1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Atmel Atmegaxx Capacitive Touch Button Driver
4  *
5  * Copyright (C) 2016 Google, inc.
6  */
7 
8 /*
9  * It's irrelevant that the HW used to develop captouch driver is based
10  * on Atmega88PA part and uses QtouchADC parts for sensing touch.
11  * Calling this driver "captouch" is an arbitrary way to distinguish
12  * the protocol this driver supported by other atmel/qtouch drivers.
13  *
14  * Captouch driver supports a newer/different version of the I2C
15  * registers/commands than the qt1070.c driver.
16  * Don't let the similarity of the general driver structure fool you.
17  *
18  * For raw i2c access from userspace, use i2cset/i2cget
19  * to poke at /dev/i2c-N devices.
20  */
21 
22 #include <linux/device.h>
23 #include <linux/kernel.h>
24 #include <linux/module.h>
25 #include <linux/init.h>
26 #include <linux/i2c.h>
27 #include <linux/input.h>
28 #include <linux/interrupt.h>
29 #include <linux/slab.h>
30 
31 /* Maximum number of buttons supported */
32 #define MAX_NUM_OF_BUTTONS		8
33 
34 /* Registers */
35 #define REG_KEY1_THRESHOLD		0x02
36 #define REG_KEY2_THRESHOLD		0x03
37 #define REG_KEY3_THRESHOLD		0x04
38 #define REG_KEY4_THRESHOLD		0x05
39 
40 #define REG_KEY1_REF_H			0x20
41 #define REG_KEY1_REF_L			0x21
42 #define REG_KEY2_REF_H			0x22
43 #define REG_KEY2_REF_L			0x23
44 #define REG_KEY3_REF_H			0x24
45 #define REG_KEY3_REF_L			0x25
46 #define REG_KEY4_REF_H			0x26
47 #define REG_KEY4_REF_L			0x27
48 
49 #define REG_KEY1_DLT_H			0x30
50 #define REG_KEY1_DLT_L			0x31
51 #define REG_KEY2_DLT_H			0x32
52 #define REG_KEY2_DLT_L			0x33
53 #define REG_KEY3_DLT_H			0x34
54 #define REG_KEY3_DLT_L			0x35
55 #define REG_KEY4_DLT_H			0x36
56 #define REG_KEY4_DLT_L			0x37
57 
58 #define REG_KEY_STATE			0x3C
59 
60 /*
61  * @i2c_client: I2C slave device client pointer
62  * @input: Input device pointer
63  * @num_btn: Number of buttons
64  * @keycodes: map of button# to KeyCode
65  * @prev_btn: Previous key state to detect button "press" or "release"
66  * @xfer_buf: I2C transfer buffer
67  */
68 struct atmel_captouch_device {
69 	struct i2c_client *client;
70 	struct input_dev *input;
71 	u32 num_btn;
72 	u32 keycodes[MAX_NUM_OF_BUTTONS];
73 	u8 prev_btn;
74 	u8 xfer_buf[8] ____cacheline_aligned;
75 };
76 
77 /*
78  * Read from I2C slave device
79  * The protocol is that the client has to provide both the register address
80  * and the length, and while reading back the device would prepend the data
81  * with address and length for verification.
82  */
83 static int atmel_read(struct atmel_captouch_device *capdev,
84 			 u8 reg, u8 *data, size_t len)
85 {
86 	struct i2c_client *client = capdev->client;
87 	struct device *dev = &client->dev;
88 	struct i2c_msg msg[2];
89 	int err;
90 
91 	if (len > sizeof(capdev->xfer_buf) - 2)
92 		return -EINVAL;
93 
94 	capdev->xfer_buf[0] = reg;
95 	capdev->xfer_buf[1] = len;
96 
97 	msg[0].addr = client->addr;
98 	msg[0].flags = 0;
99 	msg[0].buf = capdev->xfer_buf;
100 	msg[0].len = 2;
101 
102 	msg[1].addr = client->addr;
103 	msg[1].flags = I2C_M_RD;
104 	msg[1].buf = capdev->xfer_buf;
105 	msg[1].len = len + 2;
106 
107 	err = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
108 	if (err != ARRAY_SIZE(msg))
109 		return err < 0 ? err : -EIO;
110 
111 	if (capdev->xfer_buf[0] != reg) {
112 		dev_err(dev,
113 			"I2C read error: register address does not match (%#02x vs %02x)\n",
114 			capdev->xfer_buf[0], reg);
115 		return -ECOMM;
116 	}
117 
118 	memcpy(data, &capdev->xfer_buf[2], len);
119 
120 	return 0;
121 }
122 
123 /*
124  * Handle interrupt and report the key changes to the input system.
125  * Multi-touch can be supported; however, it really depends on whether
126  * the device can multi-touch.
127  */
128 static irqreturn_t atmel_captouch_isr(int irq, void *data)
129 {
130 	struct atmel_captouch_device *capdev = data;
131 	struct device *dev = &capdev->client->dev;
132 	int error;
133 	int i;
134 	u8 new_btn;
135 	u8 changed_btn;
136 
137 	error = atmel_read(capdev, REG_KEY_STATE, &new_btn, 1);
138 	if (error) {
139 		dev_err(dev, "failed to read button state: %d\n", error);
140 		goto out;
141 	}
142 
143 	dev_dbg(dev, "%s: button state %#02x\n", __func__, new_btn);
144 
145 	changed_btn = new_btn ^ capdev->prev_btn;
146 	capdev->prev_btn = new_btn;
147 
148 	for (i = 0; i < capdev->num_btn; i++) {
149 		if (changed_btn & BIT(i))
150 			input_report_key(capdev->input,
151 					 capdev->keycodes[i],
152 					 new_btn & BIT(i));
153 	}
154 
155 	input_sync(capdev->input);
156 
157 out:
158 	return IRQ_HANDLED;
159 }
160 
161 /*
162  * Probe function to setup the device, input system and interrupt
163  */
164 static int atmel_captouch_probe(struct i2c_client *client)
165 {
166 	struct atmel_captouch_device *capdev;
167 	struct device *dev = &client->dev;
168 	struct device_node *node;
169 	int i;
170 	int err;
171 
172 	if (!i2c_check_functionality(client->adapter,
173 				     I2C_FUNC_SMBUS_BYTE_DATA |
174 					I2C_FUNC_SMBUS_WORD_DATA |
175 					I2C_FUNC_SMBUS_I2C_BLOCK)) {
176 		dev_err(dev, "needed i2c functionality is not supported\n");
177 		return -EINVAL;
178 	}
179 
180 	capdev = devm_kzalloc(dev, sizeof(*capdev), GFP_KERNEL);
181 	if (!capdev)
182 		return -ENOMEM;
183 
184 	capdev->client = client;
185 
186 	err = atmel_read(capdev, REG_KEY_STATE,
187 			    &capdev->prev_btn, sizeof(capdev->prev_btn));
188 	if (err) {
189 		dev_err(dev, "failed to read initial button state: %d\n", err);
190 		return err;
191 	}
192 
193 	capdev->input = devm_input_allocate_device(dev);
194 	if (!capdev->input) {
195 		dev_err(dev, "failed to allocate input device\n");
196 		return -ENOMEM;
197 	}
198 
199 	capdev->input->id.bustype = BUS_I2C;
200 	capdev->input->id.product = 0x880A;
201 	capdev->input->id.version = 0;
202 	capdev->input->name = "ATMegaXX Capacitive Button Controller";
203 	__set_bit(EV_KEY, capdev->input->evbit);
204 
205 	node = dev->of_node;
206 	if (!node) {
207 		dev_err(dev, "failed to find matching node in device tree\n");
208 		return -EINVAL;
209 	}
210 
211 	if (of_property_read_bool(node, "autorepeat"))
212 		__set_bit(EV_REP, capdev->input->evbit);
213 
214 	capdev->num_btn = of_property_count_u32_elems(node, "linux,keymap");
215 	if (capdev->num_btn > MAX_NUM_OF_BUTTONS)
216 		capdev->num_btn = MAX_NUM_OF_BUTTONS;
217 
218 	err = of_property_read_u32_array(node, "linux,keycodes",
219 					 capdev->keycodes,
220 					 capdev->num_btn);
221 	if (err) {
222 		dev_err(dev,
223 			"failed to read linux,keycode property: %d\n", err);
224 		return err;
225 	}
226 
227 	for (i = 0; i < capdev->num_btn; i++)
228 		__set_bit(capdev->keycodes[i], capdev->input->keybit);
229 
230 	capdev->input->keycode = capdev->keycodes;
231 	capdev->input->keycodesize = sizeof(capdev->keycodes[0]);
232 	capdev->input->keycodemax = capdev->num_btn;
233 
234 	err = input_register_device(capdev->input);
235 	if (err)
236 		return err;
237 
238 	err = devm_request_threaded_irq(dev, client->irq,
239 					NULL, atmel_captouch_isr,
240 					IRQF_ONESHOT,
241 					"atmel_captouch", capdev);
242 	if (err) {
243 		dev_err(dev, "failed to request irq %d: %d\n",
244 			client->irq, err);
245 		return err;
246 	}
247 
248 	return 0;
249 }
250 
251 static const struct of_device_id atmel_captouch_of_id[] = {
252 	{
253 		.compatible = "atmel,captouch",
254 	},
255 	{ /* sentinel */ }
256 };
257 MODULE_DEVICE_TABLE(of, atmel_captouch_of_id);
258 
259 static const struct i2c_device_id atmel_captouch_id[] = {
260 	{ "atmel_captouch", 0 },
261 	{ }
262 };
263 MODULE_DEVICE_TABLE(i2c, atmel_captouch_id);
264 
265 static struct i2c_driver atmel_captouch_driver = {
266 	.probe_new	= atmel_captouch_probe,
267 	.id_table	= atmel_captouch_id,
268 	.driver		= {
269 		.name	= "atmel_captouch",
270 		.of_match_table = atmel_captouch_of_id,
271 	},
272 };
273 module_i2c_driver(atmel_captouch_driver);
274 
275 /* Module information */
276 MODULE_AUTHOR("Hung-yu Wu <hywu@google.com>");
277 MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");
278 MODULE_LICENSE("GPL v2");
279