// SPDX-License-Identifier: GPL-2.0
/*
 * System Control and Power Interface (SCMI) Protocol based clock driver
 *
 * Copyright (C) 2018 ARM Ltd.
 */

#include <linux/clk-provider.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/of.h>
#include <linux/module.h>
#include <linux/scmi_protocol.h>
#include <asm/div64.h>

struct scmi_clk {
        u32 id;
        struct clk_hw hw;
        const struct scmi_clock_info *info;
        const struct scmi_handle *handle;
};

#define to_scmi_clk(clk) container_of(clk, struct scmi_clk, hw)

static unsigned long scmi_clk_recalc_rate(struct clk_hw *hw,
                                          unsigned long parent_rate)
{
        int ret;
        u64 rate;
        struct scmi_clk *clk = to_scmi_clk(hw);

        ret = clk->handle->clk_ops->rate_get(clk->handle, clk->id, &rate);
        if (ret)
                return 0;
        return rate;
}

static long scmi_clk_round_rate(struct clk_hw *hw, unsigned long rate,
                                unsigned long *parent_rate)
{
        int step;
        u64 fmin, fmax, ftmp;
        struct scmi_clk *clk = to_scmi_clk(hw);

        /*
         * We can't figure out what rate it will be, so just return the
         * rate back to the caller. scmi_clk_recalc_rate() will be called
         * after the rate is set and we'll know what rate the clock is
         * running at then.
         */
        if (clk->info->rate_discrete)
                return rate;

        fmin = clk->info->range.min_rate;
        fmax = clk->info->range.max_rate;
        if (rate <= fmin)
                return fmin;
        else if (rate >= fmax)
                return fmax;

        ftmp = rate - fmin;
        ftmp += clk->info->range.step_size - 1; /* to round up */
        step = do_div(ftmp, clk->info->range.step_size);

        return step * clk->info->range.step_size + fmin;
}

static int scmi_clk_set_rate(struct clk_hw *hw, unsigned long rate,
                             unsigned long parent_rate)
{
        struct scmi_clk *clk = to_scmi_clk(hw);

        return clk->handle->clk_ops->rate_set(clk->handle, clk->id, 0, rate);
}

static int scmi_clk_enable(struct clk_hw *hw)
{
        struct scmi_clk *clk = to_scmi_clk(hw);

        return clk->handle->clk_ops->enable(clk->handle, clk->id);
}

static void scmi_clk_disable(struct clk_hw *hw)
{
        struct scmi_clk *clk = to_scmi_clk(hw);

        clk->handle->clk_ops->disable(clk->handle, clk->id);
}

static const struct clk_ops scmi_clk_ops = {
        .recalc_rate = scmi_clk_recalc_rate,
        .round_rate = scmi_clk_round_rate,
        .set_rate = scmi_clk_set_rate,
        /*
         * We can't provide enable/disable callback as we can't perform the same
         * in atomic context. Since the clock framework provides standard API
         * clk_prepare_enable that helps cases using clk_enable in non-atomic
         * context, it should be fine providing prepare/unprepare.
         */
        .prepare = scmi_clk_enable,
        .unprepare = scmi_clk_disable,
};

static int scmi_clk_ops_init(struct device *dev, struct scmi_clk *sclk)
{
        int ret;
        struct clk_init_data init = {
                .flags = CLK_GET_RATE_NOCACHE,
                .num_parents = 0,
                .ops = &scmi_clk_ops,
                .name = sclk->info->name,
        };

        sclk->hw.init = &init;
        ret = devm_clk_hw_register(dev, &sclk->hw);
        if (!ret)
                clk_hw_set_rate_range(&sclk->hw, sclk->info->range.min_rate,
                                      sclk->info->range.max_rate);
        return ret;
}

static int scmi_clocks_probe(struct scmi_device *sdev)
{
        int idx, count, err;
        struct clk_hw **hws;
        struct clk_hw_onecell_data *clk_data;
        struct device *dev = &sdev->dev;
        struct device_node *np = dev->of_node;
        const struct scmi_handle *handle = sdev->handle;

        if (!handle || !handle->clk_ops)
                return -ENODEV;

        count = handle->clk_ops->count_get(handle);
        if (count < 0) {
                dev_err(dev, "%s: invalid clock output count\n", np->name);
                return -EINVAL;
        }

        clk_data = devm_kzalloc(dev, sizeof(*clk_data) +
                                sizeof(*clk_data->hws) * count, GFP_KERNEL);
        if (!clk_data)
                return -ENOMEM;

        clk_data->num = count;
        hws = clk_data->hws;

        for (idx = 0; idx < count; idx++) {
                struct scmi_clk *sclk;

                sclk = devm_kzalloc(dev, sizeof(*sclk), GFP_KERNEL);
                if (!sclk)
                        return -ENOMEM;

                sclk->info = handle->clk_ops->info_get(handle, idx);
                if (!sclk->info) {
                        dev_dbg(dev, "invalid clock info for idx %d\n", idx);
                        continue;
                }

                sclk->id = idx;
                sclk->handle = handle;

                err = scmi_clk_ops_init(dev, sclk);
                if (err) {
                        dev_err(dev, "failed to register clock %d\n", idx);
                        devm_kfree(dev, sclk);
                        hws[idx] = NULL;
                } else {
                        dev_dbg(dev, "Registered clock:%s\n", sclk->info->name);
                        hws[idx] = &sclk->hw;
                }
        }

        return devm_of_clk_add_hw_provider(dev, of_clk_hw_onecell_get,
                                           clk_data);
}

static const struct scmi_device_id scmi_id_table[] = {
        { SCMI_PROTOCOL_CLOCK },
        { },
};
MODULE_DEVICE_TABLE(scmi, scmi_id_table);

static struct scmi_driver scmi_clocks_driver = {
        .name = "scmi-clocks",
        .probe = scmi_clocks_probe,
        .id_table = scmi_id_table,
};
module_scmi_driver(scmi_clocks_driver);

MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
MODULE_DESCRIPTION("ARM SCMI clock driver");
MODULE_LICENSE("GPL v2");