Root/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 flags = 0;
49    u32 reg;
50
51    set ^= enable;
52
53    if (gate->lock)
54        spin_lock_irqsave(gate->lock, flags);
55
56    reg = readl(gate->reg);
57
58    if (set)
59        reg |= BIT(gate->bit_idx);
60    else
61        reg &= ~BIT(gate->bit_idx);
62
63    writel(reg, gate->reg);
64
65    if (gate->lock)
66        spin_unlock_irqrestore(gate->lock, flags);
67}
68
69static int clk_gate_enable(struct clk_hw *hw)
70{
71    clk_gate_endisable(hw, 1);
72
73    return 0;
74}
75
76static void clk_gate_disable(struct clk_hw *hw)
77{
78    clk_gate_endisable(hw, 0);
79}
80
81static int clk_gate_is_enabled(struct clk_hw *hw)
82{
83    u32 reg;
84    struct clk_gate *gate = to_clk_gate(hw);
85
86    reg = readl(gate->reg);
87
88    /* if a set bit disables this clk, flip it before masking */
89    if (gate->flags & CLK_GATE_SET_TO_DISABLE)
90        reg ^= BIT(gate->bit_idx);
91
92    reg &= BIT(gate->bit_idx);
93
94    return reg ? 1 : 0;
95}
96
97const struct clk_ops clk_gate_ops = {
98    .enable = clk_gate_enable,
99    .disable = clk_gate_disable,
100    .is_enabled = clk_gate_is_enabled,
101};
102EXPORT_SYMBOL_GPL(clk_gate_ops);
103
104/**
105 * clk_register_gate - register a gate clock with the clock framework
106 * @dev: device that is registering this clock
107 * @name: name of this clock
108 * @parent_name: name of this clock's parent
109 * @flags: framework-specific flags for this clock
110 * @reg: register address to control gating of this clock
111 * @bit_idx: which bit in the register controls gating of this clock
112 * @clk_gate_flags: gate-specific flags for this clock
113 * @lock: shared register lock for this clock
114 */
115struct clk *clk_register_gate(struct device *dev, const char *name,
116        const char *parent_name, unsigned long flags,
117        void __iomem *reg, u8 bit_idx,
118        u8 clk_gate_flags, spinlock_t *lock)
119{
120    struct clk_gate *gate;
121    struct clk *clk;
122    struct clk_init_data init;
123
124    /* allocate the gate */
125    gate = kzalloc(sizeof(struct clk_gate), GFP_KERNEL);
126    if (!gate) {
127        pr_err("%s: could not allocate gated clk\n", __func__);
128        return ERR_PTR(-ENOMEM);
129    }
130
131    init.name = name;
132    init.ops = &clk_gate_ops;
133    init.flags = flags | CLK_IS_BASIC;
134    init.parent_names = (parent_name ? &parent_name: NULL);
135    init.num_parents = (parent_name ? 1 : 0);
136
137    /* struct clk_gate assignments */
138    gate->reg = reg;
139    gate->bit_idx = bit_idx;
140    gate->flags = clk_gate_flags;
141    gate->lock = lock;
142    gate->hw.init = &init;
143
144    clk = clk_register(dev, &gate->hw);
145
146    if (IS_ERR(clk))
147        kfree(gate);
148
149    return clk;
150}
151

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