// SPDX-License-Identifier: GPL-2.0-only
/*
 * Pinctrl based I2C DeMultiplexer
 *
 * Copyright (C) 2015-16 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
 * Copyright (C) 2015-16 by Renesas Electronics Corporation
 *
 * See the bindings doc for DTS setup and the sysfs doc for usage information.
 * (look for filenames containing 'i2c-demux-pinctrl' in Documentation/)
 */

#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/pinctrl/consumer.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/sysfs.h>

struct i2c_demux_pinctrl_chan {
        struct device_node *parent_np;
        struct i2c_adapter *parent_adap;
        struct of_changeset chgset;
};

struct i2c_demux_pinctrl_priv {
        int cur_chan;
        int num_chan;
        struct device *dev;
        const char *bus_name;
        struct i2c_adapter cur_adap;
        struct i2c_algorithm algo;
        struct i2c_demux_pinctrl_chan chan[] __counted_by(num_chan);
};

static int i2c_demux_master_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
{
        struct i2c_demux_pinctrl_priv *priv = adap->algo_data;
        struct i2c_adapter *parent = priv->chan[priv->cur_chan].parent_adap;

        return __i2c_transfer(parent, msgs, num);
}

static u32 i2c_demux_functionality(struct i2c_adapter *adap)
{
        struct i2c_demux_pinctrl_priv *priv = adap->algo_data;
        struct i2c_adapter *parent = priv->chan[priv->cur_chan].parent_adap;

        return parent->algo->functionality(parent);
}

static int i2c_demux_activate_master(struct i2c_demux_pinctrl_priv *priv, u32 new_chan)
{
        struct i2c_adapter *adap;
        struct pinctrl *p;
        int ret;

        ret = of_changeset_apply(&priv->chan[new_chan].chgset);
        if (ret)
                goto err;

        adap = of_get_i2c_adapter_by_node(priv->chan[new_chan].parent_np);
        if (!adap) {
                ret = -ENODEV;
                goto err_with_revert;
        }

        /*
         * Check if there are pinctrl states at all. Note: we can't use
         * devm_pinctrl_get_select() because we need to distinguish between
         * the -ENODEV from devm_pinctrl_get() and pinctrl_lookup_state().
         */
        p = devm_pinctrl_get(adap->dev.parent);
        if (IS_ERR(p)) {
                ret = PTR_ERR(p);
                /* continue if just no pinctrl states (e.g. i2c-gpio), otherwise exit */
                if (ret != -ENODEV)
                        goto err_with_put;
        } else {
                /* there are states. check and use them */
                struct pinctrl_state *s = pinctrl_lookup_state(p, priv->bus_name);

                if (IS_ERR(s)) {
                        ret = PTR_ERR(s);
                        goto err_with_put;
                }
                ret = pinctrl_select_state(p, s);
                if (ret < 0)
                        goto err_with_put;
        }

        priv->chan[new_chan].parent_adap = adap;
        priv->cur_chan = new_chan;

        /* Now fill out current adapter structure. cur_chan must be up to date */
        priv->algo.xfer = i2c_demux_master_xfer;
        if (adap->algo->master_xfer_atomic)
                priv->algo.xfer_atomic = i2c_demux_master_xfer;
        priv->algo.functionality = i2c_demux_functionality;

        snprintf(priv->cur_adap.name, sizeof(priv->cur_adap.name),
                 "i2c-demux (master i2c-%d)", i2c_adapter_id(adap));
        priv->cur_adap.owner = THIS_MODULE;
        priv->cur_adap.algo = &priv->algo;
        priv->cur_adap.algo_data = priv;
        priv->cur_adap.dev.parent = &adap->dev;
        priv->cur_adap.class = adap->class;
        priv->cur_adap.retries = adap->retries;
        priv->cur_adap.timeout = adap->timeout;
        priv->cur_adap.quirks = adap->quirks;
        priv->cur_adap.dev.of_node = priv->dev->of_node;
        ret = i2c_add_adapter(&priv->cur_adap);
        if (ret < 0)
                goto err_with_put;

        return 0;

 err_with_put:
        i2c_put_adapter(adap);
 err_with_revert:
        of_changeset_revert(&priv->chan[new_chan].chgset);
 err:
        dev_err(priv->dev, "failed to setup demux-adapter %d (%d)\n", new_chan, ret);
        priv->cur_chan = -EINVAL;
        return ret;
}

static int i2c_demux_deactivate_master(struct i2c_demux_pinctrl_priv *priv)
{
        int ret, cur = priv->cur_chan;

        if (cur < 0)
                return 0;

        i2c_del_adapter(&priv->cur_adap);
        i2c_put_adapter(priv->chan[cur].parent_adap);

        ret = of_changeset_revert(&priv->chan[cur].chgset);

        priv->chan[cur].parent_adap = NULL;
        priv->cur_chan = -EINVAL;

        return ret;
}

static int i2c_demux_change_master(struct i2c_demux_pinctrl_priv *priv, u32 new_chan)
{
        int ret;

        if (new_chan == priv->cur_chan)
                return 0;

        ret = i2c_demux_deactivate_master(priv);
        if (ret)
                return ret;

        return i2c_demux_activate_master(priv, new_chan);
}

static ssize_t available_masters_show(struct device *dev,
                                      struct device_attribute *attr,
                                      char *buf)
{
        struct i2c_demux_pinctrl_priv *priv = dev_get_drvdata(dev);
        int count = 0, i;

        for (i = 0; i < priv->num_chan && count < PAGE_SIZE; i++)
                count += sysfs_emit_at(buf, count, "%d:%pOF%c",
                                       i, priv->chan[i].parent_np,
                                       i == priv->num_chan - 1 ? '\n' : ' ');

        return count;
}
static DEVICE_ATTR_RO(available_masters);

static ssize_t current_master_show(struct device *dev,
                                   struct device_attribute *attr,
                                   char *buf)
{
        struct i2c_demux_pinctrl_priv *priv = dev_get_drvdata(dev);

        return sprintf(buf, "%d\n", priv->cur_chan);
}

static ssize_t current_master_store(struct device *dev,
                                    struct device_attribute *attr,
                                    const char *buf, size_t count)
{
        struct i2c_demux_pinctrl_priv *priv = dev_get_drvdata(dev);
        unsigned int val;
        int ret;

        ret = kstrtouint(buf, 0, &val);
        if (ret < 0)
                return ret;

        if (val >= priv->num_chan)
                return -EINVAL;

        ret = i2c_demux_change_master(priv, val);

        return ret < 0 ? ret : count;
}
static DEVICE_ATTR_RW(current_master);

static int i2c_demux_pinctrl_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct i2c_demux_pinctrl_priv *priv;
        struct property *props;
        int num_chan, i, j, err;

        num_chan = of_count_phandle_with_args(np, "i2c-parent", NULL);
        if (num_chan < 2) {
                dev_err(&pdev->dev, "Need at least two I2C masters to switch\n");
                return -EINVAL;
        }

        priv = devm_kzalloc(&pdev->dev, struct_size(priv, chan, num_chan),
                            GFP_KERNEL);

        props = devm_kcalloc(&pdev->dev, num_chan, sizeof(*props), GFP_KERNEL);

        if (!priv || !props)
                return -ENOMEM;

        priv->num_chan = num_chan;

        err = of_property_read_string(np, "i2c-bus-name", &priv->bus_name);
        if (err)
                return err;

        for (i = 0; i < num_chan; i++) {
                struct device_node *adap_np;

                adap_np = of_parse_phandle(np, "i2c-parent", i);
                if (!adap_np) {
                        dev_err(&pdev->dev, "can't get phandle for parent %d\n", i);
                        err = -ENOENT;
                        goto err_rollback;
                }
                priv->chan[i].parent_np = adap_np;

                props[i].name = devm_kstrdup(&pdev->dev, "status", GFP_KERNEL);
                props[i].value = devm_kstrdup(&pdev->dev, "ok", GFP_KERNEL);
                if (!props[i].name || !props[i].value) {
                        err = -ENOMEM;
                        goto err_rollback;
                }
                props[i].length = 3;

                of_changeset_init(&priv->chan[i].chgset);
                of_changeset_update_property(&priv->chan[i].chgset, adap_np, &props[i]);
        }

        priv->dev = &pdev->dev;
        platform_set_drvdata(pdev, priv);

        pm_runtime_no_callbacks(&pdev->dev);

        /* switch to first parent as active master */
        err = i2c_demux_activate_master(priv, 0);
        if (err)
                goto err_rollback;

        err = device_create_file(&pdev->dev, &dev_attr_available_masters);
        if (err)
                goto err_rollback_activation;

        err = device_create_file(&pdev->dev, &dev_attr_current_master);
        if (err)
                goto err_rollback_available;

        return 0;

err_rollback_available:
        device_remove_file(&pdev->dev, &dev_attr_available_masters);
err_rollback_activation:
        i2c_demux_deactivate_master(priv);
err_rollback:
        for (j = 0; j < i; j++) {
                of_node_put(priv->chan[j].parent_np);
                of_changeset_destroy(&priv->chan[j].chgset);
        }

        return err;
}

static void i2c_demux_pinctrl_remove(struct platform_device *pdev)
{
        struct i2c_demux_pinctrl_priv *priv = platform_get_drvdata(pdev);
        int i;

        device_remove_file(&pdev->dev, &dev_attr_current_master);
        device_remove_file(&pdev->dev, &dev_attr_available_masters);

        i2c_demux_deactivate_master(priv);

        for (i = 0; i < priv->num_chan; i++) {
                of_node_put(priv->chan[i].parent_np);
                of_changeset_destroy(&priv->chan[i].chgset);
        }
}

static const struct of_device_id i2c_demux_pinctrl_of_match[] = {
        { .compatible = "i2c-demux-pinctrl", },
        {},
};
MODULE_DEVICE_TABLE(of, i2c_demux_pinctrl_of_match);

static struct platform_driver i2c_demux_pinctrl_driver = {
        .driver = {
                .name = "i2c-demux-pinctrl",
                .of_match_table = i2c_demux_pinctrl_of_match,
        },
        .probe  = i2c_demux_pinctrl_probe,
        .remove = i2c_demux_pinctrl_remove,
};
module_platform_driver(i2c_demux_pinctrl_driver);

MODULE_DESCRIPTION("pinctrl-based I2C demux driver");
MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:i2c-demux-pinctrl");