pandora_bl.c

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/*
 * Backlight driver for Pandora handheld.
 * Pandora uses TWL4030 PWM0 -> TPS61161 combo for control backlight.
 * Based on pwm_bl.c
 *
 * Copyright 2009,2012 Gražvydas Ignotas <[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.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/fb.h>
#include <linux/backlight.h>
#include <linux/i2c/twl.h>
#include <linux/err.h>

#define TWL_PWM0_ON     0x00
#define TWL_PWM0_OFF        0x01

#define TWL_INTBR_GPBR1     0x0c
#define TWL_INTBR_PMBR1     0x0d

#define TWL_PMBR1_PWM0_MUXMASK  0x0c
#define TWL_PMBR1_PWM0      0x04
#define PWM0_CLK_ENABLE     BIT(0)
#define PWM0_ENABLE     BIT(2)

/* range accepted by hardware */
#define MIN_VALUE 9
#define MAX_VALUE 63
#define MAX_USER_VALUE (MAX_VALUE - MIN_VALUE)

#define PANDORABL_WAS_OFF BL_CORE_DRIVER1

static int pandora_backlight_update_status(struct backlight_device *bl)
{
    int brightness = bl->props.brightness;
    u8 r;

    if (bl->props.power != FB_BLANK_UNBLANK)
        brightness = 0;
    if (bl->props.state & BL_CORE_FBBLANK)
        brightness = 0;
    if (bl->props.state & BL_CORE_SUSPENDED)
        brightness = 0;

    if ((unsigned int)brightness > MAX_USER_VALUE)
        brightness = MAX_USER_VALUE;

    if (brightness == 0) {
        if (bl->props.state & PANDORABL_WAS_OFF)
            goto done;

        /* first disable PWM0 output, then clock */
        twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
        r &= ~PWM0_ENABLE;
        twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
        r &= ~PWM0_CLK_ENABLE;
        twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);

        goto done;
    }

    if (bl->props.state & PANDORABL_WAS_OFF) {
        /*
         * set PWM duty cycle to max. TPS61161 seems to use this
         * to calibrate it's PWM sensitivity when it starts.
         */
        twl_i2c_write_u8(TWL4030_MODULE_PWM0, MAX_VALUE,
                    TWL_PWM0_OFF);

        /* first enable clock, then PWM0 out */
        twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
        r &= ~PWM0_ENABLE;
        r |= PWM0_CLK_ENABLE;
        twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
        r |= PWM0_ENABLE;
        twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);

        /*
         * TI made it very easy to enable digital control, so easy that
         * it often triggers unintentionally and disabes PWM control,
         * so wait until 1 wire mode detection window ends.
         */
        usleep_range(2000, 10000);
    }

    twl_i2c_write_u8(TWL4030_MODULE_PWM0, MIN_VALUE + brightness,
                TWL_PWM0_OFF);

done:
    if (brightness != 0)
        bl->props.state &= ~PANDORABL_WAS_OFF;
    else
        bl->props.state |= PANDORABL_WAS_OFF;

    return 0;
}

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

static const struct backlight_ops pandora_backlight_ops = {
    .options    = BL_CORE_SUSPENDRESUME,
    .update_status  = pandora_backlight_update_status,
    .get_brightness = pandora_backlight_get_brightness,
};

static int pandora_backlight_probe(struct platform_device *pdev)
{
    struct backlight_properties props;
    struct backlight_device *bl;
    u8 r;

    memset(&props, 0, sizeof(props));
    props.max_brightness = MAX_USER_VALUE;
    props.type = BACKLIGHT_RAW;
    bl = backlight_device_register(pdev->name, &pdev->dev,
            NULL, &pandora_backlight_ops, &props);
    if (IS_ERR(bl)) {
        dev_err(&pdev->dev, "failed to register backlight\n");
        return PTR_ERR(bl);
    }

    platform_set_drvdata(pdev, bl);

    /* 64 cycle period, ON position 0 */
    twl_i2c_write_u8(TWL4030_MODULE_PWM0, 0x80, TWL_PWM0_ON);

    bl->props.state |= PANDORABL_WAS_OFF;
    bl->props.brightness = MAX_USER_VALUE;
    backlight_update_status(bl);

    /* enable PWM function in pin mux */
    twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_PMBR1);
    r &= ~TWL_PMBR1_PWM0_MUXMASK;
    r |= TWL_PMBR1_PWM0;
    twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_PMBR1);

    return 0;
}

static int pandora_backlight_remove(struct platform_device *pdev)
{
    struct backlight_device *bl = platform_get_drvdata(pdev);
    backlight_device_unregister(bl);
    return 0;
}

static struct platform_driver pandora_backlight_driver = {
    .driver     = {
        .name   = "pandora-backlight",
        .owner  = THIS_MODULE,
    },
    .probe      = pandora_backlight_probe,
    .remove     = pandora_backlight_remove,
};

module_platform_driver(pandora_backlight_driver);

MODULE_AUTHOR("Gražvydas Ignotas <[email protected]>");
MODULE_DESCRIPTION("Pandora Backlight Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pandora-backlight");