/*
 * Zynq PLL driver
 *
 *  Copyright (C) 2013 Xilinx
 *
 *  Sören Brinkmann <soren.brinkmann@xilinx.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License v2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
#include <linux/clk/zynq.h>
#include <linux/clk-provider.h>
#include <linux/slab.h>
#include <linux/io.h>

/**
 * struct zynq_pll
 * @hw:         Handle between common and hardware-specific interfaces
 * @pll_ctrl:   PLL control register
 * @pll_status: PLL status register
 * @lock:       Register lock
 * @lockbit:    Indicates the associated PLL_LOCKED bit in the PLL status
 *              register.
 */
struct zynq_pll {
        struct clk_hw   hw;
        void __iomem    *pll_ctrl;
        void __iomem    *pll_status;
        spinlock_t      *lock;
        u8              lockbit;
};
#define to_zynq_pll(_hw)        container_of(_hw, struct zynq_pll, hw)

/* Register bitfield defines */
#define PLLCTRL_FBDIV_MASK      0x7f000
#define PLLCTRL_FBDIV_SHIFT     12
#define PLLCTRL_BPQUAL_MASK     (1 << 3)
#define PLLCTRL_PWRDWN_MASK     2
#define PLLCTRL_PWRDWN_SHIFT    1
#define PLLCTRL_RESET_MASK      1
#define PLLCTRL_RESET_SHIFT     0

#define PLL_FBDIV_MIN   13
#define PLL_FBDIV_MAX   66

/**
 * zynq_pll_round_rate() - Round a clock frequency
 * @hw:         Handle between common and hardware-specific interfaces
 * @rate:       Desired clock frequency
 * @prate:      Clock frequency of parent clock
 * Returns frequency closest to @rate the hardware can generate.
 */
static long zynq_pll_round_rate(struct clk_hw *hw, unsigned long rate,
                unsigned long *prate)
{
        u32 fbdiv;

        fbdiv = DIV_ROUND_CLOSEST(rate, *prate);
        if (fbdiv < PLL_FBDIV_MIN)
                fbdiv = PLL_FBDIV_MIN;
        else if (fbdiv > PLL_FBDIV_MAX)
                fbdiv = PLL_FBDIV_MAX;

        return *prate * fbdiv;
}

/**
 * zynq_pll_recalc_rate() - Recalculate clock frequency
 * @hw:                 Handle between common and hardware-specific interfaces
 * @parent_rate:        Clock frequency of parent clock
 * Returns current clock frequency.
 */
static unsigned long zynq_pll_recalc_rate(struct clk_hw *hw,
                unsigned long parent_rate)
{
        struct zynq_pll *clk = to_zynq_pll(hw);
        u32 fbdiv;

        /*
         * makes probably sense to redundantly save fbdiv in the struct
         * zynq_pll to save the IO access.
         */
        fbdiv = (clk_readl(clk->pll_ctrl) & PLLCTRL_FBDIV_MASK) >>
                        PLLCTRL_FBDIV_SHIFT;

        return parent_rate * fbdiv;
}

/**
 * zynq_pll_is_enabled - Check if a clock is enabled
 * @hw:         Handle between common and hardware-specific interfaces
 * Returns 1 if the clock is enabled, 0 otherwise.
 *
 * Not sure this is a good idea, but since disabled means bypassed for
 * this clock implementation we say we are always enabled.
 */
static int zynq_pll_is_enabled(struct clk_hw *hw)
{
        unsigned long flags = 0;
        u32 reg;
        struct zynq_pll *clk = to_zynq_pll(hw);

        spin_lock_irqsave(clk->lock, flags);

        reg = clk_readl(clk->pll_ctrl);

        spin_unlock_irqrestore(clk->lock, flags);

        return !(reg & (PLLCTRL_RESET_MASK | PLLCTRL_PWRDWN_MASK));
}

/**
 * zynq_pll_enable - Enable clock
 * @hw:         Handle between common and hardware-specific interfaces
 * Returns 0 on success
 */
static int zynq_pll_enable(struct clk_hw *hw)
{
        unsigned long flags = 0;
        u32 reg;
        struct zynq_pll *clk = to_zynq_pll(hw);

        if (zynq_pll_is_enabled(hw))
                return 0;

        pr_info("PLL: enable\n");

        /* Power up PLL and wait for lock */
        spin_lock_irqsave(clk->lock, flags);

        reg = clk_readl(clk->pll_ctrl);
        reg &= ~(PLLCTRL_RESET_MASK | PLLCTRL_PWRDWN_MASK);
        clk_writel(reg, clk->pll_ctrl);
        while (!(clk_readl(clk->pll_status) & (1 << clk->lockbit)))
                ;

        spin_unlock_irqrestore(clk->lock, flags);

        return 0;
}

/**
 * zynq_pll_disable - Disable clock
 * @hw:         Handle between common and hardware-specific interfaces
 * Returns 0 on success
 */
static void zynq_pll_disable(struct clk_hw *hw)
{
        unsigned long flags = 0;
        u32 reg;
        struct zynq_pll *clk = to_zynq_pll(hw);

        if (!zynq_pll_is_enabled(hw))
                return;

        pr_info("PLL: shutdown\n");

        /* shut down PLL */
        spin_lock_irqsave(clk->lock, flags);

        reg = clk_readl(clk->pll_ctrl);
        reg |= PLLCTRL_RESET_MASK | PLLCTRL_PWRDWN_MASK;
        clk_writel(reg, clk->pll_ctrl);

        spin_unlock_irqrestore(clk->lock, flags);
}

static const struct clk_ops zynq_pll_ops = {
        .enable = zynq_pll_enable,
        .disable = zynq_pll_disable,
        .is_enabled = zynq_pll_is_enabled,
        .round_rate = zynq_pll_round_rate,
        .recalc_rate = zynq_pll_recalc_rate
};

/**
 * clk_register_zynq_pll() - Register PLL with the clock framework
 * @name        PLL name
 * @parent      Parent clock name
 * @pll_ctrl    Pointer to PLL control register
 * @pll_status  Pointer to PLL status register
 * @lock_index  Bit index to this PLL's lock status bit in @pll_status
 * @lock        Register lock
 * Returns handle to the registered clock.
 */
struct clk *clk_register_zynq_pll(const char *name, const char *parent,
                void __iomem *pll_ctrl, void __iomem *pll_status, u8 lock_index,
                spinlock_t *lock)
{
        struct zynq_pll *pll;
        struct clk *clk;
        u32 reg;
        const char *parent_arr[1] = {parent};
        unsigned long flags = 0;
        struct clk_init_data initd = {
                .name = name,
                .parent_names = parent_arr,
                .ops = &zynq_pll_ops,
                .num_parents = 1,
                .flags = 0
        };

        pll = kmalloc(sizeof(*pll), GFP_KERNEL);
        if (!pll)
                return ERR_PTR(-ENOMEM);

        /* Populate the struct */
        pll->hw.init = &initd;
        pll->pll_ctrl = pll_ctrl;
        pll->pll_status = pll_status;
        pll->lockbit = lock_index;
        pll->lock = lock;

        spin_lock_irqsave(pll->lock, flags);

        reg = clk_readl(pll->pll_ctrl);
        reg &= ~PLLCTRL_BPQUAL_MASK;
        clk_writel(reg, pll->pll_ctrl);

        spin_unlock_irqrestore(pll->lock, flags);

        clk = clk_register(NULL, &pll->hw);
        if (WARN_ON(IS_ERR(clk)))
                goto free_pll;

        return clk;

free_pll:
        kfree(pll);

        return clk;
}