242 lines
5.6 KiB
C
242 lines
5.6 KiB
C
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Generic software PWM for modulating GPIOs
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*
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* Copyright (C) 2020 Axis Communications AB
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* Copyright (C) 2020 Nicola Di Lieto
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* Copyright (C) 2024 Stefan Wahren
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* Copyright (C) 2024 Linus Walleij
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*/
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#include <linux/cleanup.h>
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#include <linux/container_of.h>
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#include <linux/device.h>
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#include <linux/err.h>
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#include <linux/gpio/consumer.h>
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#include <linux/hrtimer.h>
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#include <linux/math.h>
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#include <linux/module.h>
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#include <linux/mod_devicetable.h>
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#include <linux/platform_device.h>
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#include <linux/property.h>
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#include <linux/pwm.h>
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#include <linux/spinlock.h>
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#include <linux/time.h>
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#include <linux/types.h>
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struct pwm_gpio {
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struct hrtimer gpio_timer;
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struct gpio_desc *gpio;
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struct pwm_state state;
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struct pwm_state next_state;
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/* Protect internal state between pwm_ops and hrtimer */
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spinlock_t lock;
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bool changing;
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bool running;
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bool level;
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};
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static void pwm_gpio_round(struct pwm_state *dest, const struct pwm_state *src)
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{
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u64 dividend;
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u32 remainder;
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*dest = *src;
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/* Round down to hrtimer resolution */
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dividend = dest->period;
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remainder = do_div(dividend, hrtimer_resolution);
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dest->period -= remainder;
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dividend = dest->duty_cycle;
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remainder = do_div(dividend, hrtimer_resolution);
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dest->duty_cycle -= remainder;
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}
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static u64 pwm_gpio_toggle(struct pwm_gpio *gpwm, bool level)
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{
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const struct pwm_state *state = &gpwm->state;
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bool invert = state->polarity == PWM_POLARITY_INVERSED;
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gpwm->level = level;
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gpiod_set_value(gpwm->gpio, gpwm->level ^ invert);
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if (!state->duty_cycle || state->duty_cycle == state->period) {
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gpwm->running = false;
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return 0;
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}
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gpwm->running = true;
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return level ? state->duty_cycle : state->period - state->duty_cycle;
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}
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static enum hrtimer_restart pwm_gpio_timer(struct hrtimer *gpio_timer)
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{
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struct pwm_gpio *gpwm = container_of(gpio_timer, struct pwm_gpio,
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gpio_timer);
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u64 next_toggle;
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bool new_level;
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guard(spinlock_irqsave)(&gpwm->lock);
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/* Apply new state at end of current period */
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if (!gpwm->level && gpwm->changing) {
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gpwm->changing = false;
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gpwm->state = gpwm->next_state;
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new_level = !!gpwm->state.duty_cycle;
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} else {
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new_level = !gpwm->level;
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}
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next_toggle = pwm_gpio_toggle(gpwm, new_level);
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if (next_toggle)
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hrtimer_forward(gpio_timer, hrtimer_get_expires(gpio_timer),
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ns_to_ktime(next_toggle));
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return next_toggle ? HRTIMER_RESTART : HRTIMER_NORESTART;
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}
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static int pwm_gpio_apply(struct pwm_chip *chip, struct pwm_device *pwm,
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const struct pwm_state *state)
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{
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struct pwm_gpio *gpwm = pwmchip_get_drvdata(chip);
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bool invert = state->polarity == PWM_POLARITY_INVERSED;
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if (state->duty_cycle && state->duty_cycle < hrtimer_resolution)
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return -EINVAL;
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if (state->duty_cycle != state->period &&
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(state->period - state->duty_cycle < hrtimer_resolution))
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return -EINVAL;
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if (!state->enabled) {
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hrtimer_cancel(&gpwm->gpio_timer);
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} else if (!gpwm->running) {
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int ret;
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/*
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* This just enables the output, but pwm_gpio_toggle()
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* really starts the duty cycle.
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*/
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ret = gpiod_direction_output(gpwm->gpio, invert);
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if (ret)
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return ret;
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}
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guard(spinlock_irqsave)(&gpwm->lock);
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if (!state->enabled) {
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pwm_gpio_round(&gpwm->state, state);
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gpwm->running = false;
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gpwm->changing = false;
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gpiod_set_value(gpwm->gpio, invert);
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} else if (gpwm->running) {
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pwm_gpio_round(&gpwm->next_state, state);
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gpwm->changing = true;
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} else {
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unsigned long next_toggle;
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pwm_gpio_round(&gpwm->state, state);
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gpwm->changing = false;
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next_toggle = pwm_gpio_toggle(gpwm, !!state->duty_cycle);
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if (next_toggle)
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hrtimer_start(&gpwm->gpio_timer, next_toggle,
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HRTIMER_MODE_REL);
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}
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return 0;
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}
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static int pwm_gpio_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
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struct pwm_state *state)
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{
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struct pwm_gpio *gpwm = pwmchip_get_drvdata(chip);
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guard(spinlock_irqsave)(&gpwm->lock);
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if (gpwm->changing)
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*state = gpwm->next_state;
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else
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*state = gpwm->state;
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return 0;
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}
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static const struct pwm_ops pwm_gpio_ops = {
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.apply = pwm_gpio_apply,
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.get_state = pwm_gpio_get_state,
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};
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static void pwm_gpio_disable_hrtimer(void *data)
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{
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struct pwm_gpio *gpwm = data;
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hrtimer_cancel(&gpwm->gpio_timer);
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}
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static int pwm_gpio_probe(struct platform_device *pdev)
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{
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struct device *dev = &pdev->dev;
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struct pwm_chip *chip;
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struct pwm_gpio *gpwm;
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int ret;
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chip = devm_pwmchip_alloc(dev, 1, sizeof(*gpwm));
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if (IS_ERR(chip))
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return PTR_ERR(chip);
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gpwm = pwmchip_get_drvdata(chip);
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spin_lock_init(&gpwm->lock);
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gpwm->gpio = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
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if (IS_ERR(gpwm->gpio))
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return dev_err_probe(dev, PTR_ERR(gpwm->gpio),
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"%pfw: could not get gpio\n",
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dev_fwnode(dev));
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if (gpiod_cansleep(gpwm->gpio))
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return dev_err_probe(dev, -EINVAL,
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"%pfw: sleeping GPIO not supported\n",
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dev_fwnode(dev));
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chip->ops = &pwm_gpio_ops;
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chip->atomic = true;
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hrtimer_init(&gpwm->gpio_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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ret = devm_add_action_or_reset(dev, pwm_gpio_disable_hrtimer, gpwm);
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if (ret)
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return ret;
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gpwm->gpio_timer.function = pwm_gpio_timer;
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ret = pwmchip_add(chip);
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if (ret < 0)
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return dev_err_probe(dev, ret, "could not add pwmchip\n");
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return 0;
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}
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static const struct of_device_id pwm_gpio_dt_ids[] = {
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{ .compatible = "pwm-gpio" },
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{ /* sentinel */ }
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};
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MODULE_DEVICE_TABLE(of, pwm_gpio_dt_ids);
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static struct platform_driver pwm_gpio_driver = {
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.driver = {
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.name = "pwm-gpio",
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.of_match_table = pwm_gpio_dt_ids,
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},
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.probe = pwm_gpio_probe,
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};
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module_platform_driver(pwm_gpio_driver);
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MODULE_DESCRIPTION("PWM GPIO driver");
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MODULE_AUTHOR("Vincent Whitchurch");
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MODULE_LICENSE("GPL");
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