/*
 * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com>
 * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@linaro.org>
 *
 * 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.
 *
 * Gated clock implementation
 */

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

/**
 * DOC: basic gatable clock which can gate and ungate it's ouput
 *
 * Traits of this clock:
 * prepare - clk_(un)prepare only ensures parent is (un)prepared
 * enable - clk_enable and clk_disable are functional & control gating
 * rate - inherits rate from parent.  No clk_set_rate support
 * parent - fixed parent.  No clk_set_parent support
 */

/*
 * It works on following logic:
 *
 * For enabling clock, enable = 1
 *      set2dis = 1     -> clear bit    -> set = 0
 *      set2dis = 0     -> set bit      -> set = 1
 *
 * For disabling clock, enable = 0
 *      set2dis = 1     -> set bit      -> set = 1
 *      set2dis = 0     -> clear bit    -> set = 0
 *
 * So, result is always: enable xor set2dis.
 */
static void clk_gate_endisable(struct clk_hw *hw, int enable)
{
        struct clk_gate *gate = to_clk_gate(hw);
        int set = gate->flags & CLK_GATE_SET_TO_DISABLE ? 1 : 0;
        unsigned long uninitialized_var(flags);
        u32 reg;

        set ^= enable;

        if (gate->lock)
                spin_lock_irqsave(gate->lock, flags);
        else
                __acquire(gate->lock);

        if (gate->flags & CLK_GATE_HIWORD_MASK) {
                reg = BIT(gate->bit_idx + 16);
                if (set)
                        reg |= BIT(gate->bit_idx);
        } else {
                reg = clk_readl(gate->reg);

                if (set)
                        reg |= BIT(gate->bit_idx);
                else
                        reg &= ~BIT(gate->bit_idx);
        }

        clk_writel(reg, gate->reg);

        if (gate->lock)
                spin_unlock_irqrestore(gate->lock, flags);
        else
                __release(gate->lock);
}

static int clk_gate_enable(struct clk_hw *hw)
{
        clk_gate_endisable(hw, 1);

        return 0;
}

static void clk_gate_disable(struct clk_hw *hw)
{
        clk_gate_endisable(hw, 0);
}

int clk_gate_is_enabled(struct clk_hw *hw)
{
        u32 reg;
        struct clk_gate *gate = to_clk_gate(hw);

        reg = clk_readl(gate->reg);

        /* if a set bit disables this clk, flip it before masking */
        if (gate->flags & CLK_GATE_SET_TO_DISABLE)
                reg ^= BIT(gate->bit_idx);

        reg &= BIT(gate->bit_idx);

        return reg ? 1 : 0;
}
EXPORT_SYMBOL_GPL(clk_gate_is_enabled);

const struct clk_ops clk_gate_ops = {
        .enable = clk_gate_enable,
        .disable = clk_gate_disable,
        .is_enabled = clk_gate_is_enabled,
};
EXPORT_SYMBOL_GPL(clk_gate_ops);

/**
 * clk_hw_register_gate - register a gate clock with the clock framework
 * @dev: device that is registering this clock
 * @name: name of this clock
 * @parent_name: name of this clock's parent
 * @flags: framework-specific flags for this clock
 * @reg: register address to control gating of this clock
 * @bit_idx: which bit in the register controls gating of this clock
 * @clk_gate_flags: gate-specific flags for this clock
 * @lock: shared register lock for this clock
 */
struct clk_hw *clk_hw_register_gate(struct device *dev, const char *name,
                const char *parent_name, unsigned long flags,
                void __iomem *reg, u8 bit_idx,
                u8 clk_gate_flags, spinlock_t *lock)
{
        struct clk_gate *gate;
        struct clk_hw *hw;
        struct clk_init_data init;
        int ret;

        if (clk_gate_flags & CLK_GATE_HIWORD_MASK) {
                if (bit_idx > 15) {
                        pr_err("gate bit exceeds LOWORD field\n");
                        return ERR_PTR(-EINVAL);
                }
        }

        /* allocate the gate */
        gate = kzalloc(sizeof(*gate), GFP_KERNEL);
        if (!gate)
                return ERR_PTR(-ENOMEM);

        init.name = name;
        init.ops = &clk_gate_ops;
        init.flags = flags | CLK_IS_BASIC;
        init.parent_names = parent_name ? &parent_name : NULL;
        init.num_parents = parent_name ? 1 : 0;

        /* struct clk_gate assignments */
        gate->reg = reg;
        gate->bit_idx = bit_idx;
        gate->flags = clk_gate_flags;
        gate->lock = lock;
        gate->hw.init = &init;

        hw = &gate->hw;
        ret = clk_hw_register(dev, hw);
        if (ret) {
                kfree(gate);
                hw = ERR_PTR(ret);
        }

        return hw;
}
EXPORT_SYMBOL_GPL(clk_hw_register_gate);

struct clk *clk_register_gate(struct device *dev, const char *name,
                const char *parent_name, unsigned long flags,
                void __iomem *reg, u8 bit_idx,
                u8 clk_gate_flags, spinlock_t *lock)
{
        struct clk_hw *hw;

        hw = clk_hw_register_gate(dev, name, parent_name, flags, reg,
                                  bit_idx, clk_gate_flags, lock);
        if (IS_ERR(hw))
                return ERR_CAST(hw);
        return hw->clk;
}
EXPORT_SYMBOL_GPL(clk_register_gate);

void clk_unregister_gate(struct clk *clk)
{
        struct clk_gate *gate;
        struct clk_hw *hw;

        hw = __clk_get_hw(clk);
        if (!hw)
                return;

        gate = to_clk_gate(hw);

        clk_unregister(clk);
        kfree(gate);
}
EXPORT_SYMBOL_GPL(clk_unregister_gate);

void clk_hw_unregister_gate(struct clk_hw *hw)
{
        struct clk_gate *gate;

        gate = to_clk_gate(hw);

        clk_hw_unregister(hw);
        kfree(gate);
}
EXPORT_SYMBOL_GPL(clk_hw_unregister_gate);