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{
 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
111static const struct i2c_device_id gw_pld_id[] = {
112	{ "gw-pld", },
113	{ }
114};
115MODULE_DEVICE_TABLE(i2c, gw_pld_id);
116
117static const struct of_device_id gw_pld_dt_ids[] = {
118	{ .compatible = "gateworks,pld-gpio", },
119	{ },
120};
121MODULE_DEVICE_TABLE(of, gw_pld_dt_ids);
122
123static struct i2c_driver gw_pld_driver = {
124	.driver = {
125		.name = "gw_pld",
126		.of_match_table = gw_pld_dt_ids,
127	},
128	.probe_new = gw_pld_probe,
129	.id_table = gw_pld_id,
130};
131module_i2c_driver(gw_pld_driver);
132
133MODULE_LICENSE("GPL");
134MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");