// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * I2C multiplexer using a single register
 *
 * Copyright 2015 Freescale Semiconductor
 * York Sun  <yorksun@freescale.com>
 */

#include <linux/i2c.h>
#include <linux/i2c-mux.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_data/i2c-mux-reg.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

struct regmux {
        struct i2c_mux_reg_platform_data data;
};

static int i2c_mux_reg_set(const struct regmux *mux, unsigned int chan_id)
{
        if (!mux->data.reg)
                return -EINVAL;

        /*
         * Write to the register, followed by a read to ensure the write is
         * completed on a "posted" bus, for example PCI or write buffers.
         * The endianness of reading doesn't matter and the return data
         * is not used.
         */
        switch (mux->data.reg_size) {
        case 4:
                if (mux->data.little_endian)
                        iowrite32(chan_id, mux->data.reg);
                else
                        iowrite32be(chan_id, mux->data.reg);
                if (!mux->data.write_only)
                        ioread32(mux->data.reg);
                break;
        case 2:
                if (mux->data.little_endian)
                        iowrite16(chan_id, mux->data.reg);
                else
                        iowrite16be(chan_id, mux->data.reg);
                if (!mux->data.write_only)
                        ioread16(mux->data.reg);
                break;
        case 1:
                iowrite8(chan_id, mux->data.reg);
                if (!mux->data.write_only)
                        ioread8(mux->data.reg);
                break;
        }

        return 0;
}

static int i2c_mux_reg_select(struct i2c_mux_core *muxc, u32 chan)
{
        struct regmux *mux = i2c_mux_priv(muxc);

        return i2c_mux_reg_set(mux, chan);
}

static int i2c_mux_reg_deselect(struct i2c_mux_core *muxc, u32 chan)
{
        struct regmux *mux = i2c_mux_priv(muxc);

        if (mux->data.idle_in_use)
                return i2c_mux_reg_set(mux, mux->data.idle);

        return 0;
}

static int i2c_mux_reg_probe_fw(struct regmux *mux, struct device *dev)
{
        struct fwnode_handle *fwnode, *child;
        struct i2c_adapter *adapter;
        unsigned *values;
        int ret, i = 0;

        if (!dev_fwnode(dev))
                return -ENODEV;

        fwnode = fwnode_find_reference(dev_fwnode(dev), "i2c-parent", 0);
        if (IS_ERR(fwnode)) {
                dev_err(dev, "missing 'i2c-parent' property\n");
                return -ENODEV;
        }

        adapter = i2c_find_adapter_by_fwnode(fwnode);
        fwnode_handle_put(fwnode);
        if (!adapter)
                return -EPROBE_DEFER;

        mux->data.parent = i2c_adapter_id(adapter);
        put_device(&adapter->dev);

        mux->data.n_values = device_get_child_node_count(dev);
        if (device_property_read_bool(dev, "little-endian")) {
                mux->data.little_endian = true;
        } else if (device_property_read_bool(dev, "big-endian")) {
                mux->data.little_endian = false;
        } else {
#if defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : \
        defined(__LITTLE_ENDIAN)
                mux->data.little_endian = true;
#elif defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : \
        defined(__BIG_ENDIAN)
                mux->data.little_endian = false;
#else
#error Endianness not defined?
#endif
        }
        mux->data.write_only = device_property_read_bool(dev, "write-only");

        values = devm_kcalloc(dev, mux->data.n_values, sizeof(*mux->data.values),
                              GFP_KERNEL);
        if (!values)
                return -ENOMEM;

        device_for_each_child_node(dev, child) {
                if (is_acpi_device_node(child)) {
                        ret = acpi_get_local_address(ACPI_HANDLE_FWNODE(child),
                                                     &values[i]);
                        if (ret) {
                                fwnode_handle_put(child);
                                return dev_err_probe(dev, ret,
                                                     "Cannot get address\n");
                        }
                } else {
                        fwnode_property_read_u32(child, "reg", &values[i]);
                }

                i++;
        }
        mux->data.values = values;

        if (!device_property_read_u32(dev, "idle-state", &mux->data.idle))
                mux->data.idle_in_use = true;

        return 0;
}

static int i2c_mux_reg_probe(struct platform_device *pdev)
{
        struct i2c_mux_core *muxc;
        struct regmux *mux;
        struct i2c_adapter *parent;
        struct resource *res;
        int i, ret, nr;

        mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
        if (!mux)
                return -ENOMEM;

        if (dev_get_platdata(&pdev->dev)) {
                memcpy(&mux->data, dev_get_platdata(&pdev->dev),
                        sizeof(mux->data));
        } else {
                ret = i2c_mux_reg_probe_fw(mux, &pdev->dev);
                if (ret < 0)
                        return dev_err_probe(&pdev->dev, ret,
                                             "Error parsing firmware description\n");
        }

        if (!mux->data.reg) {
                mux->data.reg = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
                if (IS_ERR(mux->data.reg))
                        return PTR_ERR(mux->data.reg);
                mux->data.reg_size = resource_size(res);
        }

        if (mux->data.reg_size != 4 && mux->data.reg_size != 2 &&
            mux->data.reg_size != 1) {
                dev_err(&pdev->dev, "Invalid register size\n");
                return -EINVAL;
        }

        parent = i2c_get_adapter(mux->data.parent);
        if (!parent)
                return -EPROBE_DEFER;

        muxc = i2c_mux_alloc(parent, &pdev->dev, mux->data.n_values, 0, 0,
                             i2c_mux_reg_select, NULL);
        if (!muxc) {
                ret = -ENOMEM;
                goto err_put_parent;
        }
        muxc->priv = mux;

        platform_set_drvdata(pdev, muxc);

        if (mux->data.idle_in_use)
                muxc->deselect = i2c_mux_reg_deselect;

        for (i = 0; i < mux->data.n_values; i++) {
                nr = mux->data.base_nr ? (mux->data.base_nr + i) : 0;

                ret = i2c_mux_add_adapter(muxc, nr, mux->data.values[i]);
                if (ret)
                        goto err_del_mux_adapters;
        }

        dev_dbg(&pdev->dev, "%d port mux on %s adapter\n",
                 mux->data.n_values, muxc->parent->name);

        return 0;

err_del_mux_adapters:
        i2c_mux_del_adapters(muxc);
err_put_parent:
        i2c_put_adapter(parent);

        return ret;
}

static void i2c_mux_reg_remove(struct platform_device *pdev)
{
        struct i2c_mux_core *muxc = platform_get_drvdata(pdev);

        i2c_mux_del_adapters(muxc);
        i2c_put_adapter(muxc->parent);
}

static const struct of_device_id i2c_mux_reg_of_match[] = {
        { .compatible = "i2c-mux-reg", },
        {},
};
MODULE_DEVICE_TABLE(of, i2c_mux_reg_of_match);

static struct platform_driver i2c_mux_reg_driver = {
        .probe  = i2c_mux_reg_probe,
        .remove = i2c_mux_reg_remove,
        .driver = {
                .name   = "i2c-mux-reg",
                .of_match_table = i2c_mux_reg_of_match,
        },
};

module_platform_driver(i2c_mux_reg_driver);

MODULE_DESCRIPTION("Register-based I2C multiplexer driver");
MODULE_AUTHOR("York Sun <yorksun@freescale.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:i2c-mux-reg");