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                         const struct i2c_device_id *id)
  72 {
  73         struct device *dev = &client->dev;
  74         struct device_node *np = dev->of_node;
  75         struct gw_pld *gw;
  76         int ret;
  77
  78         gw = devm_kzalloc(dev, sizeof(*gw), GFP_KERNEL);
  79         if (!gw)
  80                 return -ENOMEM;
  81
  82         gw->chip.base = -1;
  83         gw->chip.can_sleep = true;
  84         gw->chip.parent = dev;
  85         gw->chip.of_node = np;
  86         gw->chip.owner = THIS_MODULE;
  87         gw->chip.label = dev_name(dev);
  88         gw->chip.ngpio = 8;
  89         gw->chip.direction_input = gw_pld_input8;
  90         gw->chip.get = gw_pld_get8;
  91         gw->chip.direction_output = gw_pld_output8;
  92         gw->chip.set = gw_pld_set8;
  93         gw->client = client;
  94
  95         /*
  96          * The Gateworks I2C PLD chip does not properly send the acknowledge
  97          * bit at all times, but we can still use the standard i2c_smbus
  98          * functions by simply ignoring this bit.
  99          */
 100         client->flags |= I2C_M_IGNORE_NAK;
 101         gw->out = 0xFF;
 102
 103         i2c_set_clientdata(client, gw);
 104
 105         ret = devm_gpiochip_add_data(dev, &gw->chip, gw);
 106         if (ret)
 107                 return ret;
 108
 109         dev_info(dev, "registered Gateworks PLD GPIO device\n");
 110
 111         return 0;
 112 }
 113
 114 static const struct i2c_device_id gw_pld_id[] = {
 115         { "gw-pld", },
 116         { }
 117 };
 118 MODULE_DEVICE_TABLE(i2c, gw_pld_id);
 119
 120 static const struct of_device_id gw_pld_dt_ids[] = {
 121         { .compatible = "gateworks,pld-gpio", },
 122         { },
 123 };
 124 MODULE_DEVICE_TABLE(of, gw_pld_dt_ids);
 125
 126 static struct i2c_driver gw_pld_driver = {
 127         .driver = {
 128                 .name = "gw_pld",
 129                 .of_match_table = gw_pld_dt_ids,
 130         },
 131         .probe = gw_pld_probe,
 132         .id_table = gw_pld_id,
 133 };
 134 module_i2c_driver(gw_pld_driver);
 135
 136 MODULE_LICENSE("GPL");
 137 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");