loopdev: fix a deadlock
[linux-2.6.git] / 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 static void clk_gate_set_bit(struct clk_gate *gate)
32 {
33         u32 reg;
34         unsigned long flags = 0;
35
36         if (gate->lock)
37                 spin_lock_irqsave(gate->lock, flags);
38
39         reg = readl(gate->reg);
40         reg |= BIT(gate->bit_idx);
41         writel(reg, gate->reg);
42
43         if (gate->lock)
44                 spin_unlock_irqrestore(gate->lock, flags);
45 }
46
47 static void clk_gate_clear_bit(struct clk_gate *gate)
48 {
49         u32 reg;
50         unsigned long flags = 0;
51
52         if (gate->lock)
53                 spin_lock_irqsave(gate->lock, flags);
54
55         reg = readl(gate->reg);
56         reg &= ~BIT(gate->bit_idx);
57         writel(reg, gate->reg);
58
59         if (gate->lock)
60                 spin_unlock_irqrestore(gate->lock, flags);
61 }
62
63 static int clk_gate_enable(struct clk_hw *hw)
64 {
65         struct clk_gate *gate = to_clk_gate(hw);
66
67         if (gate->flags & CLK_GATE_SET_TO_DISABLE)
68                 clk_gate_clear_bit(gate);
69         else
70                 clk_gate_set_bit(gate);
71
72         return 0;
73 }
74 EXPORT_SYMBOL_GPL(clk_gate_enable);
75
76 static void clk_gate_disable(struct clk_hw *hw)
77 {
78         struct clk_gate *gate = to_clk_gate(hw);
79
80         if (gate->flags & CLK_GATE_SET_TO_DISABLE)
81                 clk_gate_set_bit(gate);
82         else
83                 clk_gate_clear_bit(gate);
84 }
85 EXPORT_SYMBOL_GPL(clk_gate_disable);
86
87 static 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 = 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 EXPORT_SYMBOL_GPL(clk_gate_is_enabled);
103
104 struct clk_ops clk_gate_ops = {
105         .enable = clk_gate_enable,
106         .disable = clk_gate_disable,
107         .is_enabled = clk_gate_is_enabled,
108 };
109 EXPORT_SYMBOL_GPL(clk_gate_ops);
110
111 struct clk *clk_register_gate(struct device *dev, const char *name,
112                 const char *parent_name, unsigned long flags,
113                 void __iomem *reg, u8 bit_idx,
114                 u8 clk_gate_flags, spinlock_t *lock)
115 {
116         struct clk_gate *gate;
117         struct clk *clk;
118
119         gate = kzalloc(sizeof(struct clk_gate), GFP_KERNEL);
120
121         if (!gate) {
122                 pr_err("%s: could not allocate gated clk\n", __func__);
123                 return NULL;
124         }
125
126         /* struct clk_gate assignments */
127         gate->reg = reg;
128         gate->bit_idx = bit_idx;
129         gate->flags = clk_gate_flags;
130         gate->lock = lock;
131
132         if (parent_name) {
133                 gate->parent[0] = kstrdup(parent_name, GFP_KERNEL);
134                 if (!gate->parent[0])
135                         goto out;
136         }
137
138         clk = clk_register(dev, name,
139                         &clk_gate_ops, &gate->hw,
140                         gate->parent,
141                         (parent_name ? 1 : 0),
142                         flags);
143         if (clk)
144                 return clk;
145 out:
146         kfree(gate->parent[0]);
147         kfree(gate);
148
149         return NULL;
150 }