1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2016 Rafał Miłecki <rafal@milecki.pl>
4  */
5 
6 #include <linux/clk-provider.h>
7 #include <linux/err.h>
8 #include <linux/io.h>
9 #include <linux/mfd/syscon.h>
10 #include <linux/of.h>
11 #include <linux/of_address.h>
12 #include <linux/regmap.h>
13 #include <linux/slab.h>
14 
15 #define PMU_XTAL_FREQ_RATIO			0x66c
16 #define  XTAL_ALP_PER_4ILP			0x00001fff
17 #define  XTAL_CTL_EN				0x80000000
18 #define PMU_SLOW_CLK_PERIOD			0x6dc
19 
20 struct bcm53573_ilp {
21 	struct clk_hw hw;
22 	struct regmap *regmap;
23 };
24 
25 static int bcm53573_ilp_enable(struct clk_hw *hw)
26 {
27 	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
28 
29 	regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0x10199);
30 	regmap_write(ilp->regmap, 0x674, 0x10000);
31 
32 	return 0;
33 }
34 
35 static void bcm53573_ilp_disable(struct clk_hw *hw)
36 {
37 	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
38 
39 	regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0);
40 	regmap_write(ilp->regmap, 0x674, 0);
41 }
42 
43 static unsigned long bcm53573_ilp_recalc_rate(struct clk_hw *hw,
44 					      unsigned long parent_rate)
45 {
46 	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
47 	struct regmap *regmap = ilp->regmap;
48 	u32 last_val, cur_val;
49 	int sum = 0, num = 0, loop_num = 0;
50 	int avg;
51 
52 	/* Enable measurement */
53 	regmap_write(regmap, PMU_XTAL_FREQ_RATIO, XTAL_CTL_EN);
54 
55 	/* Read initial value */
56 	regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &last_val);
57 	last_val &= XTAL_ALP_PER_4ILP;
58 
59 	/*
60 	 * At minimum we should loop for a bit to let hardware do the
61 	 * measurement. This isn't very accurate however, so for a better
62 	 * precision lets try getting 20 different values for and use average.
63 	 */
64 	while (num < 20) {
65 		regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &cur_val);
66 		cur_val &= XTAL_ALP_PER_4ILP;
67 
68 		if (cur_val != last_val) {
69 			/* Got different value, use it */
70 			sum += cur_val;
71 			num++;
72 			loop_num = 0;
73 			last_val = cur_val;
74 		} else if (++loop_num > 5000) {
75 			/* Same value over and over, give up */
76 			sum += cur_val;
77 			num++;
78 			break;
79 		}
80 
81 		cpu_relax();
82 	}
83 
84 	/* Disable measurement to save power */
85 	regmap_write(regmap, PMU_XTAL_FREQ_RATIO, 0x0);
86 
87 	avg = sum / num;
88 
89 	return parent_rate * 4 / avg;
90 }
91 
92 static const struct clk_ops bcm53573_ilp_clk_ops = {
93 	.enable = bcm53573_ilp_enable,
94 	.disable = bcm53573_ilp_disable,
95 	.recalc_rate = bcm53573_ilp_recalc_rate,
96 };
97 
98 static void bcm53573_ilp_init(struct device_node *np)
99 {
100 	struct bcm53573_ilp *ilp;
101 	struct clk_init_data init = { };
102 	const char *parent_name;
103 	int err;
104 
105 	ilp = kzalloc(sizeof(*ilp), GFP_KERNEL);
106 	if (!ilp)
107 		return;
108 
109 	parent_name = of_clk_get_parent_name(np, 0);
110 	if (!parent_name) {
111 		err = -ENOENT;
112 		goto err_free_ilp;
113 	}
114 
115 	ilp->regmap = syscon_node_to_regmap(of_get_parent(np));
116 	if (IS_ERR(ilp->regmap)) {
117 		err = PTR_ERR(ilp->regmap);
118 		goto err_free_ilp;
119 	}
120 
121 	init.name = np->name;
122 	init.ops = &bcm53573_ilp_clk_ops;
123 	init.parent_names = &parent_name;
124 	init.num_parents = 1;
125 
126 	ilp->hw.init = &init;
127 	err = clk_hw_register(NULL, &ilp->hw);
128 	if (err)
129 		goto err_free_ilp;
130 
131 	err = of_clk_add_hw_provider(np, of_clk_hw_simple_get, &ilp->hw);
132 	if (err)
133 		goto err_clk_hw_unregister;
134 
135 	return;
136 
137 err_clk_hw_unregister:
138 	clk_hw_unregister(&ilp->hw);
139 err_free_ilp:
140 	kfree(ilp);
141 	pr_err("Failed to init ILP clock: %d\n", err);
142 }
143 
144 /* We need it very early for arch code, before device model gets ready */
145 CLK_OF_DECLARE(bcm53573_ilp_clk, "brcm,bcm53573-ilp", bcm53573_ilp_init);
146