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     Backlight driver using the PWM mode of a hardware timer.
  30
  31     The PWM duty cycle depends exponentially on the configured brightness
  32     level. This makes the brightness curve more linear to the human eye.
  33  */
  34
  35 void _backlight_set_brightness(int brightness)
  36 {
  37     /* pwm = round(sqrt(2)**x), where brightness level x = 1..16 */
  38     static const unsigned int logtable[] =
  39         {1, 2, 3, 4, 6, 8, 11, 16, 23, 32, 45, 64, 91, 128, 181, 256};
  40
  41     /* set PWM width */
  42     TCDATA0 = logtable[brightness];
  43 }
  44
  45 void _backlight_on(void)
  46 {
  47     /* configure backlight pin P0.2 as timer PWM output */
  48     PCON0 = ((PCON0 & ~(3 << 4)) | (2 << 4));
  49     _backlight_set_brightness(backlight_brightness);
  50 }
  51
  52 void _backlight_off(void)
  53 {
  54     /* configure backlight pin P0.2 as GPIO and switch off */
  55     PCON0 = ((PCON0 & ~(3 << 4)) | (1 << 4));
  56     PDAT0 &= ~(1 << 2);
  57 }
  58
  59 bool _backlight_init(void)
  60 {
  61     /* enable timer clock */
  62     PWRCON &= ~(1 << 4);
  63
  64     /* configure timer */
  65     TCCMD = (1 << 1);   /* TC_CLR */
  66     TCCON = (0 << 13) | /* TC_INT1_EN */
  67             (0 << 12) | /* TC_INT0_EN */
  68             (1 << 11) | /* TC_START */
  69             (3 << 8) |  /* TC_CS = PCLK / 64 */
  70             (1 << 4);   /* TC_MODE_SEL = PWM mode */
  71     TCDATA1 = 256;      /* set PWM period */
  72     TCPRE = 20;         /* prescaler */
  73     TCCMD = (1 << 0);   /* TC_EN */
  74
  75     _backlight_on();
  76
  77     return true;
  78 }
  79