atmel-pwm-bl.c

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/*
 * 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 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:
    platform_set_drvdata(pdev, NULL);
    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);
    platform_set_drvdata(pdev, NULL);

    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),
};

static int __init atmel_pwm_bl_init(void)
{
    return platform_driver_probe(&atmel_pwm_bl_driver, atmel_pwm_bl_probe);
}
module_init(atmel_pwm_bl_init);

static void __exit atmel_pwm_bl_exit(void)
{
    platform_driver_unregister(&atmel_pwm_bl_driver);
}
module_exit(atmel_pwm_bl_exit);

MODULE_AUTHOR("Hans-Christian egtvedt <[email protected]>");
MODULE_DESCRIPTION("Atmel PWM backlight driver");
MODULE_LICENSE("GPL");