diff options
Diffstat (limited to 'drivers/pwm/pwm-gpio.c')
| -rw-r--r-- | drivers/pwm/pwm-gpio.c | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-gpio.c b/drivers/pwm/pwm-gpio.c new file mode 100644 index 000000000000..9f8884ac7504 --- /dev/null +++ b/drivers/pwm/pwm-gpio.c @@ -0,0 +1,241 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Generic software PWM for modulating GPIOs + * + * Copyright (C) 2020 Axis Communications AB + * Copyright (C) 2020 Nicola Di Lieto + * Copyright (C) 2024 Stefan Wahren + * Copyright (C) 2024 Linus Walleij + */ + +#include <linux/cleanup.h> +#include <linux/container_of.h> +#include <linux/device.h> +#include <linux/err.h> +#include <linux/gpio/consumer.h> +#include <linux/hrtimer.h> +#include <linux/math.h> +#include <linux/module.h> +#include <linux/mod_devicetable.h> +#include <linux/platform_device.h> +#include <linux/property.h> +#include <linux/pwm.h> +#include <linux/spinlock.h> +#include <linux/time.h> +#include <linux/types.h> + +struct pwm_gpio { + struct hrtimer gpio_timer; + struct gpio_desc *gpio; + struct pwm_state state; + struct pwm_state next_state; + + /* Protect internal state between pwm_ops and hrtimer */ + spinlock_t lock; + + bool changing; + bool running; + bool level; +}; + +static void pwm_gpio_round(struct pwm_state *dest, const struct pwm_state *src) +{ + u64 dividend; + u32 remainder; + + *dest = *src; + + /* Round down to hrtimer resolution */ + dividend = dest->period; + remainder = do_div(dividend, hrtimer_resolution); + dest->period -= remainder; + + dividend = dest->duty_cycle; + remainder = do_div(dividend, hrtimer_resolution); + dest->duty_cycle -= remainder; +} + +static u64 pwm_gpio_toggle(struct pwm_gpio *gpwm, bool level) +{ + const struct pwm_state *state = &gpwm->state; + bool invert = state->polarity == PWM_POLARITY_INVERSED; + + gpwm->level = level; + gpiod_set_value(gpwm->gpio, gpwm->level ^ invert); + + if (!state->duty_cycle || state->duty_cycle == state->period) { + gpwm->running = false; + return 0; + } + + gpwm->running = true; + return level ? state->duty_cycle : state->period - state->duty_cycle; +} + +static enum hrtimer_restart pwm_gpio_timer(struct hrtimer *gpio_timer) +{ + struct pwm_gpio *gpwm = container_of(gpio_timer, struct pwm_gpio, + gpio_timer); + u64 next_toggle; + bool new_level; + + guard(spinlock_irqsave)(&gpwm->lock); + + /* Apply new state at end of current period */ + if (!gpwm->level && gpwm->changing) { + gpwm->changing = false; + gpwm->state = gpwm->next_state; + new_level = !!gpwm->state.duty_cycle; + } else { + new_level = !gpwm->level; + } + + next_toggle = pwm_gpio_toggle(gpwm, new_level); + if (next_toggle) + hrtimer_forward(gpio_timer, hrtimer_get_expires(gpio_timer), + ns_to_ktime(next_toggle)); + + return next_toggle ? HRTIMER_RESTART : HRTIMER_NORESTART; +} + +static int pwm_gpio_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) +{ + struct pwm_gpio *gpwm = pwmchip_get_drvdata(chip); + bool invert = state->polarity == PWM_POLARITY_INVERSED; + + if (state->duty_cycle && state->duty_cycle < hrtimer_resolution) + return -EINVAL; + + if (state->duty_cycle != state->period && + (state->period - state->duty_cycle < hrtimer_resolution)) + return -EINVAL; + + if (!state->enabled) { + hrtimer_cancel(&gpwm->gpio_timer); + } else if (!gpwm->running) { + int ret; + + /* + * This just enables the output, but pwm_gpio_toggle() + * really starts the duty cycle. + */ + ret = gpiod_direction_output(gpwm->gpio, invert); + if (ret) + return ret; + } + + guard(spinlock_irqsave)(&gpwm->lock); + + if (!state->enabled) { + pwm_gpio_round(&gpwm->state, state); + gpwm->running = false; + gpwm->changing = false; + + gpiod_set_value(gpwm->gpio, invert); + } else if (gpwm->running) { + pwm_gpio_round(&gpwm->next_state, state); + gpwm->changing = true; + } else { + unsigned long next_toggle; + + pwm_gpio_round(&gpwm->state, state); + gpwm->changing = false; + + next_toggle = pwm_gpio_toggle(gpwm, !!state->duty_cycle); + if (next_toggle) + hrtimer_start(&gpwm->gpio_timer, next_toggle, + HRTIMER_MODE_REL); + } + + return 0; +} + +static int pwm_gpio_get_state(struct pwm_chip *chip, struct pwm_device *pwm, + struct pwm_state *state) +{ + struct pwm_gpio *gpwm = pwmchip_get_drvdata(chip); + + guard(spinlock_irqsave)(&gpwm->lock); + + if (gpwm->changing) + *state = gpwm->next_state; + else + *state = gpwm->state; + + return 0; +} + +static const struct pwm_ops pwm_gpio_ops = { + .apply = pwm_gpio_apply, + .get_state = pwm_gpio_get_state, +}; + +static void pwm_gpio_disable_hrtimer(void *data) +{ + struct pwm_gpio *gpwm = data; + + hrtimer_cancel(&gpwm->gpio_timer); +} + +static int pwm_gpio_probe(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct pwm_chip *chip; + struct pwm_gpio *gpwm; + int ret; + + chip = devm_pwmchip_alloc(dev, 1, sizeof(*gpwm)); + if (IS_ERR(chip)) + return PTR_ERR(chip); + + gpwm = pwmchip_get_drvdata(chip); + + spin_lock_init(&gpwm->lock); + + gpwm->gpio = devm_gpiod_get(dev, NULL, GPIOD_ASIS); + if (IS_ERR(gpwm->gpio)) + return dev_err_probe(dev, PTR_ERR(gpwm->gpio), + "%pfw: could not get gpio\n", + dev_fwnode(dev)); + + if (gpiod_cansleep(gpwm->gpio)) + return dev_err_probe(dev, -EINVAL, + "%pfw: sleeping GPIO not supported\n", + dev_fwnode(dev)); + + chip->ops = &pwm_gpio_ops; + chip->atomic = true; + + hrtimer_init(&gpwm->gpio_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + ret = devm_add_action_or_reset(dev, pwm_gpio_disable_hrtimer, gpwm); + if (ret) + return ret; + + gpwm->gpio_timer.function = pwm_gpio_timer; + + ret = pwmchip_add(chip); + if (ret < 0) + return dev_err_probe(dev, ret, "could not add pwmchip\n"); + + return 0; +} + +static const struct of_device_id pwm_gpio_dt_ids[] = { + { .compatible = "pwm-gpio" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, pwm_gpio_dt_ids); + +static struct platform_driver pwm_gpio_driver = { + .driver = { + .name = "pwm-gpio", + .of_match_table = pwm_gpio_dt_ids, + }, + .probe = pwm_gpio_probe, +}; +module_platform_driver(pwm_gpio_driver); + +MODULE_DESCRIPTION("PWM GPIO driver"); +MODULE_AUTHOR("Vincent Whitchurch"); +MODULE_LICENSE("GPL"); |