linux pwm 应用

原创：kylin_zeng  http://blog.chinaunix.net/uid/23795897.html

lcd 背光灯 pwm  board配置。

#ifdef CONFIG_BACKLIGHT_RK29_BL
#define PWM_ID            3
#define PWM_MODE      PWM3
#define PWM_EFFECT_VALUE  1

static struct platform_device rk29_device_backlight = {
    .name    = "rk29_backlight",
    .id     = -1,
    .dev    = {
        .platform_data = &rk29_bl_info,
    }
};


static struct rk29_bl_info rk29_bl_info = {
        .min_brightness = 120,//65, //value must between 0~255
        .max_brightness = 255,//150, //value must between 0~255
        .brightness_mode =BRIGHTNESS_MODE_CONIC,
    .pre_div = 30 * 1000, // pwm output clk: 30k;
    .pwm_id = PWM_ID, //3
    .bl_ref = PWM_EFFECT_VALUE, //1
    .io_init = rk29_backlight_io_init,
    .io_deinit = rk29_backlight_io_deinit,
    .pwm_suspend = rk29_backlight_pwm_suspend,
    .pwm_resume = rk29_backlight_pwm_resume,
};


static int rk29_backlight_io_init(void)
{
    int ret = 0;
    iomux_set(PWM_MODE);
    return ret;
}

static int rk29_backlight_io_deinit(void)
{
    int ret = 0, pwm_gpio;
    pwm_gpio = iomux_mode_to_gpio(PWM_MODE);
    gpio_request(pwm_gpio, NULL);
    gpio_direction_output(pwm_gpio, GPIO_LOW);
    return ret;
}


static int rk29_backlight_pwm_suspend(void)
{
    int ret = 0, pwm_gpio;
    pwm_gpio = iomux_mode_to_gpio(PWM_MODE);
    if (gpio_request(pwm_gpio, NULL)) {
        printk("func %s, line %d: request gpio fail\n", __FUNCTION__, __LINE__);
        return -1;
    }
    gpio_direction_output(pwm_gpio, GPIO_LOW);
    return ret;
}

static int rk29_backlight_pwm_resume(void)
{
    int pwm_gpio = iomux_mode_to_gpio(PWM_MODE);
    gpio_free(pwm_gpio);
    iomux_set(PWM_MODE);
    return 0;
}

int iomux_mode_to_gpio(unsigned int mode)
{
        struct union_mode m;

    if(!mode_is_valid(mode)){
        INFO("<%s> mode(0x%x) is invalid\n", __func__, mode);
        return INVALID_GPIO;
    }

        m.mode = mode;
        return PIN_BASE + m.mux.bank * 32 + (m.mux.goff - 0x0A) * 8 + m.mux.off;
}