u-boot/lib_mips/time.c
Shinya Kuribayashi a55d48174c [MIPS] lib_mips/time.c: Fix CP0 count register usage and timer routines
MIPS port has two problems in timer routines. One is now we assume CFG_HZ
equals to CP0 counter frequency, but this is wrong. CFG_HZ has to be 1000
in the U-Boot system.

The other is we don't have a proper time management counter like timestamp
other ARCHs have. We need the 32-bit millisecond clock counter.

This patch introduces timestamp and CYCLES_PER_JIFFY. timestamp is a
32-bit non-overflowing CFG_HZ counter, and CYCLES_PER_JIFFY is the number
of calculated CP0 counter cycles in a CFG_HZ.

STRATEGY:

* Fix improper CFG_HZ value to have 1000

* Use CFG_MIPS_TIMER_FREQ for timer counter frequency, instead.

* timer_init: initialize timestamp and set up the first timer expiration.
  Note that we don't need to initialize CP0 count/compare registers here
  as they have been already zeroed out on the system reset. Leave them as
  they are.

* get_timer: calculate how many timestamps have been passed, then return
  base-relative timestamp. Make sure we can easily count missed timestamps
  regardless of CP0 count/compare value.

* get_ticks: return the current timestamp, that is get_timer(0).

Most parts are from good old Linux v2.6.16 kernel.

v2:
- Remove FIXME comments as they turned out to be trivial.
- Use CP0 compare register as a global variable for expirelo.
- Kill a global variable 'cycles_per_jiffy'. Use #define CYCLES_PER_JIFFY
  instead.

Signed-off-by: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
2008-06-05 22:29:00 +09:00

99 lines
2.3 KiB
C

/*
* (C) Copyright 2003
* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
*
* See file CREDITS for list of people who contributed to this
* project.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
*/
#include <common.h>
#include <asm/mipsregs.h>
static unsigned long timestamp;
/* how many counter cycles in a jiffy */
#define CYCLES_PER_JIFFY (CFG_MIPS_TIMER_FREQ + CFG_HZ / 2) / CFG_HZ
/*
* timer without interrupts
*/
int timer_init(void)
{
/* Set up the timer for the first expiration. */
timestamp = 0;
write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY);
return 0;
}
void reset_timer(void)
{
timestamp = 0;
write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY);
}
ulong get_timer(ulong base)
{
unsigned int count;
unsigned int expirelo = read_c0_compare();
/* Check to see if we have missed any timestamps. */
count = read_c0_count();
while ((count - expirelo) < 0x7fffffff) {
expirelo += CYCLES_PER_JIFFY;
timestamp++;
}
write_c0_compare(expirelo);
return (timestamp - base);
}
void set_timer(ulong t)
{
timestamp = t;
write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY);
}
void udelay(unsigned long usec)
{
unsigned int tmo;
tmo = read_c0_count() + (usec * (CFG_MIPS_TIMER_FREQ / 1000000));
while ((tmo - read_c0_count()) < 0x7fffffff)
/*NOP*/;
}
/*
* This function is derived from PowerPC code (read timebase as long long).
* On MIPS it just returns the timer value.
*/
unsigned long long get_ticks(void)
{
return get_timer(0);
}
/*
* This function is derived from PowerPC code (timebase clock frequency).
* On MIPS it returns the number of timer ticks per second.
*/
ulong get_tbclk(void)
{
return CFG_HZ;
}