tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 struct clk *clk;
65 int ret;
66
67 clk_pwm = devm_kzalloc(&pdev->dev, sizeof(*clk_pwm), GFP_KERNEL);
68 if (!clk_pwm)
69 return -ENOMEM;
70
71 pwm = devm_pwm_get(&pdev->dev, NULL);
72 if (IS_ERR(pwm))
73 return PTR_ERR(pwm);
74
75 pwm_get_args(pwm, &pargs);
76 if (!pargs.period) {
77 dev_err(&pdev->dev, "invalid PWM period\n");
78 return -EINVAL;
79 }
80
81 if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
82 clk_pwm->fixed_rate = NSEC_PER_SEC / pargs.period;
83
84 if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
85 pargs.period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
86 dev_err(&pdev->dev,
87 "clock-frequency does not match PWM period\n");
88 return -EINVAL;
89 }
90
91 /*
92 * FIXME: pwm_apply_args() should be removed when switching to the
93 * atomic PWM API.
94 */
95 pwm_apply_args(pwm);
96 ret = pwm_config(pwm, (pargs.period + 1) >> 1, pargs.period);
97 if (ret < 0)
98 return ret;
99
100 clk_name = node->name;
101 of_property_read_string(node, "clock-output-names", &clk_name);
102
103 init.name = clk_name;
104 init.ops = &clk_pwm_ops;
105 init.flags = CLK_IS_BASIC;
106 init.num_parents = 0;
107
108 clk_pwm->pwm = pwm;
109 clk_pwm->hw.init = &init;
110 clk = devm_clk_register(&pdev->dev, &clk_pwm->hw);
111 if (IS_ERR(clk))
112 return PTR_ERR(clk);
113
114 return of_clk_add_provider(node, of_clk_src_simple_get, clk);
115}
116
117static int clk_pwm_remove(struct platform_device *pdev)
118{
119 of_clk_del_provider(pdev->dev.of_node);
120
121 return 0;
122}
123
124static const struct of_device_id clk_pwm_dt_ids[] = {
125 { .compatible = "pwm-clock" },
126 { }
127};
128MODULE_DEVICE_TABLE(of, clk_pwm_dt_ids);
129
130static struct platform_driver clk_pwm_driver = {
131 .probe = clk_pwm_probe,
132 .remove = clk_pwm_remove,
133 .driver = {
134 .name = "pwm-clock",
135 .of_match_table = of_match_ptr(clk_pwm_dt_ids),
136 },
137};
138
139module_platform_driver(clk_pwm_driver);
140
141MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
142MODULE_DESCRIPTION("PWM clock driver");
143MODULE_LICENSE("GPL");