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/kernel.h>
  22#include <linux/slab.h>
  23#include <linux/gpio.h>
  24#include <linux/i2c.h>
  25#include <linux/i2c/pcf857x.h>
  26#include <linux/interrupt.h>
  27#include <linux/irq.h>
  28#include <linux/irqdomain.h>
  29#include <linux/module.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        { }
  49};
  50MODULE_DEVICE_TABLE(i2c, pcf857x_id);
  51
  52/*
  53 * The pcf857x, pca857x, and pca967x chips only expose one read and one
  54 * write register.  Writing a "one" bit (to match the reset state) lets
  55 * that pin be used as an input; it's not an open-drain model, but acts
  56 * a bit like one.  This is described as "quasi-bidirectional"; read the
  57 * chip documentation for details.
  58 *
  59 * Many other I2C GPIO expander chips (like the pca953x models) have
  60 * more complex register models and more conventional circuitry using
  61 * push/pull drivers.  They often use the same 0x20..0x27 addresses as
  62 * pcf857x parts, making the "legacy" I2C driver model problematic.
  63 */
  64struct pcf857x {
  65        struct gpio_chip        chip;
  66        struct i2c_client       *client;
  67        struct mutex            lock;           /* protect 'out' */
  68        struct work_struct      work;           /* irq demux work */
  69        struct irq_domain       *irq_domain;    /* for irq demux  */
  70        spinlock_t              slock;          /* protect irq demux */
  71        unsigned                out;            /* software latch */
  72        unsigned                status;         /* current status */
  73        int                     irq;            /* real irq number */
  74
  75        int (*write)(struct i2c_client *client, unsigned data);
  76        int (*read)(struct i2c_client *client);
  77};
  78
  79/*-------------------------------------------------------------------------*/
  80
  81/* Talk to 8-bit I/O expander */
  82
  83static int i2c_write_le8(struct i2c_client *client, unsigned data)
  84{
  85        return i2c_smbus_write_byte(client, data);
  86}
  87
  88static int i2c_read_le8(struct i2c_client *client)
  89{
  90        return (int)i2c_smbus_read_byte(client);
  91}
  92
  93/* Talk to 16-bit I/O expander */
  94
  95static int i2c_write_le16(struct i2c_client *client, unsigned word)
  96{
  97        u8 buf[2] = { word & 0xff, word >> 8, };
  98        int status;
  99
 100        status = i2c_master_send(client, buf, 2);
 101        return (status < 0) ? status : 0;
 102}
 103
 104static int i2c_read_le16(struct i2c_client *client)
 105{
 106        u8 buf[2];
 107        int status;
 108
 109        status = i2c_master_recv(client, buf, 2);
 110        if (status < 0)
 111                return status;
 112        return (buf[1] << 8) | buf[0];
 113}
 114
 115/*-------------------------------------------------------------------------*/
 116
 117static int pcf857x_input(struct gpio_chip *chip, unsigned offset)
 118{
 119        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
 120        int             status;
 121
 122        mutex_lock(&gpio->lock);
 123        gpio->out |= (1 << offset);
 124        status = gpio->write(gpio->client, gpio->out);
 125        mutex_unlock(&gpio->lock);
 126
 127        return status;
 128}
 129
 130static int pcf857x_get(struct gpio_chip *chip, unsigned offset)
 131{
 132        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
 133        int             value;
 134
 135        value = gpio->read(gpio->client);
 136        return (value < 0) ? 0 : (value & (1 << offset));
 137}
 138
 139static int pcf857x_output(struct gpio_chip *chip, unsigned offset, int value)
 140{
 141        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
 142        unsigned        bit = 1 << offset;
 143        int             status;
 144
 145        mutex_lock(&gpio->lock);
 146        if (value)
 147                gpio->out |= bit;
 148        else
 149                gpio->out &= ~bit;
 150        status = gpio->write(gpio->client, gpio->out);
 151        mutex_unlock(&gpio->lock);
 152
 153        return status;
 154}
 155
 156static void pcf857x_set(struct gpio_chip *chip, unsigned offset, int value)
 157{
 158        pcf857x_output(chip, offset, value);
 159}
 160
 161/*-------------------------------------------------------------------------*/
 162
 163static int pcf857x_to_irq(struct gpio_chip *chip, unsigned offset)
 164{
 165        struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
 166
 167        return irq_create_mapping(gpio->irq_domain, offset);
 168}
 169
 170static void pcf857x_irq_demux_work(struct work_struct *work)
 171{
 172        struct pcf857x *gpio = container_of(work,
 173                                               struct pcf857x,
 174                                               work);
 175        unsigned long change, i, status, flags;
 176
 177        status = gpio->read(gpio->client);
 178
 179        spin_lock_irqsave(&gpio->slock, flags);
 180
 181        change = gpio->status ^ status;
 182        for_each_set_bit(i, &change, gpio->chip.ngpio)
 183                generic_handle_irq(irq_find_mapping(gpio->irq_domain, i));
 184        gpio->status = status;
 185
 186        spin_unlock_irqrestore(&gpio->slock, flags);
 187}
 188
 189static irqreturn_t pcf857x_irq_demux(int irq, void *data)
 190{
 191        struct pcf857x  *gpio = data;
 192
 193        /*
 194         * pcf857x can't read/write data here,
 195         * since i2c data access might go to sleep.
 196         */
 197        schedule_work(&gpio->work);
 198
 199        return IRQ_HANDLED;
 200}
 201
 202static int pcf857x_irq_domain_map(struct irq_domain *domain, unsigned int virq,
 203                                 irq_hw_number_t hw)
 204{
 205        irq_set_chip_and_handler(virq,
 206                                 &dummy_irq_chip,
 207                                 handle_level_irq);
 208        return 0;
 209}
 210
 211static struct irq_domain_ops pcf857x_irq_domain_ops = {
 212        .map    = pcf857x_irq_domain_map,
 213};
 214
 215static void pcf857x_irq_domain_cleanup(struct pcf857x *gpio)
 216{
 217        if (gpio->irq_domain)
 218                irq_domain_remove(gpio->irq_domain);
 219
 220        if (gpio->irq)
 221                free_irq(gpio->irq, gpio);
 222}
 223
 224static int pcf857x_irq_domain_init(struct pcf857x *gpio,
 225                                   struct pcf857x_platform_data *pdata,
 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 = client->dev.platform_data;
 265        if (!pdata) {
 266                dev_dbg(&client->dev, "no platform data\n");
 267        }
 268
 269        /* Allocate, initialize, and register this gpio_chip. */
 270        gpio = kzalloc(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 (pdata && client->irq) {
 289                status = pcf857x_irq_domain_init(gpio, pdata, 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 (pdata && client->irq)
 391                pcf857x_irq_domain_cleanup(gpio);
 392
 393        kfree(gpio);
 394        return status;
 395}
 396
 397static int pcf857x_remove(struct i2c_client *client)
 398{
 399        struct pcf857x_platform_data    *pdata = client->dev.platform_data;
 400        struct pcf857x                  *gpio = i2c_get_clientdata(client);
 401        int                             status = 0;
 402
 403        if (pdata && pdata->teardown) {
 404                status = pdata->teardown(client,
 405                                gpio->chip.base, gpio->chip.ngpio,
 406                                pdata->context);
 407                if (status < 0) {
 408                        dev_err(&client->dev, "%s --> %d\n",
 409                                        "teardown", status);
 410                        return status;
 411                }
 412        }
 413
 414        if (pdata && client->irq)
 415                pcf857x_irq_domain_cleanup(gpio);
 416
 417        status = gpiochip_remove(&gpio->chip);
 418        if (status == 0)
 419                kfree(gpio);
 420        else
 421                dev_err(&client->dev, "%s --> %d\n", "remove", status);
 422        return status;
 423}
 424
 425static struct i2c_driver pcf857x_driver = {
 426        .driver = {
 427                .name   = "pcf857x",
 428                .owner  = THIS_MODULE,
 429        },
 430        .probe  = pcf857x_probe,
 431        .remove = pcf857x_remove,
 432        .id_table = pcf857x_id,
 433};
 434
 435static int __init pcf857x_init(void)
 436{
 437        return i2c_add_driver(&pcf857x_driver);
 438}
 439/* register after i2c postcore initcall and before
 440 * subsys initcalls that may rely on these GPIOs
 441 */
 442subsys_initcall(pcf857x_init);
 443
 444static void __exit pcf857x_exit(void)
 445{
 446        i2c_del_driver(&pcf857x_driver);
 447}
 448module_exit(pcf857x_exit);
 449
 450MODULE_LICENSE("GPL");
 451MODULE_AUTHOR("David Brownell");
 452
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.