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 delta = min(delta, 1000);
66 udelay(delta);
67 }
68 }
69
gpio_ir_tx_unmodulated(struct gpio_ir * gpio_ir,uint * txbuf,uint count)70 static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
71 uint count)
72 {
73 ktime_t edge;
74 int i;
75
76 local_irq_disable();
77
78 edge = ktime_get();
79
80 for (i = 0; i < count; i++) {
81 gpiod_set_value(gpio_ir->gpio, !(i % 2));
82
83 edge = ktime_add_us(edge, txbuf[i]);
84 delay_until(edge);
85 }
86
87 gpiod_set_value(gpio_ir->gpio, 0);
88 }
89
gpio_ir_tx_modulated(struct gpio_ir * gpio_ir,uint * txbuf,uint count)90 static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
91 uint count)
92 {
93 ktime_t edge;
94 /*
95 * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
96 * m68k ndelay(s64) does not compile; so use s32 rather than s64.
97 */
98 s32 delta;
99 int i;
100 unsigned int pulse, space;
101
102 /* Ensure the dividend fits into 32 bit */
103 pulse = DIV_ROUND_CLOSEST(gpio_ir->duty_cycle * (NSEC_PER_SEC / 100),
104 gpio_ir->carrier);
105 space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
106 (NSEC_PER_SEC / 100), gpio_ir->carrier);
107
108 local_irq_disable();
109
110 edge = ktime_get();
111
112 for (i = 0; i < count; i++) {
113 if (i % 2) {
114 // space
115 edge = ktime_add_us(edge, txbuf[i]);
116 delay_until(edge);
117 } else {
118 // pulse
119 ktime_t last = ktime_add_us(edge, txbuf[i]);
120
121 while (ktime_before(ktime_get(), last)) {
122 gpiod_set_value(gpio_ir->gpio, 1);
123 edge = ktime_add_ns(edge, pulse);
124 delta = ktime_to_ns(ktime_sub(edge,
125 ktime_get()));
126 if (delta > 0)
127 ndelay(delta);
128 gpiod_set_value(gpio_ir->gpio, 0);
129 edge = ktime_add_ns(edge, space);
130 delta = ktime_to_ns(ktime_sub(edge,
131 ktime_get()));
132 if (delta > 0)
133 ndelay(delta);
134 }
135
136 edge = last;
137 }
138 }
139 }
140
gpio_ir_tx(struct rc_dev * dev,unsigned int * txbuf,unsigned int count)141 static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
142 unsigned int count)
143 {
144 struct gpio_ir *gpio_ir = dev->priv;
145 unsigned long flags;
146
147 local_irq_save(flags);
148 if (gpio_ir->carrier)
149 gpio_ir_tx_modulated(gpio_ir, txbuf, count);
150 else
151 gpio_ir_tx_unmodulated(gpio_ir, txbuf, count);
152 local_irq_restore(flags);
153
154 return count;
155 }
156
gpio_ir_tx_probe(struct platform_device * pdev)157 static int gpio_ir_tx_probe(struct platform_device *pdev)
158 {
159 struct gpio_ir *gpio_ir;
160 struct rc_dev *rcdev;
161 int rc;
162
163 gpio_ir = devm_kmalloc(&pdev->dev, sizeof(*gpio_ir), GFP_KERNEL);
164 if (!gpio_ir)
165 return -ENOMEM;
166
167 rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
168 if (!rcdev)
169 return -ENOMEM;
170
171 gpio_ir->gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
172 if (IS_ERR(gpio_ir->gpio)) {
173 if (PTR_ERR(gpio_ir->gpio) != -EPROBE_DEFER)
174 dev_err(&pdev->dev, "Failed to get gpio (%ld)\n",
175 PTR_ERR(gpio_ir->gpio));
176 return PTR_ERR(gpio_ir->gpio);
177 }
178
179 rcdev->priv = gpio_ir;
180 rcdev->driver_name = DRIVER_NAME;
181 rcdev->device_name = DEVICE_NAME;
182 rcdev->tx_ir = gpio_ir_tx;
183 rcdev->s_tx_duty_cycle = gpio_ir_tx_set_duty_cycle;
184 rcdev->s_tx_carrier = gpio_ir_tx_set_carrier;
185
186 gpio_ir->carrier = 38000;
187 gpio_ir->duty_cycle = 50;
188
189 rc = devm_rc_register_device(&pdev->dev, rcdev);
190 if (rc < 0)
191 dev_err(&pdev->dev, "failed to register rc device\n");
192
193 return rc;
194 }
195
196 static struct platform_driver gpio_ir_tx_driver = {
197 .probe = gpio_ir_tx_probe,
198 .driver = {
199 .name = DRIVER_NAME,
200 .of_match_table = of_match_ptr(gpio_ir_tx_of_match),
201 },
202 };
203 module_platform_driver(gpio_ir_tx_driver);
204
205 MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
206 MODULE_AUTHOR("Sean Young <sean@mess.org>");
207 MODULE_LICENSE("GPL");
208