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

   1 Port of the SPI-GPIO driver from 2.6.29-rc4.
   2
   3 --mb
   4
   5
   6
   7 Index: linux-2.6.28.2/drivers/spi/spi_gpio.c
   8 ===================================================================
   9 --- /dev/null   1970-01-01 00:00:00.000000000 +0000
  10 +++ linux-2.6.28.2/drivers/spi/spi_gpio.c       2009-02-10 17:56:59.000000000 +0100
  11 @@ -0,0 +1,360 @@
  12 +/*
  13 + * spi_gpio.c - SPI master driver using generic bitbanged GPIO
  14 + *
  15 + * Copyright (C) 2006,2008 David Brownell
  16 + *
  17 + * This program is free software; you can redistribute it and/or modify
  18 + * it under the terms of the GNU General Public License as published by
  19 + * the Free Software Foundation; either version 2 of the License, or
  20 + * (at your option) any later version.
  21 + *
  22 + * This program is distributed in the hope that it will be useful,
  23 + * but WITHOUT ANY WARRANTY; without even the implied warranty of
  24 + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  25 + * GNU General Public License for more details.
  26 + *
  27 + * You should have received a copy of the GNU General Public License
  28 + * along with this program; if not, write to the Free Software
  29 + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  30 + */
  31 +#include <linux/kernel.h>
  32 +#include <linux/init.h>
  33 +#include <linux/platform_device.h>
  34 +#include <linux/gpio.h>
  35 +
  36 +#include <linux/spi/spi.h>
  37 +#include <linux/spi/spi_bitbang.h>
  38 +#include <linux/spi/spi_gpio.h>
  39 +
  40 +
  41 +/*
  42 + * This bitbanging SPI master driver should help make systems usable
  43 + * when a native hardware SPI engine is not available, perhaps because
  44 + * its driver isn't yet working or because the I/O pins it requires
  45 + * are used for other purposes.
  46 + *
  47 + * platform_device->driver_data ... points to spi_gpio
  48 + *
  49 + * spi->controller_state ... reserved for bitbang framework code
  50 + * spi->controller_data ... holds chipselect GPIO
  51 + *
  52 + * spi->master->dev.driver_data ... points to spi_gpio->bitbang
  53 + */
  54 +
  55 +struct spi_gpio {
  56 +       struct spi_bitbang              bitbang;
  57 +       struct spi_gpio_platform_data   pdata;
  58 +       struct platform_device          *pdev;
  59 +};
  60 +
  61 +/*----------------------------------------------------------------------*/
  62 +
  63 +/*
  64 + * Because the overhead of going through four GPIO procedure calls
  65 + * per transferred bit can make performance a problem, this code
  66 + * is set up so that you can use it in either of two ways:
  67 + *
  68 + *   - The slow generic way:  set up platform_data to hold the GPIO
  69 + *     numbers used for MISO/MOSI/SCK, and issue procedure calls for
  70 + *     each of them.  This driver can handle several such busses.
  71 + *
  72 + *   - The quicker inlined way:  only helps with platform GPIO code
  73 + *     that inlines operations for constant GPIOs.  This can give
  74 + *     you tight (fast!) inner loops, but each such bus needs a
  75 + *     new driver.  You'll define a new C file, with Makefile and
  76 + *     Kconfig support; the C code can be a total of six lines:
  77 + *
  78 + *             #define DRIVER_NAME     "myboard_spi2"
  79 + *             #define SPI_MISO_GPIO   119
  80 + *             #define SPI_MOSI_GPIO   120
  81 + *             #define SPI_SCK_GPIO    121
  82 + *             #define SPI_N_CHIPSEL   4
  83 + *             #include "spi_gpio.c"
  84 + */
  85 +
  86 +#ifndef DRIVER_NAME
  87 +#define DRIVER_NAME    "spi_gpio"
  88 +
  89 +#define GENERIC_BITBANG        /* vs tight inlines */
  90 +
  91 +/* all functions referencing these symbols must define pdata */
  92 +#define SPI_MISO_GPIO  ((pdata)->miso)
  93 +#define SPI_MOSI_GPIO  ((pdata)->mosi)
  94 +#define SPI_SCK_GPIO   ((pdata)->sck)
  95 +
  96 +#define SPI_N_CHIPSEL  ((pdata)->num_chipselect)
  97 +
  98 +#endif
  99 +
 100 +/*----------------------------------------------------------------------*/
 101 +
 102 +static inline const struct spi_gpio_platform_data * __pure
 103 +spi_to_pdata(const struct spi_device *spi)
 104 +{
 105 +       const struct spi_bitbang        *bang;
 106 +       const struct spi_gpio           *spi_gpio;
 107 +
 108 +       bang = spi_master_get_devdata(spi->master);
 109 +       spi_gpio = container_of(bang, struct spi_gpio, bitbang);
 110 +       return &spi_gpio->pdata;
 111 +}
 112 +
 113 +/* this is #defined to avoid unused-variable warnings when inlining */
 114 +#define pdata          spi_to_pdata(spi)
 115 +
 116 +static inline void setsck(const struct spi_device *spi, int is_on)
 117 +{
 118 +       gpio_set_value(SPI_SCK_GPIO, is_on);
 119 +}
 120 +
 121 +static inline void setmosi(const struct spi_device *spi, int is_on)
 122 +{
 123 +       gpio_set_value(SPI_MOSI_GPIO, is_on);
 124 +}
 125 +
 126 +static inline int getmiso(const struct spi_device *spi)
 127 +{
 128 +       return gpio_get_value(SPI_MISO_GPIO);
 129 +}
 130 +
 131 +#undef pdata
 132 +
 133 +/*
 134 + * NOTE:  this clocks "as fast as we can".  It "should" be a function of the
 135 + * requested device clock.  Software overhead means we usually have trouble
 136 + * reaching even one Mbit/sec (except when we can inline bitops), so for now
 137 + * we'll just assume we never need additional per-bit slowdowns.
 138 + */
 139 +#define spidelay(nsecs)        do {} while (0)
 140 +
 141 +#define        EXPAND_BITBANG_TXRX
 142 +#include <linux/spi/spi_bitbang.h>
 143 +
 144 +/*
 145 + * These functions can leverage inline expansion of GPIO calls to shrink
 146 + * costs for a txrx bit, often by factors of around ten (by instruction
 147 + * count).  That is particularly visible for larger word sizes, but helps
 148 + * even with default 8-bit words.
 149 + *
 150 + * REVISIT overheads calling these functions for each word also have
 151 + * significant performance costs.  Having txrx_bufs() calls that inline
 152 + * the txrx_word() logic would help performance, e.g. on larger blocks
 153 + * used with flash storage or MMC/SD.  There should also be ways to make
 154 + * GCC be less stupid about reloading registers inside the I/O loops,
 155 + * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3?
 156 + */
 157 +
 158 +static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi,
 159 +               unsigned nsecs, u32 word, u8 bits)
 160 +{
 161 +       return bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);
 162 +}
 163 +
 164 +static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi,
 165 +               unsigned nsecs, u32 word, u8 bits)
 166 +{
 167 +       return bitbang_txrx_be_cpha1(spi, nsecs, 0, word, bits);
 168 +}
 169 +
 170 +static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi,
 171 +               unsigned nsecs, u32 word, u8 bits)
 172 +{
 173 +       return bitbang_txrx_be_cpha0(spi, nsecs, 1, word, bits);
 174 +}
 175 +
 176 +static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi,
 177 +               unsigned nsecs, u32 word, u8 bits)
 178 +{
 179 +       return bitbang_txrx_be_cpha1(spi, nsecs, 1, word, bits);
 180 +}
 181 +
 182 +/*----------------------------------------------------------------------*/
 183 +
 184 +static void spi_gpio_chipselect(struct spi_device *spi, int is_active)
 185 +{
 186 +       unsigned long cs = (unsigned long) spi->controller_data;
 187 +
 188 +       /* set initial clock polarity */
 189 +       if (is_active)
 190 +               setsck(spi, spi->mode & SPI_CPOL);
 191 +
 192 +       /* SPI is normally active-low */
 193 +       gpio_set_value(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
 194 +}
 195 +
 196 +static int spi_gpio_setup(struct spi_device *spi)
 197 +{
 198 +       unsigned long   cs = (unsigned long) spi->controller_data;
 199 +       int             status = 0;
 200 +
 201 +       if (spi->bits_per_word > 32)
 202 +               return -EINVAL;
 203 +
 204 +       if (!spi->controller_state) {
 205 +               status = gpio_request(cs, spi->dev.bus_id);
 206 +               if (status)
 207 +                       return status;
 208 +               status = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
 209 +       }
 210 +       if (!status)
 211 +               status = spi_bitbang_setup(spi);
 212 +       if (status) {
 213 +               if (!spi->controller_state)
 214 +                       gpio_free(cs);
 215 +       }
 216 +       return status;
 217 +}
 218 +
 219 +static void spi_gpio_cleanup(struct spi_device *spi)
 220 +{
 221 +       unsigned long   cs = (unsigned long) spi->controller_data;
 222 +
 223 +       gpio_free(cs);
 224 +       spi_bitbang_cleanup(spi);
 225 +}
 226 +
 227 +static int __init spi_gpio_alloc(unsigned pin, const char *label, bool is_in)
 228 +{
 229 +       int value;
 230 +
 231 +       value = gpio_request(pin, label);
 232 +       if (value == 0) {
 233 +               if (is_in)
 234 +                       value = gpio_direction_input(pin);
 235 +               else
 236 +                       value = gpio_direction_output(pin, 0);
 237 +       }
 238 +       return value;
 239 +}
 240 +
 241 +static int __init
 242 +spi_gpio_request(struct spi_gpio_platform_data *pdata, const char *label)
 243 +{
 244 +       int value;
 245 +
 246 +       /* NOTE:  SPI_*_GPIO symbols may reference "pdata" */
 247 +
 248 +       value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false);
 249 +       if (value)
 250 +               goto done;
 251 +
 252 +       value = spi_gpio_alloc(SPI_MISO_GPIO, label, true);
 253 +       if (value)
 254 +               goto free_mosi;
 255 +
 256 +       value = spi_gpio_alloc(SPI_SCK_GPIO, label, false);
 257 +       if (value)
 258 +               goto free_miso;
 259 +
 260 +       goto done;
 261 +
 262 +free_miso:
 263 +       gpio_free(SPI_MISO_GPIO);
 264 +free_mosi:
 265 +       gpio_free(SPI_MOSI_GPIO);
 266 +done:
 267 +       return value;
 268 +}
 269 +
 270 +static int __init spi_gpio_probe(struct platform_device *pdev)
 271 +{
 272 +       int                             status;
 273 +       struct spi_master               *master;
 274 +       struct spi_gpio                 *spi_gpio;
 275 +       struct spi_gpio_platform_data   *pdata;
 276 +
 277 +       pdata = pdev->dev.platform_data;
 278 +#ifdef GENERIC_BITBANG
 279 +       if (!pdata || !pdata->num_chipselect)
 280 +               return -ENODEV;
 281 +#endif
 282 +
 283 +       status = spi_gpio_request(pdata, dev_name(&pdev->dev));
 284 +       if (status < 0)
 285 +               return status;
 286 +
 287 +       master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio);
 288 +       if (!master) {
 289 +               status = -ENOMEM;
 290 +               goto gpio_free;
 291 +       }
 292 +       spi_gpio = spi_master_get_devdata(master);
 293 +       platform_set_drvdata(pdev, spi_gpio);
 294 +
 295 +       spi_gpio->pdev = pdev;
 296 +       if (pdata)
 297 +               spi_gpio->pdata = *pdata;
 298 +
 299 +       master->bus_num = pdev->id;
 300 +       master->num_chipselect = SPI_N_CHIPSEL;
 301 +       master->setup = spi_gpio_setup;
 302 +       master->cleanup = spi_gpio_cleanup;
 303 +
 304 +       spi_gpio->bitbang.master = spi_master_get(master);
 305 +       spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
 306 +       spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
 307 +       spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
 308 +       spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
 309 +       spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
 310 +       spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
 311 +       spi_gpio->bitbang.flags = SPI_CS_HIGH;
 312 +
 313 +       status = spi_bitbang_start(&spi_gpio->bitbang);
 314 +       if (status < 0) {
 315 +               spi_master_put(spi_gpio->bitbang.master);
 316 +gpio_free:
 317 +               gpio_free(SPI_MISO_GPIO);
 318 +               gpio_free(SPI_MOSI_GPIO);
 319 +               gpio_free(SPI_SCK_GPIO);
 320 +               spi_master_put(master);
 321 +       }
 322 +
 323 +       return status;
 324 +}
 325 +
 326 +static int __exit spi_gpio_remove(struct platform_device *pdev)
 327 +{
 328 +       struct spi_gpio                 *spi_gpio;
 329 +       struct spi_gpio_platform_data   *pdata;
 330 +       int                             status;
 331 +
 332 +       spi_gpio = platform_get_drvdata(pdev);
 333 +       pdata = pdev->dev.platform_data;
 334 +
 335 +       /* stop() unregisters child devices too */
 336 +       status = spi_bitbang_stop(&spi_gpio->bitbang);
 337 +       spi_master_put(spi_gpio->bitbang.master);
 338 +
 339 +       platform_set_drvdata(pdev, NULL);
 340 +
 341 +       gpio_free(SPI_MISO_GPIO);
 342 +       gpio_free(SPI_MOSI_GPIO);
 343 +       gpio_free(SPI_SCK_GPIO);
 344 +
 345 +       return status;
 346 +}
 347 +
 348 +MODULE_ALIAS("platform:" DRIVER_NAME);
 349 +
 350 +static struct platform_driver spi_gpio_driver = {
 351 +       .driver.name    = DRIVER_NAME,
 352 +       .driver.owner   = THIS_MODULE,
 353 +       .remove         = __exit_p(spi_gpio_remove),
 354 +};
 355 +
 356 +static int __init spi_gpio_init(void)
 357 +{
 358 +       return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe);
 359 +}
 360 +module_init(spi_gpio_init);
 361 +
 362 +static void __exit spi_gpio_exit(void)
 363 +{
 364 +       platform_driver_unregister(&spi_gpio_driver);
 365 +}
 366 +module_exit(spi_gpio_exit);
 367 +
 368 +
 369 +MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
 370 +MODULE_AUTHOR("David Brownell");
 371 +MODULE_LICENSE("GPL");
 372 Index: linux-2.6.28.2/include/linux/spi/spi_gpio.h
 373 ===================================================================
 374 --- /dev/null   1970-01-01 00:00:00.000000000 +0000
 375 +++ linux-2.6.28.2/include/linux/spi/spi_gpio.h 2009-02-10 17:56:49.000000000 +0100
 376 @@ -0,0 +1,60 @@
 377 +#ifndef __LINUX_SPI_GPIO_H
 378 +#define __LINUX_SPI_GPIO_H
 379 +
 380 +/*
 381 + * For each bitbanged SPI bus, set up a platform_device node with:
 382 + *   - name "spi_gpio"
 383 + *   - id the same as the SPI bus number it implements
 384 + *   - dev.platform data pointing to a struct spi_gpio_platform_data
 385 + *
 386 + * Or, see the driver code for information about speedups that are
 387 + * possible on platforms that support inlined access for GPIOs (no
 388 + * spi_gpio_platform_data is used).
 389 + *
 390 + * Use spi_board_info with these busses in the usual way, being sure
 391 + * that the controller_data being the GPIO used for each device's
 392 + * chipselect:
 393 + *
 394 + *     static struct spi_board_info ... [] = {
 395 + *     ...
 396 + *             // this slave uses GPIO 42 for its chipselect
 397 + *             .controller_data = (void *) 42,
 398 + *     ...
 399 + *             // this one uses GPIO 86 for its chipselect
 400 + *             .controller_data = (void *) 86,
 401 + *     ...
 402 + *     };
 403 + *
 404 + * If the bitbanged bus is later switched to a "native" controller,
 405 + * that platform_device and controller_data should be removed.
 406 + */
 407 +
 408 +/**
 409 + * struct spi_gpio_platform_data - parameter for bitbanged SPI master
 410 + * @sck: number of the GPIO used for clock output
 411 + * @mosi: number of the GPIO used for Master Output, Slave In (MOSI) data
 412 + * @miso: number of the GPIO used for Master Input, Slave Output (MISO) data
 413 + * @num_chipselect: how many slaves to allow
 414 + *
 415 + * All GPIO signals used with the SPI bus managed through this driver
 416 + * (chipselects, MOSI, MISO, SCK) must be configured as GPIOs, instead
 417 + * of some alternate function.
 418 + *
 419 + * It can be convenient to use this driver with pins that have alternate
 420 + * functions associated with a "native" SPI controller if a driver for that
 421 + * controller is not available, or is missing important functionality.
 422 + *
 423 + * On platforms which can do so, configure MISO with a weak pullup unless
 424 + * there's an external pullup on that signal.  That saves power by avoiding
 425 + * floating signals.  (A weak pulldown would save power too, but many
 426 + * drivers expect to see all-ones data as the no slave "response".)
 427 + */
 428 +struct spi_gpio_platform_data {
 429 +       unsigned        sck;
 430 +       unsigned        mosi;
 431 +       unsigned        miso;
 432 +
 433 +       u16             num_chipselect;
 434 +};
 435 +
 436 +#endif /* __LINUX_SPI_GPIO_H */
 437 Index: linux-2.6.28.2/drivers/spi/Kconfig
 438 ===================================================================
 439 --- linux-2.6.28.2.orig/drivers/spi/Kconfig     2009-02-10 17:57:10.000000000 +0100
 440 +++ linux-2.6.28.2/drivers/spi/Kconfig  2009-02-10 18:08:31.000000000 +0100
 441 @@ -100,6 +100,22 @@ config SPI_BUTTERFLY
 442           inexpensive battery powered microcontroller evaluation board.
 443           This same cable can be used to flash new firmware.
 444
 445 +config SPI_GPIO
 446 +       tristate "GPIO-based bitbanging SPI Master"
 447 +       depends on GENERIC_GPIO
 448 +       select SPI_BITBANG
 449 +       help
 450 +         This simple GPIO bitbanging SPI master uses the arch-neutral GPIO
 451 +         interface to manage MOSI, MISO, SCK, and chipselect signals.  SPI
 452 +         slaves connected to a bus using this driver are configured as usual,
 453 +         except that the spi_board_info.controller_data holds the GPIO number
 454 +         for the chipselect used by this controller driver.
 455 +
 456 +         Note that this driver often won't achieve even 1 Mbit/sec speeds,
 457 +         making it unusually slow for SPI.  If your platform can inline
 458 +         GPIO operations, you should be able to leverage that for better
 459 +         speed with a custom version of this driver; see the source code.
 460 +
 461  config SPI_IMX
 462         tristate "Freescale iMX SPI controller"
 463         depends on ARCH_IMX && EXPERIMENTAL
 464 Index: linux-2.6.28.2/drivers/spi/Makefile
 465 ===================================================================
 466 --- linux-2.6.28.2.orig/drivers/spi/Makefile    2009-02-10 17:58:46.000000000 +0100
 467 +++ linux-2.6.28.2/drivers/spi/Makefile 2009-02-10 18:08:31.000000000 +0100
 468 @@ -16,6 +16,7 @@ obj-$(CONFIG_SPI_BFIN)                        += spi_bfin5xx.
 469  obj-$(CONFIG_SPI_BITBANG)              += spi_bitbang.o
 470  obj-$(CONFIG_SPI_AU1550)               += au1550_spi.o
 471  obj-$(CONFIG_SPI_BUTTERFLY)            += spi_butterfly.o
 472 +obj-$(CONFIG_SPI_GPIO)                 += spi_gpio.o
 473  obj-$(CONFIG_SPI_IMX)                  += spi_imx.o
 474  obj-$(CONFIG_SPI_LM70_LLP)             += spi_lm70llp.o
 475  obj-$(CONFIG_SPI_PXA2XX)               += pxa2xx_spi.o