/*
 * linux/drivers/video/backlight/pwm_bl.c
 *
 * simple PWM based backlight control, board code has to setup
 * 1) pin configuration so PWM waveforms can output
 * 2) platform_data being correctly configured
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/fb.h>
#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/pwm.h>
#include <linux/pwm_backlight.h>
#include <linux/slab.h>

struct pwm_bl_data {
        struct pwm_device       *pwm;
        struct device           *dev;
        unsigned int            period;
        unsigned int            lth_brightness;
        int                     (*notify)(struct device *,
                                          int brightness);
};

static int pwm_backlight_update_status(struct backlight_device *bl)
{
        struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
        int brightness = bl->props.brightness;
        int max = bl->props.max_brightness;

        if (bl->props.power != FB_BLANK_UNBLANK)
                brightness = 0;

        if (bl->props.fb_blank != FB_BLANK_UNBLANK)
                brightness = 0;

        if (pb->notify)
                brightness = pb->notify(pb->dev, brightness);

        if (brightness == 0) {
                pwm_config(pb->pwm, 0, pb->period);
                pwm_disable(pb->pwm);
        } else {
                brightness = pb->lth_brightness +
                        (brightness * (pb->period - pb->lth_brightness) / max);
                pwm_config(pb->pwm, brightness, pb->period);
                pwm_enable(pb->pwm);
        }
        return 0;
}

static int pwm_backlight_get_brightness(struct backlight_device *bl)
{
        return bl->props.brightness;
}

static const struct backlight_ops pwm_backlight_ops = {
        .update_status  = pwm_backlight_update_status,
        .get_brightness = pwm_backlight_get_brightness,
};

static int pwm_backlight_probe(struct platform_device *pdev)
{
        struct backlight_properties props;
        struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
        struct backlight_device *bl;
        struct pwm_bl_data *pb;
        int ret;

        if (!data) {
                dev_err(&pdev->dev, "failed to find platform data\n");
                return -EINVAL;
        }

        if (data->init) {
                ret = data->init(&pdev->dev);
                if (ret < 0)
                        return ret;
        }

        pb = kzalloc(sizeof(*pb), GFP_KERNEL);
        if (!pb) {
                dev_err(&pdev->dev, "no memory for state\n");
                ret = -ENOMEM;
                goto err_alloc;
        }

        pb->period = data->pwm_period_ns;
        pb->notify = data->notify;
        pb->lth_brightness = data->lth_brightness *
                (data->pwm_period_ns / data->max_brightness);
        pb->dev = &pdev->dev;

        pb->pwm = pwm_request(data->pwm_id, "backlight");
        if (IS_ERR(pb->pwm)) {
                dev_err(&pdev->dev, "unable to request PWM for backlight\n");
                ret = PTR_ERR(pb->pwm);
                goto err_pwm;
        } else
                dev_dbg(&pdev->dev, "got pwm for backlight\n");

        memset(&props, 0, sizeof(struct backlight_properties));
        props.max_brightness = data->max_brightness;
        bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
                                       &pwm_backlight_ops, &props);
        if (IS_ERR(bl)) {
                dev_err(&pdev->dev, "failed to register backlight\n");
                ret = PTR_ERR(bl);
                goto err_bl;
        }

        bl->props.brightness = data->dft_brightness;
        backlight_update_status(bl);

        platform_set_drvdata(pdev, bl);
        return 0;

err_bl:
        pwm_free(pb->pwm);
err_pwm:
        kfree(pb);
err_alloc:
        if (data->exit)
                data->exit(&pdev->dev);
        return ret;
}

static int pwm_backlight_remove(struct platform_device *pdev)
{
        struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
        struct backlight_device *bl = platform_get_drvdata(pdev);
        struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);

        backlight_device_unregister(bl);
        pwm_config(pb->pwm, 0, pb->period);
        pwm_disable(pb->pwm);
        pwm_free(pb->pwm);
        kfree(pb);
        if (data->exit)
                data->exit(&pdev->dev);
        return 0;
}

#ifdef CONFIG_PM
static int pwm_backlight_suspend(struct platform_device *pdev,
                                 pm_message_t state)
{
        struct backlight_device *bl = platform_get_drvdata(pdev);
        struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);

        if (pb->notify)
                pb->notify(pb->dev, 0);
        pwm_config(pb->pwm, 0, pb->period);
        pwm_disable(pb->pwm);
        return 0;
}

static int pwm_backlight_resume(struct platform_device *pdev)
{
        struct backlight_device *bl = platform_get_drvdata(pdev);

        backlight_update_status(bl);
        return 0;
}
#else
#define pwm_backlight_suspend   NULL
#define pwm_backlight_resume    NULL
#endif

static struct platform_driver pwm_backlight_driver = {
        .driver         = {
                .name   = "pwm-backlight",
                .owner  = THIS_MODULE,
        },
        .probe          = pwm_backlight_probe,
        .remove         = pwm_backlight_remove,
        .suspend        = pwm_backlight_suspend,
        .resume         = pwm_backlight_resume,
};

static int __init pwm_backlight_init(void)
{
        return platform_driver_register(&pwm_backlight_driver);
}
module_init(pwm_backlight_init);

static void __exit pwm_backlight_exit(void)
{
        platform_driver_unregister(&pwm_backlight_driver);
}
module_exit(pwm_backlight_exit);

MODULE_DESCRIPTION("PWM based Backlight Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pwm-backlight");