/*
 * Texas Instrument's System Control Interface (TI-SCI) reset driver
 *
 * Copyright (C) 2015-2017 Texas Instruments Incorporated - https://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/mutex.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
 * @lock: synchronize reset_mask read-modify-writes
 */
struct ti_sci_reset_control {
        u32 dev_id;
        u32 reset_mask;
        struct mutex lock;
};

/**
 * 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(p) \
        container_of((p), 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;

        mutex_lock(&control->lock);

        ret = dev_ops->get_device_resets(sci, control->dev_id, &reset_state);
        if (ret)
                goto out;

        if (assert)
                reset_state |= control->reset_mask;
        else
                reset_state &= ~control->reset_mask;

        ret = dev_ops->set_device_resets(sci, control->dev_id, reset_state);
out:
        mutex_unlock(&control->lock);

        return ret;
}

/**
 * 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 operation .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 const 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];
        mutex_init(&control->lock);

        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");