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_KEY_EN(x)		((x) << 7)
50 #define HOLD_EN(x)		((x) << 6)
51 #define LEVELB_VOL(x)		((x) << 4)  /* 2 bits */
52 #define SAMPLE_RATE(x)		((x) << 2)  /* 2 bits */
53 #define ENABLE(x)		((x) << 0)
54 
55 /* LRADC_INTC and LRADC_INTS bits */
56 #define CHAN1_KEYUP_IRQ		BIT(12)
57 #define CHAN1_ALRDY_HOLD_IRQ	BIT(11)
58 #define CHAN1_HOLD_IRQ		BIT(10)
59 #define	CHAN1_KEYDOWN_IRQ	BIT(9)
60 #define CHAN1_DATA_IRQ		BIT(8)
61 #define CHAN0_KEYUP_IRQ		BIT(4)
62 #define CHAN0_ALRDY_HOLD_IRQ	BIT(3)
63 #define CHAN0_HOLD_IRQ		BIT(2)
64 #define	CHAN0_KEYDOWN_IRQ	BIT(1)
65 #define CHAN0_DATA_IRQ		BIT(0)
66 
67 /* struct lradc_variant - Describe sun4i-a10-lradc-keys hardware variant
68  * @divisor_numerator:		The numerator of lradc Vref internally divisor
69  * @divisor_denominator:	The denominator of lradc Vref internally divisor
70  */
71 struct lradc_variant {
72 	u8 divisor_numerator;
73 	u8 divisor_denominator;
74 };
75 
76 static const struct lradc_variant lradc_variant_a10 = {
77 	.divisor_numerator = 2,
78 	.divisor_denominator = 3
79 };
80 
81 static const struct lradc_variant r_lradc_variant_a83t = {
82 	.divisor_numerator = 3,
83 	.divisor_denominator = 4
84 };
85 
86 struct sun4i_lradc_keymap {
87 	u32 voltage;
88 	u32 keycode;
89 };
90 
91 struct sun4i_lradc_data {
92 	struct device *dev;
93 	struct input_dev *input;
94 	void __iomem *base;
95 	struct regulator *vref_supply;
96 	struct sun4i_lradc_keymap *chan0_map;
97 	const struct lradc_variant *variant;
98 	u32 chan0_map_count;
99 	u32 chan0_keycode;
100 	u32 vref;
101 };
102 
103 static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
104 {
105 	struct sun4i_lradc_data *lradc = dev_id;
106 	u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
107 
108 	ints  = readl(lradc->base + LRADC_INTS);
109 
110 	/*
111 	 * lradc supports only one keypress at a time, release does not give
112 	 * any info as to which key was released, so we cache the keycode.
113 	 */
114 
115 	if (ints & CHAN0_KEYUP_IRQ) {
116 		input_report_key(lradc->input, lradc->chan0_keycode, 0);
117 		lradc->chan0_keycode = 0;
118 	}
119 
120 	if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
121 		val = readl(lradc->base + LRADC_DATA0) & 0x3f;
122 		voltage = val * lradc->vref / 63;
123 
124 		for (i = 0; i < lradc->chan0_map_count; i++) {
125 			diff = abs(lradc->chan0_map[i].voltage - voltage);
126 			if (diff < closest) {
127 				closest = diff;
128 				keycode = lradc->chan0_map[i].keycode;
129 			}
130 		}
131 
132 		lradc->chan0_keycode = keycode;
133 		input_report_key(lradc->input, lradc->chan0_keycode, 1);
134 	}
135 
136 	input_sync(lradc->input);
137 
138 	writel(ints, lradc->base + LRADC_INTS);
139 
140 	return IRQ_HANDLED;
141 }
142 
143 static int sun4i_lradc_open(struct input_dev *dev)
144 {
145 	struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
146 	int error;
147 
148 	error = regulator_enable(lradc->vref_supply);
149 	if (error)
150 		return error;
151 
152 	lradc->vref = regulator_get_voltage(lradc->vref_supply) *
153 		      lradc->variant->divisor_numerator /
154 		      lradc->variant->divisor_denominator;
155 	/*
156 	 * Set sample time to 4 ms / 250 Hz. Wait 2 * 4 ms for key to
157 	 * stabilize on press, wait (1 + 1) * 4 ms for key release
158 	 */
159 	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
160 		SAMPLE_RATE(0) | ENABLE(1), lradc->base + LRADC_CTRL);
161 
162 	writel(CHAN0_KEYUP_IRQ | CHAN0_KEYDOWN_IRQ, lradc->base + LRADC_INTC);
163 
164 	return 0;
165 }
166 
167 static void sun4i_lradc_close(struct input_dev *dev)
168 {
169 	struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
170 
171 	/* Disable lradc, leave other settings unchanged */
172 	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
173 		SAMPLE_RATE(2), lradc->base + LRADC_CTRL);
174 	writel(0, lradc->base + LRADC_INTC);
175 
176 	regulator_disable(lradc->vref_supply);
177 }
178 
179 static int sun4i_lradc_load_dt_keymap(struct device *dev,
180 				      struct sun4i_lradc_data *lradc)
181 {
182 	struct device_node *np, *pp;
183 	int i;
184 	int error;
185 
186 	np = dev->of_node;
187 	if (!np)
188 		return -EINVAL;
189 
190 	lradc->chan0_map_count = of_get_child_count(np);
191 	if (lradc->chan0_map_count == 0) {
192 		dev_err(dev, "keymap is missing in device tree\n");
193 		return -EINVAL;
194 	}
195 
196 	lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,
197 					      sizeof(struct sun4i_lradc_keymap),
198 					      GFP_KERNEL);
199 	if (!lradc->chan0_map)
200 		return -ENOMEM;
201 
202 	i = 0;
203 	for_each_child_of_node(np, pp) {
204 		struct sun4i_lradc_keymap *map = &lradc->chan0_map[i];
205 		u32 channel;
206 
207 		error = of_property_read_u32(pp, "channel", &channel);
208 		if (error || channel != 0) {
209 			dev_err(dev, "%pOFn: Inval channel prop\n", pp);
210 			return -EINVAL;
211 		}
212 
213 		error = of_property_read_u32(pp, "voltage", &map->voltage);
214 		if (error) {
215 			dev_err(dev, "%pOFn: Inval voltage prop\n", pp);
216 			return -EINVAL;
217 		}
218 
219 		error = of_property_read_u32(pp, "linux,code", &map->keycode);
220 		if (error) {
221 			dev_err(dev, "%pOFn: Inval linux,code prop\n", pp);
222 			return -EINVAL;
223 		}
224 
225 		i++;
226 	}
227 
228 	return 0;
229 }
230 
231 static int sun4i_lradc_probe(struct platform_device *pdev)
232 {
233 	struct sun4i_lradc_data *lradc;
234 	struct device *dev = &pdev->dev;
235 	int i;
236 	int error;
237 
238 	lradc = devm_kzalloc(dev, sizeof(struct sun4i_lradc_data), GFP_KERNEL);
239 	if (!lradc)
240 		return -ENOMEM;
241 
242 	error = sun4i_lradc_load_dt_keymap(dev, lradc);
243 	if (error)
244 		return error;
245 
246 	lradc->variant = of_device_get_match_data(&pdev->dev);
247 	if (!lradc->variant) {
248 		dev_err(&pdev->dev, "Missing sun4i-a10-lradc-keys variant\n");
249 		return -EINVAL;
250 	}
251 
252 	lradc->vref_supply = devm_regulator_get(dev, "vref");
253 	if (IS_ERR(lradc->vref_supply))
254 		return PTR_ERR(lradc->vref_supply);
255 
256 	lradc->dev = dev;
257 	lradc->input = devm_input_allocate_device(dev);
258 	if (!lradc->input)
259 		return -ENOMEM;
260 
261 	lradc->input->name = pdev->name;
262 	lradc->input->phys = "sun4i_lradc/input0";
263 	lradc->input->open = sun4i_lradc_open;
264 	lradc->input->close = sun4i_lradc_close;
265 	lradc->input->id.bustype = BUS_HOST;
266 	lradc->input->id.vendor = 0x0001;
267 	lradc->input->id.product = 0x0001;
268 	lradc->input->id.version = 0x0100;
269 
270 	__set_bit(EV_KEY, lradc->input->evbit);
271 	for (i = 0; i < lradc->chan0_map_count; i++)
272 		__set_bit(lradc->chan0_map[i].keycode, lradc->input->keybit);
273 
274 	input_set_drvdata(lradc->input, lradc);
275 
276 	lradc->base = devm_ioremap_resource(dev,
277 			      platform_get_resource(pdev, IORESOURCE_MEM, 0));
278 	if (IS_ERR(lradc->base))
279 		return PTR_ERR(lradc->base);
280 
281 	error = devm_request_irq(dev, platform_get_irq(pdev, 0),
282 				 sun4i_lradc_irq, 0,
283 				 "sun4i-a10-lradc-keys", lradc);
284 	if (error)
285 		return error;
286 
287 	error = input_register_device(lradc->input);
288 	if (error)
289 		return error;
290 
291 	return 0;
292 }
293 
294 static const struct of_device_id sun4i_lradc_of_match[] = {
295 	{ .compatible = "allwinner,sun4i-a10-lradc-keys",
296 		.data = &lradc_variant_a10 },
297 	{ .compatible = "allwinner,sun8i-a83t-r-lradc",
298 		.data = &r_lradc_variant_a83t },
299 	{ /* sentinel */ }
300 };
301 MODULE_DEVICE_TABLE(of, sun4i_lradc_of_match);
302 
303 static struct platform_driver sun4i_lradc_driver = {
304 	.driver = {
305 		.name	= "sun4i-a10-lradc-keys",
306 		.of_match_table = of_match_ptr(sun4i_lradc_of_match),
307 	},
308 	.probe	= sun4i_lradc_probe,
309 };
310 
311 module_platform_driver(sun4i_lradc_driver);
312 
313 MODULE_DESCRIPTION("Allwinner sun4i low res adc attached tablet keys driver");
314 MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
315 MODULE_LICENSE("GPL");
316