1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2021 Samsung Electronics Co., Ltd.
4 * http://www.samsung.com
5 * Author: Marek Szyprowski <m.szyprowski@samsung.com>
6 */
7
8 #include <common.h>
9 #include <adc.h>
10 #include <button.h>
11 #include <log.h>
12 #include <dm.h>
13 #include <dm/lists.h>
14 #include <dm/of_access.h>
15 #include <dm/uclass-internal.h>
16
17 /**
18 * struct button_adc_priv - private data for button-adc driver.
19 *
20 * @adc: Analog to Digital Converter device to which button is connected.
21 * @channel: channel of the ADC device to probe the button state.
22 * @min: minimal uV value to consider button as pressed.
23 * @max: maximal uV value to consider button as pressed.
24 */
25 struct button_adc_priv {
26 struct udevice *adc;
27 int channel;
28 int min;
29 int max;
30 };
31
button_adc_get_state(struct udevice * dev)32 static enum button_state_t button_adc_get_state(struct udevice *dev)
33 {
34 struct button_adc_priv *priv = dev_get_priv(dev);
35 unsigned int val;
36 int ret, uV;
37
38 ret = adc_start_channel(priv->adc, priv->channel);
39 if (ret)
40 return ret;
41
42 ret = adc_channel_data(priv->adc, priv->channel, &val);
43 if (ret)
44 return ret;
45
46 ret = adc_raw_to_uV(priv->adc, val, &uV);
47 if (ret)
48 return ret;
49
50 return (uV >= priv->min && uV < priv->max) ? BUTTON_ON : BUTTON_OFF;
51 }
52
button_adc_of_to_plat(struct udevice * dev)53 static int button_adc_of_to_plat(struct udevice *dev)
54 {
55 struct button_uc_plat *uc_plat = dev_get_uclass_plat(dev);
56 struct button_adc_priv *priv = dev_get_priv(dev);
57 struct ofnode_phandle_args args;
58 u32 down_threshold = 0, up_threshold, voltage, t;
59 ofnode node;
60 int ret;
61
62 /* Ignore the top-level button node */
63 if (!uc_plat->label)
64 return 0;
65
66 ret = dev_read_phandle_with_args(dev->parent, "io-channels",
67 "#io-channel-cells", 0, 0, &args);
68 if (ret)
69 return ret;
70
71 ret = uclass_get_device_by_ofnode(UCLASS_ADC, args.node, &priv->adc);
72 if (ret)
73 return ret;
74
75 ret = ofnode_read_u32(dev_ofnode(dev->parent),
76 "keyup-threshold-microvolt", &up_threshold);
77 if (ret)
78 return ret;
79
80 ret = ofnode_read_u32(dev_ofnode(dev), "press-threshold-microvolt",
81 &voltage);
82 if (ret)
83 return ret;
84
85 dev_for_each_subnode(node, dev->parent) {
86 ret = ofnode_read_u32(node, "press-threshold-microvolt", &t);
87 if (ret)
88 return ret;
89
90 if (t > voltage && t < up_threshold)
91 up_threshold = t;
92 else if (t < voltage && t > down_threshold)
93 down_threshold = t;
94 }
95
96 priv->channel = args.args[0];
97
98 /*
99 * Define the voltage range such that the button is only pressed
100 * when the voltage is closest to its own press-threshold-microvolt
101 */
102 if (down_threshold == 0)
103 priv->min = 0;
104 else
105 priv->min = down_threshold + (voltage - down_threshold) / 2;
106
107 priv->max = voltage + (up_threshold - voltage) / 2;
108
109 return ret;
110 }
111
button_adc_bind(struct udevice * parent)112 static int button_adc_bind(struct udevice *parent)
113 {
114 struct udevice *dev;
115 ofnode node;
116 int ret;
117
118 dev_for_each_subnode(node, parent) {
119 struct button_uc_plat *uc_plat;
120 const char *label;
121
122 label = ofnode_read_string(node, "label");
123 if (!label) {
124 debug("%s: node %s has no label\n", __func__,
125 ofnode_get_name(node));
126 return -EINVAL;
127 }
128 ret = device_bind_driver_to_node(parent, "button_adc",
129 ofnode_get_name(node),
130 node, &dev);
131 if (ret)
132 return ret;
133 uc_plat = dev_get_uclass_plat(dev);
134 uc_plat->label = label;
135 }
136
137 return 0;
138 }
139
140 static const struct button_ops button_adc_ops = {
141 .get_state = button_adc_get_state,
142 };
143
144 static const struct udevice_id button_adc_ids[] = {
145 { .compatible = "adc-keys" },
146 { }
147 };
148
149 U_BOOT_DRIVER(button_adc) = {
150 .name = "button_adc",
151 .id = UCLASS_BUTTON,
152 .of_match = button_adc_ids,
153 .ops = &button_adc_ops,
154 .priv_auto = sizeof(struct button_adc_priv),
155 .bind = button_adc_bind,
156 .of_to_plat = button_adc_of_to_plat,
157 };
158