#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/uaccess.h>
#include <asm/io.h>

static dev_t led_dev;
static struct cdev *led_cdev;
static struct class *led_class;
static struct device *led_device;

static volatile uint32_t *RCC_PLL4CR;
static volatile uint32_t *RCC_MP_AHB4ENSETR;
static volatile uint32_t *GPIOA_MODER;
static volatile uint32_t *GPIOA_BSRR;

static int led_open(struct inode *inode, struct file *filp)
{
    *RCC_PLL4CR |= (1 << 0);
    while ((*RCC_PLL4CR & (1 << 1)) == 0);
    *RCC_MP_AHB4ENSETR |= (1 << 0);
    *GPIOA_MODER &= ~(3 << 20);
    *GPIOA_MODER |= (1 << 20);
    printk(KERN_DEBUG "LED device opened.\r\n");

    return 0;
}

static int led_close(struct inode *inode, struct file *filp)
{
    printk(KERN_DEBUG "LED device closed.\r\n");
    return 0;
}

static int led_write(struct file *filp, const char __user *buff, size_t count, loff_t *offp)
{
    char val;

    copy_from_user(&val, buff, 1);
    if (val) {
        *GPIOA_BSRR = (1 << 26);
    } else {
        *GPIOA_BSRR = (1 << 10);
    }

    return 0;
}

static int led_read(struct file *filp, char __user *buff, size_t count, loff_t *offp)
{
    return 0;
}

static struct file_operations led_ops = {
    .owner = THIS_MODULE,
    .open = led_open,
    .release = led_close,
    .write = led_write,
    .read = led_read,
};

static int __init led_init(void)
{
    int ret;

    led_cdev = cdev_alloc();
    if (led_cdev == NULL) {
        printk(KERN_ERR "Failed to allocate cdev\r\n");
        return -ENOMEM;
    }
    ret = alloc_chrdev_region(&led_dev, 0, 1, "led");
    if (ret != 0) {
        printk(KERN_ERR "Failed to allocate chrdev region\r\n");
        return ret;
    }
    led_cdev->owner = THIS_MODULE;
    led_cdev->ops = &led_ops;
    cdev_add(led_cdev, led_dev, 1);
    led_class = class_create(THIS_MODULE, "led_class");
    if (led_class == NULL) {
        printk(KERN_ERR "Failed to create class\r\n");
        return -1;
    }
    led_device = device_create(led_class, NULL, led_dev, NULL, "led0");
    if (IS_ERR(led_device)) {
        printk(KERN_ERR "Failed to create device\r\n");
        return -1;
    }
    RCC_PLL4CR = ioremap(0x50000000 + 0x894, 4);
    RCC_MP_AHB4ENSETR = ioremap(0x50000000 + 0xA28, 4);
    GPIOA_MODER = ioremap(0x50002000 + 0x00, 4);
    GPIOA_BSRR = ioremap(0x50002000 + 0x18, 4);

    return 0;
}

static void __exit led_exit(void)
{
    cdev_del(led_cdev);
    unregister_chrdev_region(led_dev, 1);
    device_destroy(led_class, led_dev);
    class_destroy(led_class);
    iounmap(RCC_PLL4CR);
    iounmap(RCC_MP_AHB4ENSETR);
    iounmap(GPIOA_MODER);
    iounmap(GPIOA_BSRR);
}

module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("jzhgonha@163.com");
MODULE_VERSION("V0.1");
MODULE_DESCRIPTION("A simple LED driver for STM32MP157");