// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 ST Microelectronics
 * Viresh Kumar <vireshk@kernel.org>
 *
 * General Purpose Timer Synthesizer clock implementation
 */

#define pr_fmt(fmt) "clk-gpt-synth: " fmt

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

#define GPT_MSCALE_MASK         0xFFF
#define GPT_NSCALE_SHIFT        12
#define GPT_NSCALE_MASK         0xF

/*
 * DOC: General Purpose Timer Synthesizer clock
 *
 * Calculates gpt synth clk rate for different values of mscale and nscale
 *
 * Fout= Fin/((2 ^ (N+1)) * (M+1))
 */

#define to_clk_gpt(_hw) container_of(_hw, struct clk_gpt, hw)

static unsigned long gpt_calc_rate(struct clk_hw *hw, unsigned long prate,
                int index)
{
        struct clk_gpt *gpt = to_clk_gpt(hw);
        struct gpt_rate_tbl *rtbl = gpt->rtbl;

        prate /= ((1 << (rtbl[index].nscale + 1)) * (rtbl[index].mscale + 1));

        return prate;
}

static int clk_gpt_determine_rate(struct clk_hw *hw,
                                  struct clk_rate_request *req)
{
        struct clk_gpt *gpt = to_clk_gpt(hw);
        int unused;

        req->rate = clk_round_rate_index(hw, req->rate, req->best_parent_rate,
                                         gpt_calc_rate, gpt->rtbl_cnt, &unused);

        return 0;
}

static unsigned long clk_gpt_recalc_rate(struct clk_hw *hw,
                unsigned long parent_rate)
{
        struct clk_gpt *gpt = to_clk_gpt(hw);
        unsigned long flags = 0;
        unsigned int div = 1, val;

        if (gpt->lock)
                spin_lock_irqsave(gpt->lock, flags);

        val = readl_relaxed(gpt->reg);

        if (gpt->lock)
                spin_unlock_irqrestore(gpt->lock, flags);

        div += val & GPT_MSCALE_MASK;
        div *= 1 << (((val >> GPT_NSCALE_SHIFT) & GPT_NSCALE_MASK) + 1);

        if (!div)
                return 0;

        return parent_rate / div;
}

/* Configures new clock rate of gpt */
static int clk_gpt_set_rate(struct clk_hw *hw, unsigned long drate,
                                unsigned long prate)
{
        struct clk_gpt *gpt = to_clk_gpt(hw);
        struct gpt_rate_tbl *rtbl = gpt->rtbl;
        unsigned long flags = 0, val;
        int i;

        clk_round_rate_index(hw, drate, prate, gpt_calc_rate, gpt->rtbl_cnt,
                        &i);

        if (gpt->lock)
                spin_lock_irqsave(gpt->lock, flags);

        val = readl(gpt->reg) & ~GPT_MSCALE_MASK;
        val &= ~(GPT_NSCALE_MASK << GPT_NSCALE_SHIFT);

        val |= rtbl[i].mscale & GPT_MSCALE_MASK;
        val |= (rtbl[i].nscale & GPT_NSCALE_MASK) << GPT_NSCALE_SHIFT;

        writel_relaxed(val, gpt->reg);

        if (gpt->lock)
                spin_unlock_irqrestore(gpt->lock, flags);

        return 0;
}

static const struct clk_ops clk_gpt_ops = {
        .recalc_rate = clk_gpt_recalc_rate,
        .determine_rate = clk_gpt_determine_rate,
        .set_rate = clk_gpt_set_rate,
};

struct clk *clk_register_gpt(const char *name, const char *parent_name, unsigned
                long flags, void __iomem *reg, struct gpt_rate_tbl *rtbl, u8
                rtbl_cnt, spinlock_t *lock)
{
        struct clk_init_data init;
        struct clk_gpt *gpt;
        struct clk *clk;

        if (!name || !parent_name || !reg || !rtbl || !rtbl_cnt) {
                pr_err("Invalid arguments passed\n");
                return ERR_PTR(-EINVAL);
        }

        gpt = kzalloc_obj(*gpt);
        if (!gpt)
                return ERR_PTR(-ENOMEM);

        /* struct clk_gpt assignments */
        gpt->reg = reg;
        gpt->rtbl = rtbl;
        gpt->rtbl_cnt = rtbl_cnt;
        gpt->lock = lock;
        gpt->hw.init = &init;

        init.name = name;
        init.ops = &clk_gpt_ops;
        init.flags = flags;
        init.parent_names = &parent_name;
        init.num_parents = 1;

        clk = clk_register(NULL, &gpt->hw);
        if (!IS_ERR_OR_NULL(clk))
                return clk;

        pr_err("clk register failed\n");
        kfree(gpt);

        return NULL;
}