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 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
  69 static int clk_gate_enable(struct clk_hw *hw)
  70 {
  71         clk_gate_endisable(hw, 1);
  72
  73         return 0;
  74 }
  75
  76 static void clk_gate_disable(struct clk_hw *hw)
  77 {
  78         clk_gate_endisable(hw, 0);
  79 }
  80
  81 static 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
  97 const struct clk_ops clk_gate_ops = {
  98         .enable = clk_gate_enable,
  99         .disable = clk_gate_disable,
 100         .is_enabled = clk_gate_is_enabled,
 101 };
 102 EXPORT_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  */
 115 struct 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 }