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  */
  44 static 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
  75 static int clk_gate_enable(struct clk_hw *hw)
  76 {
  77         clk_gate_endisable(hw, 1);
  78
  79         return 0;
  80 }
  81
  82 static void clk_gate_disable(struct clk_hw *hw)
  83 {
  84         clk_gate_endisable(hw, 0);
  85 }
  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 = 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
 103 const struct clk_ops clk_gate_ops = {
 104         .enable = clk_gate_enable,
 105         .disable = clk_gate_disable,
 106         .is_enabled = clk_gate_is_enabled,
 107 };
 108 EXPORT_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  */
 121 struct 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 > 15) {
 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 }
 164 EXPORT_SYMBOL_GPL(clk_register_gate);
 165
 166 void clk_unregister_gate(struct clk *clk)
 167 {
 168         struct clk_gate *gate;
 169         struct clk_hw *hw;
 170
 171         hw = __clk_get_hw(clk);
 172         if (!hw)
 173                 return;
 174
 175         gate = to_clk_gate(hw);
 176
 177         clk_unregister(clk);
 178         kfree(gate);
 179 }
 180 EXPORT_SYMBOL_GPL(clk_unregister_gate);