Quelle  clk-pwm.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2014 Philipp Zabel, Pengutronix
 *
 * 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;
 struct pwm_state state;
 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_enable(struct clk_hw *hw)
{
 struct clk_pwm *clk_pwm = to_clk_pwm(hw);

 return pwm_apply_atomic(clk_pwm->pwm, &clk_pwm->state);
}

static void clk_pwm_disable(struct clk_hw *hw)
{
 struct clk_pwm *clk_pwm = to_clk_pwm(hw);
 struct pwm_state state = clk_pwm->state;

 state.enabled = false;

 pwm_apply_atomic(clk_pwm->pwm, &state);
}

static int clk_pwm_prepare(struct clk_hw *hw)
{
 struct clk_pwm *clk_pwm = to_clk_pwm(hw);

 return pwm_apply_might_sleep(clk_pwm->pwm, &clk_pwm->state);
}

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 int clk_pwm_get_duty_cycle(struct clk_hw *hw, struct clk_duty *duty)
{
 struct clk_pwm *clk_pwm = to_clk_pwm(hw);
 struct pwm_state state;
 int ret;

 ret = pwm_get_state_hw(clk_pwm->pwm, &state);
 if (ret)
  return ret;

 duty->num = state.duty_cycle;
 duty->den = state.period;

 return 0;
}

static const struct clk_ops clk_pwm_ops_atomic = {
 .enable = clk_pwm_enable,
 .disable = clk_pwm_disable,
 .recalc_rate = clk_pwm_recalc_rate,
 .get_duty_cycle = clk_pwm_get_duty_cycle,
};

static const struct clk_ops clk_pwm_ops = {
 .prepare = clk_pwm_prepare,
 .unprepare = clk_pwm_unprepare,
 .recalc_rate = clk_pwm_recalc_rate,
 .get_duty_cycle = clk_pwm_get_duty_cycle,
};

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;
 struct pwm_args pargs;
 const char *clk_name;
 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);

 pwm_get_args(pwm, &pargs);
 if (!pargs.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 = div64_u64(NSEC_PER_SEC, pargs.period);

 if (!clk_pwm->fixed_rate) {
  dev_err(&pdev->dev, "fixed_rate cannot be zero\n");
  return -EINVAL;
 }

 if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
     pargs.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;
 }

 pwm_init_state(pwm, &clk_pwm->state);
 pwm_set_relative_duty_cycle(&clk_pwm->state, 1, 2);
 clk_pwm->state.enabled = true;

 clk_name = node->name;
 of_property_read_string(node, "clock-output-names", &clk_name);

 init.name = clk_name;
 if (pwm_might_sleep(pwm))
  init.ops = &clk_pwm_ops;
 else
  init.ops = &clk_pwm_ops_atomic;

 init.flags = 0;
 init.num_parents = 0;

 clk_pwm->pwm = pwm;
 clk_pwm->hw.init = &init;
 ret = devm_clk_hw_register(&pdev->dev, &clk_pwm->hw);
 if (ret)
  return ret;

 return of_clk_add_hw_provider(node, of_clk_hw_simple_get, &clk_pwm->hw);
}

static void clk_pwm_remove(struct platform_device *pdev)
{
 of_clk_del_provider(pdev->dev.of_node);
}

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 = clk_pwm_dt_ids,
 },
};

module_platform_driver(clk_pwm_driver);

MODULE_AUTHOR("Philipp Zabel ");
MODULE_DESCRIPTION("PWM clock driver");
MODULE_LICENSE("GPL");