drivers/clk/clk-pwm.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Copyright (C) 2014 Philipp Zabel, Pengutronix
0004  *
0005  * PWM (mis)used as clock output
0006  */
0007 #include <linux/clk-provider.h>
0008 #include <linux/kernel.h>
0009 #include <linux/module.h>
0010 #include <linux/of.h>
0011 #include <linux/platform_device.h>
0012 #include <linux/pwm.h>
0013
0014 struct clk_pwm {
0015     struct clk_hw hw;
0016     struct pwm_device *pwm;
0017     u32 fixed_rate;
0018 };
0019
0020 static inline struct clk_pwm *to_clk_pwm(struct clk_hw *hw)
0021 {
0022     return container_of(hw, struct clk_pwm, hw);
0023 }
0024
0025 static int clk_pwm_prepare(struct clk_hw *hw)
0026 {
0027     struct clk_pwm *clk_pwm = to_clk_pwm(hw);
0028
0029     return pwm_enable(clk_pwm->pwm);
0030 }
0031
0032 static void clk_pwm_unprepare(struct clk_hw *hw)
0033 {
0034     struct clk_pwm *clk_pwm = to_clk_pwm(hw);
0035
0036     pwm_disable(clk_pwm->pwm);
0037 }
0038
0039 static unsigned long clk_pwm_recalc_rate(struct clk_hw *hw,
0040                      unsigned long parent_rate)
0041 {
0042     struct clk_pwm *clk_pwm = to_clk_pwm(hw);
0043
0044     return clk_pwm->fixed_rate;
0045 }
0046
0047 static int clk_pwm_get_duty_cycle(struct clk_hw *hw, struct clk_duty *duty)
0048 {
0049     struct clk_pwm *clk_pwm = to_clk_pwm(hw);
0050     struct pwm_state state;
0051
0052     pwm_get_state(clk_pwm->pwm, &state);
0053
0054     duty->num = state.duty_cycle;
0055     duty->den = state.period;
0056
0057     return 0;
0058 }
0059
0060 static const struct clk_ops clk_pwm_ops = {
0061     .prepare = clk_pwm_prepare,
0062     .unprepare = clk_pwm_unprepare,
0063     .recalc_rate = clk_pwm_recalc_rate,
0064     .get_duty_cycle = clk_pwm_get_duty_cycle,
0065 };
0066
0067 static int clk_pwm_probe(struct platform_device *pdev)
0068 {
0069     struct device_node *node = pdev->dev.of_node;
0070     struct clk_init_data init;
0071     struct clk_pwm *clk_pwm;
0072     struct pwm_device *pwm;
0073     struct pwm_args pargs;
0074     const char *clk_name;
0075     int ret;
0076
0077     clk_pwm = devm_kzalloc(&pdev->dev, sizeof(*clk_pwm), GFP_KERNEL);
0078     if (!clk_pwm)
0079         return -ENOMEM;
0080
0081     pwm = devm_pwm_get(&pdev->dev, NULL);
0082     if (IS_ERR(pwm))
0083         return PTR_ERR(pwm);
0084
0085     pwm_get_args(pwm, &pargs);
0086     if (!pargs.period) {
0087         dev_err(&pdev->dev, "invalid PWM period\n");
0088         return -EINVAL;
0089     }
0090
0091     if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
0092         clk_pwm->fixed_rate = div64_u64(NSEC_PER_SEC, pargs.period);
0093
0094     if (!clk_pwm->fixed_rate) {
0095         dev_err(&pdev->dev, "fixed_rate cannot be zero\n");
0096         return -EINVAL;
0097     }
0098
0099     if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
0100         pargs.period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
0101         dev_err(&pdev->dev,
0102             "clock-frequency does not match PWM period\n");
0103         return -EINVAL;
0104     }
0105
0106     /*
0107      * FIXME: pwm_apply_args() should be removed when switching to the
0108      * atomic PWM API.
0109      */
0110     pwm_apply_args(pwm);
0111     ret = pwm_config(pwm, (pargs.period + 1) >> 1, pargs.period);
0112     if (ret < 0)
0113         return ret;
0114
0115     clk_name = node->name;
0116     of_property_read_string(node, "clock-output-names", &clk_name);
0117
0118     init.name = clk_name;
0119     init.ops = &clk_pwm_ops;
0120     init.flags = 0;
0121     init.num_parents = 0;
0122
0123     clk_pwm->pwm = pwm;
0124     clk_pwm->hw.init = &init;
0125     ret = devm_clk_hw_register(&pdev->dev, &clk_pwm->hw);
0126     if (ret)
0127         return ret;
0128
0129     return of_clk_add_hw_provider(node, of_clk_hw_simple_get, &clk_pwm->hw);
0130 }
0131
0132 static int clk_pwm_remove(struct platform_device *pdev)
0133 {
0134     of_clk_del_provider(pdev->dev.of_node);
0135
0136     return 0;
0137 }
0138
0139 static const struct of_device_id clk_pwm_dt_ids[] = {
0140     { .compatible = "pwm-clock" },
0141     { }
0142 };
0143 MODULE_DEVICE_TABLE(of, clk_pwm_dt_ids);
0144
0145 static struct platform_driver clk_pwm_driver = {
0146     .probe = clk_pwm_probe,
0147     .remove = clk_pwm_remove,
0148     .driver = {
0149         .name = "pwm-clock",
0150         .of_match_table = clk_pwm_dt_ids,
0151     },
0152 };
0153
0154 module_platform_driver(clk_pwm_driver);
0155
0156 MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
0157 MODULE_DESCRIPTION("PWM clock driver");
0158 MODULE_LICENSE("GPL");