// 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/gpio/consumer.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <media/rc-core.h>

#define DRIVER_NAME     "gpio-ir-tx"
#define DEVICE_NAME     "GPIO IR Bit Banging Transmitter"

struct gpio_ir {
        struct gpio_desc *gpio;
        unsigned int carrier;
        unsigned int duty_cycle;
};

static const struct of_device_id gpio_ir_tx_of_match[] = {
        { .compatible = "gpio-ir-tx", },
        { },
};
MODULE_DEVICE_TABLE(of, gpio_ir_tx_of_match);

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

        gpio_ir->duty_cycle = duty_cycle;

        return 0;
}

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

        if (carrier > 500000)
                return -EINVAL;

        gpio_ir->carrier = carrier;

        return 0;
}

static void delay_until(ktime_t until)
{
        /*
         * delta should never exceed 1 second (IR_MAX_DURATION) and on
         * m68k ndelay(s64) does not compile; so use s32 rather than s64.
         */
        s32 delta;

        while (true) {
                delta = ktime_us_delta(until, ktime_get());
                if (delta <= 0)
                        return;

                /* udelay more than 1ms may not work */
                if (delta >= 1000) {
                        mdelay(delta / 1000);
                        continue;
                }

                udelay(delta);
                break;
        }
}

static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
                                   uint count)
{
        ktime_t edge;
        int i;

        edge = ktime_get();

        for (i = 0; i < count; i++) {
                gpiod_set_value(gpio_ir->gpio, !(i % 2));

                edge = ktime_add_us(edge, txbuf[i]);
                delay_until(edge);
        }

        gpiod_set_value(gpio_ir->gpio, 0);
}

static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
                                 uint count)
{
        ktime_t edge;
        /*
         * delta should never exceed 1 second (IR_MAX_DURATION) and on
         * m68k ndelay(s64) does not compile; so use s32 rather than s64.
         */
        s32 delta;
        int i;
        unsigned int pulse, space;

        /* Ensure the dividend fits into 32 bit */
        pulse = DIV_ROUND_CLOSEST(gpio_ir->duty_cycle * (NSEC_PER_SEC / 100),
                                  gpio_ir->carrier);
        space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
                                  (NSEC_PER_SEC / 100), gpio_ir->carrier);

        edge = ktime_get();

        for (i = 0; i < count; i++) {
                if (i % 2) {
                        // space
                        edge = ktime_add_us(edge, txbuf[i]);
                        delay_until(edge);
                } else {
                        // pulse
                        ktime_t last = ktime_add_us(edge, txbuf[i]);

                        while (ktime_before(ktime_get(), last)) {
                                gpiod_set_value(gpio_ir->gpio, 1);
                                edge = ktime_add_ns(edge, pulse);
                                delta = ktime_to_ns(ktime_sub(edge,
                                                              ktime_get()));
                                if (delta > 0)
                                        ndelay(delta);
                                gpiod_set_value(gpio_ir->gpio, 0);
                                edge = ktime_add_ns(edge, space);
                                delta = ktime_to_ns(ktime_sub(edge,
                                                              ktime_get()));
                                if (delta > 0)
                                        ndelay(delta);
                        }

                        edge = last;
                }
        }
}

static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
                      unsigned int count)
{
        struct gpio_ir *gpio_ir = dev->priv;
        unsigned long flags;

        local_irq_save(flags);
        if (gpio_ir->carrier)
                gpio_ir_tx_modulated(gpio_ir, txbuf, count);
        else
                gpio_ir_tx_unmodulated(gpio_ir, txbuf, count);
        local_irq_restore(flags);

        return count;
}

static int gpio_ir_tx_probe(struct platform_device *pdev)
{
        struct gpio_ir *gpio_ir;
        struct rc_dev *rcdev;
        int rc;

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

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

        gpio_ir->gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
        if (IS_ERR(gpio_ir->gpio))
                return dev_err_probe(&pdev->dev, PTR_ERR(gpio_ir->gpio),
                                     "Failed to get gpio\n");

        rcdev->priv = gpio_ir;
        rcdev->driver_name = DRIVER_NAME;
        rcdev->device_name = DEVICE_NAME;
        rcdev->tx_ir = gpio_ir_tx;
        rcdev->s_tx_duty_cycle = gpio_ir_tx_set_duty_cycle;
        rcdev->s_tx_carrier = gpio_ir_tx_set_carrier;

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

        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 gpio_ir_tx_driver = {
        .probe  = gpio_ir_tx_probe,
        .driver = {
                .name   = DRIVER_NAME,
                .of_match_table = gpio_ir_tx_of_match,
        },
};
module_platform_driver(gpio_ir_tx_driver);

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