1 /*
2  * Copyright 2016 Maxime Ripard
3  *
4  * Maxime Ripard <maxime.ripard@free-electrons.com>
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  * GNU General Public License for more details.
15  */
16 
17 #include <linux/clk.h>
18 #include <linux/clk-provider.h>
19 #include <linux/iopoll.h>
20 #include <linux/slab.h>
21 
22 #include "ccu_common.h"
23 #include "ccu_gate.h"
24 #include "ccu_reset.h"
25 
26 static DEFINE_SPINLOCK(ccu_lock);
27 
28 void ccu_helper_wait_for_lock(struct ccu_common *common, u32 lock)
29 {
30 	void __iomem *addr;
31 	u32 reg;
32 
33 	if (!lock)
34 		return;
35 
36 	if (common->features & CCU_FEATURE_LOCK_REG)
37 		addr = common->base + common->lock_reg;
38 	else
39 		addr = common->base + common->reg;
40 
41 	WARN_ON(readl_relaxed_poll_timeout(addr, reg, reg & lock, 100, 70000));
42 }
43 
44 /*
45  * This clock notifier is called when the frequency of a PLL clock is
46  * changed. In common PLL designs, changes to the dividers take effect
47  * almost immediately, while changes to the multipliers (implemented
48  * as dividers in the feedback loop) take a few cycles to work into
49  * the feedback loop for the PLL to stablize.
50  *
51  * Sometimes when the PLL clock rate is changed, the decrease in the
52  * divider is too much for the decrease in the multiplier to catch up.
53  * The PLL clock rate will spike, and in some cases, might lock up
54  * completely.
55  *
56  * This notifier callback will gate and then ungate the clock,
57  * effectively resetting it, so it proceeds to work. Care must be
58  * taken to reparent consumers to other temporary clocks during the
59  * rate change, and that this notifier callback must be the first
60  * to be registered.
61  */
62 static int ccu_pll_notifier_cb(struct notifier_block *nb,
63 			       unsigned long event, void *data)
64 {
65 	struct ccu_pll_nb *pll = to_ccu_pll_nb(nb);
66 	int ret = 0;
67 
68 	if (event != POST_RATE_CHANGE)
69 		goto out;
70 
71 	ccu_gate_helper_disable(pll->common, pll->enable);
72 
73 	ret = ccu_gate_helper_enable(pll->common, pll->enable);
74 	if (ret)
75 		goto out;
76 
77 	ccu_helper_wait_for_lock(pll->common, pll->lock);
78 
79 out:
80 	return notifier_from_errno(ret);
81 }
82 
83 int ccu_pll_notifier_register(struct ccu_pll_nb *pll_nb)
84 {
85 	pll_nb->clk_nb.notifier_call = ccu_pll_notifier_cb;
86 
87 	return clk_notifier_register(pll_nb->common->hw.clk,
88 				     &pll_nb->clk_nb);
89 }
90 
91 int sunxi_ccu_probe(struct device_node *node, void __iomem *reg,
92 		    const struct sunxi_ccu_desc *desc)
93 {
94 	struct ccu_reset *reset;
95 	int i, ret;
96 
97 	for (i = 0; i < desc->num_ccu_clks; i++) {
98 		struct ccu_common *cclk = desc->ccu_clks[i];
99 
100 		if (!cclk)
101 			continue;
102 
103 		cclk->base = reg;
104 		cclk->lock = &ccu_lock;
105 	}
106 
107 	for (i = 0; i < desc->hw_clks->num ; i++) {
108 		struct clk_hw *hw = desc->hw_clks->hws[i];
109 
110 		if (!hw)
111 			continue;
112 
113 		ret = clk_hw_register(NULL, hw);
114 		if (ret) {
115 			pr_err("Couldn't register clock %d - %s\n",
116 			       i, clk_hw_get_name(hw));
117 			goto err_clk_unreg;
118 		}
119 	}
120 
121 	ret = of_clk_add_hw_provider(node, of_clk_hw_onecell_get,
122 				     desc->hw_clks);
123 	if (ret)
124 		goto err_clk_unreg;
125 
126 	reset = kzalloc(sizeof(*reset), GFP_KERNEL);
127 	if (!reset) {
128 		ret = -ENOMEM;
129 		goto err_alloc_reset;
130 	}
131 
132 	reset->rcdev.of_node = node;
133 	reset->rcdev.ops = &ccu_reset_ops;
134 	reset->rcdev.owner = THIS_MODULE;
135 	reset->rcdev.nr_resets = desc->num_resets;
136 	reset->base = reg;
137 	reset->lock = &ccu_lock;
138 	reset->reset_map = desc->resets;
139 
140 	ret = reset_controller_register(&reset->rcdev);
141 	if (ret)
142 		goto err_of_clk_unreg;
143 
144 	return 0;
145 
146 err_of_clk_unreg:
147 	kfree(reset);
148 err_alloc_reset:
149 	of_clk_del_provider(node);
150 err_clk_unreg:
151 	while (--i >= 0) {
152 		struct clk_hw *hw = desc->hw_clks->hws[i];
153 
154 		if (!hw)
155 			continue;
156 		clk_hw_unregister(hw);
157 	}
158 	return ret;
159 }
160