clk-pwm.c
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/*
* Copyright (C) 2014 Philipp Zabel, Pengutronix
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* PWM (mis)used as clock output
*/
#include <linux/clk-provider.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
struct clk_pwm {
struct clk_hw hw;
struct pwm_device *pwm;
u32 fixed_rate;
};
static inline struct clk_pwm *to_clk_pwm(struct clk_hw *hw)
{
return container_of(hw, struct clk_pwm, hw);
}
static int clk_pwm_prepare(struct clk_hw *hw)
{
struct clk_pwm *clk_pwm = to_clk_pwm(hw);
return pwm_enable(clk_pwm->pwm);
}
static void clk_pwm_unprepare(struct clk_hw *hw)
{
struct clk_pwm *clk_pwm = to_clk_pwm(hw);
pwm_disable(clk_pwm->pwm);
}
static unsigned long clk_pwm_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
{
struct clk_pwm *clk_pwm = to_clk_pwm(hw);
return clk_pwm->fixed_rate;
}
static const struct clk_ops clk_pwm_ops = {
.prepare = clk_pwm_prepare,
.unprepare = clk_pwm_unprepare,
.recalc_rate = clk_pwm_recalc_rate,
};
static int clk_pwm_probe(struct platform_device *pdev)
{
struct device_node *node = pdev->dev.of_node;
struct clk_init_data init;
struct clk_pwm *clk_pwm;
struct pwm_device *pwm;
const char *clk_name;
struct clk *clk;
int ret;
clk_pwm = devm_kzalloc(&pdev->dev, sizeof(*clk_pwm), GFP_KERNEL);
if (!clk_pwm)
return -ENOMEM;
pwm = devm_pwm_get(&pdev->dev, NULL);
if (IS_ERR(pwm))
return PTR_ERR(pwm);
if (!pwm->period) {
dev_err(&pdev->dev, "invalid PWM period\n");
return -EINVAL;
}
if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
clk_pwm->fixed_rate = NSEC_PER_SEC / pwm->period;
if (pwm->period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
pwm->period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
dev_err(&pdev->dev,
"clock-frequency does not match PWM period\n");
return -EINVAL;
}
ret = pwm_config(pwm, (pwm->period + 1) >> 1, pwm->period);
if (ret < 0)
return ret;
clk_name = node->name;
of_property_read_string(node, "clock-output-names", &clk_name);
init.name = clk_name;
init.ops = &clk_pwm_ops;
init.flags = CLK_IS_BASIC | CLK_IS_ROOT;
init.num_parents = 0;
clk_pwm->pwm = pwm;
clk_pwm->hw.init = &init;
clk = devm_clk_register(&pdev->dev, &clk_pwm->hw);
if (IS_ERR(clk))
return PTR_ERR(clk);
return of_clk_add_provider(node, of_clk_src_simple_get, clk);
}
static int clk_pwm_remove(struct platform_device *pdev)
{
of_clk_del_provider(pdev->dev.of_node);
return 0;
}
static const struct of_device_id clk_pwm_dt_ids[] = {
{ .compatible = "pwm-clock" },
{ }
};
MODULE_DEVICE_TABLE(of, clk_pwm_dt_ids);
static struct platform_driver clk_pwm_driver = {
.probe = clk_pwm_probe,
.remove = clk_pwm_remove,
.driver = {
.name = "pwm-clock",
.of_match_table = of_match_ptr(clk_pwm_dt_ids),
},
};
module_platform_driver(clk_pwm_driver);
MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
MODULE_DESCRIPTION("PWM clock driver");
MODULE_LICENSE("GPL");