kernel/drivers/clk/clk-pwm.c

   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
  17 struct clk_pwm {
  18         struct clk_hw hw;
  19         struct pwm_device *pwm;
  20         u32 fixed_rate;
  21 };
  22
  23 static inline struct clk_pwm *to_clk_pwm(struct clk_hw *hw)
  24 {
  25         return container_of(hw, struct clk_pwm, hw);
  26 }
  27
  28 static 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
  35 static 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
  42 static 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
  50 static 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
  56 static 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         const char *clk_name;
  63         struct clk *clk;
  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         if (!pwm->period) {
  75                 dev_err(&pdev->dev, "invalid PWM period\n");
  76                 return -EINVAL;
  77         }
  78
  79         if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
  80                 clk_pwm->fixed_rate = NSEC_PER_SEC / pwm->period;
  81
  82         if (pwm->period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
  83             pwm->period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
  84                 dev_err(&pdev->dev,
  85                         "clock-frequency does not match PWM period\n");
  86                 return -EINVAL;
  87         }
  88
  89         ret = pwm_config(pwm, (pwm->period + 1) >> 1, pwm->period);
  90         if (ret < 0)
  91                 return ret;
  92
  93         clk_name = node->name;
  94         of_property_read_string(node, "clock-output-names", &clk_name);
  95
  96         init.name = clk_name;
  97         init.ops = &clk_pwm_ops;
  98         init.flags = CLK_IS_BASIC | CLK_IS_ROOT;
  99         init.num_parents = 0;
 100
 101         clk_pwm->pwm = pwm;
 102         clk_pwm->hw.init = &init;
 103         clk = devm_clk_register(&pdev->dev, &clk_pwm->hw);
 104         if (IS_ERR(clk))
 105                 return PTR_ERR(clk);
 106
 107         return of_clk_add_provider(node, of_clk_src_simple_get, clk);
 108 }
 109
 110 static int clk_pwm_remove(struct platform_device *pdev)
 111 {
 112         of_clk_del_provider(pdev->dev.of_node);
 113
 114         return 0;
 115 }
 116
 117 static const struct of_device_id clk_pwm_dt_ids[] = {
 118         { .compatible = "pwm-clock" },
 119         { }
 120 };
 121 MODULE_DEVICE_TABLE(of, clk_pwm_dt_ids);
 122
 123 static struct platform_driver clk_pwm_driver = {
 124         .probe = clk_pwm_probe,
 125         .remove = clk_pwm_remove,
 126         .driver = {
 127                 .name = "pwm-clock",
 128                 .of_match_table = of_match_ptr(clk_pwm_dt_ids),
 129         },
 130 };
 131
 132 module_platform_driver(clk_pwm_driver);
 133
 134 MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
 135 MODULE_DESCRIPTION("PWM clock driver");
 136 MODULE_LICENSE("GPL");