#include <linux/module.h>
#include <linux/init.h>
#include <linux/mod_devicetable.h>
#include <linux/property.h>
#include <linux/platform_device.h>
#include <linux/of_device.h>
#include <linux/gpio/consumer.h>
#include <linux/spi/spi.h>
#include <linux/interrupt.h>
#include <linux/of_irq.h>
#include <linux/workqueue.h>

#include "ls7366r.h"


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Wolfgang Hottgenroth");
MODULE_DESCRIPTION("A simple LKM to parse the device tree for a specific device and its properties");

/* leds stuff */
static int dt_leds_probe(struct platform_device *pdev);
static void dt_leds_remove(struct platform_device *pdev);

static struct of_device_id leds_driver_ids[] = {
  {
    .compatible = "hottis,leds",
  }, 
  {},
};
MODULE_DEVICE_TABLE(of, leds_driver_ids);

static struct platform_driver leds_driver = {
  .probe = dt_leds_probe,
  .remove = dt_leds_remove,
  .driver = {
    .name = "leds_device_driver",
    .of_match_table = leds_driver_ids,
  },
};

static struct gpio_desc *red_led = NULL;
static struct gpio_desc *blue_led = NULL;

static int dt_leds_probe(struct platform_device *pdev) {
  struct device *dev = &pdev->dev;

  printk("counter - leds probing\n");

  if(!device_property_present(dev, "red-led-gpio")) {
    printk("counter - Error! Device property 'red-led-gpio' not found!\n");
    return -1;
  }
  if(!device_property_present(dev, "blue-led-gpio")) {
    printk("counter - Error! Device property 'blue-led-gpio' not found!\n");
    return -1;
  }


  /* Init GPIO */
  red_led = gpiod_get(dev, "red-led", GPIOD_OUT_LOW);
  if(IS_ERR(red_led)) {
    printk("counter - Error! Could not setup the GPIO red-led\n");
    return -1 * IS_ERR(red_led);
  }
  blue_led = gpiod_get(dev, "blue-led", GPIOD_OUT_LOW);
  if(IS_ERR(blue_led)) {
    printk("counter - Error! Could not setup the GPIO blue-led\n");
    return -1 * IS_ERR(blue_led);
  }

  return 0;
}

static void dt_leds_remove(struct platform_device *pdev) {
  printk("counter - leds removing\n");
  gpiod_put(red_led);
  gpiod_put(blue_led);
}


/* spi stuff */
static int dt_ls7366r_probe(struct spi_device *client);
static void dt_ls7366r_remove(struct spi_device *client);

/*    LS7366R functions */
static int writeCmd(struct spi_device *client, u8 c) {
  u8 buf[1];
  buf[0] = c;
  return spi_write(client, buf, 1);
}

static int writeCmdData(struct spi_device *client, u8 c, u8 d) {
  u8 buf[2];
  buf[0] = c;
  buf[1] = d;
  return spi_write(client, buf, 2);
}

static int read32(struct spi_device *client, u8 c, u32 *r) {
  u8 tx_buf[5];
  tx_buf[0] = c;
  u8 rx_buf[5];
  struct spi_transfer t = {
    .tx_buf = tx_buf,
    .rx_buf = rx_buf,
    .len = 5,
  };
  int ret = spi_sync_transfer(client, &t, 1);
  if (ret < 0) {
    printk("counter - Error! spi_sync_transfer failed in read32\n");
    return ret;
  }
  *r = ((u32)rx_buf[1] << 24) | ((u32)rx_buf[2] << 16) | ((u32)rx_buf[3] << 8) | ((u32)rx_buf[4]);
  return 0;
}

static int read8(struct spi_device *client, u8 c, u8 *r) {
  u8 tx_buf[2];
  tx_buf[0] = c;
  u8 rx_buf[2];
  struct spi_transfer t = {
    .tx_buf = tx_buf,
    .rx_buf = rx_buf,
    .len = 2,
  };
  int ret = spi_sync_transfer(client, &t, 1);
  if (ret < 0) {
    printk("counter - Error! spi_sync_transfer failed in read8\n");
    return ret;
  }
  *r = rx_buf[1];
  return 0;
}


static struct of_device_id ls7366r_driver_ids[] = {
  {
    .compatible = "hottis,ls7366r",
  }, {}
};
MODULE_DEVICE_TABLE(of, ls7366r_driver_ids);

static struct spi_device_id ls7366r[] = {
  { "ls7366r", 0 },
  {},
};
MODULE_DEVICE_TABLE(spi, ls7366r);

static struct spi_driver ls7366r_driver = {
  .probe = dt_ls7366r_probe,
  .remove = dt_ls7366r_remove,
  .id_table = ls7366r,
  .driver = {
    .name = "ls7366r_device_driver",
    .of_match_table = ls7366r_driver_ids,
  },
};

static struct spi_device *spi_client;

static int dt_ls7366r_probe(struct spi_device *client) {
  printk("counter - ls7366r probing\n");
  
  int ret = spi_setup(client);
  if (ret < 0) {
    printk("counter - Error! Failed to set up the SPI bus\n");
    return ret;
  }

  ret = writeCmd(client, CMD_CLR | REG_STR);
  if (ret < 0) {
    printk("counter - Error! writeCmd 1 failed in probe\n");
    return ret;
  }
  ret = writeCmd(client, CMD_CLR | REG_CNTR);
  if (ret < 0) {
    printk("counter - Error! writeCmd 2 failed in probe\n");
    return ret;
  }
  ret = writeCmdData(client, CMD_WR | REG_MDR0, MDR0_ILO);
  if (ret < 0) {
    printk("counter - Error! writeCmdData failed in probe\n");
    return ret;
  }

  u8 x;
  ret = read8(client, CMD_RD | REG_MDR0, &x);
  if (ret < 0) {
    printk("counter - Error! read8 failed in probe\n");
    return ret;
  }
  if (x != MDR0_ILO) {
    printk("counter - Error! failed to initialize counter\n");
    return -1;
  }

  spi_client = client;

  return 0;
}

static void dt_ls7366r_remove(struct spi_device *client) {
  printk("counter - ls7366r removing\n");
}


/* interrupt stuff */
static int dt_interrupt_probe(struct platform_device *pdev);
static void dt_interrupt_remove(struct platform_device *pdev);

static struct of_device_id interrupt_driver_ids[] = {
  {
    .compatible = "hottis,intr",
  }, 
  {},
};
MODULE_DEVICE_TABLE(of, interrupt_driver_ids);

static struct platform_driver interrupt_driver = {
  .probe = dt_interrupt_probe,
  .remove = dt_interrupt_remove,
  .driver = {
    .name = "interrupt_device_driver",
    .of_match_table = interrupt_driver_ids,
  },
};

static struct gpio_desc *counter_interrupt;
static int irq_number;

// workqueue
struct counter_irq_data {
  struct work_struct work;
  u64 timestamp;
  struct spi_device *client;
  u64 last_timestamp;
  u32 last_value;
};
static struct counter_irq_data counter_irq_wq_data;

static void counter_worker(struct work_struct *work) {
  struct counter_irq_data *data = container_of(work, struct counter_irq_data, work);
  u64 ts = data->timestamp;

  u32 counter_value;
  int ret = read32(data->client, CMD_RD | REG_OTR, &counter_value);

  if (ret < 0) {
    printk("counter - Error! read32 failed in counter_worker\n");
    return;
  }

  if (data->last_value) {
    u32 period = counter_value - data->last_value;
    u64 duration = ts - data->last_timestamp;
    printk("counter - Info! ts = %llu, duration = %llu, period = %u\n", ts, duration, period);
  }
  data->last_value = counter_value;
  data->last_timestamp = ts;
}

// ISR
static irqreturn_t counter_isr(int irq, void *dev_id) {
  counter_irq_wq_data.timestamp = ktime_get();
  schedule_work(&counter_irq_wq_data.work);
  return IRQ_HANDLED;
}

static int dt_interrupt_probe(struct platform_device *pdev) {
  struct device *dev = &pdev->dev;

  printk("counter - interrupt probing\n");

  INIT_WORK(&counter_irq_wq_data.work, counter_worker);
  counter_irq_wq_data.client = spi_client;
  counter_irq_wq_data.last_value = 0;
  counter_irq_wq_data.last_timestamp = 0;

  counter_interrupt = gpiod_get(dev, "intr", GPIOD_IN);
  if (IS_ERR(counter_interrupt)) {
    printk("counter - Error! Could not setup the GPIO intr\n");
    return -1 * IS_ERR(counter_interrupt);
  }

  irq_number = gpiod_to_irq(counter_interrupt);
  if (irq_number < 0) {
    printk("counter - Error! Could not map GPIO to IRQ\n");
    gpiod_put(counter_interrupt);
    return irq_number;
  }
  printk("counter - Info! IRQ %d assigned\n", irq_number);

  int ret = request_irq(irq_number, counter_isr,
      IRQF_TRIGGER_RISING, "gpio19_irq", dev);
  if (ret) {
    printk("counter - Error! Could not request IRQ\n");
    gpiod_put(counter_interrupt);
    return ret;
  }

  printk("counter - Info! Interrupt assigned\n");

  return 0;
}

static void dt_interrupt_remove(struct platform_device *pdev) {
  printk("counter - interrupt removing\n");
  struct device *dev = &pdev->dev;
  free_irq(irq_number, dev);
  gpiod_put(counter_interrupt);
}



/* module loading and unloading */
static int __init my_init(void) {
  printk("counter - Loading the leds driver...\n");
  if(platform_driver_register(&leds_driver)) {
    printk("dt_gpio - Error! Could not load leds driver\n");
    return -1;
  }

  printk("counter - Loading the ls7366r driver...\n");
  if (spi_register_driver(&ls7366r_driver)) {
    printk("counter - Error! Could not load spi driver\n");
    return -1;
  }

  printk("counter - Loading the interrupt driver...\n");
  if(platform_driver_register(&interrupt_driver)) {
    printk("dt_gpio - Error! Could not load interrupt driver\n");
    return -1;
  }


  printk("counter - red led on\n");
  gpiod_set_value(red_led, 1);

  return 0;
}

static void __exit my_exit(void) {
  printk("counter - red led off\n");
  gpiod_set_value(red_led, 0);

  printk("counter - Unloading the leds driver...\n");
  platform_driver_unregister(&leds_driver);

  printk("counter - Unloading the ls7366r driver...\n");
  spi_unregister_driver(&ls7366r_driver);

  printk("counter - Unloading the interrupt driver...\n");
  platform_driver_unregister(&interrupt_driver);
}

module_init(my_init);
module_exit(my_exit);