// SPDX-License-Identifier: GPL-2.0-only

  /*
   * GPIO driver for Exar XR17V35X chip
   *
   * Copyright (C) 2015 Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>

   */
  #include <linux/bitops.h>
  #include <linux/device.h>
  #include <linux/gpio/driver.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/pci.h>
  #include <linux/platform_device.h>
  
  #define EXAR_OFFSET_MPIOLVL_LO 0x90
  #define EXAR_OFFSET_MPIOSEL_LO 0x93
  #define EXAR_OFFSET_MPIOLVL_HI 0x96
  #define EXAR_OFFSET_MPIOSEL_HI 0x99
  
  #define DRIVER_NAME "gpio_exar"
  
  static DEFINE_IDA(ida_index);
  
  struct exar_gpio_chip {
  	struct gpio_chip gpio_chip;
  	struct mutex lock;
  	int index;
  	void __iomem *regs;
  	char name[20];

  	unsigned int first_pin;

  };
  
  static void exar_update(struct gpio_chip *chip, unsigned int reg, int val,
  			unsigned int offset)
  {
  	struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
  	int temp;
  
  	mutex_lock(&exar_gpio->lock);
  	temp = readb(exar_gpio->regs + reg);
  	temp &= ~BIT(offset);
  	if (val)
  		temp |= BIT(offset);
  	writeb(temp, exar_gpio->regs + reg);
  	mutex_unlock(&exar_gpio->lock);
  }
  
  static int exar_set_direction(struct gpio_chip *chip, int direction,
  			      unsigned int offset)
  {

  	struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
  	unsigned int addr = (offset + exar_gpio->first_pin) / 8 ?
  		EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
  	unsigned int bit  = (offset + exar_gpio->first_pin) % 8;

  	exar_update(chip, addr, direction, bit);

  	return 0;
  }

  static int exar_get(struct gpio_chip *chip, unsigned int reg)
  {
  	struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
  	int value;
  
  	mutex_lock(&exar_gpio->lock);
  	value = readb(exar_gpio->regs + reg);
  	mutex_unlock(&exar_gpio->lock);

  	return value;

  }
  
  static int exar_get_direction(struct gpio_chip *chip, unsigned int offset)
  {

  	struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
  	unsigned int addr = (offset + exar_gpio->first_pin) / 8 ?
  		EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
  	unsigned int bit  = (offset + exar_gpio->first_pin) % 8;

  	if (exar_get(chip, addr) & BIT(bit))
  		return GPIO_LINE_DIRECTION_IN;
  
  	return GPIO_LINE_DIRECTION_OUT;

  }
  
  static int exar_get_value(struct gpio_chip *chip, unsigned int offset)
  {

  	struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
  	unsigned int addr = (offset + exar_gpio->first_pin) / 8 ?
  		EXAR_OFFSET_MPIOLVL_HI : EXAR_OFFSET_MPIOLVL_LO;
  	unsigned int bit  = (offset + exar_gpio->first_pin) % 8;

  	return !!(exar_get(chip, addr) & BIT(bit));

  }
  
  static void exar_set_value(struct gpio_chip *chip, unsigned int offset,
  			   int value)
  {

  	struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip);
  	unsigned int addr = (offset + exar_gpio->first_pin) / 8 ?
  		EXAR_OFFSET_MPIOLVL_HI : EXAR_OFFSET_MPIOLVL_LO;
  	unsigned int bit  = (offset + exar_gpio->first_pin) % 8;

  	exar_update(chip, addr, value, bit);

  }

  static int exar_direction_output(struct gpio_chip *chip, unsigned int offset,
  				 int value)
  {
  	exar_set_value(chip, offset, value);
  	return exar_set_direction(chip, 0, offset);
  }
  
  static int exar_direction_input(struct gpio_chip *chip, unsigned int offset)
  {
  	return exar_set_direction(chip, 1, offset);
  }

  static int gpio_exar_probe(struct platform_device *pdev)
  {

  	struct pci_dev *pcidev = to_pci_dev(pdev->dev.parent);

  	struct exar_gpio_chip *exar_gpio;

  	u32 first_pin, ngpios;

  	void __iomem *p;
  	int index, ret;

  	/*

  	 * The UART driver must have mapped region 0 prior to registering this
  	 * device - use it.

  	 */

  	p = pcim_iomap_table(pcidev)[0];

  	if (!p)
  		return -ENOMEM;

  	ret = device_property_read_u32(&pdev->dev, "exar,first-pin",

  				       &first_pin);
  	if (ret)
  		return ret;
  
  	ret = device_property_read_u32(&pdev->dev, "ngpios", &ngpios);
  	if (ret)
  		return ret;

  	exar_gpio = devm_kzalloc(&pdev->dev, sizeof(*exar_gpio), GFP_KERNEL);

  	if (!exar_gpio)
  		return -ENOMEM;
  
  	mutex_init(&exar_gpio->lock);
  
  	index = ida_simple_get(&ida_index, 0, 0, GFP_KERNEL);

  	if (index < 0) {
  		ret = index;
  		goto err_mutex_destroy;
  	}

  
  	sprintf(exar_gpio->name, "exar_gpio%d", index);
  	exar_gpio->gpio_chip.label = exar_gpio->name;

  	exar_gpio->gpio_chip.parent = &pdev->dev;

  	exar_gpio->gpio_chip.direction_output = exar_direction_output;
  	exar_gpio->gpio_chip.direction_input = exar_direction_input;
  	exar_gpio->gpio_chip.get_direction = exar_get_direction;
  	exar_gpio->gpio_chip.get = exar_get_value;
  	exar_gpio->gpio_chip.set = exar_set_value;
  	exar_gpio->gpio_chip.base = -1;

  	exar_gpio->gpio_chip.ngpio = ngpios;

  	exar_gpio->regs = p;
  	exar_gpio->index = index;

  	exar_gpio->first_pin = first_pin;

  	ret = devm_gpiochip_add_data(&pdev->dev,

  				     &exar_gpio->gpio_chip, exar_gpio);
  	if (ret)
  		goto err_destroy;
  
  	platform_set_drvdata(pdev, exar_gpio);
  
  	return 0;
  
  err_destroy:
  	ida_simple_remove(&ida_index, index);

  err_mutex_destroy:

  	mutex_destroy(&exar_gpio->lock);
  	return ret;
  }
  
  static int gpio_exar_remove(struct platform_device *pdev)
  {
  	struct exar_gpio_chip *exar_gpio = platform_get_drvdata(pdev);
  
  	ida_simple_remove(&ida_index, exar_gpio->index);
  	mutex_destroy(&exar_gpio->lock);
  
  	return 0;
  }
  
  static struct platform_driver gpio_exar_driver = {
  	.probe	= gpio_exar_probe,
  	.remove	= gpio_exar_remove,
  	.driver	= {
  		.name = DRIVER_NAME,
  	},
  };
  
  module_platform_driver(gpio_exar_driver);
  
  MODULE_ALIAS("platform:" DRIVER_NAME);
  MODULE_DESCRIPTION("Exar GPIO driver");
  MODULE_AUTHOR("Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>");
  MODULE_LICENSE("GPL");