systems usable
  41 + * when a native hardware SPI engine is not available, perhaps because
  42 + * its driver isn't yet working or because the I/O pins it requires
  43 + * are used for other purposes.
  44 + *
  45 + * platform_device->driver_data ... points to spi_gpio
  46 + *
  47 + * spi->controller_state ... reserved for bitbang framework code
  48 + * spi->controller_data ... holds chipselect GPIO
  49 + *
  50 + * spi->master->dev.driver_data ... points to spi_gpio->bitbang
  51 + */
  52 +
  53 +struct spi_gpio {
  54 +       struct spi_bitbang              bitbang;
  55 +       struct spi_gpio_platform_data   pdata;
  56 +       struct platform_device          *pdev;
  57 +};
  58 +
  59 +/*----------------------------------------------------------------------*/
  60 +
  61 +/*
  62 + * Because the overhead of going through four GPIO procedure calls
  63 + * per transferred bit can make performance a problem, this code
  64 + * is set up so that you can use it in either of two ways:
  65 + *
  66 + *   - The slow generic way:  set up platform_data to hold the GPIO
  67 + *     numbers used for MISO/MOSI/SCK, and issue procedure calls for
  68 + *     each of them.  This driver can handle several such busses.
  69 + *
  70 + *   - The quicker inlined way:  only helps with platform GPIO code
  71 + *     that inlines operations for constant GPIOs.  This can give
  72 + *     you tight (fast!) inner loops, but each such bus needs a
  73 + *     new driver.  You'll define a new C file, with Makefile and
  74 + *     Kconfig support; the C code can be a total of six lines:
  75 + *
  76 + *             #define DRIVER_NAME     "myboard_spi2"
  77 + *             #define SPI_MISO_GPIO   119
  78 + *             #define SPI_MOSI_GPIO   120
  79 + *             #define SPI_SCK_GPIO    121
  80 + *             #define SPI_N_CHIPSEL   4
  81 + *             #include "spi_gpio.c"
  82 + */
  83 +
  84 +#ifndef DRIVER_NAME
  85 +#define DRIVER_NAME    "spi_gpio"
  86 +
  87 +#define GENERIC_BITBANG        /* vs tight inlines */
  88 +
  89 +/* all functions referencing these symbols must define pdata */
  90 +#define SPI_MISO_GPIO  ((pdata)->miso)
  91 +#define SPI_MOSI_GPIO  ((pdata)->mosi)
  92 +#define SPI_SCK_GPIO   ((pdata)->sck)
  93 +
  94 +#define SPI_N_CHIPSEL  ((pdata)->num_chipselect)
  95 +
  96 +#endif
  97 +
  98 +/*----------------------------------------------------------------------*/
  99 +
 100 +static inline const struct spi_gpio_platform_data * __pure
 101 +spi_to_pdata(const struct spi_device *spi)
 102 +{
 103 +       const struct spi_bitbang        *bang;
 104 +       const struct spi_gpio           *spi_gpio;
 105 +
 106 +       bang = spi_master_get_devdata(spi->master);
 107 +       spi_gpio = container_of(bang, struct spi_gpio, bitbang);
 108 +       return &spi_gpio->pdata;
 109 +}
 110 +
 111 +/* this is #defined to avoid unused-variable warnings when inlining */
 112 +#define pdata          spi_to_pdata(spi)
 113 +
 114 +static inline void setsck(const struct spi_device *spi, int is_on)
 115 +{
 116 +       gpio_set_value(SPI_SCK_GPIO, is_on);
 117 +}
 118 +
 119 +static inline void setmosi(const struct spi_device *spi, int is_on)
 120 +{
 121 +       gpio_set_value(SPI_MOSI_GPIO, is_on);
 122 +}
 123 +
 124 +static inline int getmiso(const struct spi_device *spi)
 125 +{
 126 +       return gpio_get_value(SPI_MISO_GPIO);
 127 +}
 128 +
 129 +#undef pdata
 130 +
 131 +/*
 132 + * NOTE:  this clocks "as fast as we can".  It "should" be a function of the
 133 + * requested device clock.  Software overhead means we usually have trouble
 134 + * reaching even one Mbit/sec (except when we can inline bitops), so for now
 135 + * we'll just assume we never need additional per-bit slowdowns.
 136 + */
 137 +#define spidelay(nsecs)        do {} while (0)
 138 +
 139 +#define        EXPAND_BITBANG_TXRX
 140 +#include <linux/spi/spi_bitbang.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, 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, 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, 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, word, bits);
 178 +}
 179 +
 180 +/*----------------------------------------------------------------------*/
 181 +
 182 +static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
 183 +{
 184 +       unsigned long cs = (unsigned long) spi->controller_data;
 185 +
 186 +       /* set initial clock polarity */
 187 +       if (is_active)
 188 +               setsck(spi, spi->mode & SPI_CPOL);
 189 +
 190 +       /* SPI is normally active-low */
 191 +       gpio_set_value(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
 192 +}
 193 +
 194 +static int spi_gpio_setup(struct spi_device *spi)
 195 +{
 196 +       unsigned long   cs = (unsigned long) spi->controller_data;
 197 +       int             status = 0;
 198 +
 199 +       if (spi->bits_per_word > 32)
 200 +               return -EINVAL;
 201 +
 202 +       if (!spi->controller_state) {
 203 +               status = gpio_request(cs, spi->dev.bus_id);
 204 +               if (status)
 205 +                       return status;
 206 +               status = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
 207 +       }
 208 +       if (!status)
 209 +               status = spi_bitbang_setup(spi);
 210 +       if (status) {
 211 +               if (!spi->controller_state)
 212 +                       gpio_free(cs);
 213 +       }
 214 +       return status;
 215 +}
 216 +
 217 +static void spi_gpio_cleanup(struct spi_device *spi)
 218 +{
 219 +       unsigned long   cs = (unsigned long) spi->controller_data;
 220 +
 221 +       gpio_free(cs);
 222 +       spi_bitbang_cleanup(spi);
 223 +}
 224 +
 225 +static int __init spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
 226 +{
 227 +       int value;
 228 +
 229 +       value = gpio_request(pin, label);
 230 +       if (value == 0) {
 231 +               if (is_in)
 232 +                       value = gpio_direction_input(pin);
 233 +               else
 234 +                       value = gpio_direction_output(pin, 0);
 235 +       }
 236 +       return value;
 237 +}
 238 +
 239 +static int __init
 240 +spi_gpio_request(struct spi_gpio_platform_data *pdata, const char *label)
 241 +{
 242 +       int value;
 243 +
 244 +       /* NOTE:  SPI_*_GPIO symbols may reference "pdata" */
 245 +
 246 +       value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false);
 247 +       if (value)
 248 +               goto done;
 249 +
 250 +       value = spi_gpio_alloc(SPI_MISO_GPIO, label, true);
 251 +       if (value)
 252 +               goto free_mosi;
 253 +
 254 +       value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
 255 +       if (value)
 256 +               goto free_miso;
 257 +
 258 +       goto done;
 259 +
 260 +free_miso:
 261 +       gpio_free(SPI_MISO_GPIO);
 262 +free_mosi:
 263 +       gpio_free(SPI_MOSI_GPIO);
 264 +done:
 265 +       return value;
 266 +}
 267 +
 268 +static int __init spi_gpio_probe(struct platform_device *pdev)
 269 +{
 270 +       int                             status;
 271 +       struct spi_master               *master;
 272 +       struct spi_gpio                 *spi_gpio;
 273 +       struct spi_gpio_platform_data   *pdata;
 274 +
 275 +       pdata = pdev->dev.platform_data;
 276 +#ifdef GENERIC_BITBANG
 277 +       if (!pdata || !pdata->num_chipselect)
 278 +               return -ENODEV;
 279 +#endif
 280 +
 281 +       status = spi_gpio_request(pdata, dev_name(&pdev->dev));
 282 +       if (status < 0)
 283 +               return status;
 284 +
 285 +       master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio);
 286 +       if (!master) {
 287 +               status = -ENOMEM;
 288 +               goto gpio_free;
 289 +       }
 290 +       spi_gpio = spi_master_get_devdata(master);
 291 +       platform_set_drvdata(pdev, spi_gpio);
 292 +
 293 +       spi_gpio->pdev = pdev;
 294 +       if (pdata)
 295 +               spi_gpio->pdata = *pdata;
 296 +
 297 +       master->bus_num = pdev->id;
 298 +       master->num_chipselect = SPI_N_CHIPSEL;
 299 +       master->setup = spi_gpio_setup;
 300 +       master->cleanup = spi_gpio_cleanup;
 301 +
 302 +       spi_gpio->bitbang.master = spi_master_get(master);
 303 +       spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
 304 +       spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
 305 +       spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
 306 +       spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
 307 +       spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
 308 +       spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
 309 +       spi_gpio->bitbang.flags = SPI_CS_HIGH;
 310 +
 311 +       status = spi_bitbang_start(&spi_gpio->bitbang);
 312 +       if (status < 0) {
 313 +               spi_master_put(spi_gpio->bitbang.master);
 314 +gpio_free:
 315 +               gpio_free(SPI_MISO_GPIO);
 316 +               gpio_free(SPI_MOSI_GPIO);
 317 +               gpio_free(SPI_SCK_GPIO);
 318 +               spi_master_put(master);
 319 +       }
 320 +
 321 +       return status;
 322 +}
 323 +
 324 +static int __exit spi_gpio_remove(struct platform_device *pdev)
 325 +{
 326 +       struct spi_gpio                 *spi_gpio;
 327 +       struct spi_gpio_platform_data   *pdata;
 328 +       int                             status;
 329 +
 330 +       spi_gpio = platform_get_drvdata(pdev);
 331 +       pdata = pdev->dev.platform_data;
 332 +
 333 +       /* stop() unregisters child devices too */
 334 +       status = spi_bitbang_stop(&spi_gpio->bitbang);
 335 +       spi_master_put(spi_gpio->bitbang.master);
 336 +
 337 +       platform_set_drvdata(pdev, NULL);
 338 +
 339 +       gpio_free(SPI_MISO_GPIO);
 340 +       gpio_free(SPI_MOSI_GPIO);
 341 +       gpio_free(SPI_SCK_GPIO);
 342 +
 343 +       return status;
 344 +}
 345 +
 346 +MODULE_ALIAS("platform:" DRIVER_NAME);
 347 +
 348 +static struct platform_driver spi_gpio_driver = {
 349 +       .driver.name    = DRIVER_NAME,
 350 +       .driver.owner   = THIS_MODULE,
 351 +       .remove         = __exit_p(spi_gpio_remove),
 352 +};
 353 +
 354 +static int __init spi_gpio_init(void)
 355 +{
 356 +       return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe);
 357 +}
 358 +module_init(spi_gpio_init);
 359 +
 360 +static void __exit spi_gpio_exit(void)
 361 +{
 362 +       platform_driver_unregister(&spi_gpio_driver);
 363 +}
 364 +module_exit(spi_gpio_exit);
 365 +
 366 +
 367 +MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
 368 +MODULE_AUTHOR("David Brownell");
 369 +MODULE_LICENSE("GPL");
 370 --- /dev/null
 371 +++ b/include/linux/spi/spi_gpio.h
 372 @@ -0,0 +1,60 @@
 373 +#ifndef __LINUX_SPI_GPIO_H
 374 +#define __LINUX_SPI_GPIO_H
 375 +
 376 +/*
 377 + * For each bitbanged SPI bus, set up a platform_device node with:
 378 + *   - name "spi_gpio"
 379 + *   - id the same as the SPI bus number it implements
 380 + *   - dev.platform data pointing to a struct spi_gpio_platform_data
 381 + *
 382 + * Or, see the driver code for information about speedups that are
 383 + * possible on platforms that support inlined access for GPIOs (no
 384 + * spi_gpio_platform_data is used).
 385 + *
 386 + * Use spi_board_info with these busses in the usual way, being sure
 387 + * that the controller_data being the GPIO used for each device's
 388 + * chipselect:
 389 + *
 390 + *     static struct spi_board_info ... [] = {
 391 + *     ...
 392 + *             // this slave uses GPIO 42 for its chipselect
 393 + *             .controller_data = (void *) 42,
 394 + *     ...
 395 + *             // this one uses GPIO 86 for its chipselect
 396 + *             .controller_data = (void *) 86,
 397 + *     ...
 398 + *     };
 399 + *
 400 + * If the bitbanged bus is later switched to a "native" controller,
 401 + * that platform_device and controller_data should be removed.
 402 + */
 403 +
 404 +/**
 405 + * struct spi_gpio_platform_data - parameter for bitbanged SPI master
 406 + * @sck: number of the GPIO used for clock output
 407 + * @mosi: number of the GPIO used for Master Output, Slave In (MOSI) data
 408 + * @miso: number of the GPIO used for Master Input, Slave Output (MISO) data
 409 + * @num_chipselect: how many slaves to allow
 410 + *
 411 + * All GPIO signals used with the SPI bus managed through this driver
 412 + * (chipselects, MOSI, MISO, SCK) must be configured as GPIOs, instead
 413 + * of some alternate function.
 414 + *
 415 + * It can be convenient to use this driver with pins that have alternate
 416 + * functions associated with a "native" SPI controller if a driver for that
 417 + * controller is not available, or is missing important functionality.
 418 + *
 419 + * On platforms which can do so, configure MISO with a weak pullup unless
 420 + * there's an external pullup on that signal.  That saves power by avoiding
 421 + * floating signals.  (A weak pulldown would save power too, but many
 422 + * drivers expect to see all-ones data as the no slave "response".)
 423 + */
 424 +struct spi_gpio_platform_data {
 425 +       unsigned        sck;
 426 +       unsigned        mosi;
 427 +       unsigned        miso;
 428 +
 429 +       u16             num_chipselect;
 430 +};
 431 +
 432 +#endif /* __LINUX_SPI_GPIO_H */
 433 --- a/drivers/spi/Kconfig
 434 +++ b/drivers/spi/Kconfig
 435 @@ -100,6 +100,22 @@ config SPI_BUTTERFLY
 436           inexpensive battery powered microcontroller evaluation board.
 437           This same cable can be used to flash new firmware.
 438
 439 +config SPI_GPIO
 440 +       tristate "GPIO-based bitbanging SPI Master"
 441 +       depends on GENERIC_GPIO
 442 +       select SPI_BITBANG
 443 +       help
 444 +         This simple GPIO bitbanging SPI master uses the arch-neutral GPIO
 445 +         interface to manage MOSI, MISO, SCK, and chipselect signals.  SPI
 446 +         slaves connected to a bus using this driver are configured as usual,
 447 +         except that the spi_board_info.controller_data holds the GPIO number
 448 +         for the chipselect used by this controller driver.
 449 +
 450 +         Note that this driver often won't achieve even 1 Mbit/sec speeds,
 451 +         making it unusually slow for SPI.  If your platform can inline
 452 +         GPIO operations, you should be able to leverage that for better
 453 +         speed with a custom version of this driver; see the source code.
 454 +
 455  config SPI_IMX
 456         tristate "Freescale iMX SPI controller"
 457         depends on ARCH_IMX && EXPERIMENTAL
 458 --- a/drivers/spi/Makefile
 459 +++ b/drivers/spi/Makefile
 460 @@ -16,6 +16,7 @@ obj-$(CONFIG_SPI_BFIN)                        += spi_bfin5xx.
 461  obj-$(CONFIG_SPI_BITBANG)              += spi_bitbang.o
 462  obj-$(CONFIG_SPI_AU1550)               += au1550_spi.o
 463  obj-$(CONFIG_SPI_BUTTERFLY)            += spi_butterfly.o
 464 +obj-$(CONFIG_SPI_GPIO)                 += spi_gpio.o
 465  obj-$(CONFIG_SPI_IMX)                  += spi_imx.o
 466  obj-$(CONFIG_SPI_LM70_LLP)             += spi_lm70llp.o
 467  obj-$(CONFIG_SPI_PXA2XX)               += pxa2xx_spi.o