// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2016 Rafał Miłecki <rafal@milecki.pl>
 */

#include <linux/clk-provider.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/mfd/syscon.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/regmap.h>
#include <linux/slab.h>

#define PMU_XTAL_FREQ_RATIO                     0x66c
#define  XTAL_ALP_PER_4ILP                      0x00001fff
#define  XTAL_CTL_EN                            0x80000000
#define PMU_SLOW_CLK_PERIOD                     0x6dc

struct bcm53573_ilp {
        struct clk_hw hw;
        struct regmap *regmap;
};

static int bcm53573_ilp_enable(struct clk_hw *hw)
{
        struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);

        regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0x10199);
        regmap_write(ilp->regmap, 0x674, 0x10000);

        return 0;
}

static void bcm53573_ilp_disable(struct clk_hw *hw)
{
        struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);

        regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0);
        regmap_write(ilp->regmap, 0x674, 0);
}

static unsigned long bcm53573_ilp_recalc_rate(struct clk_hw *hw,
                                              unsigned long parent_rate)
{
        struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
        struct regmap *regmap = ilp->regmap;
        u32 last_val, cur_val;
        int sum = 0, num = 0, loop_num = 0;
        int avg;

        /* Enable measurement */
        regmap_write(regmap, PMU_XTAL_FREQ_RATIO, XTAL_CTL_EN);

        /* Read initial value */
        regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &last_val);
        last_val &= XTAL_ALP_PER_4ILP;

        /*
         * At minimum we should loop for a bit to let hardware do the
         * measurement. This isn't very accurate however, so for a better
         * precision let's try getting 20 different values and use average.
         */
        while (num < 20) {
                regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &cur_val);
                cur_val &= XTAL_ALP_PER_4ILP;

                if (cur_val != last_val) {
                        /* Got different value, use it */
                        sum += cur_val;
                        num++;
                        loop_num = 0;
                        last_val = cur_val;
                } else if (++loop_num > 5000) {
                        /* Same value over and over, give up */
                        sum += cur_val;
                        num++;
                        break;
                }

                cpu_relax();
        }

        /* Disable measurement to save power */
        regmap_write(regmap, PMU_XTAL_FREQ_RATIO, 0x0);

        avg = sum / num;

        return parent_rate * 4 / avg;
}

static const struct clk_ops bcm53573_ilp_clk_ops = {
        .enable = bcm53573_ilp_enable,
        .disable = bcm53573_ilp_disable,
        .recalc_rate = bcm53573_ilp_recalc_rate,
};

static void bcm53573_ilp_init(struct device_node *np)
{
        struct bcm53573_ilp *ilp;
        struct clk_init_data init = { };
        const char *parent_name;
        int err;

        ilp = kzalloc_obj(*ilp);
        if (!ilp)
                return;

        parent_name = of_clk_get_parent_name(np, 0);
        if (!parent_name) {
                err = -ENOENT;
                goto err_free_ilp;
        }

        ilp->regmap = syscon_node_to_regmap(np->parent);
        if (IS_ERR(ilp->regmap)) {
                err = PTR_ERR(ilp->regmap);
                goto err_free_ilp;
        }

        init.name = np->name;
        init.ops = &bcm53573_ilp_clk_ops;
        init.parent_names = &parent_name;
        init.num_parents = 1;

        ilp->hw.init = &init;
        err = clk_hw_register(NULL, &ilp->hw);
        if (err)
                goto err_free_ilp;

        err = of_clk_add_hw_provider(np, of_clk_hw_simple_get, &ilp->hw);
        if (err)
                goto err_clk_hw_unregister;

        return;

err_clk_hw_unregister:
        clk_hw_unregister(&ilp->hw);
err_free_ilp:
        kfree(ilp);
        pr_err("Failed to init ILP clock: %d\n", err);
}

/* We need it very early for arch code, before device model gets ready */
CLK_OF_DECLARE(bcm53573_ilp_clk, "brcm,bcm53573-ilp", bcm53573_ilp_init);