1/*
2 * Digital I/O driver for Technologic Systems I2C FPGA Core
3 *
4 * Copyright (C) 2015, 2018 Technologic Systems
5 * Copyright (C) 2016 Savoir-Faire Linux
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
12 * kind, whether expressed or implied; without even the implied warranty
13 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License version 2 for more details.
15 */
16
17#include <linux/gpio/driver.h>
18#include <linux/i2c.h>
19#include <linux/of_device.h>
20#include <linux/module.h>
21#include <linux/regmap.h>
22
23#define DEFAULT_PIN_NUMBER	32
24/*
25 * Register bits used by the GPIO device
26 * Some boards, such as TS-7970 do not have a separate input bit
27 */
28#define TS4900_GPIO_OE		0x01
29#define TS4900_GPIO_OUT		0x02
30#define TS4900_GPIO_IN		0x04
31#define TS7970_GPIO_IN		0x02
32
33struct ts4900_gpio_priv {
34	struct regmap *regmap;
35	struct gpio_chip gpio_chip;
36	unsigned int input_bit;
37};
38
39static int ts4900_gpio_get_direction(struct gpio_chip *chip,
40				     unsigned int offset)
41{
42	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
43	unsigned int reg;
44
45	regmap_read(priv->regmap, offset, &reg);
46
47	if (reg & TS4900_GPIO_OE)
48		return GPIO_LINE_DIRECTION_OUT;
49
50	return GPIO_LINE_DIRECTION_IN;
51}
52
53static int ts4900_gpio_direction_input(struct gpio_chip *chip,
54				       unsigned int offset)
55{
56	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
57
58	/* Only clear the OE bit here, requires a RMW. Prevents potential issue
59	 * with OE and data getting to the physical pin at different times.
60	 */
61	return regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OE, 0);
62}
63
64static int ts4900_gpio_direction_output(struct gpio_chip *chip,
65					unsigned int offset, int value)
66{
67	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
68	unsigned int reg;
69	int ret;
70
71	/* If changing from an input to an output, we need to first set the
72	 * proper data bit to what is requested and then set OE bit. This
73	 * prevents a glitch that can occur on the IO line
74	 */
75	regmap_read(priv->regmap, offset, &reg);
76	if (!(reg & TS4900_GPIO_OE)) {
77		if (value)
78			reg = TS4900_GPIO_OUT;
79		else
80			reg &= ~TS4900_GPIO_OUT;
81
82		regmap_write(priv->regmap, offset, reg);
83	}
84
85	if (value)
86		ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE |
87							 TS4900_GPIO_OUT);
88	else
89		ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE);
90
91	return ret;
92}
93
94static int ts4900_gpio_get(struct gpio_chip *chip, unsigned int offset)
95{
96	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
97	unsigned int reg;
98
99	regmap_read(priv->regmap, offset, &reg);
100
101	return !!(reg & priv->input_bit);
102}
103
104static void ts4900_gpio_set(struct gpio_chip *chip, unsigned int offset,
105			    int value)
106{
107	struct ts4900_gpio_priv *priv = gpiochip_get_data(chip);
108
109	if (value)
110		regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OUT,
111				   TS4900_GPIO_OUT);
112	else
113		regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OUT, 0);
114}
115
116static const struct regmap_config ts4900_regmap_config = {
117	.reg_bits = 16,
118	.val_bits = 8,
119};
120
121static const struct gpio_chip template_chip = {
122	.label			= "ts4900-gpio",
123	.owner			= THIS_MODULE,
124	.get_direction		= ts4900_gpio_get_direction,
125	.direction_input	= ts4900_gpio_direction_input,
126	.direction_output	= ts4900_gpio_direction_output,
127	.get			= ts4900_gpio_get,
128	.set			= ts4900_gpio_set,
129	.base			= -1,
130	.can_sleep		= true,
131};
132
133static const struct of_device_id ts4900_gpio_of_match_table[] = {
134	{
135		.compatible = "technologic,ts4900-gpio",
136		.data = (void *)TS4900_GPIO_IN,
137	}, {
138		.compatible = "technologic,ts7970-gpio",
139		.data = (void *)TS7970_GPIO_IN,
140	},
141	{ /* sentinel */ },
142};
143MODULE_DEVICE_TABLE(of, ts4900_gpio_of_match_table);
144
145static int ts4900_gpio_probe(struct i2c_client *client,
146			const struct i2c_device_id *id)
147{
148	struct ts4900_gpio_priv *priv;
149	u32 ngpio;
150	int ret;
151
152	if (of_property_read_u32(client->dev.of_node, "ngpios", &ngpio))
153		ngpio = DEFAULT_PIN_NUMBER;
154
155	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
156	if (!priv)
157		return -ENOMEM;
158
159	priv->gpio_chip = template_chip;
160	priv->gpio_chip.label = "ts4900-gpio";
161	priv->gpio_chip.ngpio = ngpio;
162	priv->gpio_chip.parent = &client->dev;
163	priv->input_bit = (uintptr_t)of_device_get_match_data(&client->dev);
164
165	priv->regmap = devm_regmap_init_i2c(client, &ts4900_regmap_config);
166	if (IS_ERR(priv->regmap)) {
167		ret = PTR_ERR(priv->regmap);
168		dev_err(&client->dev, "Failed to allocate register map: %d\n",
169			ret);
170		return ret;
171	}
172
173	ret = devm_gpiochip_add_data(&client->dev, &priv->gpio_chip, priv);
174	if (ret < 0) {
175		dev_err(&client->dev, "Unable to register gpiochip\n");
176		return ret;
177	}
178
179	i2c_set_clientdata(client, priv);
180
181	return 0;
182}
183
184static const struct i2c_device_id ts4900_gpio_id_table[] = {
185	{ "ts4900-gpio", },
186	{ /* sentinel */ }
187};
188MODULE_DEVICE_TABLE(i2c, ts4900_gpio_id_table);
189
190static struct i2c_driver ts4900_gpio_driver = {
191	.driver = {
192		.name = "ts4900-gpio",
193		.of_match_table = ts4900_gpio_of_match_table,
194	},
195	.probe = ts4900_gpio_probe,
196	.id_table = ts4900_gpio_id_table,
197};
198module_i2c_driver(ts4900_gpio_driver);
199
200MODULE_AUTHOR("Technologic Systems");
201MODULE_DESCRIPTION("GPIO interface for Technologic Systems I2C-FPGA core");
202MODULE_LICENSE("GPL");
203