1 /*
2  * Allwinner sun4i low res adc attached tablet keys driver
3  *
4  * Copyright (C) 2014 Hans de Goede <hdegoede@redhat.com>
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  * GNU General Public License for more details.
15  */
16 
17 /*
18  * Allwinnner sunxi SoCs have a lradc which is specifically designed to have
19  * various (tablet) keys (ie home, back, search, etc). attached to it using
20  * a resistor network. This driver is for the keys on such boards.
21  *
22  * There are 2 channels, currently this driver only supports channel 0 since
23  * there are no boards known to use channel 1.
24  */
25 
26 #include <linux/err.h>
27 #include <linux/init.h>
28 #include <linux/input.h>
29 #include <linux/interrupt.h>
30 #include <linux/io.h>
31 #include <linux/module.h>
32 #include <linux/of_platform.h>
33 #include <linux/platform_device.h>
34 #include <linux/regulator/consumer.h>
35 #include <linux/slab.h>
36 
37 #define LRADC_CTRL		0x00
38 #define LRADC_INTC		0x04
39 #define LRADC_INTS		0x08
40 #define LRADC_DATA0		0x0c
41 #define LRADC_DATA1		0x10
42 
43 /* LRADC_CTRL bits */
44 #define FIRST_CONVERT_DLY(x)	((x) << 24) /* 8 bits */
45 #define CHAN_SELECT(x)		((x) << 22) /* 2 bits */
46 #define CONTINUE_TIME_SEL(x)	((x) << 16) /* 4 bits */
47 #define KEY_MODE_SEL(x)		((x) << 12) /* 2 bits */
48 #define LEVELA_B_CNT(x)		((x) << 8)  /* 4 bits */
49 #define HOLD_EN(x)		((x) << 6)
50 #define LEVELB_VOL(x)		((x) << 4)  /* 2 bits */
51 #define SAMPLE_RATE(x)		((x) << 2)  /* 2 bits */
52 #define ENABLE(x)		((x) << 0)
53 
54 /* LRADC_INTC and LRADC_INTS bits */
55 #define CHAN1_KEYUP_IRQ		BIT(12)
56 #define CHAN1_ALRDY_HOLD_IRQ	BIT(11)
57 #define CHAN1_HOLD_IRQ		BIT(10)
58 #define	CHAN1_KEYDOWN_IRQ	BIT(9)
59 #define CHAN1_DATA_IRQ		BIT(8)
60 #define CHAN0_KEYUP_IRQ		BIT(4)
61 #define CHAN0_ALRDY_HOLD_IRQ	BIT(3)
62 #define CHAN0_HOLD_IRQ		BIT(2)
63 #define	CHAN0_KEYDOWN_IRQ	BIT(1)
64 #define CHAN0_DATA_IRQ		BIT(0)
65 
66 struct sun4i_lradc_keymap {
67 	u32 voltage;
68 	u32 keycode;
69 };
70 
71 struct sun4i_lradc_data {
72 	struct device *dev;
73 	struct input_dev *input;
74 	void __iomem *base;
75 	struct regulator *vref_supply;
76 	struct sun4i_lradc_keymap *chan0_map;
77 	u32 chan0_map_count;
78 	u32 chan0_keycode;
79 	u32 vref;
80 };
81 
82 static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
83 {
84 	struct sun4i_lradc_data *lradc = dev_id;
85 	u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
86 
87 	ints  = readl(lradc->base + LRADC_INTS);
88 
89 	/*
90 	 * lradc supports only one keypress at a time, release does not give
91 	 * any info as to which key was released, so we cache the keycode.
92 	 */
93 
94 	if (ints & CHAN0_KEYUP_IRQ) {
95 		input_report_key(lradc->input, lradc->chan0_keycode, 0);
96 		lradc->chan0_keycode = 0;
97 	}
98 
99 	if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
100 		val = readl(lradc->base + LRADC_DATA0) & 0x3f;
101 		voltage = val * lradc->vref / 63;
102 
103 		for (i = 0; i < lradc->chan0_map_count; i++) {
104 			diff = abs(lradc->chan0_map[i].voltage - voltage);
105 			if (diff < closest) {
106 				closest = diff;
107 				keycode = lradc->chan0_map[i].keycode;
108 			}
109 		}
110 
111 		lradc->chan0_keycode = keycode;
112 		input_report_key(lradc->input, lradc->chan0_keycode, 1);
113 	}
114 
115 	input_sync(lradc->input);
116 
117 	writel(ints, lradc->base + LRADC_INTS);
118 
119 	return IRQ_HANDLED;
120 }
121 
122 static int sun4i_lradc_open(struct input_dev *dev)
123 {
124 	struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
125 	int error;
126 
127 	error = regulator_enable(lradc->vref_supply);
128 	if (error)
129 		return error;
130 
131 	/* lradc Vref internally is divided by 2/3 */
132 	lradc->vref = regulator_get_voltage(lradc->vref_supply) * 2 / 3;
133 
134 	/*
135 	 * Set sample time to 4 ms / 250 Hz. Wait 2 * 4 ms for key to
136 	 * stabilize on press, wait (1 + 1) * 4 ms for key release
137 	 */
138 	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
139 		SAMPLE_RATE(0) | ENABLE(1), lradc->base + LRADC_CTRL);
140 
141 	writel(CHAN0_KEYUP_IRQ | CHAN0_KEYDOWN_IRQ, lradc->base + LRADC_INTC);
142 
143 	return 0;
144 }
145 
146 static void sun4i_lradc_close(struct input_dev *dev)
147 {
148 	struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
149 
150 	/* Disable lradc, leave other settings unchanged */
151 	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
152 		SAMPLE_RATE(2), lradc->base + LRADC_CTRL);
153 	writel(0, lradc->base + LRADC_INTC);
154 
155 	regulator_disable(lradc->vref_supply);
156 }
157 
158 static int sun4i_lradc_load_dt_keymap(struct device *dev,
159 				      struct sun4i_lradc_data *lradc)
160 {
161 	struct device_node *np, *pp;
162 	int i;
163 	int error;
164 
165 	np = dev->of_node;
166 	if (!np)
167 		return -EINVAL;
168 
169 	lradc->chan0_map_count = of_get_child_count(np);
170 	if (lradc->chan0_map_count == 0) {
171 		dev_err(dev, "keymap is missing in device tree\n");
172 		return -EINVAL;
173 	}
174 
175 	lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,
176 					      sizeof(struct sun4i_lradc_keymap),
177 					      GFP_KERNEL);
178 	if (!lradc->chan0_map)
179 		return -ENOMEM;
180 
181 	i = 0;
182 	for_each_child_of_node(np, pp) {
183 		struct sun4i_lradc_keymap *map = &lradc->chan0_map[i];
184 		u32 channel;
185 
186 		error = of_property_read_u32(pp, "channel", &channel);
187 		if (error || channel != 0) {
188 			dev_err(dev, "%s: Inval channel prop\n", pp->name);
189 			return -EINVAL;
190 		}
191 
192 		error = of_property_read_u32(pp, "voltage", &map->voltage);
193 		if (error) {
194 			dev_err(dev, "%s: Inval voltage prop\n", pp->name);
195 			return -EINVAL;
196 		}
197 
198 		error = of_property_read_u32(pp, "linux,code", &map->keycode);
199 		if (error) {
200 			dev_err(dev, "%s: Inval linux,code prop\n", pp->name);
201 			return -EINVAL;
202 		}
203 
204 		i++;
205 	}
206 
207 	return 0;
208 }
209 
210 static int sun4i_lradc_probe(struct platform_device *pdev)
211 {
212 	struct sun4i_lradc_data *lradc;
213 	struct device *dev = &pdev->dev;
214 	int i;
215 	int error;
216 
217 	lradc = devm_kzalloc(dev, sizeof(struct sun4i_lradc_data), GFP_KERNEL);
218 	if (!lradc)
219 		return -ENOMEM;
220 
221 	error = sun4i_lradc_load_dt_keymap(dev, lradc);
222 	if (error)
223 		return error;
224 
225 	lradc->vref_supply = devm_regulator_get(dev, "vref");
226 	if (IS_ERR(lradc->vref_supply))
227 		return PTR_ERR(lradc->vref_supply);
228 
229 	lradc->dev = dev;
230 	lradc->input = devm_input_allocate_device(dev);
231 	if (!lradc->input)
232 		return -ENOMEM;
233 
234 	lradc->input->name = pdev->name;
235 	lradc->input->phys = "sun4i_lradc/input0";
236 	lradc->input->open = sun4i_lradc_open;
237 	lradc->input->close = sun4i_lradc_close;
238 	lradc->input->id.bustype = BUS_HOST;
239 	lradc->input->id.vendor = 0x0001;
240 	lradc->input->id.product = 0x0001;
241 	lradc->input->id.version = 0x0100;
242 
243 	__set_bit(EV_KEY, lradc->input->evbit);
244 	for (i = 0; i < lradc->chan0_map_count; i++)
245 		__set_bit(lradc->chan0_map[i].keycode, lradc->input->keybit);
246 
247 	input_set_drvdata(lradc->input, lradc);
248 
249 	lradc->base = devm_ioremap_resource(dev,
250 			      platform_get_resource(pdev, IORESOURCE_MEM, 0));
251 	if (IS_ERR(lradc->base))
252 		return PTR_ERR(lradc->base);
253 
254 	error = devm_request_irq(dev, platform_get_irq(pdev, 0),
255 				 sun4i_lradc_irq, 0,
256 				 "sun4i-a10-lradc-keys", lradc);
257 	if (error)
258 		return error;
259 
260 	error = input_register_device(lradc->input);
261 	if (error)
262 		return error;
263 
264 	platform_set_drvdata(pdev, lradc);
265 	return 0;
266 }
267 
268 static const struct of_device_id sun4i_lradc_of_match[] = {
269 	{ .compatible = "allwinner,sun4i-a10-lradc-keys", },
270 	{ /* sentinel */ }
271 };
272 MODULE_DEVICE_TABLE(of, sun4i_lradc_of_match);
273 
274 static struct platform_driver sun4i_lradc_driver = {
275 	.driver = {
276 		.name	= "sun4i-a10-lradc-keys",
277 		.of_match_table = of_match_ptr(sun4i_lradc_of_match),
278 	},
279 	.probe	= sun4i_lradc_probe,
280 };
281 
282 module_platform_driver(sun4i_lradc_driver);
283 
284 MODULE_DESCRIPTION("Allwinner sun4i low res adc attached tablet keys driver");
285 MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
286 MODULE_LICENSE("GPL");
287