// SPDX-License-Identifier: GPL-2.0
//
// System Control and Management Interface (SCMI) based regulator driver
//
// Copyright (C) 2020-2021 ARM Ltd.
//
// Implements a regulator driver on top of the SCMI Voltage Protocol.
//
// The ARM SCMI Protocol aims in general to hide as much as possible all the
// underlying operational details while providing an abstracted interface for
// its users to operate upon: as a consequence the resulting operational
// capabilities and configurability of this regulator device are much more
// limited than the ones usually available on a standard physical regulator.
//
// The supported SCMI regulator ops are restricted to the bare minimum:
//
//  - 'status_ops': enable/disable/is_enabled
//  - 'voltage_ops': get_voltage_sel/set_voltage_sel
//                   list_voltage/map_voltage
//
// Each SCMI regulator instance is associated, through the means of a proper DT
// entry description, to a specific SCMI Voltage Domain.

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/linear_range.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/regulator/driver.h>
#include <linux/regulator/machine.h>
#include <linux/regulator/of_regulator.h>
#include <linux/scmi_protocol.h>
#include <linux/slab.h>
#include <linux/types.h>

static const struct scmi_voltage_proto_ops *voltage_ops;

struct scmi_regulator {
        u32 id;
        struct scmi_device *sdev;
        struct scmi_protocol_handle *ph;
        struct regulator_dev *rdev;
        struct device_node *of_node;
        struct regulator_desc desc;
        struct regulator_config conf;
};

struct scmi_regulator_info {
        int num_doms;
        struct scmi_regulator **sregv;
};

static int scmi_reg_enable(struct regulator_dev *rdev)
{
        struct scmi_regulator *sreg = rdev_get_drvdata(rdev);

        return voltage_ops->config_set(sreg->ph, sreg->id,
                                       SCMI_VOLTAGE_ARCH_STATE_ON);
}

static int scmi_reg_disable(struct regulator_dev *rdev)
{
        struct scmi_regulator *sreg = rdev_get_drvdata(rdev);

        return voltage_ops->config_set(sreg->ph, sreg->id,
                                       SCMI_VOLTAGE_ARCH_STATE_OFF);
}

static int scmi_reg_is_enabled(struct regulator_dev *rdev)
{
        int ret;
        u32 config;
        struct scmi_regulator *sreg = rdev_get_drvdata(rdev);

        ret = voltage_ops->config_get(sreg->ph, sreg->id, &config);
        if (ret) {
                dev_err(&sreg->sdev->dev,
                        "Error %d reading regulator %s status.\n",
                        ret, sreg->desc.name);
                return ret;
        }

        return config & SCMI_VOLTAGE_ARCH_STATE_ON;
}

static int scmi_reg_get_voltage_sel(struct regulator_dev *rdev)
{
        int ret;
        s32 volt_uV;
        struct scmi_regulator *sreg = rdev_get_drvdata(rdev);

        ret = voltage_ops->level_get(sreg->ph, sreg->id, &volt_uV);
        if (ret)
                return ret;

        return sreg->desc.ops->map_voltage(rdev, volt_uV, volt_uV);
}

static int scmi_reg_set_voltage_sel(struct regulator_dev *rdev,
                                    unsigned int selector)
{
        s32 volt_uV;
        struct scmi_regulator *sreg = rdev_get_drvdata(rdev);

        volt_uV = sreg->desc.ops->list_voltage(rdev, selector);
        if (volt_uV <= 0)
                return -EINVAL;

        return voltage_ops->level_set(sreg->ph, sreg->id, 0x0, volt_uV);
}

static const struct regulator_ops scmi_reg_fixed_ops = {
        .enable = scmi_reg_enable,
        .disable = scmi_reg_disable,
        .is_enabled = scmi_reg_is_enabled,
};

static const struct regulator_ops scmi_reg_linear_ops = {
        .enable = scmi_reg_enable,
        .disable = scmi_reg_disable,
        .is_enabled = scmi_reg_is_enabled,
        .get_voltage_sel = scmi_reg_get_voltage_sel,
        .set_voltage_sel = scmi_reg_set_voltage_sel,
        .list_voltage = regulator_list_voltage_linear,
        .map_voltage = regulator_map_voltage_linear,
};

static const struct regulator_ops scmi_reg_discrete_ops = {
        .enable = scmi_reg_enable,
        .disable = scmi_reg_disable,
        .is_enabled = scmi_reg_is_enabled,
        .get_voltage_sel = scmi_reg_get_voltage_sel,
        .set_voltage_sel = scmi_reg_set_voltage_sel,
        .list_voltage = regulator_list_voltage_table,
        .map_voltage = regulator_map_voltage_iterate,
};

static int
scmi_config_linear_regulator_mappings(struct scmi_regulator *sreg,
                                      const struct scmi_voltage_info *vinfo)
{
        s32 delta_uV;

        /*
         * Note that SCMI voltage domains describable by linear ranges
         * (segments) {low, high, step} are guaranteed to come in one single
         * triplet by the SCMI Voltage Domain protocol support itself.
         */

        delta_uV = (vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_HIGH] -
                        vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_LOW]);

        /* Rule out buggy negative-intervals answers from fw */
        if (delta_uV < 0) {
                dev_err(&sreg->sdev->dev,
                        "Invalid volt-range %d-%duV for domain %d\n",
                        vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_LOW],
                        vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_HIGH],
                        sreg->id);
                return -EINVAL;
        }

        if (!delta_uV) {
                /* Just one fixed voltage exposed by SCMI */
                sreg->desc.fixed_uV =
                        vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_LOW];
                sreg->desc.n_voltages = 1;
                sreg->desc.ops = &scmi_reg_fixed_ops;
        } else {
                /* One simple linear mapping. */
                sreg->desc.min_uV =
                        vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_LOW];
                sreg->desc.uV_step =
                        vinfo->levels_uv[SCMI_VOLTAGE_SEGMENT_STEP];
                sreg->desc.linear_min_sel = 0;
                sreg->desc.n_voltages = (delta_uV / sreg->desc.uV_step) + 1;
                sreg->desc.ops = &scmi_reg_linear_ops;
        }

        return 0;
}

static int
scmi_config_discrete_regulator_mappings(struct scmi_regulator *sreg,
                                        const struct scmi_voltage_info *vinfo)
{
        /* Discrete non linear levels are mapped to volt_table */
        sreg->desc.n_voltages = vinfo->num_levels;

        if (sreg->desc.n_voltages > 1) {
                sreg->desc.volt_table = (const unsigned int *)vinfo->levels_uv;
                sreg->desc.ops = &scmi_reg_discrete_ops;
        } else {
                sreg->desc.fixed_uV = vinfo->levels_uv[0];
                sreg->desc.ops = &scmi_reg_fixed_ops;
        }

        return 0;
}

static int scmi_regulator_common_init(struct scmi_regulator *sreg)
{
        int ret;
        struct device *dev = &sreg->sdev->dev;
        const struct scmi_voltage_info *vinfo;

        vinfo = voltage_ops->info_get(sreg->ph, sreg->id);
        if (!vinfo) {
                dev_warn(dev, "Failure to get voltage domain %d\n",
                         sreg->id);
                return -ENODEV;
        }

        /*
         * Regulator framework does not fully support negative voltages
         * so we discard any voltage domain reported as supporting negative
         * voltages: as a consequence each levels_uv entry is guaranteed to
         * be non-negative from here on.
         */
        if (vinfo->negative_volts_allowed) {
                dev_warn(dev, "Negative voltages NOT supported...skip %s\n",
                         sreg->of_node->full_name);
                return -EOPNOTSUPP;
        }

        sreg->desc.name = devm_kasprintf(dev, GFP_KERNEL, "%s", vinfo->name);
        if (!sreg->desc.name)
                return -ENOMEM;

        sreg->desc.id = sreg->id;
        sreg->desc.type = REGULATOR_VOLTAGE;
        sreg->desc.owner = THIS_MODULE;
        sreg->desc.of_match_full_name = true;
        sreg->desc.of_match = sreg->of_node->full_name;
        sreg->desc.regulators_node = "regulators";
        if (vinfo->segmented)
                ret = scmi_config_linear_regulator_mappings(sreg, vinfo);
        else
                ret = scmi_config_discrete_regulator_mappings(sreg, vinfo);
        if (ret)
                return ret;

        /*
         * Using the scmi device here to have DT searched from Voltage
         * protocol node down.
         */
        sreg->conf.dev = dev;

        /* Store for later retrieval via rdev_get_drvdata() */
        sreg->conf.driver_data = sreg;

        return 0;
}

static int process_scmi_regulator_of_node(struct scmi_device *sdev,
                                          struct scmi_protocol_handle *ph,
                                          struct device_node *np,
                                          struct scmi_regulator_info *rinfo)
{
        u32 dom, ret;

        ret = of_property_read_u32(np, "reg", &dom);
        if (ret)
                return ret;

        if (dom >= rinfo->num_doms)
                return -ENODEV;

        if (rinfo->sregv[dom]) {
                dev_err(&sdev->dev,
                        "SCMI Voltage Domain %d already in use. Skipping: %s\n",
                        dom, np->full_name);
                return -EINVAL;
        }

        rinfo->sregv[dom] = devm_kzalloc(&sdev->dev,
                                         sizeof(struct scmi_regulator),
                                         GFP_KERNEL);
        if (!rinfo->sregv[dom])
                return -ENOMEM;

        rinfo->sregv[dom]->id = dom;
        rinfo->sregv[dom]->sdev = sdev;
        rinfo->sregv[dom]->ph = ph;

        /* get hold of good nodes */
        of_node_get(np);
        rinfo->sregv[dom]->of_node = np;

        dev_dbg(&sdev->dev,
                "Found SCMI Regulator entry -- OF node [%d] -> %s\n",
                dom, np->full_name);

        return 0;
}

static int scmi_regulator_probe(struct scmi_device *sdev)
{
        int d, ret, num_doms;
        struct device_node *np, *child;
        const struct scmi_handle *handle = sdev->handle;
        struct scmi_regulator_info *rinfo;
        struct scmi_protocol_handle *ph;

        if (!handle)
                return -ENODEV;

        voltage_ops = handle->devm_protocol_get(sdev,
                                                SCMI_PROTOCOL_VOLTAGE, &ph);
        if (IS_ERR(voltage_ops))
                return PTR_ERR(voltage_ops);

        num_doms = voltage_ops->num_domains_get(ph);
        if (num_doms <= 0) {
                if (!num_doms) {
                        dev_err(&sdev->dev,
                                "number of voltage domains invalid\n");
                        num_doms = -EINVAL;
                } else {
                        dev_err(&sdev->dev,
                                "failed to get voltage domains - err:%d\n",
                                num_doms);
                }

                return num_doms;
        }

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

        /* Allocate pointers array for all possible domains */
        rinfo->sregv = devm_kcalloc(&sdev->dev, num_doms,
                                    sizeof(void *), GFP_KERNEL);
        if (!rinfo->sregv)
                return -ENOMEM;

        rinfo->num_doms = num_doms;

        /*
         * Start collecting into rinfo->sregv possibly good SCMI Regulators as
         * described by a well-formed DT entry and associated with an existing
         * plausible SCMI Voltage Domain number, all belonging to this SCMI
         * platform instance node (handle->dev->of_node).
         */
        np = of_find_node_by_name(handle->dev->of_node, "regulators");
        for_each_child_of_node(np, child) {
                ret = process_scmi_regulator_of_node(sdev, ph, child, rinfo);
                /* abort on any mem issue */
                if (ret == -ENOMEM) {
                        of_node_put(child);
                        return ret;
                }
        }

        /*
         * Register a regulator for each valid regulator-DT-entry that we
         * can successfully reach via SCMI and has a valid associated voltage
         * domain.
         */
        for (d = 0; d < num_doms; d++) {
                struct scmi_regulator *sreg = rinfo->sregv[d];

                /* Skip empty slots */
                if (!sreg)
                        continue;

                ret = scmi_regulator_common_init(sreg);
                /* Skip invalid voltage domains */
                if (ret)
                        continue;

                sreg->rdev = devm_regulator_register(&sdev->dev, &sreg->desc,
                                                     &sreg->conf);
                if (IS_ERR(sreg->rdev)) {
                        sreg->rdev = NULL;
                        continue;
                }

                dev_info(&sdev->dev,
                         "Regulator %s registered for domain [%d]\n",
                         sreg->desc.name, sreg->id);
        }

        dev_set_drvdata(&sdev->dev, rinfo);

        return 0;
}

static void scmi_regulator_remove(struct scmi_device *sdev)
{
        int d;
        struct scmi_regulator_info *rinfo;

        rinfo = dev_get_drvdata(&sdev->dev);
        if (!rinfo)
                return;

        for (d = 0; d < rinfo->num_doms; d++) {
                if (!rinfo->sregv[d])
                        continue;
                of_node_put(rinfo->sregv[d]->of_node);
        }
}

static const struct scmi_device_id scmi_regulator_id_table[] = {
        { SCMI_PROTOCOL_VOLTAGE,  "regulator" },
        { },
};
MODULE_DEVICE_TABLE(scmi, scmi_regulator_id_table);

static struct scmi_driver scmi_drv = {
        .name           = "scmi-regulator",
        .probe          = scmi_regulator_probe,
        .remove         = scmi_regulator_remove,
        .id_table       = scmi_regulator_id_table,
};

module_scmi_driver(scmi_drv);

MODULE_AUTHOR("Cristian Marussi <cristian.marussi@arm.com>");
MODULE_DESCRIPTION("ARM SCMI regulator driver");
MODULE_LICENSE("GPL v2");