1 /*
2 * Copyright (C) 2017 Sean Young <sean@mess.org>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2, or
6 * (at your option) any later version.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 */
13
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/gpio/consumer.h>
17 #include <linux/delay.h>
18 #include <linux/slab.h>
19 #include <linux/of.h>
20 #include <linux/platform_device.h>
21 #include <media/rc-core.h>
22
23 #define DRIVER_NAME "gpio-ir-tx"
24 #define DEVICE_NAME "GPIO IR Bit Banging Transmitter"
25
26 struct gpio_ir {
27 struct gpio_desc *gpio;
28 unsigned int carrier;
29 unsigned int duty_cycle;
30 /* we need a spinlock to hold the cpu while transmitting */
31 spinlock_t lock;
32 };
33
34 static const struct of_device_id gpio_ir_tx_of_match[] = {
35 { .compatible = "gpio-ir-tx", },
36 { },
37 };
38 MODULE_DEVICE_TABLE(of, gpio_ir_tx_of_match);
39
gpio_ir_tx_set_duty_cycle(struct rc_dev * dev,u32 duty_cycle)40 static int gpio_ir_tx_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
41 {
42 struct gpio_ir *gpio_ir = dev->priv;
43
44 gpio_ir->duty_cycle = duty_cycle;
45
46 return 0;
47 }
48
gpio_ir_tx_set_carrier(struct rc_dev * dev,u32 carrier)49 static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier)
50 {
51 struct gpio_ir *gpio_ir = dev->priv;
52
53 if (!carrier)
54 return -EINVAL;
55
56 gpio_ir->carrier = carrier;
57
58 return 0;
59 }
60
gpio_ir_tx(struct rc_dev * dev,unsigned int * txbuf,unsigned int count)61 static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
62 unsigned int count)
63 {
64 struct gpio_ir *gpio_ir = dev->priv;
65 unsigned long flags;
66 ktime_t edge;
67 /*
68 * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
69 * m68k ndelay(s64) does not compile; so use s32 rather than s64.
70 */
71 s32 delta;
72 int i;
73 unsigned int pulse, space;
74
75 /* Ensure the dividend fits into 32 bit */
76 pulse = DIV_ROUND_CLOSEST(gpio_ir->duty_cycle * (NSEC_PER_SEC / 100),
77 gpio_ir->carrier);
78 space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
79 (NSEC_PER_SEC / 100), gpio_ir->carrier);
80
81 spin_lock_irqsave(&gpio_ir->lock, flags);
82
83 edge = ktime_get();
84
85 for (i = 0; i < count; i++) {
86 if (i % 2) {
87 // space
88 edge = ktime_add_us(edge, txbuf[i]);
89 delta = ktime_us_delta(edge, ktime_get());
90 if (delta > 0)
91 udelay(delta);
92 } else {
93 // pulse
94 ktime_t last = ktime_add_us(edge, txbuf[i]);
95
96 while (ktime_before(ktime_get(), last)) {
97 gpiod_set_value(gpio_ir->gpio, 1);
98 edge = ktime_add_ns(edge, pulse);
99 delta = ktime_to_ns(ktime_sub(edge,
100 ktime_get()));
101 if (delta > 0)
102 ndelay(delta);
103 gpiod_set_value(gpio_ir->gpio, 0);
104 edge = ktime_add_ns(edge, space);
105 delta = ktime_to_ns(ktime_sub(edge,
106 ktime_get()));
107 if (delta > 0)
108 ndelay(delta);
109 }
110
111 edge = last;
112 }
113 }
114
115 spin_unlock_irqrestore(&gpio_ir->lock, flags);
116
117 return count;
118 }
119
gpio_ir_tx_probe(struct platform_device * pdev)120 static int gpio_ir_tx_probe(struct platform_device *pdev)
121 {
122 struct gpio_ir *gpio_ir;
123 struct rc_dev *rcdev;
124 int rc;
125
126 gpio_ir = devm_kmalloc(&pdev->dev, sizeof(*gpio_ir), GFP_KERNEL);
127 if (!gpio_ir)
128 return -ENOMEM;
129
130 rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
131 if (!rcdev)
132 return -ENOMEM;
133
134 gpio_ir->gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
135 if (IS_ERR(gpio_ir->gpio)) {
136 if (PTR_ERR(gpio_ir->gpio) != -EPROBE_DEFER)
137 dev_err(&pdev->dev, "Failed to get gpio (%ld)\n",
138 PTR_ERR(gpio_ir->gpio));
139 return PTR_ERR(gpio_ir->gpio);
140 }
141
142 rcdev->priv = gpio_ir;
143 rcdev->driver_name = DRIVER_NAME;
144 rcdev->device_name = DEVICE_NAME;
145 rcdev->tx_ir = gpio_ir_tx;
146 rcdev->s_tx_duty_cycle = gpio_ir_tx_set_duty_cycle;
147 rcdev->s_tx_carrier = gpio_ir_tx_set_carrier;
148
149 gpio_ir->carrier = 38000;
150 gpio_ir->duty_cycle = 50;
151 spin_lock_init(&gpio_ir->lock);
152
153 rc = devm_rc_register_device(&pdev->dev, rcdev);
154 if (rc < 0)
155 dev_err(&pdev->dev, "failed to register rc device\n");
156
157 return rc;
158 }
159
160 static struct platform_driver gpio_ir_tx_driver = {
161 .probe = gpio_ir_tx_probe,
162 .driver = {
163 .name = DRIVER_NAME,
164 .of_match_table = of_match_ptr(gpio_ir_tx_of_match),
165 },
166 };
167 module_platform_driver(gpio_ir_tx_driver);
168
169 MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
170 MODULE_AUTHOR("Sean Young <sean@mess.org>");
171 MODULE_LICENSE("GPL");
172