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linux/drivers/leds/leds-pwm.c
Uwe Kleine-König 76fe464c8e leds: pwm: Don't disable the PWM when the LED should be off
Disabling a PWM (i.e. calling pwm_apply_state with .enabled = false)
gives no guarantees what the PWM output does. It might freeze where it
currently is, or go in a High-Z state or drive the active or inactive
state, it might even continue to toggle.

To ensure that the LED gets really disabled, don't disable the PWM even
when .duty_cycle is zero.

This fixes disabling a leds-pwm LED on i.MX28. The PWM on this SoC is
one of those that freezes its output on disable, so if you disable an
LED that is full on, it stays on. If you disable a LED with half
brightness it goes off in 50% of the cases and full on in the other 50%.

Fixes: 41c42ff5db ("leds: simple driver for pwm driven LEDs")
Reported-by: Rogan Dawes <rogan@dawes.za.net>
Reported-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Fabio Estevam <festevam@denx.de>
Link: https://lore.kernel.org/r/20230922192834.1695727-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Lee Jones <lee@kernel.org>
2023-11-01 11:28:50 +00:00

218 lines
4.9 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/drivers/leds-pwm.c
*
* simple PWM based LED control
*
* Copyright 2009 Luotao Fu @ Pengutronix (l.fu@pengutronix.de)
*
* based on leds-gpio.c by Raphael Assenat <raph@8d.com>
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/leds.h>
#include <linux/err.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include "leds.h"
struct led_pwm {
const char *name;
u8 active_low;
u8 default_state;
unsigned int max_brightness;
};
struct led_pwm_data {
struct led_classdev cdev;
struct pwm_device *pwm;
struct pwm_state pwmstate;
unsigned int active_low;
};
struct led_pwm_priv {
int num_leds;
struct led_pwm_data leds[];
};
static int led_pwm_set(struct led_classdev *led_cdev,
enum led_brightness brightness)
{
struct led_pwm_data *led_dat =
container_of(led_cdev, struct led_pwm_data, cdev);
unsigned int max = led_dat->cdev.max_brightness;
unsigned long long duty = led_dat->pwmstate.period;
duty *= brightness;
do_div(duty, max);
if (led_dat->active_low)
duty = led_dat->pwmstate.period - duty;
led_dat->pwmstate.duty_cycle = duty;
led_dat->pwmstate.enabled = true;
return pwm_apply_state(led_dat->pwm, &led_dat->pwmstate);
}
__attribute__((nonnull))
static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
struct led_pwm *led, struct fwnode_handle *fwnode)
{
struct led_pwm_data *led_data = &priv->leds[priv->num_leds];
struct led_init_data init_data = { .fwnode = fwnode };
int ret;
led_data->active_low = led->active_low;
led_data->cdev.name = led->name;
led_data->cdev.brightness = LED_OFF;
led_data->cdev.max_brightness = led->max_brightness;
led_data->cdev.flags = LED_CORE_SUSPENDRESUME;
led_data->pwm = devm_fwnode_pwm_get(dev, fwnode, NULL);
if (IS_ERR(led_data->pwm))
return dev_err_probe(dev, PTR_ERR(led_data->pwm),
"unable to request PWM for %s\n",
led->name);
led_data->cdev.brightness_set_blocking = led_pwm_set;
/* init PWM state */
switch (led->default_state) {
case LEDS_DEFSTATE_KEEP:
pwm_get_state(led_data->pwm, &led_data->pwmstate);
if (led_data->pwmstate.period)
break;
led->default_state = LEDS_DEFSTATE_OFF;
dev_warn(dev,
"failed to read period for %s, default to off",
led->name);
fallthrough;
default:
pwm_init_state(led_data->pwm, &led_data->pwmstate);
break;
}
/* set brightness */
switch (led->default_state) {
case LEDS_DEFSTATE_ON:
led_data->cdev.brightness = led->max_brightness;
break;
case LEDS_DEFSTATE_KEEP:
{
uint64_t brightness;
brightness = led->max_brightness;
brightness *= led_data->pwmstate.duty_cycle;
do_div(brightness, led_data->pwmstate.period);
led_data->cdev.brightness = brightness;
}
break;
}
ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data);
if (ret) {
dev_err(dev, "failed to register PWM led for %s: %d\n",
led->name, ret);
return ret;
}
if (led->default_state != LEDS_DEFSTATE_KEEP) {
ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
if (ret) {
dev_err(dev, "failed to set led PWM value for %s: %d",
led->name, ret);
return ret;
}
}
priv->num_leds++;
return 0;
}
static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
{
struct fwnode_handle *fwnode;
struct led_pwm led;
int ret;
device_for_each_child_node(dev, fwnode) {
memset(&led, 0, sizeof(led));
ret = fwnode_property_read_string(fwnode, "label", &led.name);
if (ret && is_of_node(fwnode))
led.name = to_of_node(fwnode)->name;
if (!led.name) {
ret = -EINVAL;
goto err_child_out;
}
led.active_low = fwnode_property_read_bool(fwnode,
"active-low");
fwnode_property_read_u32(fwnode, "max-brightness",
&led.max_brightness);
led.default_state = led_init_default_state_get(fwnode);
ret = led_pwm_add(dev, priv, &led, fwnode);
if (ret)
goto err_child_out;
}
return 0;
err_child_out:
fwnode_handle_put(fwnode);
return ret;
}
static int led_pwm_probe(struct platform_device *pdev)
{
struct led_pwm_priv *priv;
int ret = 0;
int count;
count = device_get_child_node_count(&pdev->dev);
if (!count)
return -EINVAL;
priv = devm_kzalloc(&pdev->dev, struct_size(priv, leds, count),
GFP_KERNEL);
if (!priv)
return -ENOMEM;
ret = led_pwm_create_fwnode(&pdev->dev, priv);
if (ret)
return ret;
platform_set_drvdata(pdev, priv);
return 0;
}
static const struct of_device_id of_pwm_leds_match[] = {
{ .compatible = "pwm-leds", },
{},
};
MODULE_DEVICE_TABLE(of, of_pwm_leds_match);
static struct platform_driver led_pwm_driver = {
.probe = led_pwm_probe,
.driver = {
.name = "leds_pwm",
.of_match_table = of_pwm_leds_match,
},
};
module_platform_driver(led_pwm_driver);
MODULE_AUTHOR("Luotao Fu <l.fu@pengutronix.de>");
MODULE_DESCRIPTION("generic PWM LED driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:leds-pwm");