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	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
 95static 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
146static 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
162static 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
198static struct platform_driver gpio_ir_tx_driver = {
199	.probe	= gpio_ir_tx_probe,
200	.driver = {
201		.name	= DRIVER_NAME,
202		.of_match_table = of_match_ptr(gpio_ir_tx_of_match),
203	},
204};
205module_platform_driver(gpio_ir_tx_driver);
206
207MODULE_DESCRIPTION("GPIO IR Bit Banging Transmitter");
208MODULE_AUTHOR("Sean Young <sean@mess.org>");
209MODULE_LICENSE("GPL");