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TMS320DM320: Use TIMER1 (tick generator) to make udelay() precise.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31376 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Tomasz Moń 2011-12-20 12:49:59 +00:00
parent 1a4aea3ad8
commit 4aec001244
1 changed files with 31 additions and 7 deletions
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38
firmware/target/arm/tms320dm320/system-dm320.c
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@ -412,14 +412,38 @@ void set_cpu_frequency(long frequency)
} }
#endif #endif
/* This function is pretty crude. It is not acurate to a usec, but errors on
* longer.
*/
void udelay(int usec) { void udelay(int usec) {
volatile int temp=usec*(175000/200); unsigned short count = IO_TIMER1_TMCNT;
unsigned short stop;
while(temp) { unsigned short tmp = IO_TIMER1_TMDIV;
temp--; int prev_tick = current_tick;
/*
* On Sansa Connect tick timer counts from 0 to 26999
* in this case stop will overflow only if usec > 10000
* such long delays shouldn't be blocking (use sleep() instead)
*/
stop = count + usec*((tmp+1)/10000);
stop += (unsigned short)(((unsigned long)(usec)*((tmp%10000)+1))/10000);
/* stop values over tmdiv won't ever be reached */
if (stop > tmp)
{
stop -= tmp;
}
if (stop < count)
{
/* udelay will end after counter reset (tick) */
while ((((tmp = IO_TIMER1_TMCNT) < stop) &&
(current_tick != prev_tick)) ||
(current_tick == prev_tick)); /* ensure new tick */
}
else
{
/* udelay will end before counter reset (tick) */
while (((tmp = IO_TIMER1_TMCNT) < stop) &&
(current_tick == prev_tick));
} }
} }