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