/*
 * Copyright (C) 2013 Emilio López <emilio@elopez.com.ar>
 *
 * 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.
 *
 * Adjustable factor-based clock implementation
 */

#include <linux/clk-provider.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/of_address.h>
#include <linux/slab.h>
#include <linux/string.h>

#include "clk-factors.h"

/*
 * DOC: basic adjustable factor-based clock
 *
 * Traits of this clock:
 * prepare - clk_prepare only ensures that parents are prepared
 * enable - clk_enable only ensures that parents are enabled
 * rate - rate is adjustable.
 *        clk->rate = (parent->rate * N * (K + 1) >> P) / (M + 1)
 * parent - fixed parent.  No clk_set_parent support
 */

#define to_clk_factors(_hw) container_of(_hw, struct clk_factors, hw)

#define FACTORS_MAX_PARENTS             5

#define SETMASK(len, pos)               (((1U << (len)) - 1) << (pos))
#define CLRMASK(len, pos)               (~(SETMASK(len, pos)))
#define FACTOR_GET(bit, len, reg)       (((reg) & SETMASK(len, bit)) >> (bit))

#define FACTOR_SET(bit, len, reg, val) \
        (((reg) & CLRMASK(len, bit)) | (val << (bit)))

static unsigned long clk_factors_recalc_rate(struct clk_hw *hw,
                                             unsigned long parent_rate)
{
        u8 n = 1, k = 0, p = 0, m = 0;
        u32 reg;
        unsigned long rate;
        struct clk_factors *factors = to_clk_factors(hw);
        const struct clk_factors_config *config = factors->config;

        /* Fetch the register value */
        reg = readl(factors->reg);

        /* Get each individual factor if applicable */
        if (config->nwidth != SUNXI_FACTORS_NOT_APPLICABLE)
                n = FACTOR_GET(config->nshift, config->nwidth, reg);
        if (config->kwidth != SUNXI_FACTORS_NOT_APPLICABLE)
                k = FACTOR_GET(config->kshift, config->kwidth, reg);
        if (config->mwidth != SUNXI_FACTORS_NOT_APPLICABLE)
                m = FACTOR_GET(config->mshift, config->mwidth, reg);
        if (config->pwidth != SUNXI_FACTORS_NOT_APPLICABLE)
                p = FACTOR_GET(config->pshift, config->pwidth, reg);

        if (factors->recalc) {
                struct factors_request factors_req = {
                        .parent_rate = parent_rate,
                        .n = n,
                        .k = k,
                        .m = m,
                        .p = p,
                };

                /* get mux details from mux clk structure */
                if (factors->mux)
                        factors_req.parent_index =
                                (reg >> factors->mux->shift) &
                                factors->mux->mask;

                factors->recalc(&factors_req);

                return factors_req.rate;
        }

        /* Calculate the rate */
        rate = (parent_rate * (n + config->n_start) * (k + 1) >> p) / (m + 1);

        return rate;
}

static int clk_factors_determine_rate(struct clk_hw *hw,
                                      struct clk_rate_request *req)
{
        struct clk_factors *factors = to_clk_factors(hw);
        struct clk_hw *parent, *best_parent = NULL;
        int i, num_parents;
        unsigned long parent_rate, best = 0, child_rate, best_child_rate = 0;

        /* find the parent that can help provide the fastest rate <= rate */
        num_parents = clk_hw_get_num_parents(hw);
        for (i = 0; i < num_parents; i++) {
                struct factors_request factors_req = {
                        .rate = req->rate,
                        .parent_index = i,
                };
                parent = clk_hw_get_parent_by_index(hw, i);
                if (!parent)
                        continue;
                if (clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT)
                        parent_rate = clk_hw_round_rate(parent, req->rate);
                else
                        parent_rate = clk_hw_get_rate(parent);

                factors_req.parent_rate = parent_rate;
                factors->get_factors(&factors_req);
                child_rate = factors_req.rate;

                if (child_rate <= req->rate && child_rate > best_child_rate) {
                        best_parent = parent;
                        best = parent_rate;
                        best_child_rate = child_rate;
                }
        }

        if (!best_parent)
                return -EINVAL;

        req->best_parent_hw = best_parent;
        req->best_parent_rate = best;
        req->rate = best_child_rate;

        return 0;
}

static int clk_factors_set_rate(struct clk_hw *hw, unsigned long rate,
                                unsigned long parent_rate)
{
        struct factors_request req = {
                .rate = rate,
                .parent_rate = parent_rate,
        };
        u32 reg;
        struct clk_factors *factors = to_clk_factors(hw);
        const struct clk_factors_config *config = factors->config;
        unsigned long flags = 0;

        factors->get_factors(&req);

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

        /* Fetch the register value */
        reg = readl(factors->reg);

        /* Set up the new factors - macros do not do anything if width is 0 */
        reg = FACTOR_SET(config->nshift, config->nwidth, reg, req.n);
        reg = FACTOR_SET(config->kshift, config->kwidth, reg, req.k);
        reg = FACTOR_SET(config->mshift, config->mwidth, reg, req.m);
        reg = FACTOR_SET(config->pshift, config->pwidth, reg, req.p);

        /* Apply them now */
        writel(reg, factors->reg);

        /* delay 500us so pll stabilizes */
        __delay((rate >> 20) * 500 / 2);

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

        return 0;
}

static const struct clk_ops clk_factors_ops = {
        .determine_rate = clk_factors_determine_rate,
        .recalc_rate = clk_factors_recalc_rate,
        .set_rate = clk_factors_set_rate,
};

static struct clk *__sunxi_factors_register(struct device_node *node,
                                            const struct factors_data *data,
                                            spinlock_t *lock, void __iomem *reg,
                                            unsigned long flags)
{
        struct clk *clk;
        struct clk_factors *factors;
        struct clk_gate *gate = NULL;
        struct clk_mux *mux = NULL;
        struct clk_hw *gate_hw = NULL;
        struct clk_hw *mux_hw = NULL;
        const char *clk_name = node->name;
        const char *parents[FACTORS_MAX_PARENTS];
        int ret, i = 0;

        /* if we have a mux, we will have >1 parents */
        i = of_clk_parent_fill(node, parents, FACTORS_MAX_PARENTS);

        /*
         * some factor clocks, such as pll5 and pll6, may have multiple
         * outputs, and have their name designated in factors_data
         */
        if (data->name)
                clk_name = data->name;
        else
                of_property_read_string(node, "clock-output-names", &clk_name);

        factors = kzalloc(sizeof(struct clk_factors), GFP_KERNEL);
        if (!factors)
                goto err_factors;

        /* set up factors properties */
        factors->reg = reg;
        factors->config = data->table;
        factors->get_factors = data->getter;
        factors->recalc = data->recalc;
        factors->lock = lock;

        /* Add a gate if this factor clock can be gated */
        if (data->enable) {
                gate = kzalloc(sizeof(struct clk_gate), GFP_KERNEL);
                if (!gate)
                        goto err_gate;

                factors->gate = gate;

                /* set up gate properties */
                gate->reg = reg;
                gate->bit_idx = data->enable;
                gate->lock = factors->lock;
                gate_hw = &gate->hw;
        }

        /* Add a mux if this factor clock can be muxed */
        if (data->mux) {
                mux = kzalloc(sizeof(struct clk_mux), GFP_KERNEL);
                if (!mux)
                        goto err_mux;

                factors->mux = mux;

                /* set up gate properties */
                mux->reg = reg;
                mux->shift = data->mux;
                mux->mask = data->muxmask;
                mux->lock = factors->lock;
                mux_hw = &mux->hw;
        }

        clk = clk_register_composite(NULL, clk_name,
                        parents, i,
                        mux_hw, &clk_mux_ops,
                        &factors->hw, &clk_factors_ops,
                        gate_hw, &clk_gate_ops, CLK_IS_CRITICAL);
        if (IS_ERR(clk))
                goto err_register;

        ret = of_clk_add_provider(node, of_clk_src_simple_get, clk);
        if (ret)
                goto err_provider;

        return clk;

err_provider:
        /* TODO: The composite clock stuff will leak a bit here. */
        clk_unregister(clk);
err_register:
        kfree(mux);
err_mux:
        kfree(gate);
err_gate:
        kfree(factors);
err_factors:
        return NULL;
}

struct clk *sunxi_factors_register(struct device_node *node,
                                   const struct factors_data *data,
                                   spinlock_t *lock,
                                   void __iomem *reg)
{
        return __sunxi_factors_register(node, data, lock, reg, 0);
}

struct clk *sunxi_factors_register_critical(struct device_node *node,
                                            const struct factors_data *data,
                                            spinlock_t *lock,
                                            void __iomem *reg)
{
        return __sunxi_factors_register(node, data, lock, reg, CLK_IS_CRITICAL);
}

void sunxi_factors_unregister(struct device_node *node, struct clk *clk)
{
        struct clk_hw *hw = __clk_get_hw(clk);
        struct clk_factors *factors;

        if (!hw)
                return;

        factors = to_clk_factors(hw);

        of_clk_del_provider(node);
        /* TODO: The composite clock stuff will leak a bit here. */
        clk_unregister(clk);
        kfree(factors->mux);
        kfree(factors->gate);
        kfree(factors);
}