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"); 137