152 строки
3.6 KiB
C
152 строки
3.6 KiB
C
#include <linux/kernel.h>
|
|
#include <linux/platform_device.h>
|
|
#include <linux/leds.h>
|
|
#include <linux/io.h>
|
|
#include <linux/atmel_pwm.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/module.h>
|
|
|
|
|
|
struct pwmled {
|
|
struct led_classdev cdev;
|
|
struct pwm_channel pwmc;
|
|
struct gpio_led *desc;
|
|
u32 mult;
|
|
u8 active_low;
|
|
};
|
|
|
|
|
|
/*
|
|
* For simplicity, we use "brightness" as if it were a linear function
|
|
* of PWM duty cycle. However, a logarithmic function of duty cycle is
|
|
* probably a better match for perceived brightness: two is half as bright
|
|
* as four, four is half as bright as eight, etc
|
|
*/
|
|
static void pwmled_brightness(struct led_classdev *cdev, enum led_brightness b)
|
|
{
|
|
struct pwmled *led;
|
|
|
|
/* update the duty cycle for the *next* period */
|
|
led = container_of(cdev, struct pwmled, cdev);
|
|
pwm_channel_writel(&led->pwmc, PWM_CUPD, led->mult * (unsigned) b);
|
|
}
|
|
|
|
/*
|
|
* NOTE: we reuse the platform_data structure of GPIO leds,
|
|
* but repurpose its "gpio" number as a PWM channel number.
|
|
*/
|
|
static int __devinit pwmled_probe(struct platform_device *pdev)
|
|
{
|
|
const struct gpio_led_platform_data *pdata;
|
|
struct pwmled *leds;
|
|
int i;
|
|
int status;
|
|
|
|
pdata = pdev->dev.platform_data;
|
|
if (!pdata || pdata->num_leds < 1)
|
|
return -ENODEV;
|
|
|
|
leds = kcalloc(pdata->num_leds, sizeof(*leds), GFP_KERNEL);
|
|
if (!leds)
|
|
return -ENOMEM;
|
|
|
|
for (i = 0; i < pdata->num_leds; i++) {
|
|
struct pwmled *led = leds + i;
|
|
const struct gpio_led *dat = pdata->leds + i;
|
|
u32 tmp;
|
|
|
|
led->cdev.name = dat->name;
|
|
led->cdev.brightness = LED_OFF;
|
|
led->cdev.brightness_set = pwmled_brightness;
|
|
led->cdev.default_trigger = dat->default_trigger;
|
|
|
|
led->active_low = dat->active_low;
|
|
|
|
status = pwm_channel_alloc(dat->gpio, &led->pwmc);
|
|
if (status < 0)
|
|
goto err;
|
|
|
|
/*
|
|
* Prescale clock by 2^x, so PWM counts in low MHz.
|
|
* Start each cycle with the LED active, so increasing
|
|
* the duty cycle gives us more time on (== brighter).
|
|
*/
|
|
tmp = 5;
|
|
if (!led->active_low)
|
|
tmp |= PWM_CPR_CPOL;
|
|
pwm_channel_writel(&led->pwmc, PWM_CMR, tmp);
|
|
|
|
/*
|
|
* Pick a period so PWM cycles at 100+ Hz; and a multiplier
|
|
* for scaling duty cycle: brightness * mult.
|
|
*/
|
|
tmp = (led->pwmc.mck / (1 << 5)) / 100;
|
|
tmp /= 255;
|
|
led->mult = tmp;
|
|
pwm_channel_writel(&led->pwmc, PWM_CDTY,
|
|
led->cdev.brightness * 255);
|
|
pwm_channel_writel(&led->pwmc, PWM_CPRD,
|
|
LED_FULL * tmp);
|
|
|
|
pwm_channel_enable(&led->pwmc);
|
|
|
|
/* Hand it over to the LED framework */
|
|
status = led_classdev_register(&pdev->dev, &led->cdev);
|
|
if (status < 0) {
|
|
pwm_channel_free(&led->pwmc);
|
|
goto err;
|
|
}
|
|
}
|
|
|
|
platform_set_drvdata(pdev, leds);
|
|
return 0;
|
|
|
|
err:
|
|
if (i > 0) {
|
|
for (i = i - 1; i >= 0; i--) {
|
|
led_classdev_unregister(&leds[i].cdev);
|
|
pwm_channel_free(&leds[i].pwmc);
|
|
}
|
|
}
|
|
kfree(leds);
|
|
|
|
return status;
|
|
}
|
|
|
|
static int __exit pwmled_remove(struct platform_device *pdev)
|
|
{
|
|
const struct gpio_led_platform_data *pdata;
|
|
struct pwmled *leds;
|
|
unsigned i;
|
|
|
|
pdata = pdev->dev.platform_data;
|
|
leds = platform_get_drvdata(pdev);
|
|
|
|
for (i = 0; i < pdata->num_leds; i++) {
|
|
struct pwmled *led = leds + i;
|
|
|
|
led_classdev_unregister(&led->cdev);
|
|
pwm_channel_free(&led->pwmc);
|
|
}
|
|
|
|
kfree(leds);
|
|
platform_set_drvdata(pdev, NULL);
|
|
return 0;
|
|
}
|
|
|
|
static struct platform_driver pwmled_driver = {
|
|
.driver = {
|
|
.name = "leds-atmel-pwm",
|
|
.owner = THIS_MODULE,
|
|
},
|
|
/* REVISIT add suspend() and resume() methods */
|
|
.probe = pwmled_probe,
|
|
.remove = __exit_p(pwmled_remove),
|
|
};
|
|
|
|
module_platform_driver(pwmled_driver);
|
|
|
|
MODULE_DESCRIPTION("Driver for LEDs with PWM-controlled brightness");
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_ALIAS("platform:leds-atmel-pwm");
|