LXR linux/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 */
  24struct 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 */
  35static 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
  43static 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
  53static 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
  65static void gw_pld_set8(struct gpio_chip *gc, unsigned offset, int value)
  66{
  67        gw_pld_output8(gc, offset, value);
  68}
  69
  70static 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
 114static const struct i2c_device_id gw_pld_id[] = {
 115        { "gw-pld", },
 116        { }
 117};
 118MODULE_DEVICE_TABLE(i2c, gw_pld_id);
 119
 120static const struct of_device_id gw_pld_dt_ids[] = {
 121        { .compatible = "gateworks,pld-gpio", },
 122        { },
 123};
 124MODULE_DEVICE_TABLE(of, gw_pld_dt_ids);
 125
 126static 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};
 134module_i2c_driver(gw_pld_driver);
 135
 136MODULE_LICENSE("GPL");
 137MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
 138