/*
 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
 * Author: Thomas Abraham <thomas.ab@samsung.com>
 *
 * Copyright (c) 2015 Samsung Electronics Co., Ltd.
 * Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This file contains the utility function to register CPU clock for Samsung
 * Exynos platforms. 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/errno.h>
#include <linux/slab.h>
#include <linux/clk.h>
#include <linux/clk-provider.h>
#include "clk-cpu.h"

#define E4210_SRC_CPU           0x0
#define E4210_STAT_CPU          0x200
#define E4210_DIV_CPU0          0x300
#define E4210_DIV_CPU1          0x304
#define E4210_DIV_STAT_CPU0     0x400
#define E4210_DIV_STAT_CPU1     0x404

#define E4210_DIV0_RATIO0_MASK  0x7
#define E4210_DIV1_HPM_MASK     (0x7 << 4)
#define E4210_DIV1_COPY_MASK    (0x7 << 0)
#define E4210_MUX_HPM_MASK      (1 << 20)
#define E4210_DIV0_ATB_SHIFT    16
#define E4210_DIV0_ATB_MASK     (DIV_MASK << E4210_DIV0_ATB_SHIFT)

#define MAX_DIV                 8
#define DIV_MASK                7
#define DIV_MASK_ALL            0xffffffff
#define MUX_MASK                7

/*
 * Helper function to wait until divider(s) have stabilized after the divider
 * value has changed.
 */
static void wait_until_divider_stable(void __iomem *div_reg, unsigned long mask)
{
        unsigned long timeout = jiffies + msecs_to_jiffies(10);

        do {
                if (!(readl(div_reg) & mask))
                        return;
        } while (time_before(jiffies, timeout));

        if (!(readl(div_reg) & mask))
                return;

        pr_err("%s: timeout in divider stablization\n", __func__);
}

/*
 * Helper function to wait until mux has stabilized after the mux selection
 * value was changed.
 */
static void wait_until_mux_stable(void __iomem *mux_reg, u32 mux_pos,
                                        unsigned long mux_value)
{
        unsigned long timeout = jiffies + msecs_to_jiffies(10);

        do {
                if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
                        return;
        } while (time_before(jiffies, timeout));

        if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
                return;

        pr_err("%s: re-parenting mux timed-out\n", __func__);
}

/* common round rate callback useable for all types of CPU clocks */
static long exynos_cpuclk_round_rate(struct clk_hw *hw,
                        unsigned long drate, unsigned long *prate)
{
        struct clk_hw *parent = clk_hw_get_parent(hw);
        *prate = clk_hw_round_rate(parent, drate);
        return *prate;
}

/* common recalc rate callback useable for all types of CPU clocks */
static unsigned long exynos_cpuclk_recalc_rate(struct clk_hw *hw,
                        unsigned long parent_rate)
{
        /*
         * The CPU clock output (armclk) rate is the same as its parent
         * rate. Although there exist certain dividers inside the CPU
         * clock block that could be used to divide the parent clock,
         * the driver does not make use of them currently, except during
         * frequency transitions.
         */
        return parent_rate;
}

static const struct clk_ops exynos_cpuclk_clk_ops = {
        .recalc_rate = exynos_cpuclk_recalc_rate,
        .round_rate = exynos_cpuclk_round_rate,
};

/*
 * Helper function to set the 'safe' dividers for the CPU clock. The parameters
 * div and mask contain the divider value and the register bit mask of the
 * dividers to be programmed.
 */
static void exynos_set_safe_div(void __iomem *base, unsigned long div,
                                        unsigned long mask)
{
        unsigned long div0;

        div0 = readl(base + E4210_DIV_CPU0);
        div0 = (div0 & ~mask) | (div & mask);
        writel(div0, base + E4210_DIV_CPU0);
        wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, mask);
}

/* handler for pre-rate change notification from parent clock */
static int exynos_cpuclk_pre_rate_change(struct clk_notifier_data *ndata,
                        struct exynos_cpuclk *cpuclk, void __iomem *base)
{
        const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
        unsigned long alt_prate = clk_get_rate(cpuclk->alt_parent);
        unsigned long alt_div = 0, alt_div_mask = DIV_MASK;
        unsigned long div0, div1 = 0, mux_reg;
        unsigned long flags;

        /* find out the divider values to use for clock data */
        while ((cfg_data->prate * 1000) != ndata->new_rate) {
                if (cfg_data->prate == 0)
                        return -EINVAL;
                cfg_data++;
        }

        spin_lock_irqsave(cpuclk->lock, flags);

        /*
         * For the selected PLL clock frequency, get the pre-defined divider
         * values. If the clock for sclk_hpm is not sourced from apll, then
         * the values for DIV_COPY and DIV_HPM dividers need not be set.
         */
        div0 = cfg_data->div0;
        if (cpuclk->flags & CLK_CPU_HAS_DIV1) {
                div1 = cfg_data->div1;
                if (readl(base + E4210_SRC_CPU) & E4210_MUX_HPM_MASK)
                        div1 = readl(base + E4210_DIV_CPU1) &
                                (E4210_DIV1_HPM_MASK | E4210_DIV1_COPY_MASK);
        }

        /*
         * 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_prate until the dividers are
         * set.  Also workaround the issue of the dividers being set to lower
         * values before the parent clock speed is set to new lower speed
         * (this can result in too high speed of armclk output clocks).
         */
        if (alt_prate > ndata->old_rate || ndata->old_rate > ndata->new_rate) {
                unsigned long tmp_rate = min(ndata->old_rate, ndata->new_rate);

                alt_div = DIV_ROUND_UP(alt_prate, tmp_rate) - 1;
                WARN_ON(alt_div >= MAX_DIV);

                if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
                        /*
                         * In Exynos4210, ATB clock parent is also mout_core. So
                         * ATB clock also needs to be mantained at safe speed.
                         */
                        alt_div |= E4210_DIV0_ATB_MASK;
                        alt_div_mask |= E4210_DIV0_ATB_MASK;
                }
                exynos_set_safe_div(base, alt_div, alt_div_mask);
                div0 |= alt_div;
        }

        /* select sclk_mpll as the alternate parent */
        mux_reg = readl(base + E4210_SRC_CPU);
        writel(mux_reg | (1 << 16), base + E4210_SRC_CPU);
        wait_until_mux_stable(base + E4210_STAT_CPU, 16, 2);

        /* alternate parent is active now. set the dividers */
        writel(div0, base + E4210_DIV_CPU0);
        wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, DIV_MASK_ALL);

        if (cpuclk->flags & CLK_CPU_HAS_DIV1) {
                writel(div1, base + E4210_DIV_CPU1);
                wait_until_divider_stable(base + E4210_DIV_STAT_CPU1,
                                DIV_MASK_ALL);
        }

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

/* handler for post-rate change notification from parent clock */
static int exynos_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
                        struct exynos_cpuclk *cpuclk, void __iomem *base)
{
        const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
        unsigned long div = 0, div_mask = DIV_MASK;
        unsigned long mux_reg;
        unsigned long flags;

        /* find out the divider values to use for clock data */
        if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
                while ((cfg_data->prate * 1000) != ndata->new_rate) {
                        if (cfg_data->prate == 0)
                                return -EINVAL;
                        cfg_data++;
                }
        }

        spin_lock_irqsave(cpuclk->lock, flags);

        /* select mout_apll as the alternate parent */
        mux_reg = readl(base + E4210_SRC_CPU);
        writel(mux_reg & ~(1 << 16), base + E4210_SRC_CPU);
        wait_until_mux_stable(base + E4210_STAT_CPU, 16, 1);

        if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
                div |= (cfg_data->div0 & E4210_DIV0_ATB_MASK);
                div_mask |= E4210_DIV0_ATB_MASK;
        }

        exynos_set_safe_div(base, div, div_mask);
        spin_unlock_irqrestore(cpuclk->lock, flags);
        return 0;
}

/*
 * This notifier function is called for the pre-rate and post-rate change
 * notifications of the parent clock of cpuclk.
 */
static int exynos_cpuclk_notifier_cb(struct notifier_block *nb,
                                unsigned long event, void *data)
{
        struct clk_notifier_data *ndata = data;
        struct exynos_cpuclk *cpuclk;
        void __iomem *base;
        int err = 0;

        cpuclk = container_of(nb, struct exynos_cpuclk, clk_nb);
        base = cpuclk->ctrl_base;

        if (event == PRE_RATE_CHANGE)
                err = exynos_cpuclk_pre_rate_change(ndata, cpuclk, base);
        else if (event == POST_RATE_CHANGE)
                err = exynos_cpuclk_post_rate_change(ndata, cpuclk, base);

        return notifier_from_errno(err);
}

/* helper function to register a CPU clock */
int __init exynos_register_cpu_clock(struct samsung_clk_provider *ctx,
                unsigned int lookup_id, const char *name, const char *parent,
                const char *alt_parent, unsigned long offset,
                const struct exynos_cpuclk_cfg_data *cfg,
                unsigned long num_cfgs, unsigned long flags)
{
        struct exynos_cpuclk *cpuclk;
        struct clk_init_data init;
        struct clk *clk;
        int ret = 0;

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

        init.name = name;
        init.flags = CLK_SET_RATE_PARENT;
        init.parent_names = &parent;
        init.num_parents = 1;
        init.ops = &exynos_cpuclk_clk_ops;

        cpuclk->hw.init = &init;
        cpuclk->ctrl_base = ctx->reg_base + offset;
        cpuclk->lock = &ctx->lock;
        cpuclk->flags = flags;
        cpuclk->clk_nb.notifier_call = exynos_cpuclk_notifier_cb;

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

        clk = __clk_lookup(parent);
        if (!clk) {
                pr_err("%s: could not lookup parent clock %s\n",
                                __func__, parent);
                ret = -EINVAL;
                goto free_cpuclk;
        }

        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_cpuclk;
        }

        cpuclk->cfg = kmemdup(cfg, sizeof(*cfg) * num_cfgs, GFP_KERNEL);
        if (!cpuclk->cfg) {
                pr_err("%s: could not allocate memory for cpuclk data\n",
                                __func__);
                ret = -ENOMEM;
                goto unregister_clk_nb;
        }

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

        samsung_clk_add_lookup(ctx, clk, lookup_id);
        return 0;

free_cpuclk_data:
        kfree(cpuclk->cfg);
unregister_clk_nb:
        clk_notifier_unregister(__clk_lookup(parent), &cpuclk->clk_nb);
free_cpuclk:
        kfree(cpuclk);
        return ret;
}