621cf62702
detect wraps so we don't miss the value we were waiting for fix audio stuttering on fuzev2 git-svn-id: svn://svn.rockbox.org/rockbox/trunk@25740 a1c6a512-1295-4272-9138-f99709370657
118 lines
3.6 KiB
C
118 lines
3.6 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2008 Rafaël Carré
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#ifndef SYSTEM_TARGET_H
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#define SYSTEM_TARGET_H
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#include "system-arm.h"
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#include "mmu-arm.h"
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#include "panic.h"
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#include "clock-target.h" /* CPUFREQ_* are defined here */
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/* We can use a interrupt-based mechanism on the fuzev2 */
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#define INCREASED_SCROLLWHEEL_POLLING \
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(defined(HAVE_SCROLLWHEEL) && (CONFIG_CPU == AS3525))
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#if INCREASED_SCROLLWHEEL_POLLING
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/* let the timer interrupt twice as often for the scrollwheel polling */
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#define KERNEL_TIMER_FREQ (TIMER_FREQ/2)
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#else
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#define KERNEL_TIMER_FREQ TIMER_FREQ
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#endif
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#ifdef BOOTLOADER
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#define UNCACHED_ADDR(a) (a)
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#else
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#define UNCACHED_ADDR(a) ((typeof(a)) ((uintptr_t)(a) + 0x10000000))
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#endif
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#ifdef SANSA_C200V2
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/* 0: Backlight on A5, 1: Backlight on A7 */
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extern int c200v2_variant;
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/* c200v2 changes the timer interval often due to software pwm */
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#define TIMER_PERIOD TIMER2_BGLOAD
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#else
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#define TIMER_PERIOD (KERNEL_TIMER_FREQ/HZ)
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#endif
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/*
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* This function is not overly accurate, so rather call it with an usec more
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* than less (see below comment)
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*
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* if inlined it expands to a really small and fast function if it's called
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* with compile time constants */
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static inline void udelay(unsigned usecs) __attribute__((always_inline));
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static inline void udelay(unsigned usecs)
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{
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unsigned now;
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int end;
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/**
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* we're limited to 1.5us multiplies due to the odd timer frequency (1.5MHz),
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* to avoid calculating which is safer (need to round up for small values)
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* and saves spending time in the divider we have a lut for
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* small us values, it should be roughly us*2/3
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**/
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static const unsigned char udelay_lut[] =
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{
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0, 1, 2, 2, 3, 4, 4, 5, 6, 6,
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7, 8, 8, 9, 10, 10, 11, 12, 12, 13,
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};
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now = TIMER2_VALUE;
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/* we don't want to handle multiple overflows, so limit the numbers
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* (if you want to wait more than a tick just poll current_tick, or
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* call sleep()) */
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if (UNLIKELY(usecs >= TIMER_PERIOD))
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panicf("%s(): %d too high!", __func__, usecs);
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if (UNLIKELY(usecs <= 0))
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return;
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if (usecs < ARRAYLEN(udelay_lut))
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{ /* the timer decrements */
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end = now - udelay_lut[usecs];
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}
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else
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{ /* to usecs */
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int delay = usecs * 2 / 3; /* us * 1.5 = us*timer_period */
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end = now - delay;
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}
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unsigned old;
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/* underrun ? */
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if (end < 0)
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{
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do {
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old = now;
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now = TIMER2_VALUE;
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} while(now <= old); /* if the new value is higher then we wrapped */
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end += TIMER_PERIOD;
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}
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do {
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/* if timer wraps then we missed our end value */
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old = now;
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now = TIMER2_VALUE;
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} while(now > (unsigned)end && now <= old);
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}
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#endif /* SYSTEM_TARGET_H */
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