drivers/gpio/max7301.c

   1 /**
   2  * drivers/gpio/max7301.c
   3  *
   4  * Copyright (C) 2006 Juergen Beisert, Pengutronix
   5  * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * The Maxim's MAX7301 device is an SPI driven GPIO expander. There are
  12  * 28 GPIOs. 8 of them can trigger an interrupt. See datasheet for more
  13  * details
  14  * Note:
  15  * - DIN must be stable at the rising edge of clock.
  16  * - when writing:
  17  *   - always clock in 16 clocks at once
  18  *   - at DIN: D15 first, D0 last
  19  *   - D0..D7 = databyte, D8..D14 = commandbyte
  20  *   - D15 = low -> write command
  21  * - when reading
  22  *   - always clock in 16 clocks at once
  23  *   - at DIN: D15 first, D0 last
  24  *   - D0..D7 = dummy, D8..D14 = register address
  25  *   - D15 = high -> read command
  26  *   - raise CS and assert it again
  27  *   - always clock in 16 clocks at once
  28  *   - at DOUT: D15 first, D0 last
  29  *   - D0..D7 contains the data from the first cycle
  30  *
  31  * The driver exports a standard gpiochip interface
  32  */
  33
  34 #include <linux/init.h>
  35 #include <linux/platform_device.h>
  36 #include <linux/mutex.h>
  37 #include <linux/spi/spi.h>
  38 #include <linux/spi/max7301.h>
  39 #include <linux/gpio.h>
  40
  41 #define DRIVER_NAME "max7301"
  42
  43 /*
  44  * Pin configurations, see MAX7301 datasheet page 6
  45  */
  46 #define PIN_CONFIG_MASK 0x03
  47 #define PIN_CONFIG_IN_PULLUP 0x03
  48 #define PIN_CONFIG_IN_WO_PULLUP 0x02
  49 #define PIN_CONFIG_OUT 0x01
  50
  51 #define PIN_NUMBER 28
  52
  53
  54 /*
  55  * Some registers must be read back to modify.
  56  * To save time we cache them here in memory
  57  */
  58 struct max7301 {
  59         struct mutex    lock;
  60         u8              port_config[8]; /* field 0 is unused */
  61         u32             out_level;      /* cached output levels */
  62         struct gpio_chip chip;
  63         struct spi_device *spi;
  64 };
  65
  66 /**
  67  * max7301_write - Write a new register content
  68  * @spi: The SPI device
  69  * @reg: Register offset
  70  * @val: Value to write
  71  *
  72  * A write to the MAX7301 means one message with one transfer
  73  *
  74  * Returns 0 if successful or a negative value on error
  75  */
  76 static int max7301_write(struct spi_device *spi, unsigned int reg, unsigned int val)
  77 {
  78         u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);
  79         return spi_write(spi, (const u8 *)&word, sizeof(word));
  80 }
  81
  82 /**
  83  * max7301_read - Read back register content
  84  * @spi: The SPI device
  85  * @reg: Register offset
  86  *
  87  * A read from the MAX7301 means two transfers; here, one message each
  88  *
  89  * Returns positive 8 bit value from device if successful or a
  90  * negative value on error
  91  */
  92 static int max7301_read(struct spi_device *spi, unsigned int reg)
  93 {
  94         int ret;
  95         u16 word;
  96
  97         word = 0x8000 | (reg << 8);
  98         ret = spi_write(spi, (const u8 *)&word, sizeof(word));
  99         if (ret)
 100                 return ret;
 101         /*
 102          * This relies on the fact, that a transfer with NULL tx_buf shifts out
 103          * zero bytes (=NOOP for MAX7301)
 104          */
 105         ret = spi_read(spi, (u8 *)&word, sizeof(word));
 106         if (ret)
 107                 return ret;
 108         return word & 0xff;
 109 }
 110
 111 static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
 112 {
 113         struct max7301 *ts = container_of(chip, struct max7301, chip);
 114         u8 *config;
 115         int ret;
 116
 117         /* First 4 pins are unused in the controller */
 118         offset += 4;
 119
 120         config = &ts->port_config[offset >> 2];
 121
 122         mutex_lock(&ts->lock);
 123
 124         /* Standard GPIO API doesn't support pull-ups, has to be extended.
 125          * Hard-coding no pollup for now. */
 126         *config = (*config & ~(3 << (offset & 3))) | (1 << (offset & 3));
 127
 128         ret = max7301_write(ts->spi, 0x08 + (offset >> 2), *config);
 129
 130         mutex_unlock(&ts->lock);
 131
 132         return ret;
 133 }
 134
 135 static int __max7301_set(struct max7301 *ts, unsigned offset, int value)
 136 {
 137         if (value) {
 138                 ts->out_level |= 1 << offset;
 139                 return max7301_write(ts->spi, 0x20 + offset, 0x01);
 140         } else {
 141                 ts->out_level &= ~(1 << offset);
 142                 return max7301_write(ts->spi, 0x20 + offset, 0x00);
 143         }
 144 }
 145
 146 static int max7301_direction_output(struct gpio_chip *chip, unsigned offset,
 147                                     int value)
 148 {
 149         struct max7301 *ts = container_of(chip, struct max7301, chip);
 150         u8 *config;
 151         int ret;
 152
 153         /* First 4 pins are unused in the controller */
 154         offset += 4;
 155
 156         config = &ts->port_config[offset >> 2];
 157
 158         mutex_lock(&ts->lock);
 159
 160         *config = (*config & ~(3 << (offset & 3))) | (1 << (offset & 3));
 161
 162         ret = __max7301_set(ts, offset, value);
 163
 164         if (!ret)
 165                 ret = max7301_write(ts->spi, 0x08 + (offset >> 2), *config);
 166
 167         mutex_unlock(&ts->lock);
 168
 169         return ret;
 170 }
 171
 172 static int max7301_get(struct gpio_chip *chip, unsigned offset)
 173 {
 174         struct max7301 *ts = container_of(chip, struct max7301, chip);
 175         int config, level = -EINVAL;
 176
 177         /* First 4 pins are unused in the controller */
 178         offset += 4;
 179
 180         mutex_lock(&ts->lock);
 181
 182         config = (ts->port_config[offset >> 2] >> ((offset & 3) * 2)) & 3;
 183
 184         switch (config) {
 185         case 1:
 186                 /* Output: return cached level */
 187                 level =  !!(ts->out_level & (1 << offset));
 188                 break;
 189         case 2:
 190         case 3:
 191                 /* Input: read out */
 192                 level = max7301_read(ts->spi, 0x20 + offset) & 0x01;
 193         }
 194         mutex_unlock(&ts->lock);
 195
 196         return level;
 197 }
 198
 199 static void max7301_set(struct gpio_chip *chip, unsigned offset, int value)
 200 {
 201         struct max7301 *ts = container_of(chip, struct max7301, chip);
 202
 203         /* First 4 pins are unused in the controller */
 204         offset += 4;
 205
 206         mutex_lock(&ts->lock);
 207
 208         __max7301_set(ts, offset, value);
 209
 210         mutex_unlock(&ts->lock);
 211 }
 212
 213 static int __devinit max7301_probe(struct spi_device *spi)
 214 {
 215         struct max7301 *ts;
 216         struct max7301_platform_data *pdata;
 217         int i, ret;
 218
 219         pdata = spi->dev.platform_data;
 220         if (!pdata || !pdata->base) {
 221                 dev_dbg(&spi->dev, "incorrect or missing platform data\n");
 222                 return -EINVAL;
 223         }
 224
 225         /*
 226          * bits_per_word cannot be configured in platform data
 227          */
 228         spi->bits_per_word = 16;
 229
 230         ret = spi_setup(spi);
 231         if (ret < 0)
 232                 return ret;
 233
 234         ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
 235         if (!ts)
 236                 return -ENOMEM;
 237
 238         mutex_init(&ts->lock);
 239
 240         dev_set_drvdata(&spi->dev, ts);
 241
 242         /* Power up the chip and disable IRQ output */
 243         max7301_write(spi, 0x04, 0x01);
 244
 245         ts->spi = spi;
 246
 247         ts->chip.label = DRIVER_NAME,
 248
 249         ts->chip.direction_input = max7301_direction_input;
 250         ts->chip.get = max7301_get;
 251         ts->chip.direction_output = max7301_direction_output;
 252         ts->chip.set = max7301_set;
 253
 254         ts->chip.base = pdata->base;
 255         ts->chip.ngpio = PIN_NUMBER;
 256         ts->chip.can_sleep = 1;
 257         ts->chip.dev = &spi->dev;
 258         ts->chip.owner = THIS_MODULE;
 259
 260         /*
 261          * tristate all pins in hardware and cache the
 262          * register values for later use.
 263          */
 264         for (i = 1; i < 8; i++) {
 265                 int j;
 266                 /* 0xAA means input with internal pullup disabled */
 267                 max7301_write(spi, 0x08 + i, 0xAA);
 268                 ts->port_config[i] = 0xAA;
 269                 for (j = 0; j < 4; j++) {
 270                         int offset = (i - 1) * 4 + j;
 271                         ret = max7301_direction_input(&ts->chip, offset);
 272                         if (ret)
 273                                 goto exit_destroy;
 274                 }
 275         }
 276
 277         ret = gpiochip_add(&ts->chip);
 278         if (ret)
 279                 goto exit_destroy;
 280
 281         return ret;
 282
 283 exit_destroy:
 284         dev_set_drvdata(&spi->dev, NULL);
 285         mutex_destroy(&ts->lock);
 286         kfree(ts);
 287         return ret;
 288 }
 289
 290 static int __devexit max7301_remove(struct spi_device *spi)
 291 {
 292         struct max7301 *ts;
 293         int ret;
 294
 295         ts = dev_get_drvdata(&spi->dev);
 296         if (ts == NULL)
 297                 return -ENODEV;
 298
 299         dev_set_drvdata(&spi->dev, NULL);
 300
 301         /* Power down the chip and disable IRQ output */
 302         max7301_write(spi, 0x04, 0x00);
 303
 304         ret = gpiochip_remove(&ts->chip);
 305         if (!ret) {
 306                 mutex_destroy(&ts->lock);
 307                 kfree(ts);
 308         } else
 309                 dev_err(&spi->dev, "Failed to remove the GPIO controller: %d\n",
 310                         ret);
 311
 312         return ret;
 313 }
 314
 315 static struct spi_driver max7301_driver = {
 316         .driver = {
 317                 .name           = DRIVER_NAME,
 318                 .owner          = THIS_MODULE,
 319         },
 320         .probe          = max7301_probe,
 321         .remove         = __devexit_p(max7301_remove),
 322 };
 323
 324 static int __init max7301_init(void)
 325 {
 326         return spi_register_driver(&max7301_driver);
 327 }
 328 /* register after spi postcore initcall and before
 329  * subsys initcalls that may rely on these GPIOs
 330  */
 331 subsys_initcall(max7301_init);
 332
 333 static void __exit max7301_exit(void)
 334 {
 335         spi_unregister_driver(&max7301_driver);
 336 }
 337 module_exit(max7301_exit);
 338
 339 MODULE_AUTHOR("Juergen Beisert");
 340 MODULE_LICENSE("GPL v2");
 341 MODULE_DESCRIPTION("MAX7301 SPI based GPIO-Expander");