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};
23
24static const struct of_device_id gpio_ir_tx_of_match[] = {
25	{ .compatible = "gpio-ir-tx", },
26	{ },
27};
28MODULE_DEVICE_TABLE(of, gpio_ir_tx_of_match);
29
30static 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
39static 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
51static 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
70static 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
90static 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
141static 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
157static 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
196static 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};
203module_platform_driver(gpio_ir_tx_driver);
204
205MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
206MODULE_AUTHOR("Sean Young <sean@mess.org>");
207MODULE_LICENSE("GPL");
208