drivers/gpio/gpio-gw-pld.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 //
   3 // Gateworks I2C PLD GPIO expander
   4 //
   5 // Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
   6 //
   7 // Based on code and know-how from the OpenWrt driver:
   8 // Copyright (C) 2009 Gateworks Corporation
   9 // Authors: Chris Lang, Imre Kaloz
  10
  11 #include <linux/bits.h>
  12 #include <linux/kernel.h>
  13 #include <linux/slab.h>
  14 #include <linux/gpio/driver.h>
  15 #include <linux/i2c.h>
  16 #include <linux/module.h>
  17
  18 /**
  19  * struct gw_pld - State container for Gateworks PLD
  20  * @chip: GPIO chip instance
  21  * @client: I2C client
  22  * @out: shadow register for the output bute
  23  */
  24 struct gw_pld {
  25         struct gpio_chip chip;
  26         struct i2c_client *client;
  27         u8 out;
  28 };
  29
  30 /*
  31  * The Gateworks I2C PLD chip only expose one read and one write register.
  32  * Writing a "one" bit (to match the reset state) lets that pin be used as an
  33  * input. It is an open-drain model.
  34  */
  35 static int gw_pld_input8(struct gpio_chip *gc, unsigned offset)
  36 {
  37         struct gw_pld *gw = gpiochip_get_data(gc);
  38
  39         gw->out |= BIT(offset);
  40         return i2c_smbus_write_byte(gw->client, gw->out);
  41 }
  42
  43 static int gw_pld_get8(struct gpio_chip *gc, unsigned offset)
  44 {
  45         struct gw_pld *gw = gpiochip_get_data(gc);
  46         s32 val;
  47
  48         val = i2c_smbus_read_byte(gw->client);
  49
  50         return (val < 0) ? 0 : !!(val & BIT(offset));
  51 }
  52
  53 static int gw_pld_output8(struct gpio_chip *gc, unsigned offset, int value)
  54 {
  55         struct gw_pld *gw = gpiochip_get_data(gc);
  56
  57         if (value)
  58                 gw->out |= BIT(offset);
  59         else
  60                 gw->out &= ~BIT(offset);
  61
  62         return i2c_smbus_write_byte(gw->client, gw->out);
  63 }
  64
  65 static void gw_pld_set8(struct gpio_chip *gc, unsigned offset, int value)
  66 {
  67         gw_pld_output8(gc, offset, value);
  68 }
  69
  70 static int gw_pld_probe(struct i2c_client *client)
  71 {
  72         struct device *dev = &client->dev;
  73         struct gw_pld *gw;
  74         int ret;
  75
  76         gw = devm_kzalloc(dev, sizeof(*gw), GFP_KERNEL);
  77         if (!gw)
  78                 return -ENOMEM;
  79
  80         gw->chip.base = -1;
  81         gw->chip.can_sleep = true;
  82         gw->chip.parent = dev;
  83         gw->chip.owner = THIS_MODULE;
  84         gw->chip.label = dev_name(dev);
  85         gw->chip.ngpio = 8;
  86         gw->chip.direction_input = gw_pld_input8;
  87         gw->chip.get = gw_pld_get8;
  88         gw->chip.direction_output = gw_pld_output8;
  89         gw->chip.set = gw_pld_set8;
  90         gw->client = client;
  91
  92         /*
  93          * The Gateworks I2C PLD chip does not properly send the acknowledge
  94          * bit at all times, but we can still use the standard i2c_smbus
  95          * functions by simply ignoring this bit.
  96          */
  97         client->flags |= I2C_M_IGNORE_NAK;
  98         gw->out = 0xFF;
  99
 100         i2c_set_clientdata(client, gw);
 101
 102         ret = devm_gpiochip_add_data(dev, &gw->chip, gw);
 103         if (ret)
 104                 return ret;
 105
 106         dev_info(dev, "registered Gateworks PLD GPIO device\n");
 107
 108         return 0;
 109 }
 110
 111 static const struct i2c_device_id gw_pld_id[] = {
 112         { "gw-pld", },
 113         { }
 114 };
 115 MODULE_DEVICE_TABLE(i2c, gw_pld_id);
 116
 117 static const struct of_device_id gw_pld_dt_ids[] = {
 118         { .compatible = "gateworks,pld-gpio", },
 119         { },
 120 };
 121 MODULE_DEVICE_TABLE(of, gw_pld_dt_ids);
 122
 123 static struct i2c_driver gw_pld_driver = {
 124         .driver = {
 125                 .name = "gw_pld",
 126                 .of_match_table = gw_pld_dt_ids,
 127         },
 128         .probe = gw_pld_probe,
 129         .id_table = gw_pld_id,
 130 };
 131 module_i2c_driver(gw_pld_driver);
 132
 133 MODULE_DESCRIPTION("Gateworks I2C PLD GPIO expander");
 134 MODULE_LICENSE("GPL");
 135 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");