ot200_bl.c

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/*
 * Copyright (C) 2012 Bachmann electronic GmbH
 *  Christian Gmeiner <[email protected]>
 *
 * Backlight driver for ot200 visualisation device from
 * Bachmann electronic GmbH.
 *
 * 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/fb.h>
#include <linux/backlight.h>
#include <linux/gpio.h>
#include <linux/cs5535.h>

static struct cs5535_mfgpt_timer *pwm_timer;

/* this array defines the mapping of brightness in % to pwm frequency */
static const u8 dim_table[101] = {0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2,
                  2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4,
                  4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 9,
                  10, 10, 11, 11, 12, 12, 13, 14, 15, 15, 16,
                  17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28,
                  30, 31, 33, 35, 37, 39, 41, 43, 45, 47, 50,
                  53, 55, 58, 61, 65, 68, 72, 75, 79, 84, 88,
                  93, 97, 103, 108, 114, 120, 126, 133, 140,
                  147, 155, 163};

struct ot200_backlight_data {
    int current_brightness;
};

#define GPIO_DIMM   27
#define SCALE       1
#define CMP1MODE    0x2 /* compare on GE; output high on compare
                 * greater than or equal */
#define PWM_SETUP   (SCALE | CMP1MODE << 6 | MFGPT_SETUP_CNTEN)
#define MAX_COMP2   163

static int ot200_backlight_update_status(struct backlight_device *bl)
{
    struct ot200_backlight_data *data = bl_get_data(bl);
    int brightness = bl->props.brightness;

    if (bl->props.state & BL_CORE_FBBLANK)
        brightness = 0;

    /* enable or disable PWM timer */
    if (brightness == 0)
        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, 0);
    else if (data->current_brightness == 0) {
        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
        cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP,
            MFGPT_SETUP_CNTEN);
    }

    /* apply new brightness value */
    cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
        MAX_COMP2 - dim_table[brightness]);
    data->current_brightness = brightness;

    return 0;
}

static int ot200_backlight_get_brightness(struct backlight_device *bl)
{
    struct ot200_backlight_data *data = bl_get_data(bl);
    return data->current_brightness;
}

static const struct backlight_ops ot200_backlight_ops = {
    .update_status  = ot200_backlight_update_status,
    .get_brightness = ot200_backlight_get_brightness,
};

static int ot200_backlight_probe(struct platform_device *pdev)
{
    struct backlight_device *bl;
    struct ot200_backlight_data *data;
    struct backlight_properties props;
    int retval = 0;

    /* request gpio */
    if (devm_gpio_request(&pdev->dev, GPIO_DIMM,
                "ot200 backlight dimmer") < 0) {
        dev_err(&pdev->dev, "failed to request GPIO %d\n", GPIO_DIMM);
        return -ENODEV;
    }

    /* request timer */
    pwm_timer = cs5535_mfgpt_alloc_timer(7, MFGPT_DOMAIN_ANY);
    if (!pwm_timer) {
        dev_err(&pdev->dev, "MFGPT 7 not available\n");
        return -ENODEV;
    }

    data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
    if (!data) {
        retval = -ENOMEM;
        goto error_devm_kzalloc;
    }

    /* setup gpio */
    cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_ENABLE);
    cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_AUX1);

    /* setup timer */
    cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1, 0);
    cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP2, MAX_COMP2);
    cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, PWM_SETUP);

    data->current_brightness = 100;
    props.max_brightness = 100;
    props.brightness = 100;
    props.type = BACKLIGHT_RAW;

    bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, data,
                    &ot200_backlight_ops, &props);
    if (IS_ERR(bl)) {
        dev_err(&pdev->dev, "failed to register backlight\n");
        retval = PTR_ERR(bl);
        goto error_devm_kzalloc;
    }

    platform_set_drvdata(pdev, bl);

    return 0;

error_devm_kzalloc:
    cs5535_mfgpt_free_timer(pwm_timer);
    return retval;
}

static int ot200_backlight_remove(struct platform_device *pdev)
{
    struct backlight_device *bl = platform_get_drvdata(pdev);

    backlight_device_unregister(bl);

    /* on module unload set brightness to 100% */
    cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
    cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);
    cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
        MAX_COMP2 - dim_table[100]);

    cs5535_mfgpt_free_timer(pwm_timer);

    return 0;
}

static struct platform_driver ot200_backlight_driver = {
    .driver     = {
        .name   = "ot200-backlight",
        .owner  = THIS_MODULE,
    },
    .probe      = ot200_backlight_probe,
    .remove     = ot200_backlight_remove,
};

module_platform_driver(ot200_backlight_driver);

MODULE_DESCRIPTION("backlight driver for ot200 visualisation device");
MODULE_AUTHOR("Christian Gmeiner <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ot200-backlight");