LXR linux/drivers/clk/clk-gate.c

   1/*
   2 * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com>
   3 * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@linaro.org>
   4 *
   5 * This program is free software; you can redistribute it and/or modify
   6 * it under the terms of the GNU General Public License version 2 as
   7 * published by the Free Software Foundation.
   8 *
   9 * Gated clock implementation
  10 */
  11
  12#include <linux/clk-provider.h>
  13#include <linux/module.h>
  14#include <linux/slab.h>
  15#include <linux/io.h>
  16#include <linux/err.h>
  17#include <linux/string.h>
  18
  19/**
  20 * DOC: basic gatable clock which can gate and ungate it's ouput
  21 *
  22 * Traits of this clock:
  23 * prepare - clk_(un)prepare only ensures parent is (un)prepared
  24 * enable - clk_enable and clk_disable are functional & control gating
  25 * rate - inherits rate from parent.  No clk_set_rate support
  26 * parent - fixed parent.  No clk_set_parent support
  27 */
  28
  29#define to_clk_gate(_hw) container_of(_hw, struct clk_gate, hw)
  30
  31/*
  32 * It works on following logic:
  33 *
  34 * For enabling clock, enable = 1
  35 *      set2dis = 1     -> clear bit    -> set = 0
  36 *      set2dis = 0     -> set bit      -> set = 1
  37 *
  38 * For disabling clock, enable = 0
  39 *      set2dis = 1     -> set bit      -> set = 1
  40 *      set2dis = 0     -> clear bit    -> set = 0
  41 *
  42 * So, result is always: enable xor set2dis.
  43 */
  44static void clk_gate_endisable(struct clk_hw *hw, int enable)
  45{
  46        struct clk_gate *gate = to_clk_gate(hw);
  47        int set = gate->flags & CLK_GATE_SET_TO_DISABLE ? 1 : 0;
  48        unsigned long uninitialized_var(flags);
  49        u32 reg;
  50
  51        set ^= enable;
  52
  53        if (gate->lock)
  54                spin_lock_irqsave(gate->lock, flags);
  55
  56        if (gate->flags & CLK_GATE_HIWORD_MASK) {
  57                reg = BIT(gate->bit_idx + 16);
  58                if (set)
  59                        reg |= BIT(gate->bit_idx);
  60        } else {
  61                reg = clk_readl(gate->reg);
  62
  63                if (set)
  64                        reg |= BIT(gate->bit_idx);
  65                else
  66                        reg &= ~BIT(gate->bit_idx);
  67        }
  68
  69        clk_writel(reg, gate->reg);
  70
  71        if (gate->lock)
  72                spin_unlock_irqrestore(gate->lock, flags);
  73}
  74
  75static int clk_gate_enable(struct clk_hw *hw)
  76{
  77        clk_gate_endisable(hw, 1);
  78
  79        return 0;
  80}
  81
  82static void clk_gate_disable(struct clk_hw *hw)
  83{
  84        clk_gate_endisable(hw, 0);
  85}
  86
  87static int clk_gate_is_enabled(struct clk_hw *hw)
  88{
  89        u32 reg;
  90        struct clk_gate *gate = to_clk_gate(hw);
  91
  92        reg = clk_readl(gate->reg);
  93
  94        /* if a set bit disables this clk, flip it before masking */
  95        if (gate->flags & CLK_GATE_SET_TO_DISABLE)
  96                reg ^= BIT(gate->bit_idx);
  97
  98        reg &= BIT(gate->bit_idx);
  99
 100        return reg ? 1 : 0;
 101}
 102
 103const struct clk_ops clk_gate_ops = {
 104        .enable = clk_gate_enable,
 105        .disable = clk_gate_disable,
 106        .is_enabled = clk_gate_is_enabled,
 107};
 108EXPORT_SYMBOL_GPL(clk_gate_ops);
 109
 110/**
 111 * clk_register_gate - register a gate clock with the clock framework
 112 * @dev: device that is registering this clock
 113 * @name: name of this clock
 114 * @parent_name: name of this clock's parent
 115 * @flags: framework-specific flags for this clock
 116 * @reg: register address to control gating of this clock
 117 * @bit_idx: which bit in the register controls gating of this clock
 118 * @clk_gate_flags: gate-specific flags for this clock
 119 * @lock: shared register lock for this clock
 120 */
 121struct clk *clk_register_gate(struct device *dev, const char *name,
 122                const char *parent_name, unsigned long flags,
 123                void __iomem *reg, u8 bit_idx,
 124                u8 clk_gate_flags, spinlock_t *lock)
 125{
 126        struct clk_gate *gate;
 127        struct clk *clk;
 128        struct clk_init_data init;
 129
 130        if (clk_gate_flags & CLK_GATE_HIWORD_MASK) {
 131                if (bit_idx > 16) {
 132                        pr_err("gate bit exceeds LOWORD field\n");
 133                        return ERR_PTR(-EINVAL);
 134                }
 135        }
 136
 137        /* allocate the gate */
 138        gate = kzalloc(sizeof(struct clk_gate), GFP_KERNEL);
 139        if (!gate) {
 140                pr_err("%s: could not allocate gated clk\n", __func__);
 141                return ERR_PTR(-ENOMEM);
 142        }
 143
 144        init.name = name;
 145        init.ops = &clk_gate_ops;
 146        init.flags = flags | CLK_IS_BASIC;
 147        init.parent_names = (parent_name ? &parent_name: NULL);
 148        init.num_parents = (parent_name ? 1 : 0);
 149
 150        /* struct clk_gate assignments */
 151        gate->reg = reg;
 152        gate->bit_idx = bit_idx;
 153        gate->flags = clk_gate_flags;
 154        gate->lock = lock;
 155        gate->hw.init = &init;
 156
 157        clk = clk_register(dev, &gate->hw);
 158
 159        if (IS_ERR(clk))
 160                kfree(gate);
 161
 162        return clk;
 163}
 164EXPORT_SYMBOL_GPL(clk_register_gate);
 165