firmware/target/arm/s5l8700/backlight-meizu.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2009 by Bertrik Sikken
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21 #include <stdbool.h>
  22
  23 #include "config.h"
  24 #include "backlight.h"
  25 #include "backlight-target.h"
  26 #include "system.h"
  27
  28 /*
  29     Interrupt-driven backlight driver using the PWM mode of a hardware timer.
  30
  31     Backlight brightness is implemented by configuring one of the timers in
  32     the SoC for PWM mode. In this mode, two interrupts are generated for each
  33     cycle, one at the start of the cycle and another one sometime between the
  34     first interrupt and the start of the next cycle. The backlight is switched
  35     on at the first interrupt and switched off at the second interrupt. This
  36     way, the position in time of the second interrupt determines the duty cycle
  37     and thereby the brightness of the backlight.
  38     The backlight is switched on and off by means of a GPIO pin.
  39  */
  40
  41 void INT_TIMERA(void)
  42 {
  43     unsigned int tacon = TACON;
  44
  45     /* clear interrupts */
  46     TACON = tacon;
  47
  48     /* TA_INT1, start of PWM cycle: enable backlight */
  49     if (tacon & (1 << 17)) {
  50         PDAT0 |= (1 << 2);
  51     }
  52
  53     /* TA_INT0, disable backlight until next cycle */
  54     if (tacon & (1 << 16)) {
  55         PDAT0 &= ~(1 << 2);
  56     }
  57 }
  58
  59 void _backlight_set_brightness(int brightness)
  60 {
  61     static const unsigned char logtable[] = {0, 1, 2, 3, 5, 7, 10, 15, 22, 31, 44, 63, 90, 127, 180, 255};
  62
  63     if (brightness == MIN_BRIGHTNESS_SETTING) {
  64         /* turn backlight fully off and disable interrupt */
  65         PDAT0 &= ~(1 << 2);
  66         INTMSK &= ~(1 << 5);
  67     }
  68     else if (brightness == MAX_BRIGHTNESS_SETTING) {
  69         /* turn backlight fully on and disable interrupt */
  70         PDAT0 |= (1 << 2);
  71         INTMSK &= ~(1 << 5);
  72     }
  73     else {
  74         /* set PWM width and enable interrupt */
  75         TADATA0 = logtable[brightness];
  76         INTMSK |= (1 << 5);
  77     }
  78 }
  79
  80 void _backlight_on(void)
  81 {
  82     _backlight_set_brightness(backlight_brightness);
  83 }
  84
  85 void _backlight_off(void)
  86 {
  87     _backlight_set_brightness(MIN_BRIGHTNESS_SETTING);
  88 }
  89
  90 bool _backlight_init(void)
  91 {
  92     /* enable backlight pin as GPIO */
  93     PCON0 = ((PCON0 & ~(3 << 4)) | (1 << 4));
  94
  95     /* enable timer clock */
  96     PWRCON &= ~(1 << 4);
  97
  98     /* configure timer */
  99     TACMD = (1 << 1);   /* TA_CLR */
 100     TACMD = (1 << 0);   /* TA_EN */
 101     TACON = (1 << 13) | /* TA_INT1_EN */
 102             (1 << 12) | /* TA_INT0_EN */
 103             (1 << 11) | /* TA_START */
 104             (3 << 8) |  /* TA_CS = PCLK / 64 */
 105             (1 << 4);   /* TA_MODE_SEL = PWM mode */
 106     TADATA1 = 255;   /* set PWM period */
 107     TAPRE = 30;    /* prescaler */
 108
 109     _backlight_on();
 110
 111     return true;
 112 }
 113