Nyaaori/rockbox
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

as3525*: make udelay() be a simple busy loop

Browse source 
it achieves all the requirements, work fine on c200v2, and is much simpler

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@26933 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Rafaël Carré 2010-06-18 19:14:08 +00:00
parent 955bb4004f
commit 7a9033179f
3 changed files with 22 additions and 64 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

20
firmware/target/arm/as3525/system-as3525.c
View file

@ -326,6 +326,26 @@ int system_memory_guard(int newmode)
return 0;
}
void udelay(unsigned short usecs)
{
unsigned cycles_per_usec;
unsigned delay;
if (cpu_frequency == CPUFREQ_MAX) {
cycles_per_usec = (CPUFREQ_MAX + 999999) / 1000000;
} else {
cycles_per_usec = (CPUFREQ_NORMAL + 999999) / 1000000;
}
delay = (usecs * cycles_per_usec + 3) / 4;
asm volatile(
"1: subs %0, %0, #1 \n" /* 1 cycle */
" bne 1b \n" /* 3 cycles */
: : "r"(delay)
);
}
#ifndef BOOTLOADER
#ifdef HAVE_ADJUSTABLE_CPU_FREQ

63
firmware/target/arm/as3525/system-target.h
View file

@ -49,66 +49,5 @@ extern int c200v2_variant;
#define TIMER_PERIOD (KERNEL_TIMER_FREQ/HZ)
#endif
/*
* This function is not overly accurate, so rather call it with an usec more
* than less (see below comment)
*
* if inlined it expands to a really small and fast function if it's called
* with compile time constants */
static inline void udelay(unsigned usecs) __attribute__((always_inline));
static inline void udelay(unsigned usecs)
{
unsigned now;
int end;
/**
* we're limited to 0.666us multiplies due to the odd timer frequency (1.5MHz),
* to avoid calculating which is safer (need to round up for small values)
* and saves spending time in the divider we have a lut for
* small us values, it should be roughly us*3/2
**/
static const unsigned char udelay_lut[] =
{
0, 2, 3, 5, 6, 8, 9, 11, 12, 14,
15, 17, 18, 20, 21, 23, 24, 26, 27, 29,
};
now = TIMER2_VALUE;
/* we don't want to handle multiple overflows, so limit the numbers
* (if you want to wait more than a tick just poll current_tick, or
* call sleep()) */
if (UNLIKELY(usecs >= (TIMER_PERIOD*2/3)))
panicf("%s(): %d too high!", __func__, usecs);
if (UNLIKELY(usecs <= 0))
return;
if (usecs < ARRAYLEN(udelay_lut))
{ /* the timer decrements */
end = now - udelay_lut[usecs];
}
else
{ /* to usecs */
int delay = usecs * 3 / 2; /* us * 0.666 = us*timer_period */
end = now - delay;
}
unsigned old;
/* underrun ? */
if (end < 0)
{
do {
old = now;
now = TIMER2_VALUE;
} while(now <= old); /* if the new value is higher then we wrapped */
end += TIMER_PERIOD;
}
do {
/* if timer wraps then we missed our end value */
old = now;
now = TIMER2_VALUE;
} while(now > (unsigned)end && now <= old);
}
void udelay(unsigned short usecs);
#endif /* SYSTEM_TARGET_H */

3
firmware/target/arm/as3525/usb-drv-as3525.c
View file

@ -80,8 +80,7 @@ void usb_attach(void)
/* delay is in milliseconds */
static inline void usb_delay(int delay)
{
while(delay--)
udelay(1000);
udelay(1000 * delay);
}
static void usb_phy_on(void)