clk-ref.c

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/*
 * Copyright 2012 Freescale Semiconductor, Inc.
 *
 * The code contained herein is licensed under the GNU General Public
 * License. You may obtain a copy of the GNU General Public License
 * Version 2 or later at the following locations:
 *
 * http://www.opensource.org/licenses/gpl-license.html
 * http://www.gnu.org/copyleft/gpl.html
 */

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

struct clk_ref {
    struct clk_hw hw;
    void __iomem *reg;
    u8 idx;
};

#define to_clk_ref(_hw) container_of(_hw, struct clk_ref, hw)

static int clk_ref_enable(struct clk_hw *hw)
{
    struct clk_ref *ref = to_clk_ref(hw);

    writel_relaxed(1 << ((ref->idx + 1) * 8 - 1), ref->reg + CLR);

    return 0;
}

static void clk_ref_disable(struct clk_hw *hw)
{
    struct clk_ref *ref = to_clk_ref(hw);

    writel_relaxed(1 << ((ref->idx + 1) * 8 - 1), ref->reg + SET);
}

static unsigned long clk_ref_recalc_rate(struct clk_hw *hw,
                     unsigned long parent_rate)
{
    struct clk_ref *ref = to_clk_ref(hw);
    u64 tmp = parent_rate;
    u8 frac = (readl_relaxed(ref->reg) >> (ref->idx * 8)) & 0x3f;

    tmp *= 18;
    do_div(tmp, frac);

    return tmp;
}

static long clk_ref_round_rate(struct clk_hw *hw, unsigned long rate,
                   unsigned long *prate)
{
    unsigned long parent_rate = *prate;
    u64 tmp = parent_rate;
    u8 frac;

    tmp = tmp * 18 + rate / 2;
    do_div(tmp, rate);
    frac = tmp;

    if (frac < 18)
        frac = 18;
    else if (frac > 35)
        frac = 35;

    tmp = parent_rate;
    tmp *= 18;
    do_div(tmp, frac);

    return tmp;
}

static int clk_ref_set_rate(struct clk_hw *hw, unsigned long rate,
                unsigned long parent_rate)
{
    struct clk_ref *ref = to_clk_ref(hw);
    unsigned long flags;
    u64 tmp = parent_rate;
    u32 val;
    u8 frac, shift = ref->idx * 8;

    tmp = tmp * 18 + rate / 2;
    do_div(tmp, rate);
    frac = tmp;

    if (frac < 18)
        frac = 18;
    else if (frac > 35)
        frac = 35;

    spin_lock_irqsave(&mxs_lock, flags);

    val = readl_relaxed(ref->reg);
    val &= ~(0x3f << shift);
    val |= frac << shift;
    writel_relaxed(val, ref->reg);

    spin_unlock_irqrestore(&mxs_lock, flags);

    return 0;
}

static const struct clk_ops clk_ref_ops = {
    .enable     = clk_ref_enable,
    .disable    = clk_ref_disable,
    .recalc_rate    = clk_ref_recalc_rate,
    .round_rate = clk_ref_round_rate,
    .set_rate   = clk_ref_set_rate,
};

struct clk *mxs_clk_ref(const char *name, const char *parent_name,
            void __iomem *reg, u8 idx)
{
    struct clk_ref *ref;
    struct clk *clk;
    struct clk_init_data init;

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

    init.name = name;
    init.ops = &clk_ref_ops;
    init.flags = 0;
    init.parent_names = (parent_name ? &parent_name: NULL);
    init.num_parents = (parent_name ? 1 : 0);

    ref->reg = reg;
    ref->idx = idx;
    ref->hw.init = &init;

    clk = clk_register(NULL, &ref->hw);
    if (IS_ERR(clk))
        kfree(ref);

    return clk;
}