1/*
2 * Atmel Atmegaxx Capacitive Touch Button Driver
3 *
4 * Copyright (C) 2016 Google, inc.
5 *
6 * This software is licensed under the terms of the GNU General Public
7 * License version 2, as published by the Free Software Foundation, and
8 * may be copied, distributed, and modified under those terms.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 */
15
16/*
17 * It's irrelevant that the HW used to develop captouch driver is based
18 * on Atmega88PA part and uses QtouchADC parts for sensing touch.
19 * Calling this driver "captouch" is an arbitrary way to distinguish
20 * the protocol this driver supported by other atmel/qtouch drivers.
21 *
22 * Captouch driver supports a newer/different version of the I2C
23 * registers/commands than the qt1070.c driver.
24 * Don't let the similarity of the general driver structure fool you.
25 *
26 * For raw i2c access from userspace, use i2cset/i2cget
27 * to poke at /dev/i2c-N devices.
28 */
29
30#include <linux/device.h>
31#include <linux/kernel.h>
32#include <linux/module.h>
33#include <linux/init.h>
34#include <linux/i2c.h>
35#include <linux/input.h>
36#include <linux/interrupt.h>
37#include <linux/slab.h>
38
39/* Maximum number of buttons supported */
40#define MAX_NUM_OF_BUTTONS 8
41
42/* Registers */
43#define REG_KEY1_THRESHOLD 0x02
44#define REG_KEY2_THRESHOLD 0x03
45#define REG_KEY3_THRESHOLD 0x04
46#define REG_KEY4_THRESHOLD 0x05
47
48#define REG_KEY1_REF_H 0x20
49#define REG_KEY1_REF_L 0x21
50#define REG_KEY2_REF_H 0x22
51#define REG_KEY2_REF_L 0x23
52#define REG_KEY3_REF_H 0x24
53#define REG_KEY3_REF_L 0x25
54#define REG_KEY4_REF_H 0x26
55#define REG_KEY4_REF_L 0x27
56
57#define REG_KEY1_DLT_H 0x30
58#define REG_KEY1_DLT_L 0x31
59#define REG_KEY2_DLT_H 0x32
60#define REG_KEY2_DLT_L 0x33
61#define REG_KEY3_DLT_H 0x34
62#define REG_KEY3_DLT_L 0x35
63#define REG_KEY4_DLT_H 0x36
64#define REG_KEY4_DLT_L 0x37
65
66#define REG_KEY_STATE 0x3C
67
68/*
69 * @i2c_client: I2C slave device client pointer
70 * @input: Input device pointer
71 * @num_btn: Number of buttons
72 * @keycodes: map of button# to KeyCode
73 * @prev_btn: Previous key state to detect button "press" or "release"
74 * @xfer_buf: I2C transfer buffer
75 */
76struct atmel_captouch_device {
77 struct i2c_client *client;
78 struct input_dev *input;
79 u32 num_btn;
80 u32 keycodes[MAX_NUM_OF_BUTTONS];
81 u8 prev_btn;
82 u8 xfer_buf[8] ____cacheline_aligned;
83};
84
85/*
86 * Read from I2C slave device
87 * The protocol is that the client has to provide both the register address
88 * and the length, and while reading back the device would prepend the data
89 * with address and length for verification.
90 */
91static int atmel_read(struct atmel_captouch_device *capdev,
92 u8 reg, u8 *data, size_t len)
93{
94 struct i2c_client *client = capdev->client;
95 struct device *dev = &client->dev;
96 struct i2c_msg msg[2];
97 int err;
98
99 if (len > sizeof(capdev->xfer_buf) - 2)
100 return -EINVAL;
101
102 capdev->xfer_buf[0] = reg;
103 capdev->xfer_buf[1] = len;
104
105 msg[0].addr = client->addr;
106 msg[0].flags = 0;
107 msg[0].buf = capdev->xfer_buf;
108 msg[0].len = 2;
109
110 msg[1].addr = client->addr;
111 msg[1].flags = I2C_M_RD;
112 msg[1].buf = capdev->xfer_buf;
113 msg[1].len = len + 2;
114
115 err = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
116 if (err != ARRAY_SIZE(msg))
117 return err < 0 ? err : -EIO;
118
119 if (capdev->xfer_buf[0] != reg) {
120 dev_err(dev,
121 "I2C read error: register address does not match (%#02x vs %02x)\n",
122 capdev->xfer_buf[0], reg);
123 return -ECOMM;
124 }
125
126 memcpy(data, &capdev->xfer_buf[2], len);
127
128 return 0;
129}
130
131/*
132 * Handle interrupt and report the key changes to the input system.
133 * Multi-touch can be supported; however, it really depends on whether
134 * the device can multi-touch.
135 */
136static irqreturn_t atmel_captouch_isr(int irq, void *data)
137{
138 struct atmel_captouch_device *capdev = data;
139 struct device *dev = &capdev->client->dev;
140 int error;
141 int i;
142 u8 new_btn;
143 u8 changed_btn;
144
145 error = atmel_read(capdev, REG_KEY_STATE, &new_btn, 1);
146 if (error) {
147 dev_err(dev, "failed to read button state: %d\n", error);
148 goto out;
149 }
150
151 dev_dbg(dev, "%s: button state %#02x\n", __func__, new_btn);
152
153 changed_btn = new_btn ^ capdev->prev_btn;
154 capdev->prev_btn = new_btn;
155
156 for (i = 0; i < capdev->num_btn; i++) {
157 if (changed_btn & BIT(i))
158 input_report_key(capdev->input,
159 capdev->keycodes[i],
160 new_btn & BIT(i));
161 }
162
163 input_sync(capdev->input);
164
165out:
166 return IRQ_HANDLED;
167}
168
169/*
170 * Probe function to setup the device, input system and interrupt
171 */
172static int atmel_captouch_probe(struct i2c_client *client,
173 const struct i2c_device_id *id)
174{
175 struct atmel_captouch_device *capdev;
176 struct device *dev = &client->dev;
177 struct device_node *node;
178 int i;
179 int err;
180
181 if (!i2c_check_functionality(client->adapter,
182 I2C_FUNC_SMBUS_BYTE_DATA |
183 I2C_FUNC_SMBUS_WORD_DATA |
184 I2C_FUNC_SMBUS_I2C_BLOCK)) {
185 dev_err(dev, "needed i2c functionality is not supported\n");
186 return -EINVAL;
187 }
188
189 capdev = devm_kzalloc(dev, sizeof(*capdev), GFP_KERNEL);
190 if (!capdev)
191 return -ENOMEM;
192
193 capdev->client = client;
194
195 err = atmel_read(capdev, REG_KEY_STATE,
196 &capdev->prev_btn, sizeof(capdev->prev_btn));
197 if (err) {
198 dev_err(dev, "failed to read initial button state: %d\n", err);
199 return err;
200 }
201
202 capdev->input = devm_input_allocate_device(dev);
203 if (!capdev->input) {
204 dev_err(dev, "failed to allocate input device\n");
205 return -ENOMEM;
206 }
207
208 capdev->input->id.bustype = BUS_I2C;
209 capdev->input->id.product = 0x880A;
210 capdev->input->id.version = 0;
211 capdev->input->name = "ATMegaXX Capacitive Button Controller";
212 __set_bit(EV_KEY, capdev->input->evbit);
213
214 node = dev->of_node;
215 if (!node) {
216 dev_err(dev, "failed to find matching node in device tree\n");
217 return -EINVAL;
218 }
219
220 if (of_property_read_bool(node, "autorepeat"))
221 __set_bit(EV_REP, capdev->input->evbit);
222
223 capdev->num_btn = of_property_count_u32_elems(node, "linux,keymap");
224 if (capdev->num_btn > MAX_NUM_OF_BUTTONS)
225 capdev->num_btn = MAX_NUM_OF_BUTTONS;
226
227 err = of_property_read_u32_array(node, "linux,keycodes",
228 capdev->keycodes,
229 capdev->num_btn);
230 if (err) {
231 dev_err(dev,
232 "failed to read linux,keycode property: %d\n", err);
233 return err;
234 }
235
236 for (i = 0; i < capdev->num_btn; i++)
237 __set_bit(capdev->keycodes[i], capdev->input->keybit);
238
239 capdev->input->keycode = capdev->keycodes;
240 capdev->input->keycodesize = sizeof(capdev->keycodes[0]);
241 capdev->input->keycodemax = capdev->num_btn;
242
243 err = input_register_device(capdev->input);
244 if (err)
245 return err;
246
247 err = devm_request_threaded_irq(dev, client->irq,
248 NULL, atmel_captouch_isr,
249 IRQF_ONESHOT,
250 "atmel_captouch", capdev);
251 if (err) {
252 dev_err(dev, "failed to request irq %d: %d\n",
253 client->irq, err);
254 return err;
255 }
256
257 return 0;
258}
259
260#ifdef CONFIG_OF
261static const struct of_device_id atmel_captouch_of_id[] = {
262 {
263 .compatible = "atmel,captouch",
264 },
265 { /* sentinel */ }
266};
267MODULE_DEVICE_TABLE(of, atmel_captouch_of_id);
268#endif
269
270static const struct i2c_device_id atmel_captouch_id[] = {
271 { "atmel_captouch", 0 },
272 { }
273};
274MODULE_DEVICE_TABLE(i2c, atmel_captouch_id);
275
276static struct i2c_driver atmel_captouch_driver = {
277 .probe = atmel_captouch_probe,
278 .id_table = atmel_captouch_id,
279 .driver = {
280 .name = "atmel_captouch",
281 .of_match_table = of_match_ptr(atmel_captouch_of_id),
282 },
283};
284module_i2c_driver(atmel_captouch_driver);
285
286/* Module information */
287MODULE_AUTHOR("Hung-yu Wu <hywu@google.com>");
288MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");
289MODULE_LICENSE("GPL v2");
290