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 }