1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * ADC generic resistive touchscreen (GRTS)
4 * This is a generic input driver that connects to an ADC
5 * given the channels in device tree, and reports events to the input
6 * subsystem.
7 *
8 * Copyright (C) 2017,2018 Microchip Technology,
9 * Author: Eugen Hristev <eugen.hristev@microchip.com>
10 *
11 */
12 #include <linux/input.h>
13 #include <linux/input/touchscreen.h>
14 #include <linux/iio/consumer.h>
15 #include <linux/iio/iio.h>
16 #include <linux/mod_devicetable.h>
17 #include <linux/module.h>
18 #include <linux/platform_device.h>
19 #include <linux/property.h>
20
21 #define DRIVER_NAME "resistive-adc-touch"
22 #define GRTS_DEFAULT_PRESSURE_MIN 50000
23 #define GRTS_DEFAULT_PRESSURE_MAX 65535
24 #define GRTS_MAX_POS_MASK GENMASK(11, 0)
25 #define GRTS_MAX_CHANNELS 4
26
27 enum grts_ch_type {
28 GRTS_CH_X,
29 GRTS_CH_Y,
30 GRTS_CH_PRESSURE,
31 GRTS_CH_Z1,
32 GRTS_CH_Z2,
33 GRTS_CH_MAX = GRTS_CH_Z2 + 1
34 };
35
36 /**
37 * struct grts_state - generic resistive touch screen information struct
38 * @x_plate_ohms: resistance of the X plate
39 * @pressure_min: number representing the minimum for the pressure
40 * @pressure: are we getting pressure info or not
41 * @iio_chans: list of channels acquired
42 * @iio_cb: iio_callback buffer for the data
43 * @input: the input device structure that we register
44 * @prop: touchscreen properties struct
45 * @ch_map: map of channels that are defined for the touchscreen
46 */
47 struct grts_state {
48 u32 x_plate_ohms;
49 u32 pressure_min;
50 bool pressure;
51 struct iio_channel *iio_chans;
52 struct iio_cb_buffer *iio_cb;
53 struct input_dev *input;
54 struct touchscreen_properties prop;
55 u8 ch_map[GRTS_CH_MAX];
56 };
57
grts_cb(const void * data,void * private)58 static int grts_cb(const void *data, void *private)
59 {
60 const u16 *touch_info = data;
61 struct grts_state *st = private;
62 unsigned int x, y, press = 0;
63
64 x = touch_info[st->ch_map[GRTS_CH_X]];
65 y = touch_info[st->ch_map[GRTS_CH_Y]];
66
67 if (st->ch_map[GRTS_CH_PRESSURE] < GRTS_MAX_CHANNELS) {
68 press = touch_info[st->ch_map[GRTS_CH_PRESSURE]];
69 } else if (st->ch_map[GRTS_CH_Z1] < GRTS_MAX_CHANNELS) {
70 unsigned int z1 = touch_info[st->ch_map[GRTS_CH_Z1]];
71 unsigned int z2 = touch_info[st->ch_map[GRTS_CH_Z2]];
72 unsigned int Rt;
73
74 if (likely(x && z1)) {
75 Rt = z2;
76 Rt -= z1;
77 Rt *= st->x_plate_ohms;
78 Rt = DIV_ROUND_CLOSEST(Rt, 16);
79 Rt *= x;
80 Rt /= z1;
81 Rt = DIV_ROUND_CLOSEST(Rt, 256);
82 /*
83 * On increased pressure the resistance (Rt) is
84 * decreasing so, convert values to make it looks as
85 * real pressure.
86 */
87 if (Rt < GRTS_DEFAULT_PRESSURE_MAX)
88 press = GRTS_DEFAULT_PRESSURE_MAX - Rt;
89 }
90 }
91
92 if ((!x && !y) || (st->pressure && (press < st->pressure_min))) {
93 /* report end of touch */
94 input_report_key(st->input, BTN_TOUCH, 0);
95 input_sync(st->input);
96 return 0;
97 }
98
99 /* report proper touch to subsystem*/
100 touchscreen_report_pos(st->input, &st->prop, x, y, false);
101 if (st->pressure)
102 input_report_abs(st->input, ABS_PRESSURE, press);
103 input_report_key(st->input, BTN_TOUCH, 1);
104 input_sync(st->input);
105
106 return 0;
107 }
108
grts_open(struct input_dev * dev)109 static int grts_open(struct input_dev *dev)
110 {
111 int error;
112 struct grts_state *st = input_get_drvdata(dev);
113
114 error = iio_channel_start_all_cb(st->iio_cb);
115 if (error) {
116 dev_err(dev->dev.parent, "failed to start callback buffer.\n");
117 return error;
118 }
119 return 0;
120 }
121
grts_close(struct input_dev * dev)122 static void grts_close(struct input_dev *dev)
123 {
124 struct grts_state *st = input_get_drvdata(dev);
125
126 iio_channel_stop_all_cb(st->iio_cb);
127 }
128
grts_disable(void * data)129 static void grts_disable(void *data)
130 {
131 iio_channel_release_all_cb(data);
132 }
133
grts_map_channel(struct grts_state * st,struct device * dev,enum grts_ch_type type,const char * name,bool optional)134 static int grts_map_channel(struct grts_state *st, struct device *dev,
135 enum grts_ch_type type, const char *name,
136 bool optional)
137 {
138 int idx;
139
140 idx = device_property_match_string(dev, "io-channel-names", name);
141 if (idx < 0) {
142 if (!optional)
143 return idx;
144 idx = GRTS_MAX_CHANNELS;
145 } else if (idx >= GRTS_MAX_CHANNELS) {
146 return -EOVERFLOW;
147 }
148
149 st->ch_map[type] = idx;
150 return 0;
151 }
152
grts_get_properties(struct grts_state * st,struct device * dev)153 static int grts_get_properties(struct grts_state *st, struct device *dev)
154 {
155 int error;
156
157 error = grts_map_channel(st, dev, GRTS_CH_X, "x", false);
158 if (error)
159 return error;
160
161 error = grts_map_channel(st, dev, GRTS_CH_Y, "y", false);
162 if (error)
163 return error;
164
165 /* pressure is optional */
166 error = grts_map_channel(st, dev, GRTS_CH_PRESSURE, "pressure", true);
167 if (error)
168 return error;
169
170 if (st->ch_map[GRTS_CH_PRESSURE] < GRTS_MAX_CHANNELS) {
171 st->pressure = true;
172 return 0;
173 }
174
175 /* if no pressure is defined, try optional z1 + z2 */
176 error = grts_map_channel(st, dev, GRTS_CH_Z1, "z1", true);
177 if (error)
178 return error;
179
180 if (st->ch_map[GRTS_CH_Z1] >= GRTS_MAX_CHANNELS)
181 return 0;
182
183 /* if z1 is provided z2 is not optional */
184 error = grts_map_channel(st, dev, GRTS_CH_Z2, "z2", true);
185 if (error)
186 return error;
187
188 error = device_property_read_u32(dev,
189 "touchscreen-x-plate-ohms",
190 &st->x_plate_ohms);
191 if (error) {
192 dev_err(dev, "can't get touchscreen-x-plate-ohms property\n");
193 return error;
194 }
195
196 st->pressure = true;
197 return 0;
198 }
199
grts_probe(struct platform_device * pdev)200 static int grts_probe(struct platform_device *pdev)
201 {
202 struct grts_state *st;
203 struct input_dev *input;
204 struct device *dev = &pdev->dev;
205 int error;
206
207 st = devm_kzalloc(dev, sizeof(struct grts_state), GFP_KERNEL);
208 if (!st)
209 return -ENOMEM;
210
211 /* get the channels from IIO device */
212 st->iio_chans = devm_iio_channel_get_all(dev);
213 if (IS_ERR(st->iio_chans))
214 return dev_err_probe(dev, PTR_ERR(st->iio_chans), "can't get iio channels\n");
215
216 if (!device_property_present(dev, "io-channel-names"))
217 return -ENODEV;
218
219 error = grts_get_properties(st, dev);
220 if (error) {
221 dev_err(dev, "Failed to parse properties\n");
222 return error;
223 }
224
225 if (st->pressure) {
226 error = device_property_read_u32(dev,
227 "touchscreen-min-pressure",
228 &st->pressure_min);
229 if (error) {
230 dev_dbg(dev, "can't get touchscreen-min-pressure property.\n");
231 st->pressure_min = GRTS_DEFAULT_PRESSURE_MIN;
232 }
233 }
234
235 input = devm_input_allocate_device(dev);
236 if (!input) {
237 dev_err(dev, "failed to allocate input device.\n");
238 return -ENOMEM;
239 }
240
241 input->name = DRIVER_NAME;
242 input->id.bustype = BUS_HOST;
243 input->open = grts_open;
244 input->close = grts_close;
245
246 input_set_abs_params(input, ABS_X, 0, GRTS_MAX_POS_MASK - 1, 0, 0);
247 input_set_abs_params(input, ABS_Y, 0, GRTS_MAX_POS_MASK - 1, 0, 0);
248 if (st->pressure)
249 input_set_abs_params(input, ABS_PRESSURE, st->pressure_min,
250 GRTS_DEFAULT_PRESSURE_MAX, 0, 0);
251
252 input_set_capability(input, EV_KEY, BTN_TOUCH);
253
254 /* parse optional device tree properties */
255 touchscreen_parse_properties(input, false, &st->prop);
256
257 st->input = input;
258 input_set_drvdata(input, st);
259
260 error = input_register_device(input);
261 if (error) {
262 dev_err(dev, "failed to register input device.");
263 return error;
264 }
265
266 st->iio_cb = iio_channel_get_all_cb(dev, grts_cb, st);
267 if (IS_ERR(st->iio_cb)) {
268 dev_err(dev, "failed to allocate callback buffer.\n");
269 return PTR_ERR(st->iio_cb);
270 }
271
272 error = devm_add_action_or_reset(dev, grts_disable, st->iio_cb);
273 if (error) {
274 dev_err(dev, "failed to add disable action.\n");
275 return error;
276 }
277
278 return 0;
279 }
280
281 static const struct of_device_id grts_of_match[] = {
282 {
283 .compatible = "resistive-adc-touch",
284 }, {
285 /* sentinel */
286 },
287 };
288
289 MODULE_DEVICE_TABLE(of, grts_of_match);
290
291 static struct platform_driver grts_driver = {
292 .probe = grts_probe,
293 .driver = {
294 .name = DRIVER_NAME,
295 .of_match_table = grts_of_match,
296 },
297 };
298
299 module_platform_driver(grts_driver);
300
301 MODULE_AUTHOR("Eugen Hristev <eugen.hristev@microchip.com>");
302 MODULE_DESCRIPTION("Generic ADC Resistive Touch Driver");
303 MODULE_LICENSE("GPL v2");
304