/*
   * Texas Instrument's System Control Interface (TI-SCI) reset driver for TI's
   * Keystone generation devices
   *
   * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
   *	Andrew F. Davis <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/idr.h>
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/platform_device.h>
  #include <linux/reset-controller.h>
  #include <linux/soc/ti/ti_sci_protocol.h>
  
  /**
   * struct ti_sci_reset_control - reset control structure
   * @dev_id: SoC-specific device identifier
   * @reset_mask: reset mask to use for toggling reset
   */
  struct ti_sci_reset_control {
  	u32 dev_id;
  	u32 reset_mask;
  };
  
  /**
   * struct ti_sci_reset_data - reset controller information structure
   * @rcdev: reset controller entity
   * @dev: reset controller device pointer
   * @sci: TI SCI handle used for communication with system controller
   * @idr: idr structure for mapping ids to reset control structures
   */
  struct ti_sci_reset_data {
  	struct reset_controller_dev rcdev;
  	struct device *dev;
  	const struct ti_sci_handle *sci;
  	struct idr idr;
  };
  
  #define to_ti_sci_reset_data(rcdev)	\
  	container_of(rcdev, struct ti_sci_reset_data, rcdev)
  
  /**
   * ti_sci_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 TI SCI protocol. The device's reset is asserted if the
   * @assert argument is true, or deasserted if @assert argument is false.
   * The mechanism itself is a read-modify-write procedure, the current device
   * reset register is read using a TI SCI device operation, the new value is
   * set or un-set using the reset's mask, and the new reset value written by
   * using another TI SCI device operation.
   *
   * Return: 0 for successful request, else a corresponding error value
   */
  static int ti_sci_reset_set(struct reset_controller_dev *rcdev,
  			    unsigned long id, bool assert)
  {
  	struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
  	const struct ti_sci_handle *sci = data->sci;
  	const struct ti_sci_dev_ops *dev_ops = &sci->ops.dev_ops;
  	struct ti_sci_reset_control *control;
  	u32 reset_state;
  	int ret;
  
  	control = idr_find(&data->idr, id);
  	if (!control)
  		return -EINVAL;
  
  	ret = dev_ops->get_device_resets(sci, control->dev_id,
  					 &reset_state);
  	if (ret)
  		return ret;
  
  	if (assert)
  		reset_state |= control->reset_mask;
  	else
  		reset_state &= ~control->reset_mask;
  
  	return dev_ops->set_device_resets(sci, control->dev_id,
  					  reset_state);
  }
  
  /**
   * ti_sci_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
   * using the TI SCI protocol. This invokes the function ti_sci_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 ti_sci_reset_assert(struct reset_controller_dev *rcdev,
  			       unsigned long id)
  {
  	return ti_sci_reset_set(rcdev, id, true);
  }
  
  /**
   * ti_sci_reset_deassert() - deassert device reset
   * @rcdev: reset controller entity
   * @id: ID of the reset to be deasserted
   *
   * This function implements the reset driver op to deassert a device's reset
   * using the TI SCI protocol. This invokes the function ti_sci_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 ti_sci_reset_deassert(struct reset_controller_dev *rcdev,
  				 unsigned long id)
  {
  	return ti_sci_reset_set(rcdev, id, false);
  }
  
  /**
   * ti_sci_reset_status() - check device reset status
   * @rcdev: reset controller entity
   * @id: ID of reset to be checked
   *
   * This function implements the reset driver op to return the status of a
   * device's reset using the TI SCI protocol. The reset register value is read
   * by invoking the TI SCI device opertation .get_device_resets(), and the
   * status of the specific reset is extracted and returned using this reset's
   * reset mask.
   *
   * Return: 0 if reset is deasserted, or a non-zero value if reset is asserted
   */
  static int ti_sci_reset_status(struct reset_controller_dev *rcdev,
  			       unsigned long id)
  {
  	struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
  	const struct ti_sci_handle *sci = data->sci;
  	const struct ti_sci_dev_ops *dev_ops = &sci->ops.dev_ops;
  	struct ti_sci_reset_control *control;
  	u32 reset_state;
  	int ret;
  
  	control = idr_find(&data->idr, id);
  	if (!control)
  		return -EINVAL;
  
  	ret = dev_ops->get_device_resets(sci, control->dev_id,
  					 &reset_state);
  	if (ret)
  		return ret;
  
  	return reset_state & control->reset_mask;
  }
  
  static struct reset_control_ops ti_sci_reset_ops = {
  	.assert		= ti_sci_reset_assert,
  	.deassert	= ti_sci_reset_deassert,
  	.status		= ti_sci_reset_status,
  };
  
  /**
   * ti_sci_reset_of_xlate() - translate a set of OF arguments to a reset ID
   * @rcdev: reset controller entity
   * @reset_spec: OF reset argument specifier
   *
   * This function performs the translation of the reset argument specifier
   * values defined in a reset consumer device node. The function allocates a
   * reset control structure for that device reset, and will be used by the
   * driver for performing any reset functions on that reset. An idr structure
   * is allocated and used to map to the reset control structure. This idr
   * is used by the driver to do reset lookups.
   *
   * Return: 0 for successful request, else a corresponding error value
   */
  static int ti_sci_reset_of_xlate(struct reset_controller_dev *rcdev,
  				 const struct of_phandle_args *reset_spec)
  {
  	struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
  	struct ti_sci_reset_control *control;
  
  	if (WARN_ON(reset_spec->args_count != rcdev->of_reset_n_cells))
  		return -EINVAL;
  
  	control = devm_kzalloc(data->dev, sizeof(*control), GFP_KERNEL);
  	if (!control)
  		return -ENOMEM;
  
  	control->dev_id = reset_spec->args[0];
  	control->reset_mask = reset_spec->args[1];
  
  	return idr_alloc(&data->idr, control, 0, 0, GFP_KERNEL);
  }
  
  static const struct of_device_id ti_sci_reset_of_match[] = {
  	{ .compatible = "ti,sci-reset", },
  	{ /* sentinel */ },
  };
  MODULE_DEVICE_TABLE(of, ti_sci_reset_of_match);
  
  static int ti_sci_reset_probe(struct platform_device *pdev)
  {
  	struct ti_sci_reset_data *data;
  
  	if (!pdev->dev.of_node)
  		return -ENODEV;
  
  	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;
  
  	data->sci = devm_ti_sci_get_handle(&pdev->dev);
  	if (IS_ERR(data->sci))
  		return PTR_ERR(data->sci);
  
  	data->rcdev.ops = &ti_sci_reset_ops;
  	data->rcdev.owner = THIS_MODULE;
  	data->rcdev.of_node = pdev->dev.of_node;
  	data->rcdev.of_reset_n_cells = 2;
  	data->rcdev.of_xlate = ti_sci_reset_of_xlate;
  	data->dev = &pdev->dev;
  	idr_init(&data->idr);
  
  	platform_set_drvdata(pdev, data);
  
  	return reset_controller_register(&data->rcdev);
  }
  
  static int ti_sci_reset_remove(struct platform_device *pdev)
  {
  	struct ti_sci_reset_data *data = platform_get_drvdata(pdev);
  
  	reset_controller_unregister(&data->rcdev);
  
  	idr_destroy(&data->idr);
  
  	return 0;
  }
  
  static struct platform_driver ti_sci_reset_driver = {
  	.probe = ti_sci_reset_probe,
  	.remove = ti_sci_reset_remove,
  	.driver = {
  		.name = "ti-sci-reset",
  		.of_match_table = ti_sci_reset_of_match,
  	},
  };
  module_platform_driver(ti_sci_reset_driver);
  
  MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
  MODULE_DESCRIPTION("TI System Control Interface (TI SCI) Reset driver");
  MODULE_LICENSE("GPL v2");