242 lines · c
1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Generic software PWM for modulating GPIOs4 *5 * Copyright (C) 2020 Axis Communications AB6 * Copyright (C) 2020 Nicola Di Lieto7 * Copyright (C) 2024 Stefan Wahren8 * Copyright (C) 2024 Linus Walleij9 */10 11#include <linux/cleanup.h>12#include <linux/container_of.h>13#include <linux/device.h>14#include <linux/err.h>15#include <linux/gpio/consumer.h>16#include <linux/hrtimer.h>17#include <linux/math.h>18#include <linux/module.h>19#include <linux/mod_devicetable.h>20#include <linux/platform_device.h>21#include <linux/property.h>22#include <linux/pwm.h>23#include <linux/spinlock.h>24#include <linux/time.h>25#include <linux/types.h>26 27struct pwm_gpio {28 struct hrtimer gpio_timer;29 struct gpio_desc *gpio;30 struct pwm_state state;31 struct pwm_state next_state;32 33 /* Protect internal state between pwm_ops and hrtimer */34 spinlock_t lock;35 36 bool changing;37 bool running;38 bool level;39};40 41static void pwm_gpio_round(struct pwm_state *dest, const struct pwm_state *src)42{43 u64 dividend;44 u32 remainder;45 46 *dest = *src;47 48 /* Round down to hrtimer resolution */49 dividend = dest->period;50 remainder = do_div(dividend, hrtimer_resolution);51 dest->period -= remainder;52 53 dividend = dest->duty_cycle;54 remainder = do_div(dividend, hrtimer_resolution);55 dest->duty_cycle -= remainder;56}57 58static u64 pwm_gpio_toggle(struct pwm_gpio *gpwm, bool level)59{60 const struct pwm_state *state = &gpwm->state;61 bool invert = state->polarity == PWM_POLARITY_INVERSED;62 63 gpwm->level = level;64 gpiod_set_value(gpwm->gpio, gpwm->level ^ invert);65 66 if (!state->duty_cycle || state->duty_cycle == state->period) {67 gpwm->running = false;68 return 0;69 }70 71 gpwm->running = true;72 return level ? state->duty_cycle : state->period - state->duty_cycle;73}74 75static enum hrtimer_restart pwm_gpio_timer(struct hrtimer *gpio_timer)76{77 struct pwm_gpio *gpwm = container_of(gpio_timer, struct pwm_gpio,78 gpio_timer);79 u64 next_toggle;80 bool new_level;81 82 guard(spinlock_irqsave)(&gpwm->lock);83 84 /* Apply new state at end of current period */85 if (!gpwm->level && gpwm->changing) {86 gpwm->changing = false;87 gpwm->state = gpwm->next_state;88 new_level = !!gpwm->state.duty_cycle;89 } else {90 new_level = !gpwm->level;91 }92 93 next_toggle = pwm_gpio_toggle(gpwm, new_level);94 if (next_toggle)95 hrtimer_forward(gpio_timer, hrtimer_get_expires(gpio_timer),96 ns_to_ktime(next_toggle));97 98 return next_toggle ? HRTIMER_RESTART : HRTIMER_NORESTART;99}100 101static int pwm_gpio_apply(struct pwm_chip *chip, struct pwm_device *pwm,102 const struct pwm_state *state)103{104 struct pwm_gpio *gpwm = pwmchip_get_drvdata(chip);105 bool invert = state->polarity == PWM_POLARITY_INVERSED;106 107 if (state->duty_cycle && state->duty_cycle < hrtimer_resolution)108 return -EINVAL;109 110 if (state->duty_cycle != state->period &&111 (state->period - state->duty_cycle < hrtimer_resolution))112 return -EINVAL;113 114 if (!state->enabled) {115 hrtimer_cancel(&gpwm->gpio_timer);116 } else if (!gpwm->running) {117 int ret;118 119 /*120 * This just enables the output, but pwm_gpio_toggle()121 * really starts the duty cycle.122 */123 ret = gpiod_direction_output(gpwm->gpio, invert);124 if (ret)125 return ret;126 }127 128 guard(spinlock_irqsave)(&gpwm->lock);129 130 if (!state->enabled) {131 pwm_gpio_round(&gpwm->state, state);132 gpwm->running = false;133 gpwm->changing = false;134 135 gpiod_set_value(gpwm->gpio, invert);136 } else if (gpwm->running) {137 pwm_gpio_round(&gpwm->next_state, state);138 gpwm->changing = true;139 } else {140 unsigned long next_toggle;141 142 pwm_gpio_round(&gpwm->state, state);143 gpwm->changing = false;144 145 next_toggle = pwm_gpio_toggle(gpwm, !!state->duty_cycle);146 if (next_toggle)147 hrtimer_start(&gpwm->gpio_timer, next_toggle,148 HRTIMER_MODE_REL);149 }150 151 return 0;152}153 154static int pwm_gpio_get_state(struct pwm_chip *chip, struct pwm_device *pwm,155 struct pwm_state *state)156{157 struct pwm_gpio *gpwm = pwmchip_get_drvdata(chip);158 159 guard(spinlock_irqsave)(&gpwm->lock);160 161 if (gpwm->changing)162 *state = gpwm->next_state;163 else164 *state = gpwm->state;165 166 return 0;167}168 169static const struct pwm_ops pwm_gpio_ops = {170 .apply = pwm_gpio_apply,171 .get_state = pwm_gpio_get_state,172};173 174static void pwm_gpio_disable_hrtimer(void *data)175{176 struct pwm_gpio *gpwm = data;177 178 hrtimer_cancel(&gpwm->gpio_timer);179}180 181static int pwm_gpio_probe(struct platform_device *pdev)182{183 struct device *dev = &pdev->dev;184 struct pwm_chip *chip;185 struct pwm_gpio *gpwm;186 int ret;187 188 chip = devm_pwmchip_alloc(dev, 1, sizeof(*gpwm));189 if (IS_ERR(chip))190 return PTR_ERR(chip);191 192 gpwm = pwmchip_get_drvdata(chip);193 194 spin_lock_init(&gpwm->lock);195 196 gpwm->gpio = devm_gpiod_get(dev, NULL, GPIOD_ASIS);197 if (IS_ERR(gpwm->gpio))198 return dev_err_probe(dev, PTR_ERR(gpwm->gpio),199 "%pfw: could not get gpio\n",200 dev_fwnode(dev));201 202 if (gpiod_cansleep(gpwm->gpio))203 return dev_err_probe(dev, -EINVAL,204 "%pfw: sleeping GPIO not supported\n",205 dev_fwnode(dev));206 207 chip->ops = &pwm_gpio_ops;208 chip->atomic = true;209 210 hrtimer_init(&gpwm->gpio_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);211 ret = devm_add_action_or_reset(dev, pwm_gpio_disable_hrtimer, gpwm);212 if (ret)213 return ret;214 215 gpwm->gpio_timer.function = pwm_gpio_timer;216 217 ret = pwmchip_add(chip);218 if (ret < 0)219 return dev_err_probe(dev, ret, "could not add pwmchip\n");220 221 return 0;222}223 224static const struct of_device_id pwm_gpio_dt_ids[] = {225 { .compatible = "pwm-gpio" },226 { /* sentinel */ }227};228MODULE_DEVICE_TABLE(of, pwm_gpio_dt_ids);229 230static struct platform_driver pwm_gpio_driver = {231 .driver = {232 .name = "pwm-gpio",233 .of_match_table = pwm_gpio_dt_ids,234 },235 .probe = pwm_gpio_probe,236};237module_platform_driver(pwm_gpio_driver);238 239MODULE_DESCRIPTION("PWM GPIO driver");240MODULE_AUTHOR("Vincent Whitchurch");241MODULE_LICENSE("GPL");242