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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 */
68struct 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 */
83static 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 */
128static 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
157out:
158 return IRQ_HANDLED;
159}
160
161/*
162 * Probe function to setup the device, input system and interrupt
163 */
164static 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
251static const struct of_device_id atmel_captouch_of_id[] = {
252 {
253 .compatible = "atmel,captouch",
254 },
255 { /* sentinel */ }
256};
257MODULE_DEVICE_TABLE(of, atmel_captouch_of_id);
258
259static const struct i2c_device_id atmel_captouch_id[] = {
260 { .name = "atmel_captouch" },
261 { }
262};
263MODULE_DEVICE_TABLE(i2c, atmel_captouch_id);
264
265static struct i2c_driver atmel_captouch_driver = {
266 .probe = 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};
273module_i2c_driver(atmel_captouch_driver);
274
275/* Module information */
276MODULE_AUTHOR("Hung-yu Wu <[email protected]>");
277MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");
278MODULE_LICENSE("GPL v2");