drivers/gpio/gpio-pcf857x.c

   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
  34 static 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 };
  50 MODULE_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  */
  64 struct 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
  83 static int i2c_write_le8(struct i2c_client *client, unsigned data)
  84 {
  85         return i2c_smbus_write_byte(client, data);
  86 }
  87
  88 static 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
  95 static 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
 104 static 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
 117 static 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
 130 static 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
 139 static 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
 156 static void pcf857x_set(struct gpio_chip *chip, unsigned offset, int value)
 157 {
 158         pcf857x_output(chip, offset, value);
 159 }
 160
 161 /*-------------------------------------------------------------------------*/
 162
 163 static 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
 170 static 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
 189 static 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
 202 static 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
 211 static struct irq_domain_ops pcf857x_irq_domain_ops = {
 212         .map    = pcf857x_irq_domain_map,
 213 };
 214
 215 static 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
 224 static int pcf857x_irq_domain_init(struct pcf857x *gpio,
 225                                    struct pcf857x_platform_data *pdata,
 226                                    struct device *dev)
 227 {
 228         int status;
 229
 230         gpio->irq_domain = irq_domain_add_linear(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(pdata->irq, pcf857x_irq_demux, 0,
 239                              dev_name(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               = pdata->irq;
 247
 248         return 0;
 249
 250 fail:
 251         pcf857x_irq_domain_cleanup(gpio);
 252         return -EINVAL;
 253 }
 254
 255 /*-------------------------------------------------------------------------*/
 256
 257 static 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 && pdata->irq) {
 289                 status = pcf857x_irq_domain_init(gpio, pdata, &client->dev);
 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         /* NOTE: these chips can issue "some pin-changed" IRQs, which we
 372          * don't yet even try to use.  Among other issues, the relevant
 373          * genirq state isn't available to modular drivers; and most irq
 374          * methods can't be called from sleeping contexts.
 375          */
 376
 377         dev_info(&client->dev, "%s\n",
 378                         client->irq ? " (irq ignored)" : "");
 379
 380         /* Let platform code set up the GPIOs and their users.
 381          * Now is the first time anyone could use them.
 382          */
 383         if (pdata && pdata->setup) {
 384                 status = pdata->setup(client,
 385                                 gpio->chip.base, gpio->chip.ngpio,
 386                                 pdata->context);
 387                 if (status < 0)
 388                         dev_warn(&client->dev, "setup --> %d\n", status);
 389         }
 390
 391         return 0;
 392
 393 fail:
 394         dev_dbg(&client->dev, "probe error %d for '%s'\n",
 395                         status, client->name);
 396
 397         if (pdata && pdata->irq)
 398                 pcf857x_irq_domain_cleanup(gpio);
 399
 400         kfree(gpio);
 401         return status;
 402 }
 403
 404 static int pcf857x_remove(struct i2c_client *client)
 405 {
 406         struct pcf857x_platform_data    *pdata = client->dev.platform_data;
 407         struct pcf857x                  *gpio = i2c_get_clientdata(client);
 408         int                             status = 0;
 409
 410         if (pdata && pdata->teardown) {
 411                 status = pdata->teardown(client,
 412                                 gpio->chip.base, gpio->chip.ngpio,
 413                                 pdata->context);
 414                 if (status < 0) {
 415                         dev_err(&client->dev, "%s --> %d\n",
 416                                         "teardown", status);
 417                         return status;
 418                 }
 419         }
 420
 421         if (pdata && pdata->irq)
 422                 pcf857x_irq_domain_cleanup(gpio);
 423
 424         status = gpiochip_remove(&gpio->chip);
 425         if (status == 0)
 426                 kfree(gpio);
 427         else
 428                 dev_err(&client->dev, "%s --> %d\n", "remove", status);
 429         return status;
 430 }
 431
 432 static struct i2c_driver pcf857x_driver = {
 433         .driver = {
 434                 .name   = "pcf857x",
 435                 .owner  = THIS_MODULE,
 436         },
 437         .probe  = pcf857x_probe,
 438         .remove = pcf857x_remove,
 439         .id_table = pcf857x_id,
 440 };
 441
 442 static int __init pcf857x_init(void)
 443 {
 444         return i2c_add_driver(&pcf857x_driver);
 445 }
 446 /* register after i2c postcore initcall and before
 447  * subsys initcalls that may rely on these GPIOs
 448  */
 449 subsys_initcall(pcf857x_init);
 450
 451 static void __exit pcf857x_exit(void)
 452 {
 453         i2c_del_driver(&pcf857x_driver);
 454 }
 455 module_exit(pcf857x_exit);
 456
 457 MODULE_LICENSE("GPL");
 458 MODULE_AUTHOR("David Brownell");