1/*
2 * Copyright (C) 2014 Philipp Zabel, Pengutronix
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 *
8 * PWM (mis)used as clock output
9 */
10#include <linux/clk-provider.h>
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/of.h>
14#include <linux/platform_device.h>
15#include <linux/pwm.h>
16
17struct clk_pwm {
18 struct clk_hw hw;
19 struct pwm_device *pwm;
20 u32 fixed_rate;
21};
22
23static inline struct clk_pwm *to_clk_pwm(struct clk_hw *hw)
24{
25 return container_of(hw, struct clk_pwm, hw);
26}
27
28static int clk_pwm_prepare(struct clk_hw *hw)
29{
30 struct clk_pwm *clk_pwm = to_clk_pwm(hw);
31
32 return pwm_enable(clk_pwm->pwm);
33}
34
35static void clk_pwm_unprepare(struct clk_hw *hw)
36{
37 struct clk_pwm *clk_pwm = to_clk_pwm(hw);
38
39 pwm_disable(clk_pwm->pwm);
40}
41
42static unsigned long clk_pwm_recalc_rate(struct clk_hw *hw,
43 unsigned long parent_rate)
44{
45 struct clk_pwm *clk_pwm = to_clk_pwm(hw);
46
47 return clk_pwm->fixed_rate;
48}
49
50static const struct clk_ops clk_pwm_ops = {
51 .prepare = clk_pwm_prepare,
52 .unprepare = clk_pwm_unprepare,
53 .recalc_rate = clk_pwm_recalc_rate,
54};
55
56static int clk_pwm_probe(struct platform_device *pdev)
57{
58 struct device_node *node = pdev->dev.of_node;
59 struct clk_init_data init;
60 struct clk_pwm *clk_pwm;
61 struct pwm_device *pwm;
62 struct pwm_args pargs;
63 const char *clk_name;
64 int ret;
65
66 clk_pwm = devm_kzalloc(&pdev->dev, sizeof(*clk_pwm), GFP_KERNEL);
67 if (!clk_pwm)
68 return -ENOMEM;
69
70 pwm = devm_pwm_get(&pdev->dev, NULL);
71 if (IS_ERR(pwm))
72 return PTR_ERR(pwm);
73
74 pwm_get_args(pwm, &pargs);
75 if (!pargs.period) {
76 dev_err(&pdev->dev, "invalid PWM period\n");
77 return -EINVAL;
78 }
79
80 if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
81 clk_pwm->fixed_rate = NSEC_PER_SEC / pargs.period;
82
83 if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
84 pargs.period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
85 dev_err(&pdev->dev,
86 "clock-frequency does not match PWM period\n");
87 return -EINVAL;
88 }
89
90 /*
91 * FIXME: pwm_apply_args() should be removed when switching to the
92 * atomic PWM API.
93 */
94 pwm_apply_args(pwm);
95 ret = pwm_config(pwm, (pargs.period + 1) >> 1, pargs.period);
96 if (ret < 0)
97 return ret;
98
99 clk_name = node->name;
100 of_property_read_string(node, "clock-output-names", &clk_name);
101
102 init.name = clk_name;
103 init.ops = &clk_pwm_ops;
104 init.flags = CLK_IS_BASIC;
105 init.num_parents = 0;
106
107 clk_pwm->pwm = pwm;
108 clk_pwm->hw.init = &init;
109 ret = devm_clk_hw_register(&pdev->dev, &clk_pwm->hw);
110 if (ret)
111 return ret;
112
113 return of_clk_add_hw_provider(node, of_clk_hw_simple_get, &clk_pwm->hw);
114}
115
116static int clk_pwm_remove(struct platform_device *pdev)
117{
118 of_clk_del_provider(pdev->dev.of_node);
119
120 return 0;
121}
122
123static const struct of_device_id clk_pwm_dt_ids[] = {
124 { .compatible = "pwm-clock" },
125 { }
126};
127MODULE_DEVICE_TABLE(of, clk_pwm_dt_ids);
128
129static struct platform_driver clk_pwm_driver = {
130 .probe = clk_pwm_probe,
131 .remove = clk_pwm_remove,
132 .driver = {
133 .name = "pwm-clock",
134 .of_match_table = of_match_ptr(clk_pwm_dt_ids),
135 },
136};
137
138module_platform_driver(clk_pwm_driver);
139
140MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
141MODULE_DESCRIPTION("PWM clock driver");
142MODULE_LICENSE("GPL");
143