linux/drivers/gpio/gpio-pcf857x.c
<<
>>
Prefs
   1/*
   2 * Driver for pcf857x, pca857x, and pca967x I2C GPIO expanders
   3 *
   4 * Copyright (C) 2007 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
  21#include <linux/gpio.h>
  22#include <linux/i2c.h>
  23#include <linux/i2c/pcf857x.h>
  24#include <linux/interrupt.h>
  25#include <linux/irq.h>
  26#include <linux/irqdomain.h>
  27#include <linux/kernel.h>
  28#include <linux/module.h>
  29#include <linux/slab.h>
  30#include <linux/spinlock.h>
  31#include <linux/workqueue.h>
  32
  33
  34static const struct i2c_device_id pcf857x_id[] = {
  35        { "pcf8574", 8 },
  36        { "pcf8574a", 8 },
  37        { "pca8574", 8 },
  38        { "pca9670", 8 },
  39        { "pca9672", 8 },
  40        { "pca9674", 8 },
  41        { "pcf8575", 16 },
  42        { "pca8575", 16 },
  43        { "pca9671", 16 },
  44        { "pca9673", 16 },
  45        { "pca9675", 16 },
  46        { "max7328", 8 },
  47        { "max7329", 8 },
  48        { "tca9554", 8 },
  49        { }
  50};
  51MODULE_DEVICE_TABLE(i2c, pcf857x_id);
  52
  53/*
  54 * The pcf857x, pca857x, and pca967x chips only expose one read and one
  55 * write register.  Writing a "one" bit (to match the reset state) lets
  56 * that pin be used as an input; it's not an open-drain model, but acts
  57 * a bit like one.  This is described as "quasi-bidirectional"; read the
  58 * chip documentation for details.
  59 *
  60 * Many other I2C GPIO expander chips (like the pca953x models) have
  61 * more complex register models and more conventional circuitry using
  62 * push/pull drivers.  They often use the same 0x20..0x27 addresses as
  63 * pcf857x parts, making the "legacy" I2C driver model problematic.
  64 */
  65struct pcf857x {
  66        struct gpio_chip        chip;
  67        struct i2c_client       *client;
  68        struct mutex            lock;           /* protect 'out' */
  69        struct work_struct      work;           /* irq demux work */
  70        struct irq_domain       *irq_domain;    /* for irq demux  */
  71        spinlock_t              slock;          /* protect irq demux */
  72        unsigned                out;            /* software latch */
  73        unsigned                status;         /* current status */
  74        int                     irq;            /* real irq number */
  75
  76        int (*write)(struct i2c_client *client, unsigned data);
  77        int (*read)(struct i2c_client *client);
  78};
  79
  80/*-------------------------------------------------------------------------*/
  81
  82/* Talk to 8-bit I/O expander */
  83
  84static int i2c_write_le8(struct i2c_client *client, unsigned data)
  85{
  86        return i2c_smbus_write_byte(client, data);
  87}
  88
  89static int i2c_read_le8(struct i2c_client *client)
  90{
  91        return (int)i2c_smbus_read_byte(client);
  92}
  93
  94/* Talk to 16-bit I/O expander */
  95
  96static int i2c_write_le16(struct i2c_client *client, unsigned word)
  97{
  98        u8 buf[2] = { word & 0xff, word >> 8, };
  99        int status;
 100
 101        status = i2c_master_send(client, buf, 2);
 102        return (status < 0) ? status : 0;
 103}
 104
 105static int i2c_read_le16(struct i2c_client *client)
 106{
 107        u8 buf[2];
 108        int status;
 109
 110        status = i2c_master_recv(client, buf, 2);
 111        if (status < 0)
 112                return status;
 113        return (buf[1] << 8) | buf[0];
 114}
 115
 116/*-------------------------------------------------------------------------*/
 117
 118static int pcf857x_input(struct gpio_chip *chip, unsigned offset)
 119{
 120        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
 121        int             status;
 122
 123        mutex_lock(&gpio->lock);
 124        gpio->out |= (1 << offset);
 125        status = gpio->write(gpio->client, gpio->out);
 126        mutex_unlock(&gpio->lock);
 127
 128        return status;
 129}
 130
 131static int pcf857x_get(struct gpio_chip *chip, unsigned offset)
 132{
 133        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
 134        int             value;
 135
 136        value = gpio->read(gpio->client);
 137        return (value < 0) ? 0 : (value & (1 << offset));
 138}
 139
 140static int pcf857x_output(struct gpio_chip *chip, unsigned offset, int value)
 141{
 142        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
 143        unsigned        bit = 1 << offset;
 144        int             status;
 145
 146        mutex_lock(&gpio->lock);
 147        if (value)
 148                gpio->out |= bit;
 149        else
 150                gpio->out &= ~bit;
 151        status = gpio->write(gpio->client, gpio->out);
 152        mutex_unlock(&gpio->lock);
 153
 154        return status;
 155}
 156
 157static void pcf857x_set(struct gpio_chip *chip, unsigned offset, int value)
 158{
 159        pcf857x_output(chip, offset, value);
 160}
 161
 162/*-------------------------------------------------------------------------*/
 163
 164static int pcf857x_to_irq(struct gpio_chip *chip, unsigned offset)
 165{
 166        struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
 167
 168        return irq_create_mapping(gpio->irq_domain, offset);
 169}
 170
 171static void pcf857x_irq_demux_work(struct work_struct *work)
 172{
 173        struct pcf857x *gpio = container_of(work,
 174                                               struct pcf857x,
 175                                               work);
 176        unsigned long change, i, status, flags;
 177
 178        status = gpio->read(gpio->client);
 179
 180        spin_lock_irqsave(&gpio->slock, flags);
 181
 182        change = gpio->status ^ status;
 183        for_each_set_bit(i, &change, gpio->chip.ngpio)
 184                generic_handle_irq(irq_find_mapping(gpio->irq_domain, i));
 185        gpio->status = status;
 186
 187        spin_unlock_irqrestore(&gpio->slock, flags);
 188}
 189
 190static irqreturn_t pcf857x_irq_demux(int irq, void *data)
 191{
 192        struct pcf857x  *gpio = data;
 193
 194        /*
 195         * pcf857x can't read/write data here,
 196         * since i2c data access might go to sleep.
 197         */
 198        schedule_work(&gpio->work);
 199
 200        return IRQ_HANDLED;
 201}
 202
 203static int pcf857x_irq_domain_map(struct irq_domain *domain, unsigned int virq,
 204                                 irq_hw_number_t hw)
 205{
 206        irq_set_chip_and_handler(virq,
 207                                 &dummy_irq_chip,
 208                                 handle_level_irq);
 209        return 0;
 210}
 211
 212static struct irq_domain_ops pcf857x_irq_domain_ops = {
 213        .map    = pcf857x_irq_domain_map,
 214};
 215
 216static void pcf857x_irq_domain_cleanup(struct pcf857x *gpio)
 217{
 218        if (gpio->irq_domain)
 219                irq_domain_remove(gpio->irq_domain);
 220
 221        if (gpio->irq)
 222                free_irq(gpio->irq, gpio);
 223}
 224
 225static int pcf857x_irq_domain_init(struct pcf857x *gpio,
 226                                   struct i2c_client *client)
 227{
 228        int status;
 229
 230        gpio->irq_domain = irq_domain_add_linear(client->dev.of_node,
 231                                                 gpio->chip.ngpio,
 232                                                 &pcf857x_irq_domain_ops,
 233                                                 NULL);
 234        if (!gpio->irq_domain)
 235                goto fail;
 236
 237        /* enable real irq */
 238        status = request_irq(client->irq, pcf857x_irq_demux, 0,
 239                             dev_name(&client->dev), gpio);
 240        if (status)
 241                goto fail;
 242
 243        /* enable gpio_to_irq() */
 244        INIT_WORK(&gpio->work, pcf857x_irq_demux_work);
 245        gpio->chip.to_irq       = pcf857x_to_irq;
 246        gpio->irq               = client->irq;
 247
 248        return 0;
 249
 250fail:
 251        pcf857x_irq_domain_cleanup(gpio);
 252        return -EINVAL;
 253}
 254
 255/*-------------------------------------------------------------------------*/
 256
 257static int pcf857x_probe(struct i2c_client *client,
 258                         const struct i2c_device_id *id)
 259{
 260        struct pcf857x_platform_data    *pdata;
 261        struct pcf857x                  *gpio;
 262        int                             status;
 263
 264        pdata = dev_get_platdata(&client->dev);
 265        if (!pdata) {
 266                dev_dbg(&client->dev, "no platform data\n");
 267        }
 268
 269        /* Allocate, initialize, and register this gpio_chip. */
 270        gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL);
 271        if (!gpio)
 272                return -ENOMEM;
 273
 274        mutex_init(&gpio->lock);
 275        spin_lock_init(&gpio->slock);
 276
 277        gpio->chip.base                 = pdata ? pdata->gpio_base : -1;
 278        gpio->chip.can_sleep            = 1;
 279        gpio->chip.dev                  = &client->dev;
 280        gpio->chip.owner                = THIS_MODULE;
 281        gpio->chip.get                  = pcf857x_get;
 282        gpio->chip.set                  = pcf857x_set;
 283        gpio->chip.direction_input      = pcf857x_input;
 284        gpio->chip.direction_output     = pcf857x_output;
 285        gpio->chip.ngpio                = id->driver_data;
 286
 287        /* enable gpio_to_irq() if platform has settings */
 288        if (client->irq) {
 289                status = pcf857x_irq_domain_init(gpio, client);
 290                if (status < 0) {
 291                        dev_err(&client->dev, "irq_domain init failed\n");
 292                        goto fail;
 293                }
 294        }
 295
 296        /* NOTE:  the OnSemi jlc1562b is also largely compatible with
 297         * these parts, notably for output.  It has a low-resolution
 298         * DAC instead of pin change IRQs; and its inputs can be the
 299         * result of comparators.
 300         */
 301
 302        /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
 303         * 9670, 9672, 9764, and 9764a use quite a variety.
 304         *
 305         * NOTE: we don't distinguish here between *4 and *4a parts.
 306         */
 307        if (gpio->chip.ngpio == 8) {
 308                gpio->write     = i2c_write_le8;
 309                gpio->read      = i2c_read_le8;
 310
 311                if (!i2c_check_functionality(client->adapter,
 312                                I2C_FUNC_SMBUS_BYTE))
 313                        status = -EIO;
 314
 315                /* fail if there's no chip present */
 316                else
 317                        status = i2c_smbus_read_byte(client);
 318
 319        /* '75/'75c addresses are 0x20..0x27, just like the '74;
 320         * the '75c doesn't have a current source pulling high.
 321         * 9671, 9673, and 9765 use quite a variety of addresses.
 322         *
 323         * NOTE: we don't distinguish here between '75 and '75c parts.
 324         */
 325        } else if (gpio->chip.ngpio == 16) {
 326                gpio->write     = i2c_write_le16;
 327                gpio->read      = i2c_read_le16;
 328
 329                if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 330                        status = -EIO;
 331
 332                /* fail if there's no chip present */
 333                else
 334                        status = i2c_read_le16(client);
 335
 336        } else {
 337                dev_dbg(&client->dev, "unsupported number of gpios\n");
 338                status = -EINVAL;
 339        }
 340
 341        if (status < 0)
 342                goto fail;
 343
 344        gpio->chip.label = client->name;
 345
 346        gpio->client = client;
 347        i2c_set_clientdata(client, gpio);
 348
 349        /* NOTE:  these chips have strange "quasi-bidirectional" I/O pins.
 350         * We can't actually know whether a pin is configured (a) as output
 351         * and driving the signal low, or (b) as input and reporting a low
 352         * value ... without knowing the last value written since the chip
 353         * came out of reset (if any).  We can't read the latched output.
 354         *
 355         * In short, the only reliable solution for setting up pin direction
 356         * is to do it explicitly.  The setup() method can do that, but it
 357         * may cause transient glitching since it can't know the last value
 358         * written (some pins may need to be driven low).
 359         *
 360         * Using pdata->n_latch avoids that trouble.  When left initialized
 361         * to zero, our software copy of the "latch" then matches the chip's
 362         * all-ones reset state.  Otherwise it flags pins to be driven low.
 363         */
 364        gpio->out = pdata ? ~pdata->n_latch : ~0;
 365        gpio->status = gpio->out;
 366
 367        status = gpiochip_add(&gpio->chip);
 368        if (status < 0)
 369                goto fail;
 370
 371        /* Let platform code set up the GPIOs and their users.
 372         * Now is the first time anyone could use them.
 373         */
 374        if (pdata && pdata->setup) {
 375                status = pdata->setup(client,
 376                                gpio->chip.base, gpio->chip.ngpio,
 377                                pdata->context);
 378                if (status < 0)
 379                        dev_warn(&client->dev, "setup --> %d\n", status);
 380        }
 381
 382        dev_info(&client->dev, "probed\n");
 383
 384        return 0;
 385
 386fail:
 387        dev_dbg(&client->dev, "probe error %d for '%s'\n",
 388                        status, client->name);
 389
 390        if (client->irq)
 391                pcf857x_irq_domain_cleanup(gpio);
 392
 393        return status;
 394}
 395
 396static int pcf857x_remove(struct i2c_client *client)
 397{
 398        struct pcf857x_platform_data    *pdata = dev_get_platdata(&client->dev);
 399        struct pcf857x                  *gpio = i2c_get_clientdata(client);
 400        int                             status = 0;
 401
 402        if (pdata && pdata->teardown) {
 403                status = pdata->teardown(client,
 404                                gpio->chip.base, gpio->chip.ngpio,
 405                                pdata->context);
 406                if (status < 0) {
 407                        dev_err(&client->dev, "%s --> %d\n",
 408                                        "teardown", status);
 409                        return status;
 410                }
 411        }
 412
 413        if (client->irq)
 414                pcf857x_irq_domain_cleanup(gpio);
 415
 416        status = gpiochip_remove(&gpio->chip);
 417        if (status)
 418                dev_err(&client->dev, "%s --> %d\n", "remove", status);
 419        return status;
 420}
 421
 422static struct i2c_driver pcf857x_driver = {
 423        .driver = {
 424                .name   = "pcf857x",
 425                .owner  = THIS_MODULE,
 426        },
 427        .probe  = pcf857x_probe,
 428        .remove = pcf857x_remove,
 429        .id_table = pcf857x_id,
 430};
 431
 432static int __init pcf857x_init(void)
 433{
 434        return i2c_add_driver(&pcf857x_driver);
 435}
 436/* register after i2c postcore initcall and before
 437 * subsys initcalls that may rely on these GPIOs
 438 */
 439subsys_initcall(pcf857x_init);
 440
 441static void __exit pcf857x_exit(void)
 442{
 443        i2c_del_driver(&pcf857x_driver);
 444}
 445module_exit(pcf857x_exit);
 446
 447MODULE_LICENSE("GPL");
 448MODULE_AUTHOR("David Brownell");
 449
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.