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