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