firmware/target/arm/as3525/system-target.h

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2008 Rafaël Carré
  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 #ifndef SYSTEM_TARGET_H
  22 #define SYSTEM_TARGET_H
  23
  24 #include "system-arm.h"
  25 #include "mmu-arm.h"
  26 #include "panic.h"
  27
  28 #include "clock-target.h" /* CPUFREQ_* are defined here */
  29
  30 /* We can use a interrupt-based mechanism on the fuzev2 */
  31 #define INCREASED_SCROLLWHEEL_POLLING \
  32     (defined(HAVE_SCROLLWHEEL) && (CONFIG_CPU == AS3525))
  33
  34 #if INCREASED_SCROLLWHEEL_POLLING
  35 /* let the timer interrupt twice as often for the scrollwheel polling */
  36 #define KERNEL_TIMER_FREQ (TIMER_FREQ/2)
  37 #else
  38 #define KERNEL_TIMER_FREQ TIMER_FREQ
  39 #endif
  40
  41 #ifdef BOOTLOADER
  42 #define UNCACHED_ADDR(a) (a)
  43 #else
  44 #define UNCACHED_ADDR(a) ((typeof(a)) ((uintptr_t)(a) + 0x10000000))
  45 #endif
  46
  47 #ifdef SANSA_C200V2
  48 /* 0: Backlight on A5, 1: Backlight on A7 */
  49 extern int c200v2_variant;
  50 /* c200v2 changes the timer interval often due to software pwm */
  51 #define TIMER_PERIOD TIMER2_BGLOAD
  52 #else
  53 #define TIMER_PERIOD (KERNEL_TIMER_FREQ/HZ)
  54 #endif
  55
  56 /*
  57  * This function is not overly accurate, so rather call it with an usec more
  58  * than less (see below comment)
  59  *
  60  * if inlined it expands to a really small and fast function if it's called
  61  * with compile time constants */
  62 static inline void udelay(unsigned usecs) __attribute__((always_inline));
  63 static inline void udelay(unsigned usecs)
  64 {
  65     unsigned now;
  66     int end;
  67
  68     /**
  69      * we're limited to 1.5us multiplies due to the odd timer frequency (1.5MHz),
  70      * to avoid calculating which is safer (need to round up for small values)
  71      * and saves spending time in the divider we have a lut for
  72      * small us values, it should be roughly us*2/3
  73      **/
  74     static const unsigned char udelay_lut[] =
  75     {
  76         0, 1, 2, 2,  3,  4,  4,  5,  6,  6,
  77         7, 8, 8, 9, 10, 10, 11, 12, 12, 13,
  78     };
  79
  80
  81     now = TIMER2_VALUE;
  82     /* we don't want to handle multiple overflows, so limit the numbers
  83      * (if you want to wait more than a tick just poll current_tick, or
  84      * call sleep()) */
  85     if (UNLIKELY(usecs >= TIMER_PERIOD))
  86         panicf("%s(): %d too high!", __func__, usecs);
  87     if (UNLIKELY(usecs <= 0))
  88         return;
  89     if (usecs < ARRAYLEN(udelay_lut))
  90     {   /* the timer decrements */
  91         end = now - udelay_lut[usecs];
  92     }
  93     else
  94     {   /* to usecs */
  95         int delay = usecs * 2 / 3; /* us * 1.5 = us*timer_period */
  96         end = now - delay;
  97     }
  98
  99     unsigned old;
 100
 101     /* underrun ? */
 102     if (end < 0)
 103     {
 104         do {
 105             old = now;
 106             now = TIMER2_VALUE;
 107         } while(now <= old);  /* if the new value is higher then we wrapped */
 108
 109         end += TIMER_PERIOD;
 110     }
 111
 112     do {
 113         /* if timer wraps then we missed our end value */
 114         old = now;
 115         now = TIMER2_VALUE;
 116     } while(now > (unsigned)end && now <= old);
 117 }
 118 #endif /* SYSTEM_TARGET_H */