LXR linux/drivers/clk/mxs/clk-ref.c

   1/*
   2 * Copyright 2012 Freescale Semiconductor, Inc.
   3 *
   4 * The code contained herein is licensed under the GNU General Public
   5 * License. You may obtain a copy of the GNU General Public License
   6 * Version 2 or later at the following locations:
   7 *
   8 * http://www.opensource.org/licenses/gpl-license.html
   9 * http://www.gnu.org/copyleft/gpl.html
  10 */
  11
  12#include <linux/clk.h>
  13#include <linux/clk-provider.h>
  14#include <linux/err.h>
  15#include <linux/io.h>
  16#include <linux/slab.h>
  17#include "clk.h"
  18
  19/**
  20 * struct clk_ref - mxs reference clock
  21 * @hw: clk_hw for the reference clock
  22 * @reg: register address
  23 * @idx: the index of the reference clock within the same register
  24 *
  25 * The mxs reference clock sources from pll.  Every 4 reference clocks share
  26 * one register space, and @idx is used to identify them.  Each reference
  27 * clock has a gate control and a fractional * divider.  The rate is calculated
  28 * as pll rate  * (18 / FRAC), where FRAC = 18 ~ 35.
  29 */
  30struct clk_ref {
  31        struct clk_hw hw;
  32        void __iomem *reg;
  33        u8 idx;
  34};
  35
  36#define to_clk_ref(_hw) container_of(_hw, struct clk_ref, hw)
  37
  38static int clk_ref_enable(struct clk_hw *hw)
  39{
  40        struct clk_ref *ref = to_clk_ref(hw);
  41
  42        writel_relaxed(1 << ((ref->idx + 1) * 8 - 1), ref->reg + CLR);
  43
  44        return 0;
  45}
  46
  47static void clk_ref_disable(struct clk_hw *hw)
  48{
  49        struct clk_ref *ref = to_clk_ref(hw);
  50
  51        writel_relaxed(1 << ((ref->idx + 1) * 8 - 1), ref->reg + SET);
  52}
  53
  54static unsigned long clk_ref_recalc_rate(struct clk_hw *hw,
  55                                         unsigned long parent_rate)
  56{
  57        struct clk_ref *ref = to_clk_ref(hw);
  58        u64 tmp = parent_rate;
  59        u8 frac = (readl_relaxed(ref->reg) >> (ref->idx * 8)) & 0x3f;
  60
  61        tmp *= 18;
  62        do_div(tmp, frac);
  63
  64        return tmp;
  65}
  66
  67static long clk_ref_round_rate(struct clk_hw *hw, unsigned long rate,
  68                               unsigned long *prate)
  69{
  70        unsigned long parent_rate = *prate;
  71        u64 tmp = parent_rate;
  72        u8 frac;
  73
  74        tmp = tmp * 18 + rate / 2;
  75        do_div(tmp, rate);
  76        frac = tmp;
  77
  78        if (frac < 18)
  79                frac = 18;
  80        else if (frac > 35)
  81                frac = 35;
  82
  83        tmp = parent_rate;
  84        tmp *= 18;
  85        do_div(tmp, frac);
  86
  87        return tmp;
  88}
  89
  90static int clk_ref_set_rate(struct clk_hw *hw, unsigned long rate,
  91                            unsigned long parent_rate)
  92{
  93        struct clk_ref *ref = to_clk_ref(hw);
  94        unsigned long flags;
  95        u64 tmp = parent_rate;
  96        u32 val;
  97        u8 frac, shift = ref->idx * 8;
  98
  99        tmp = tmp * 18 + rate / 2;
 100        do_div(tmp, rate);
 101        frac = tmp;
 102
 103        if (frac < 18)
 104                frac = 18;
 105        else if (frac > 35)
 106                frac = 35;
 107
 108        spin_lock_irqsave(&mxs_lock, flags);
 109
 110        val = readl_relaxed(ref->reg);
 111        val &= ~(0x3f << shift);
 112        val |= frac << shift;
 113        writel_relaxed(val, ref->reg);
 114
 115        spin_unlock_irqrestore(&mxs_lock, flags);
 116
 117        return 0;
 118}
 119
 120static const struct clk_ops clk_ref_ops = {
 121        .enable         = clk_ref_enable,
 122        .disable        = clk_ref_disable,
 123        .recalc_rate    = clk_ref_recalc_rate,
 124        .round_rate     = clk_ref_round_rate,
 125        .set_rate       = clk_ref_set_rate,
 126};
 127
 128struct clk *mxs_clk_ref(const char *name, const char *parent_name,
 129                        void __iomem *reg, u8 idx)
 130{
 131        struct clk_ref *ref;
 132        struct clk *clk;
 133        struct clk_init_data init;
 134
 135        ref = kzalloc(sizeof(*ref), GFP_KERNEL);
 136        if (!ref)
 137                return ERR_PTR(-ENOMEM);
 138
 139        init.name = name;
 140        init.ops = &clk_ref_ops;
 141        init.flags = 0;
 142        init.parent_names = (parent_name ? &parent_name: NULL);
 143        init.num_parents = (parent_name ? 1 : 0);
 144
 145        ref->reg = reg;
 146        ref->idx = idx;
 147        ref->hw.init = &init;
 148
 149        clk = clk_register(NULL, &ref->hw);
 150        if (IS_ERR(clk))
 151                kfree(ref);
 152
 153        return clk;
 154}
 155