1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2017 Sean Young <sean@mess.org>
4 */
5
6 #include <linux/kernel.h>
7 #include <linux/module.h>
8 #include <linux/gpio/consumer.h>
9 #include <linux/delay.h>
10 #include <linux/slab.h>
11 #include <linux/of.h>
12 #include <linux/platform_device.h>
13 #include <media/rc-core.h>
14
15 #define DRIVER_NAME "gpio-ir-tx"
16 #define DEVICE_NAME "GPIO IR Bit Banging Transmitter"
17
18 struct gpio_ir {
19 struct gpio_desc *gpio;
20 unsigned int carrier;
21 unsigned int duty_cycle;
22 };
23
24 static const struct of_device_id gpio_ir_tx_of_match[] = {
25 { .compatible = "gpio-ir-tx", },
26 { },
27 };
28 MODULE_DEVICE_TABLE(of, gpio_ir_tx_of_match);
29
gpio_ir_tx_set_duty_cycle(struct rc_dev * dev,u32 duty_cycle)30 static int gpio_ir_tx_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
31 {
32 struct gpio_ir *gpio_ir = dev->priv;
33
34 gpio_ir->duty_cycle = duty_cycle;
35
36 return 0;
37 }
38
gpio_ir_tx_set_carrier(struct rc_dev * dev,u32 carrier)39 static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier)
40 {
41 struct gpio_ir *gpio_ir = dev->priv;
42
43 if (carrier > 500000)
44 return -EINVAL;
45
46 gpio_ir->carrier = carrier;
47
48 return 0;
49 }
50
delay_until(ktime_t until)51 static void delay_until(ktime_t until)
52 {
53 /*
54 * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
55 * m68k ndelay(s64) does not compile; so use s32 rather than s64.
56 */
57 s32 delta;
58
59 while (true) {
60 delta = ktime_us_delta(until, ktime_get());
61 if (delta <= 0)
62 return;
63
64 /* udelay more than 1ms may not work */
65 if (delta >= 1000) {
66 mdelay(delta / 1000);
67 continue;
68 }
69
70 udelay(delta);
71 break;
72 }
73 }
74
gpio_ir_tx_unmodulated(struct gpio_ir * gpio_ir,uint * txbuf,uint count)75 static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
76 uint count)
77 {
78 ktime_t edge;
79 int i;
80
81 local_irq_disable();
82
83 edge = ktime_get();
84
85 for (i = 0; i < count; i++) {
86 gpiod_set_value(gpio_ir->gpio, !(i % 2));
87
88 edge = ktime_add_us(edge, txbuf[i]);
89 delay_until(edge);
90 }
91
92 gpiod_set_value(gpio_ir->gpio, 0);
93 }
94
gpio_ir_tx_modulated(struct gpio_ir * gpio_ir,uint * txbuf,uint count)95 static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
96 uint count)
97 {
98 ktime_t edge;
99 /*
100 * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
101 * m68k ndelay(s64) does not compile; so use s32 rather than s64.
102 */
103 s32 delta;
104 int i;
105 unsigned int pulse, space;
106
107 /* Ensure the dividend fits into 32 bit */
108 pulse = DIV_ROUND_CLOSEST(gpio_ir->duty_cycle * (NSEC_PER_SEC / 100),
109 gpio_ir->carrier);
110 space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
111 (NSEC_PER_SEC / 100), gpio_ir->carrier);
112
113 local_irq_disable();
114
115 edge = ktime_get();
116
117 for (i = 0; i < count; i++) {
118 if (i % 2) {
119 // space
120 edge = ktime_add_us(edge, txbuf[i]);
121 delay_until(edge);
122 } else {
123 // pulse
124 ktime_t last = ktime_add_us(edge, txbuf[i]);
125
126 while (ktime_before(ktime_get(), last)) {
127 gpiod_set_value(gpio_ir->gpio, 1);
128 edge = ktime_add_ns(edge, pulse);
129 delta = ktime_to_ns(ktime_sub(edge,
130 ktime_get()));
131 if (delta > 0)
132 ndelay(delta);
133 gpiod_set_value(gpio_ir->gpio, 0);
134 edge = ktime_add_ns(edge, space);
135 delta = ktime_to_ns(ktime_sub(edge,
136 ktime_get()));
137 if (delta > 0)
138 ndelay(delta);
139 }
140
141 edge = last;
142 }
143 }
144 }
145
gpio_ir_tx(struct rc_dev * dev,unsigned int * txbuf,unsigned int count)146 static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
147 unsigned int count)
148 {
149 struct gpio_ir *gpio_ir = dev->priv;
150 unsigned long flags;
151
152 local_irq_save(flags);
153 if (gpio_ir->carrier)
154 gpio_ir_tx_modulated(gpio_ir, txbuf, count);
155 else
156 gpio_ir_tx_unmodulated(gpio_ir, txbuf, count);
157 local_irq_restore(flags);
158
159 return count;
160 }
161
gpio_ir_tx_probe(struct platform_device * pdev)162 static int gpio_ir_tx_probe(struct platform_device *pdev)
163 {
164 struct gpio_ir *gpio_ir;
165 struct rc_dev *rcdev;
166 int rc;
167
168 gpio_ir = devm_kmalloc(&pdev->dev, sizeof(*gpio_ir), GFP_KERNEL);
169 if (!gpio_ir)
170 return -ENOMEM;
171
172 rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
173 if (!rcdev)
174 return -ENOMEM;
175
176 gpio_ir->gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
177 if (IS_ERR(gpio_ir->gpio))
178 return dev_err_probe(&pdev->dev, PTR_ERR(gpio_ir->gpio),
179 "Failed to get gpio\n");
180
181 rcdev->priv = gpio_ir;
182 rcdev->driver_name = DRIVER_NAME;
183 rcdev->device_name = DEVICE_NAME;
184 rcdev->tx_ir = gpio_ir_tx;
185 rcdev->s_tx_duty_cycle = gpio_ir_tx_set_duty_cycle;
186 rcdev->s_tx_carrier = gpio_ir_tx_set_carrier;
187
188 gpio_ir->carrier = 38000;
189 gpio_ir->duty_cycle = 50;
190
191 rc = devm_rc_register_device(&pdev->dev, rcdev);
192 if (rc < 0)
193 dev_err(&pdev->dev, "failed to register rc device\n");
194
195 return rc;
196 }
197
198 static struct platform_driver gpio_ir_tx_driver = {
199 .probe = gpio_ir_tx_probe,
200 .driver = {
201 .name = DRIVER_NAME,
202 .of_match_table = gpio_ir_tx_of_match,
203 },
204 };
205 module_platform_driver(gpio_ir_tx_driver);
206
207 MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
208 MODULE_AUTHOR("Sean Young <sean@mess.org>");
209 MODULE_LICENSE("GPL");
210
