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         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
 117 static int clk_pwm_remove(struct platform_device *pdev)
 118 {
 119         of_clk_del_provider(pdev->dev.of_node);
 120
 121         return 0;
 122 }
 123
 124 static const struct of_device_id clk_pwm_dt_ids[] = {
 125         { .compatible = "pwm-clock" },
 126         { }
 127 };
 128 MODULE_DEVICE_TABLE(of, clk_pwm_dt_ids);
 129
 130 static 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
 139 module_platform_driver(clk_pwm_driver);
 140
 141 MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
 142 MODULE_DESCRIPTION("PWM clock driver");
 143 MODULE_LICENSE("GPL");