drivers/clk/clk-pwm.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2014 Philipp Zabel, Pengutronix
   4  *
   5  * PWM (mis)used as clock output
   6  */
   7 #include <linux/clk-provider.h>
   8 #include <linux/kernel.h>
   9 #include <linux/module.h>
  10 #include <linux/of.h>
  11 #include <linux/platform_device.h>
  12 #include <linux/pwm.h>
  13
  14 struct clk_pwm {
  15         struct clk_hw hw;
  16         struct pwm_device *pwm;
  17         u32 fixed_rate;
  18 };
  19
  20 static inline struct clk_pwm *to_clk_pwm(struct clk_hw *hw)
  21 {
  22         return container_of(hw, struct clk_pwm, hw);
  23 }
  24
  25 static int clk_pwm_prepare(struct clk_hw *hw)
  26 {
  27         struct clk_pwm *clk_pwm = to_clk_pwm(hw);
  28
  29         return pwm_enable(clk_pwm->pwm);
  30 }
  31
  32 static void clk_pwm_unprepare(struct clk_hw *hw)
  33 {
  34         struct clk_pwm *clk_pwm = to_clk_pwm(hw);
  35
  36         pwm_disable(clk_pwm->pwm);
  37 }
  38
  39 static unsigned long clk_pwm_recalc_rate(struct clk_hw *hw,
  40                                          unsigned long parent_rate)
  41 {
  42         struct clk_pwm *clk_pwm = to_clk_pwm(hw);
  43
  44         return clk_pwm->fixed_rate;
  45 }
  46
  47 static const struct clk_ops clk_pwm_ops = {
  48         .prepare = clk_pwm_prepare,
  49         .unprepare = clk_pwm_unprepare,
  50         .recalc_rate = clk_pwm_recalc_rate,
  51 };
  52
  53 static int clk_pwm_probe(struct platform_device *pdev)
  54 {
  55         struct device_node *node = pdev->dev.of_node;
  56         struct clk_init_data init;
  57         struct clk_pwm *clk_pwm;
  58         struct pwm_device *pwm;
  59         struct pwm_args pargs;
  60         const char *clk_name;
  61         int ret;
  62
  63         clk_pwm = devm_kzalloc(&pdev->dev, sizeof(*clk_pwm), GFP_KERNEL);
  64         if (!clk_pwm)
  65                 return -ENOMEM;
  66
  67         pwm = devm_pwm_get(&pdev->dev, NULL);
  68         if (IS_ERR(pwm))
  69                 return PTR_ERR(pwm);
  70
  71         pwm_get_args(pwm, &pargs);
  72         if (!pargs.period) {
  73                 dev_err(&pdev->dev, "invalid PWM period\n");
  74                 return -EINVAL;
  75         }
  76
  77         if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
  78                 clk_pwm->fixed_rate = NSEC_PER_SEC / pargs.period;
  79
  80         if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
  81             pargs.period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
  82                 dev_err(&pdev->dev,
  83                         "clock-frequency does not match PWM period\n");
  84                 return -EINVAL;
  85         }
  86
  87         /*
  88          * FIXME: pwm_apply_args() should be removed when switching to the
  89          * atomic PWM API.
  90          */
  91         pwm_apply_args(pwm);
  92         ret = pwm_config(pwm, (pargs.period + 1) >> 1, pargs.period);
  93         if (ret < 0)
  94                 return ret;
  95
  96         clk_name = node->name;
  97         of_property_read_string(node, "clock-output-names", &clk_name);
  98
  99         init.name = clk_name;
 100         init.ops = &clk_pwm_ops;
 101         init.flags = 0;
 102         init.num_parents = 0;
 103
 104         clk_pwm->pwm = pwm;
 105         clk_pwm->hw.init = &init;
 106         ret = devm_clk_hw_register(&pdev->dev, &clk_pwm->hw);
 107         if (ret)
 108                 return ret;
 109
 110         return of_clk_add_hw_provider(node, of_clk_hw_simple_get, &clk_pwm->hw);
 111 }
 112
 113 static int clk_pwm_remove(struct platform_device *pdev)
 114 {
 115         of_clk_del_provider(pdev->dev.of_node);
 116
 117         return 0;
 118 }
 119
 120 static const struct of_device_id clk_pwm_dt_ids[] = {
 121         { .compatible = "pwm-clock" },
 122         { }
 123 };
 124 MODULE_DEVICE_TABLE(of, clk_pwm_dt_ids);
 125
 126 static struct platform_driver clk_pwm_driver = {
 127         .probe = clk_pwm_probe,
 128         .remove = clk_pwm_remove,
 129         .driver = {
 130                 .name = "pwm-clock",
 131                 .of_match_table = of_match_ptr(clk_pwm_dt_ids),
 132         },
 133 };
 134
 135 module_platform_driver(clk_pwm_driver);
 136
 137 MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
 138 MODULE_DESCRIPTION("PWM clock driver");
 139 MODULE_LICENSE("GPL");