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	{ "atmel_captouch", 0 },
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 <hywu@google.com>");
277MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");
278MODULE_LICENSE("GPL v2");
279