LXR linux/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
  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