ep93xx_bl.c

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/*
 * Driver for the Cirrus EP93xx lcd backlight
 *
 * Copyright (c) 2010 H Hartley Sweeten <[email protected]>
 *
 * 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.
 *
 * This driver controls the pulse width modulated brightness control output,
 * BRIGHT, on the Cirrus EP9307, EP9312, and EP9315 processors.
 */

#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/fb.h>
#include <linux/backlight.h>

#define EP93XX_MAX_COUNT        255
#define EP93XX_MAX_BRIGHT       255
#define EP93XX_DEF_BRIGHT       128

struct ep93xxbl {
    void __iomem *mmio;
    int brightness;
};

static int ep93xxbl_set(struct backlight_device *bl, int brightness)
{
    struct ep93xxbl *ep93xxbl = bl_get_data(bl);

    writel((brightness << 8) | EP93XX_MAX_COUNT, ep93xxbl->mmio);

    ep93xxbl->brightness = brightness;

    return 0;
}

static int ep93xxbl_update_status(struct backlight_device *bl)
{
    int brightness = bl->props.brightness;

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

    return ep93xxbl_set(bl, brightness);
}

static int ep93xxbl_get_brightness(struct backlight_device *bl)
{
    struct ep93xxbl *ep93xxbl = bl_get_data(bl);

    return ep93xxbl->brightness;
}

static const struct backlight_ops ep93xxbl_ops = {
    .update_status  = ep93xxbl_update_status,
    .get_brightness = ep93xxbl_get_brightness,
};

static int __init ep93xxbl_probe(struct platform_device *dev)
{
    struct ep93xxbl *ep93xxbl;
    struct backlight_device *bl;
    struct backlight_properties props;
    struct resource *res;

    ep93xxbl = devm_kzalloc(&dev->dev, sizeof(*ep93xxbl), GFP_KERNEL);
    if (!ep93xxbl)
        return -ENOMEM;

    res = platform_get_resource(dev, IORESOURCE_MEM, 0);
    if (!res)
        return -ENXIO;

    /*
     * FIXME - We don't do a request_mem_region here because we are
     * sharing the register space with the framebuffer driver (see
     * drivers/video/ep93xx-fb.c) and doing so will cause the second
     * loaded driver to return -EBUSY.
     *
     * NOTE: No locking is required; the framebuffer does not touch
     * this register.
     */
    ep93xxbl->mmio = devm_ioremap(&dev->dev, res->start,
                      resource_size(res));
    if (!ep93xxbl->mmio)
        return -ENXIO;

    memset(&props, 0, sizeof(struct backlight_properties));
    props.type = BACKLIGHT_RAW;
    props.max_brightness = EP93XX_MAX_BRIGHT;
    bl = backlight_device_register(dev->name, &dev->dev, ep93xxbl,
                       &ep93xxbl_ops, &props);
    if (IS_ERR(bl))
        return PTR_ERR(bl);

    bl->props.brightness = EP93XX_DEF_BRIGHT;

    platform_set_drvdata(dev, bl);

    ep93xxbl_update_status(bl);

    return 0;
}

static int ep93xxbl_remove(struct platform_device *dev)
{
    struct backlight_device *bl = platform_get_drvdata(dev);

    backlight_device_unregister(bl);
    platform_set_drvdata(dev, NULL);
    return 0;
}

#ifdef CONFIG_PM
static int ep93xxbl_suspend(struct platform_device *dev, pm_message_t state)
{
    struct backlight_device *bl = platform_get_drvdata(dev);

    return ep93xxbl_set(bl, 0);
}

static int ep93xxbl_resume(struct platform_device *dev)
{
    struct backlight_device *bl = platform_get_drvdata(dev);

    backlight_update_status(bl);
    return 0;
}
#else
#define ep93xxbl_suspend    NULL
#define ep93xxbl_resume     NULL
#endif

static struct platform_driver ep93xxbl_driver = {
    .driver     = {
        .name   = "ep93xx-bl",
        .owner  = THIS_MODULE,
    },
    .probe      = ep93xxbl_probe,
    .remove     = __devexit_p(ep93xxbl_remove),
    .suspend    = ep93xxbl_suspend,
    .resume     = ep93xxbl_resume,
};

module_platform_driver(ep93xxbl_driver);

MODULE_DESCRIPTION("EP93xx Backlight Driver");
MODULE_AUTHOR("H Hartley Sweeten <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ep93xx-bl");