clk-frac.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_frac {
    struct clk_hw hw;
    void __iomem *reg;
    u8 shift;
    u8 width;
    u8 busy;
};

#define to_clk_frac(_hw) container_of(_hw, struct clk_frac, hw)

static unsigned long clk_frac_recalc_rate(struct clk_hw *hw,
                      unsigned long parent_rate)
{
    struct clk_frac *frac = to_clk_frac(hw);
    u32 div;

    div = readl_relaxed(frac->reg) >> frac->shift;
    div &= (1 << frac->width) - 1;

    return (parent_rate >> frac->width) * div;
}

static long clk_frac_round_rate(struct clk_hw *hw, unsigned long rate,
                unsigned long *prate)
{
    struct clk_frac *frac = to_clk_frac(hw);
    unsigned long parent_rate = *prate;
    u32 div;
    u64 tmp;

    if (rate > parent_rate)
        return -EINVAL;

    tmp = rate;
    tmp <<= frac->width;
    do_div(tmp, parent_rate);
    div = tmp;

    if (!div)
        return -EINVAL;

    return (parent_rate >> frac->width) * div;
}

static int clk_frac_set_rate(struct clk_hw *hw, unsigned long rate,
                 unsigned long parent_rate)
{
    struct clk_frac *frac = to_clk_frac(hw);
    unsigned long flags;
    u32 div, val;
    u64 tmp;

    if (rate > parent_rate)
        return -EINVAL;

    tmp = rate;
    tmp <<= frac->width;
    do_div(tmp, parent_rate);
    div = tmp;

    if (!div)
        return -EINVAL;

    spin_lock_irqsave(&mxs_lock, flags);

    val = readl_relaxed(frac->reg);
    val &= ~(((1 << frac->width) - 1) << frac->shift);
    val |= div << frac->shift;
    writel_relaxed(val, frac->reg);

    spin_unlock_irqrestore(&mxs_lock, flags);

    return mxs_clk_wait(frac->reg, frac->busy);
}

static struct clk_ops clk_frac_ops = {
    .recalc_rate = clk_frac_recalc_rate,
    .round_rate = clk_frac_round_rate,
    .set_rate = clk_frac_set_rate,
};

struct clk *mxs_clk_frac(const char *name, const char *parent_name,
             void __iomem *reg, u8 shift, u8 width, u8 busy)
{
    struct clk_frac *frac;
    struct clk *clk;
    struct clk_init_data init;

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

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

    frac->reg = reg;
    frac->shift = shift;
    frac->width = width;
    frac->busy = busy;
    frac->hw.init = &init;

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

    return clk;
}