pwm-ir-tx.c

  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/pwm.h>
  9#include <linux/delay.h>
 10#include <linux/slab.h>
 11#include <linux/of.h>
 12#include <linux/platform_device.h>
 13#include <linux/hrtimer.h>
 14#include <linux/completion.h>
 15#include <media/rc-core.h>
 16
 17#define DRIVER_NAME	"pwm-ir-tx"
 18#define DEVICE_NAME	"PWM IR Transmitter"
 19
 20struct pwm_ir {
 21	struct pwm_device *pwm;
 22	struct hrtimer timer;
 23	struct completion tx_done;
 24	struct pwm_state *state;
 25	u32 carrier;
 26	u32 duty_cycle;
 27	const unsigned int *txbuf;
 28	unsigned int txbuf_len;
 29	unsigned int txbuf_index;
 30};
 31
 32static const struct of_device_id pwm_ir_of_match[] = {
 33	{ .compatible = "pwm-ir-tx", },
 34	{ .compatible = "nokia,n900-ir" },
 35	{ },
 36};
 37MODULE_DEVICE_TABLE(of, pwm_ir_of_match);
 38
 39static int pwm_ir_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
 40{
 41	struct pwm_ir *pwm_ir = dev->priv;
 42
 43	pwm_ir->duty_cycle = duty_cycle;
 44
 45	return 0;
 46}
 47
 48static int pwm_ir_set_carrier(struct rc_dev *dev, u32 carrier)
 49{
 50	struct pwm_ir *pwm_ir = dev->priv;
 51
 52	if (!carrier)
 53		return -EINVAL;
 54
 55	pwm_ir->carrier = carrier;
 56
 57	return 0;
 58}
 59
 60static int pwm_ir_tx_sleep(struct rc_dev *dev, unsigned int *txbuf,
 61			   unsigned int count)
 62{
 63	struct pwm_ir *pwm_ir = dev->priv;
 64	struct pwm_device *pwm = pwm_ir->pwm;
 65	struct pwm_state state;
 66	int i;
 67	ktime_t edge;
 68	long delta;
 69
 70	pwm_init_state(pwm, &state);
 71
 72	state.period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, pwm_ir->carrier);
 73	pwm_set_relative_duty_cycle(&state, pwm_ir->duty_cycle, 100);
 74
 75	edge = ktime_get();
 76
 77	for (i = 0; i < count; i++) {
 78		state.enabled = !(i % 2);
 79		pwm_apply_might_sleep(pwm, &state);
 80
 81		edge = ktime_add_us(edge, txbuf[i]);
 82		delta = ktime_us_delta(edge, ktime_get());
 83		if (delta > 0)
 84			usleep_range(delta, delta + 10);
 85	}
 86
 87	state.enabled = false;
 88	pwm_apply_might_sleep(pwm, &state);
 89
 90	return count;
 91}
 92
 93static int pwm_ir_tx_atomic(struct rc_dev *dev, unsigned int *txbuf,
 94			    unsigned int count)
 95{
 96	struct pwm_ir *pwm_ir = dev->priv;
 97	struct pwm_device *pwm = pwm_ir->pwm;
 98	struct pwm_state state;
 99
100	pwm_init_state(pwm, &state);
101
102	state.period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, pwm_ir->carrier);
103	pwm_set_relative_duty_cycle(&state, pwm_ir->duty_cycle, 100);
104
105	pwm_ir->txbuf = txbuf;
106	pwm_ir->txbuf_len = count;
107	pwm_ir->txbuf_index = 0;
108	pwm_ir->state = &state;
109
110	hrtimer_start(&pwm_ir->timer, 0, HRTIMER_MODE_REL);
111
112	wait_for_completion(&pwm_ir->tx_done);
113
114	return count;
115}
116
117static enum hrtimer_restart pwm_ir_timer(struct hrtimer *timer)
118{
119	struct pwm_ir *pwm_ir = container_of(timer, struct pwm_ir, timer);
120
121	/*
122	 * If we happen to hit an odd latency spike, loop through the
123	 * pulses until we catch up.
124	 */
125	do {
126		u64 ns;
127
128		pwm_ir->state->enabled = !(pwm_ir->txbuf_index % 2);
129		pwm_apply_atomic(pwm_ir->pwm, pwm_ir->state);
130
131		if (pwm_ir->txbuf_index >= pwm_ir->txbuf_len) {
132			complete(&pwm_ir->tx_done);
133
134			return HRTIMER_NORESTART;
135		}
136
137		ns = US_TO_NS(pwm_ir->txbuf[pwm_ir->txbuf_index]);
138		hrtimer_add_expires_ns(timer, ns);
139
140		pwm_ir->txbuf_index++;
141	} while (hrtimer_expires_remaining(timer) > 0);
142
143	return HRTIMER_RESTART;
144}
145
146static int pwm_ir_probe(struct platform_device *pdev)
147{
148	struct pwm_ir *pwm_ir;
149	struct rc_dev *rcdev;
150	int rc;
151
152	pwm_ir = devm_kmalloc(&pdev->dev, sizeof(*pwm_ir), GFP_KERNEL);
153	if (!pwm_ir)
154		return -ENOMEM;
155
156	pwm_ir->pwm = devm_pwm_get(&pdev->dev, NULL);
157	if (IS_ERR(pwm_ir->pwm))
158		return PTR_ERR(pwm_ir->pwm);
159
160	pwm_ir->carrier = 38000;
161	pwm_ir->duty_cycle = 50;
162
163	rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
164	if (!rcdev)
165		return -ENOMEM;
166
167	if (pwm_might_sleep(pwm_ir->pwm)) {
168		dev_info(&pdev->dev, "TX will not be accurate as PWM device might sleep\n");
169		rcdev->tx_ir = pwm_ir_tx_sleep;
170	} else {
171		init_completion(&pwm_ir->tx_done);
172		hrtimer_setup(&pwm_ir->timer, pwm_ir_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
173		rcdev->tx_ir = pwm_ir_tx_atomic;
174	}
175
176	rcdev->priv = pwm_ir;
177	rcdev->driver_name = DRIVER_NAME;
178	rcdev->device_name = DEVICE_NAME;
179	rcdev->s_tx_duty_cycle = pwm_ir_set_duty_cycle;
180	rcdev->s_tx_carrier = pwm_ir_set_carrier;
181
182	rc = devm_rc_register_device(&pdev->dev, rcdev);
183	if (rc < 0)
184		dev_err(&pdev->dev, "failed to register rc device\n");
185
186	return rc;
187}
188
189static struct platform_driver pwm_ir_driver = {
190	.probe = pwm_ir_probe,
191	.driver = {
192		.name	= DRIVER_NAME,
193		.of_match_table = pwm_ir_of_match,
194	},
195};
196module_platform_driver(pwm_ir_driver);
197
198MODULE_DESCRIPTION("PWM IR Transmitter");
199MODULE_AUTHOR("Sean Young <sean@mess.org>");
200MODULE_LICENSE("GPL");