// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2014 MundoReader S.L.
 * Author: Heiko Stuebner <heiko@sntech.de>
 *
 * based on clk/samsung/clk-cpu.c
 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
 * Author: Thomas Abraham <thomas.ab@samsung.com>
 *
 * A CPU clock is defined as a clock supplied to a CPU or a group of CPUs.
 * The CPU clock is typically derived from a hierarchy of clock
 * blocks which includes mux and divider blocks. There are a number of other
 * auxiliary clocks supplied to the CPU domain such as the debug blocks and AXI
 * clock for CPU domain. The rates of these auxiliary clocks are related to the
 * CPU clock rate and this relation is usually specified in the hardware manual
 * of the SoC or supplied after the SoC characterization.
 *
 * The below implementation of the CPU clock allows the rate changes of the CPU
 * clock and the corresponding rate changes of the auxillary clocks of the CPU
 * domain. The platform clock driver provides a clock register configuration
 * for each configurable rate which is then used to program the clock hardware
 * registers to acheive a fast co-oridinated rate change for all the CPU domain
 * clocks.
 *
 * On a rate change request for the CPU clock, the rate change is propagated
 * upto the PLL supplying the clock to the CPU domain clock blocks. While the
 * CPU domain PLL is reconfigured, the CPU domain clocks are driven using an
 * alternate clock source. If required, the alternate clock source is divided
 * down in order to keep the output clock rate within the previous OPP limits.
 */

#include <linux/of.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/clk-provider.h>
#include "clk.h"

/**
 * struct rockchip_cpuclk: information about clock supplied to a CPU core.
 * @hw:         handle between ccf and cpu clock.
 * @alt_parent: alternate parent clock to use when switching the speed
 *              of the primary parent clock.
 * @reg_base:   base register for cpu-clock values.
 * @clk_nb:     clock notifier registered for changes in clock speed of the
 *              primary parent clock.
 * @rate_count: number of rates in the rate_table
 * @rate_table: pll-rates and their associated dividers
 * @reg_data:   cpu-specific register settings
 * @lock:       clock lock
 */
struct rockchip_cpuclk {
        struct clk_hw                           hw;
        struct clk                              *alt_parent;
        void __iomem                            *reg_base;
        struct notifier_block                   clk_nb;
        unsigned int                            rate_count;
        struct rockchip_cpuclk_rate_table       *rate_table;
        const struct rockchip_cpuclk_reg_data   *reg_data;
        spinlock_t                              *lock;
};

#define to_rockchip_cpuclk_hw(hw) container_of(hw, struct rockchip_cpuclk, hw)
#define to_rockchip_cpuclk_nb(nb) \
                        container_of(nb, struct rockchip_cpuclk, clk_nb)

static const struct rockchip_cpuclk_rate_table *rockchip_get_cpuclk_settings(
                            struct rockchip_cpuclk *cpuclk, unsigned long rate)
{
        const struct rockchip_cpuclk_rate_table *rate_table =
                                                        cpuclk->rate_table;
        int i;

        for (i = 0; i < cpuclk->rate_count; i++) {
                if (rate == rate_table[i].prate)
                        return &rate_table[i];
        }

        return NULL;
}

static unsigned long rockchip_cpuclk_recalc_rate(struct clk_hw *hw,
                                        unsigned long parent_rate)
{
        struct rockchip_cpuclk *cpuclk = to_rockchip_cpuclk_hw(hw);
        const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
        u32 clksel0 = readl_relaxed(cpuclk->reg_base + reg_data->core_reg[0]);

        clksel0 >>= reg_data->div_core_shift[0];
        clksel0 &= reg_data->div_core_mask[0];
        return parent_rate / (clksel0 + 1);
}

static const struct clk_ops rockchip_cpuclk_ops = {
        .recalc_rate = rockchip_cpuclk_recalc_rate,
};

static void rockchip_cpuclk_set_dividers(struct rockchip_cpuclk *cpuclk,
                                const struct rockchip_cpuclk_rate_table *rate)
{
        int i;

        /* alternate parent is active now. set the dividers */
        for (i = 0; i < ARRAY_SIZE(rate->divs); i++) {
                const struct rockchip_cpuclk_clksel *clksel = &rate->divs[i];

                if (!clksel->reg)
                        continue;

                pr_debug("%s: setting reg 0x%x to 0x%x\n",
                         __func__, clksel->reg, clksel->val);
                writel(clksel->val, cpuclk->reg_base + clksel->reg);
        }
}

static int rockchip_cpuclk_pre_rate_change(struct rockchip_cpuclk *cpuclk,
                                           struct clk_notifier_data *ndata)
{
        const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
        const struct rockchip_cpuclk_rate_table *rate;
        unsigned long alt_prate, alt_div;
        unsigned long flags;
        int i = 0;

        /* check validity of the new rate */
        rate = rockchip_get_cpuclk_settings(cpuclk, ndata->new_rate);
        if (!rate) {
                pr_err("%s: Invalid rate : %lu for cpuclk\n",
                       __func__, ndata->new_rate);
                return -EINVAL;
        }

        alt_prate = clk_get_rate(cpuclk->alt_parent);

        spin_lock_irqsave(cpuclk->lock, flags);

        /*
         * If the old parent clock speed is less than the clock speed
         * of the alternate parent, then it should be ensured that at no point
         * the armclk speed is more than the old_rate until the dividers are
         * set.
         */
        if (alt_prate > ndata->old_rate) {
                /* calculate dividers */
                alt_div =  DIV_ROUND_UP(alt_prate, ndata->old_rate) - 1;
                if (alt_div > reg_data->div_core_mask[0]) {
                        pr_warn("%s: limiting alt-divider %lu to %d\n",
                                __func__, alt_div, reg_data->div_core_mask[0]);
                        alt_div = reg_data->div_core_mask[0];
                }

                /*
                 * Change parents and add dividers in a single transaction.
                 *
                 * NOTE: we do this in a single transaction so we're never
                 * dividing the primary parent by the extra dividers that were
                 * needed for the alt.
                 */
                pr_debug("%s: setting div %lu as alt-rate %lu > old-rate %lu\n",
                         __func__, alt_div, alt_prate, ndata->old_rate);

                for (i = 0; i < reg_data->num_cores; i++) {
                        writel(HIWORD_UPDATE(alt_div, reg_data->div_core_mask[i],
                                             reg_data->div_core_shift[i]),
                               cpuclk->reg_base + reg_data->core_reg[i]);
                }
        }
        /* select alternate parent */
        writel(HIWORD_UPDATE(reg_data->mux_core_alt,
                             reg_data->mux_core_mask,
                             reg_data->mux_core_shift),
               cpuclk->reg_base + reg_data->core_reg[0]);

        spin_unlock_irqrestore(cpuclk->lock, flags);
        return 0;
}

static int rockchip_cpuclk_post_rate_change(struct rockchip_cpuclk *cpuclk,
                                            struct clk_notifier_data *ndata)
{
        const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
        const struct rockchip_cpuclk_rate_table *rate;
        unsigned long flags;
        int i = 0;

        rate = rockchip_get_cpuclk_settings(cpuclk, ndata->new_rate);
        if (!rate) {
                pr_err("%s: Invalid rate : %lu for cpuclk\n",
                       __func__, ndata->new_rate);
                return -EINVAL;
        }

        spin_lock_irqsave(cpuclk->lock, flags);

        if (ndata->old_rate < ndata->new_rate)
                rockchip_cpuclk_set_dividers(cpuclk, rate);

        /*
         * post-rate change event, re-mux to primary parent and remove dividers.
         *
         * NOTE: we do this in a single transaction so we're never dividing the
         * primary parent by the extra dividers that were needed for the alt.
         */

        writel(HIWORD_UPDATE(reg_data->mux_core_main,
                             reg_data->mux_core_mask,
                             reg_data->mux_core_shift),
               cpuclk->reg_base + reg_data->core_reg[0]);

        /* remove dividers */
        for (i = 0; i < reg_data->num_cores; i++) {
                writel(HIWORD_UPDATE(0, reg_data->div_core_mask[i],
                                     reg_data->div_core_shift[i]),
                       cpuclk->reg_base + reg_data->core_reg[i]);
        }

        if (ndata->old_rate > ndata->new_rate)
                rockchip_cpuclk_set_dividers(cpuclk, rate);

        spin_unlock_irqrestore(cpuclk->lock, flags);
        return 0;
}

/*
 * This clock notifier is called when the frequency of the parent clock
 * of cpuclk is to be changed. This notifier handles the setting up all
 * the divider clocks, remux to temporary parent and handling the safe
 * frequency levels when using temporary parent.
 */
static int rockchip_cpuclk_notifier_cb(struct notifier_block *nb,
                                        unsigned long event, void *data)
{
        struct clk_notifier_data *ndata = data;
        struct rockchip_cpuclk *cpuclk = to_rockchip_cpuclk_nb(nb);
        int ret = 0;

        pr_debug("%s: event %lu, old_rate %lu, new_rate: %lu\n",
                 __func__, event, ndata->old_rate, ndata->new_rate);
        if (event == PRE_RATE_CHANGE)
                ret = rockchip_cpuclk_pre_rate_change(cpuclk, ndata);
        else if (event == POST_RATE_CHANGE)
                ret = rockchip_cpuclk_post_rate_change(cpuclk, ndata);

        return notifier_from_errno(ret);
}

struct clk *rockchip_clk_register_cpuclk(const char *name,
                        const char *const *parent_names, u8 num_parents,
                        const struct rockchip_cpuclk_reg_data *reg_data,
                        const struct rockchip_cpuclk_rate_table *rates,
                        int nrates, void __iomem *reg_base, spinlock_t *lock)
{
        struct rockchip_cpuclk *cpuclk;
        struct clk_init_data init;
        struct clk *clk, *cclk;
        int ret;

        if (num_parents < 2) {
                pr_err("%s: needs at least two parent clocks\n", __func__);
                return ERR_PTR(-EINVAL);
        }

        cpuclk = kzalloc(sizeof(*cpuclk), GFP_KERNEL);
        if (!cpuclk)
                return ERR_PTR(-ENOMEM);

        init.name = name;
        init.parent_names = &parent_names[reg_data->mux_core_main];
        init.num_parents = 1;
        init.ops = &rockchip_cpuclk_ops;

        /* only allow rate changes when we have a rate table */
        init.flags = (nrates > 0) ? CLK_SET_RATE_PARENT : 0;

        /* disallow automatic parent changes by ccf */
        init.flags |= CLK_SET_RATE_NO_REPARENT;

        init.flags |= CLK_GET_RATE_NOCACHE;

        cpuclk->reg_base = reg_base;
        cpuclk->lock = lock;
        cpuclk->reg_data = reg_data;
        cpuclk->clk_nb.notifier_call = rockchip_cpuclk_notifier_cb;
        cpuclk->hw.init = &init;

        cpuclk->alt_parent = __clk_lookup(parent_names[reg_data->mux_core_alt]);
        if (!cpuclk->alt_parent) {
                pr_err("%s: could not lookup alternate parent: (%d)\n",
                       __func__, reg_data->mux_core_alt);
                ret = -EINVAL;
                goto free_cpuclk;
        }

        ret = clk_prepare_enable(cpuclk->alt_parent);
        if (ret) {
                pr_err("%s: could not enable alternate parent\n",
                       __func__);
                goto free_cpuclk;
        }

        clk = __clk_lookup(parent_names[reg_data->mux_core_main]);
        if (!clk) {
                pr_err("%s: could not lookup parent clock: (%d) %s\n",
                       __func__, reg_data->mux_core_main,
                       parent_names[reg_data->mux_core_main]);
                ret = -EINVAL;
                goto free_alt_parent;
        }

        ret = clk_notifier_register(clk, &cpuclk->clk_nb);
        if (ret) {
                pr_err("%s: failed to register clock notifier for %s\n",
                                __func__, name);
                goto free_alt_parent;
        }

        if (nrates > 0) {
                cpuclk->rate_count = nrates;
                cpuclk->rate_table = kmemdup(rates,
                                             sizeof(*rates) * nrates,
                                             GFP_KERNEL);
                if (!cpuclk->rate_table) {
                        ret = -ENOMEM;
                        goto unregister_notifier;
                }
        }

        cclk = clk_register(NULL, &cpuclk->hw);
        if (IS_ERR(cclk)) {
                pr_err("%s: could not register cpuclk %s\n", __func__,  name);
                ret = PTR_ERR(cclk);
                goto free_rate_table;
        }

        return cclk;

free_rate_table:
        kfree(cpuclk->rate_table);
unregister_notifier:
        clk_notifier_unregister(clk, &cpuclk->clk_nb);
free_alt_parent:
        clk_disable_unprepare(cpuclk->alt_parent);
free_cpuclk:
        kfree(cpuclk);
        return ERR_PTR(ret);
}