/*
 * Copyright (C) 2008 Atmel Corporation
 *
 * Backlight driver using Atmel PWM peripheral.
 *
 * 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/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/fb.h>
#include <linux/clk.h>
#include <linux/gpio.h>
#include <linux/backlight.h>
#include <linux/atmel_pwm.h>
#include <linux/atmel-pwm-bl.h>
#include <linux/slab.h>

struct atmel_pwm_bl {
        const struct atmel_pwm_bl_platform_data *pdata;
        struct backlight_device                 *bldev;
        struct platform_device                  *pdev;
        struct pwm_channel                      pwmc;
        int                                     gpio_on;
};

static int atmel_pwm_bl_set_intensity(struct backlight_device *bd)
{
        struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
        int intensity = bd->props.brightness;
        int pwm_duty;

        if (bd->props.power != FB_BLANK_UNBLANK)
                intensity = 0;
        if (bd->props.fb_blank != FB_BLANK_UNBLANK)
                intensity = 0;

        if (pwmbl->pdata->pwm_active_low)
                pwm_duty = pwmbl->pdata->pwm_duty_min + intensity;
        else
                pwm_duty = pwmbl->pdata->pwm_duty_max - intensity;

        if (pwm_duty > pwmbl->pdata->pwm_duty_max)
                pwm_duty = pwmbl->pdata->pwm_duty_max;
        if (pwm_duty < pwmbl->pdata->pwm_duty_min)
                pwm_duty = pwmbl->pdata->pwm_duty_min;

        if (!intensity) {
                if (pwmbl->gpio_on != -1) {
                        gpio_set_value(pwmbl->gpio_on,
                                        0 ^ pwmbl->pdata->on_active_low);
                }
                pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
                pwm_channel_disable(&pwmbl->pwmc);
        } else {
                pwm_channel_enable(&pwmbl->pwmc);
                pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
                if (pwmbl->gpio_on != -1) {
                        gpio_set_value(pwmbl->gpio_on,
                                        1 ^ pwmbl->pdata->on_active_low);
                }
        }

        return 0;
}

static int atmel_pwm_bl_get_intensity(struct backlight_device *bd)
{
        struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
        u8 intensity;

        if (pwmbl->pdata->pwm_active_low) {
                intensity = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) -
                        pwmbl->pdata->pwm_duty_min;
        } else {
                intensity = pwmbl->pdata->pwm_duty_max -
                        pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY);
        }

        return intensity;
}

static int atmel_pwm_bl_init_pwm(struct atmel_pwm_bl *pwmbl)
{
        unsigned long pwm_rate = pwmbl->pwmc.mck;
        unsigned long prescale = DIV_ROUND_UP(pwm_rate,
                        (pwmbl->pdata->pwm_frequency *
                         pwmbl->pdata->pwm_compare_max)) - 1;

        /*
         * Prescale must be power of two and maximum 0xf in size because of
         * hardware limit. PWM speed will be:
         *      PWM module clock speed / (2 ^ prescale).
         */
        prescale = fls(prescale);
        if (prescale > 0xf)
                prescale = 0xf;

        pwm_channel_writel(&pwmbl->pwmc, PWM_CMR, prescale);
        pwm_channel_writel(&pwmbl->pwmc, PWM_CDTY,
                        pwmbl->pdata->pwm_duty_min +
                        pwmbl->bldev->props.brightness);
        pwm_channel_writel(&pwmbl->pwmc, PWM_CPRD,
                        pwmbl->pdata->pwm_compare_max);

        dev_info(&pwmbl->pdev->dev, "Atmel PWM backlight driver (%lu Hz)\n",
                pwmbl->pwmc.mck / pwmbl->pdata->pwm_compare_max /
                (1 << prescale));

        return pwm_channel_enable(&pwmbl->pwmc);
}

static const struct backlight_ops atmel_pwm_bl_ops = {
        .get_brightness = atmel_pwm_bl_get_intensity,
        .update_status  = atmel_pwm_bl_set_intensity,
};

static int __init atmel_pwm_bl_probe(struct platform_device *pdev)
{
        struct backlight_properties props;
        const struct atmel_pwm_bl_platform_data *pdata;
        struct backlight_device *bldev;
        struct atmel_pwm_bl *pwmbl;
        int retval;

        pwmbl = devm_kzalloc(&pdev->dev, sizeof(struct atmel_pwm_bl),
                                GFP_KERNEL);
        if (!pwmbl)
                return -ENOMEM;

        pwmbl->pdev = pdev;

        pdata = pdev->dev.platform_data;
        if (!pdata) {
                retval = -ENODEV;
                goto err_free_mem;
        }

        if (pdata->pwm_compare_max < pdata->pwm_duty_max ||
                        pdata->pwm_duty_min > pdata->pwm_duty_max ||
                        pdata->pwm_frequency == 0) {
                retval = -EINVAL;
                goto err_free_mem;
        }

        pwmbl->pdata = pdata;
        pwmbl->gpio_on = pdata->gpio_on;

        retval = pwm_channel_alloc(pdata->pwm_channel, &pwmbl->pwmc);
        if (retval)
                goto err_free_mem;

        if (pwmbl->gpio_on != -1) {
                retval = devm_gpio_request(&pdev->dev, pwmbl->gpio_on,
                                        "gpio_atmel_pwm_bl");
                if (retval) {
                        pwmbl->gpio_on = -1;
                        goto err_free_pwm;
                }

                /* Turn display off by default. */
                retval = gpio_direction_output(pwmbl->gpio_on,
                                0 ^ pdata->on_active_low);
                if (retval)
                        goto err_free_pwm;
        }

        memset(&props, 0, sizeof(struct backlight_properties));
        props.type = BACKLIGHT_RAW;
        props.max_brightness = pdata->pwm_duty_max - pdata->pwm_duty_min;
        bldev = backlight_device_register("atmel-pwm-bl", &pdev->dev, pwmbl,
                                          &atmel_pwm_bl_ops, &props);
        if (IS_ERR(bldev)) {
                retval = PTR_ERR(bldev);
                goto err_free_pwm;
        }

        pwmbl->bldev = bldev;

        platform_set_drvdata(pdev, pwmbl);

        /* Power up the backlight by default at middle intesity. */
        bldev->props.power = FB_BLANK_UNBLANK;
        bldev->props.brightness = bldev->props.max_brightness / 2;

        retval = atmel_pwm_bl_init_pwm(pwmbl);
        if (retval)
                goto err_free_bl_dev;

        atmel_pwm_bl_set_intensity(bldev);

        return 0;

err_free_bl_dev:
        backlight_device_unregister(bldev);
err_free_pwm:
        pwm_channel_free(&pwmbl->pwmc);
err_free_mem:
        return retval;
}

static int __exit atmel_pwm_bl_remove(struct platform_device *pdev)
{
        struct atmel_pwm_bl *pwmbl = platform_get_drvdata(pdev);

        if (pwmbl->gpio_on != -1)
                gpio_set_value(pwmbl->gpio_on, 0);
        pwm_channel_disable(&pwmbl->pwmc);
        pwm_channel_free(&pwmbl->pwmc);
        backlight_device_unregister(pwmbl->bldev);

        return 0;
}

static struct platform_driver atmel_pwm_bl_driver = {
        .driver = {
                .name = "atmel-pwm-bl",
        },
        /* REVISIT add suspend() and resume() */
        .remove = __exit_p(atmel_pwm_bl_remove),
};

module_platform_driver_probe(atmel_pwm_bl_driver, atmel_pwm_bl_probe);

MODULE_AUTHOR("Hans-Christian egtvedt <hans-christian.egtvedt@atmel.com>");
MODULE_DESCRIPTION("Atmel PWM backlight driver");
MODULE_LICENSE("GPL");