/*
   * SYSCON regmap reset driver
   *
   * Copyright (C) 2015-2016 Texas Instruments Incorporated - http://www.ti.com/
   *	Andrew F. Davis <afd@ti.com>
   *	Suman Anna <afd@ti.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed "as is" WITHOUT ANY WARRANTY of any
   * kind, whether express or implied; without even the implied warranty
   * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */
  
  #include <linux/mfd/syscon.h>
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/of_address.h>
  #include <linux/platform_device.h>
  #include <linux/regmap.h>
  #include <linux/reset-controller.h>
  
  /**
   * struct syscon_reset_control - reset control structure
   * @offset: reset control register offset from syscon base
   * @reset_bit: reset bit in the reset control register
   * @assert_high: flag to indicate if setting the bit high asserts the reset
   * @status_offset: reset status register offset from syscon base
   * @status_reset_bit: reset status bit in the reset status register
   * @status_assert_high: flag to indicate if a set bit represents asserted state
   * @toggle: flag to indicate this reset has no readable status register
   */
  struct syscon_reset_control {
  	unsigned int offset;
  	unsigned int reset_bit;
  	bool assert_high;
  	unsigned int status_offset;
  	unsigned int status_reset_bit;
  	bool status_assert_high;
  	bool toggle;
  };
  
  /**
   * struct syscon_reset_data - reset controller information structure
   * @rcdev: reset controller entity
   * @dev: reset controller device pointer
   * @memory: regmap handle containing the memory-mapped reset registers
   * @idr: idr structure for mapping ids to reset control structures
   */
  struct syscon_reset_data {
  	struct reset_controller_dev rcdev;
  	struct device *dev;
  	struct regmap *memory;
  };
  
  #define to_syscon_reset_data(rcdev)	\
  	container_of(rcdev, struct syscon_reset_data, rcdev)
  
  /**
   * syscon_reset_get_control() - get reset control info from DT node
   * @data: reset controller data
   * @id: ID address of control data node
   * @control: control data struct to fill
   *
   * Search DT for a child node at the specified address that contains
   * reset control info and use that to fill in control data.
   *
   * XXX: Evaluate if parsing needs to be done in probe to improve
   *      lookup at runtime.
   *
   * Return: 0 for successful request, else a corresponding error value
   */
  static int syscon_reset_get_control(struct syscon_reset_data *data,
  				    unsigned long id,
  				    struct syscon_reset_control *control)
  {
  	struct device_node *child;
  	const __be32 *address;
  	const __be32 *list;
  	int size;
  
  	for_each_child_of_node(data->rcdev.of_node, child) {
  		address = of_get_address(child, 0, NULL, NULL);
  		if (!address || be32_to_cpup(address) != id)
  			continue;
  
  		list = of_get_property(child, "reset-control", &size);
  		if (!list || size != (3 * sizeof(*list)))
  			return -EINVAL;
  		control->offset = be32_to_cpup(list++);
  		control->reset_bit = be32_to_cpup(list++);
  		control->assert_high = be32_to_cpup(list) == 1;
  
  		if (of_find_property(child, "reset-toggle", NULL)) {
  			control->toggle = true;
  			return 0;
  		}
  		control->toggle = false;
  
  		list = of_get_property(child, "reset-status", &size);
  		if (!list) {
  			/* use control register values */
  			control->status_offset = control->offset;
  			control->status_reset_bit = control->reset_bit;
  			control->status_assert_high = control->assert_high;
  			return 0;
  		}
  
  		if (size != (3 * sizeof(*list)))
  			return -EINVAL;
  		control->status_offset = be32_to_cpup(list++);
  		control->status_reset_bit = be32_to_cpup(list++);
  		control->status_assert_high = be32_to_cpup(list) == 1;
  		return 0;
  	}
  
  	return -ENOENT;
  }
  
  /**
   * syscon_reset_set() - program a device's reset
   * @rcdev: reset controller entity
   * @id: ID of the reset to toggle
   * @assert: boolean flag to indicate assert or deassert
   *
   * This is a common internal function used to assert or deassert a device's
   * reset using the regmap API. The device's reset is asserted if the @assert
   * argument is true, or deasserted if the @assert argument is false.
   *
   * Return: 0 for successful request, else a corresponding error value
   */
  static int syscon_reset_set(struct reset_controller_dev *rcdev,
  			    unsigned long id, bool assert)
  {
  	struct syscon_reset_data *data = to_syscon_reset_data(rcdev);
  	struct syscon_reset_control control;
  	unsigned int mask, value;
  	int ret;
  
  	ret = syscon_reset_get_control(data, id, &control);
  	if (ret)
  		return ret;
  
  	mask = BIT(control.reset_bit);
  	value = (assert == control.assert_high) ? mask : 0x0;
  
  	return regmap_update_bits(data->memory, control.offset, mask, value);
  }
  
  /**
   * syscon_reset_assert() - assert device reset
   * @rcdev: reset controller entity
   * @id: ID of the reset to be asserted
   *
   * This function implements the reset driver op to assert a device's reset.
   * This invokes the function syscon_reset_set() with the corresponding
   * parameters as passed in, but with the @assert argument set to true for
   * asserting the reset.
   *
   * Return: 0 for successful request, else a corresponding error value
   */
  static int syscon_reset_assert(struct reset_controller_dev *rcdev,
  			       unsigned long id)
  {
  	return syscon_reset_set(rcdev, id, true);
  }
  
  /**
   * syscon_reset_deassert() - deassert device reset
   * @rcdev: reset controller entity
   * @id: ID of reset to be deasserted
   *
   * This function implements the reset driver op to deassert a device's reset.
   * This invokes the function syscon_reset_set() with the corresponding
   * parameters as passed in, but with the @assert argument set to false for
   * deasserting the reset.
   *
   * Return: 0 for successful request, else a corresponding error value
   */
  static int syscon_reset_deassert(struct reset_controller_dev *rcdev,
  				 unsigned long id)
  {
  	return syscon_reset_set(rcdev, id, false);
  }
  
  /**
   * syscon_reset_status() - check device reset status
   * @rcdev: reset controller entity
   * @id: ID of the reset for which the status is being requested
   *
   * This function implements the reset driver op to return the status of a
   * device's reset.
   *
   * Return: 0 if reset is deasserted, true if reset is asserted, else a
   * corresponding error value
   */
  static int syscon_reset_status(struct reset_controller_dev *rcdev,
  			       unsigned long id)
  {
  	struct syscon_reset_data *data = to_syscon_reset_data(rcdev);
  	struct syscon_reset_control control;
  	unsigned int reset_state;
  	int ret;
  
  	ret = syscon_reset_get_control(data, id, &control);
  	if (ret)
  		return ret;
  
  	if (control.toggle)
  		return -ENOSYS; /* status not supported for this reset */
  
  	ret = regmap_read(data->memory, control.status_offset, &reset_state);
  	if (ret)
  		return ret;
  
  	return (reset_state & BIT(control.status_reset_bit)) ==
  			control.status_assert_high;
  }
  
  static struct reset_control_ops syscon_reset_ops = {
  	.assert		= syscon_reset_assert,
  	.deassert	= syscon_reset_deassert,
  	.status		= syscon_reset_status,
  };
  
  static int syscon_reset_probe(struct platform_device *pdev)
  {
  	struct syscon_reset_data *data;
  	struct device *dev = &pdev->dev;
  	struct device_node *np = dev->of_node;
  	struct regmap *memory;
  
  	if (!np)
  		return -ENODEV;
  
  	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;
  
  	memory = syscon_node_to_regmap(np->parent);
  	if (IS_ERR(memory))
  		return PTR_ERR(memory);
  
  	data->rcdev.ops = &syscon_reset_ops;
  	data->rcdev.owner = THIS_MODULE;
  	data->rcdev.of_node = np;
  	data->rcdev.nr_resets = of_get_child_count(np);
  	data->dev = dev;
  	data->memory = memory;
  	platform_set_drvdata(pdev, data);
  
  	return reset_controller_register(&data->rcdev);
  }
  
  static int syscon_reset_remove(struct platform_device *pdev)
  {
  	struct syscon_reset_data *data = platform_get_drvdata(pdev);
  
  	reset_controller_unregister(&data->rcdev);
  
  	return 0;
  }
  
  static const struct of_device_id syscon_reset_of_match[] = {
  	{ .compatible = "syscon-reset", },
  	{ /* sentinel */ },
  };
  MODULE_DEVICE_TABLE(of, syscon_reset_of_match);
  
  static struct platform_driver syscon_reset_driver = {
  	.probe = syscon_reset_probe,
  	.remove = syscon_reset_remove,
  	.driver = {
  		.name = "syscon-reset",
  		.of_match_table = syscon_reset_of_match,
  	},
  };
  module_platform_driver(syscon_reset_driver);
  
  MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
  MODULE_AUTHOR("Suman Anna <s-anna@ti.com>");
  MODULE_DESCRIPTION("SYSCON Regmap Reset Driver");
  MODULE_LICENSE("GPL v2");