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 */
gw_pld_input8(struct gpio_chip * gc,unsigned offset)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
gw_pld_get8(struct gpio_chip * gc,unsigned offset)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
gw_pld_output8(struct gpio_chip * gc,unsigned offset,int value)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
gw_pld_set8(struct gpio_chip * gc,unsigned offset,int value)65 static void gw_pld_set8(struct gpio_chip *gc, unsigned offset, int value)
66 {
67 gw_pld_output8(gc, offset, value);
68 }
69
gw_pld_probe(struct i2c_client * client)70 static 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
111 static const struct i2c_device_id gw_pld_id[] = {
112 { "gw-pld", },
113 { }
114 };
115 MODULE_DEVICE_TABLE(i2c, gw_pld_id);
116
117 static const struct of_device_id gw_pld_dt_ids[] = {
118 { .compatible = "gateworks,pld-gpio", },
119 { },
120 };
121 MODULE_DEVICE_TABLE(of, gw_pld_dt_ids);
122
123 static struct i2c_driver gw_pld_driver = {
124 .driver = {
125 .name = "gw_pld",
126 .of_match_table = gw_pld_dt_ids,
127 },
128 .probe = gw_pld_probe,
129 .id_table = gw_pld_id,
130 };
131 module_i2c_driver(gw_pld_driver);
132
133 MODULE_LICENSE("GPL");
134 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
135