// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2017 Sean Young <sean@mess.org>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pwm.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/hrtimer.h>
#include <linux/completion.h>
#include <media/rc-core.h>

#define DRIVER_NAME     "pwm-ir-tx"
#define DEVICE_NAME     "PWM IR Transmitter"

struct pwm_ir {
        struct pwm_device *pwm;
        struct hrtimer timer;
        struct completion tx_done;
        struct pwm_state *state;
        u32 carrier;
        u32 duty_cycle;
        const unsigned int *txbuf;
        unsigned int txbuf_len;
        unsigned int txbuf_index;
};

static const struct of_device_id pwm_ir_of_match[] = {
        { .compatible = "pwm-ir-tx", },
        { .compatible = "nokia,n900-ir" },
        { },
};
MODULE_DEVICE_TABLE(of, pwm_ir_of_match);

static int pwm_ir_set_duty_cycle(struct rc_dev *dev, u32 duty_cycle)
{
        struct pwm_ir *pwm_ir = dev->priv;

        pwm_ir->duty_cycle = duty_cycle;

        return 0;
}

static int pwm_ir_set_carrier(struct rc_dev *dev, u32 carrier)
{
        struct pwm_ir *pwm_ir = dev->priv;

        if (!carrier)
                return -EINVAL;

        pwm_ir->carrier = carrier;

        return 0;
}

static int pwm_ir_tx_sleep(struct rc_dev *dev, unsigned int *txbuf,
                           unsigned int count)
{
        struct pwm_ir *pwm_ir = dev->priv;
        struct pwm_device *pwm = pwm_ir->pwm;
        struct pwm_state state;
        int i;
        ktime_t edge;
        long delta;

        pwm_init_state(pwm, &state);

        state.period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, pwm_ir->carrier);
        pwm_set_relative_duty_cycle(&state, pwm_ir->duty_cycle, 100);

        edge = ktime_get();

        for (i = 0; i < count; i++) {
                state.enabled = !(i % 2);
                pwm_apply_might_sleep(pwm, &state);

                edge = ktime_add_us(edge, txbuf[i]);
                delta = ktime_us_delta(edge, ktime_get());
                if (delta > 0)
                        usleep_range(delta, delta + 10);
        }

        state.enabled = false;
        pwm_apply_might_sleep(pwm, &state);

        return count;
}

static int pwm_ir_tx_atomic(struct rc_dev *dev, unsigned int *txbuf,
                            unsigned int count)
{
        struct pwm_ir *pwm_ir = dev->priv;
        struct pwm_device *pwm = pwm_ir->pwm;
        struct pwm_state state;

        pwm_init_state(pwm, &state);

        state.period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, pwm_ir->carrier);
        pwm_set_relative_duty_cycle(&state, pwm_ir->duty_cycle, 100);

        pwm_ir->txbuf = txbuf;
        pwm_ir->txbuf_len = count;
        pwm_ir->txbuf_index = 0;
        pwm_ir->state = &state;

        hrtimer_start(&pwm_ir->timer, 0, HRTIMER_MODE_REL);

        wait_for_completion(&pwm_ir->tx_done);

        return count;
}

static enum hrtimer_restart pwm_ir_timer(struct hrtimer *timer)
{
        struct pwm_ir *pwm_ir = container_of(timer, struct pwm_ir, timer);

        /*
         * If we happen to hit an odd latency spike, loop through the
         * pulses until we catch up.
         */
        do {
                u64 ns;

                pwm_ir->state->enabled = !(pwm_ir->txbuf_index % 2);
                pwm_apply_atomic(pwm_ir->pwm, pwm_ir->state);

                if (pwm_ir->txbuf_index >= pwm_ir->txbuf_len) {
                        complete(&pwm_ir->tx_done);

                        return HRTIMER_NORESTART;
                }

                ns = US_TO_NS(pwm_ir->txbuf[pwm_ir->txbuf_index]);
                hrtimer_add_expires_ns(timer, ns);

                pwm_ir->txbuf_index++;
        } while (hrtimer_expires_remaining(timer) > 0);

        return HRTIMER_RESTART;
}

static int pwm_ir_probe(struct platform_device *pdev)
{
        struct pwm_ir *pwm_ir;
        struct rc_dev *rcdev;
        int rc;

        pwm_ir = devm_kmalloc(&pdev->dev, sizeof(*pwm_ir), GFP_KERNEL);
        if (!pwm_ir)
                return -ENOMEM;

        pwm_ir->pwm = devm_pwm_get(&pdev->dev, NULL);
        if (IS_ERR(pwm_ir->pwm))
                return PTR_ERR(pwm_ir->pwm);

        pwm_ir->carrier = 38000;
        pwm_ir->duty_cycle = 50;

        rcdev = devm_rc_allocate_device(&pdev->dev, RC_DRIVER_IR_RAW_TX);
        if (!rcdev)
                return -ENOMEM;

        if (pwm_might_sleep(pwm_ir->pwm)) {
                dev_info(&pdev->dev, "TX will not be accurate as PWM device might sleep\n");
                rcdev->tx_ir = pwm_ir_tx_sleep;
        } else {
                init_completion(&pwm_ir->tx_done);
                hrtimer_setup(&pwm_ir->timer, pwm_ir_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
                rcdev->tx_ir = pwm_ir_tx_atomic;
        }

        rcdev->priv = pwm_ir;
        rcdev->driver_name = DRIVER_NAME;
        rcdev->device_name = DEVICE_NAME;
        rcdev->s_tx_duty_cycle = pwm_ir_set_duty_cycle;
        rcdev->s_tx_carrier = pwm_ir_set_carrier;

        rc = devm_rc_register_device(&pdev->dev, rcdev);
        if (rc < 0)
                dev_err(&pdev->dev, "failed to register rc device\n");

        return rc;
}

static struct platform_driver pwm_ir_driver = {
        .probe = pwm_ir_probe,
        .driver = {
                .name   = DRIVER_NAME,
                .of_match_table = pwm_ir_of_match,
        },
};
module_platform_driver(pwm_ir_driver);

MODULE_DESCRIPTION("PWM IR Transmitter");
MODULE_AUTHOR("Sean Young <sean@mess.org>");
MODULE_LICENSE("GPL");