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https://github.com/brain-hackers/u-boot-brain
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a55d48174c
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>
99 lines
2.3 KiB
C
99 lines
2.3 KiB
C
/*
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* (C) Copyright 2003
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* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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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 as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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#include <common.h>
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#include <asm/mipsregs.h>
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static unsigned long timestamp;
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/* how many counter cycles in a jiffy */
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#define CYCLES_PER_JIFFY (CFG_MIPS_TIMER_FREQ + CFG_HZ / 2) / CFG_HZ
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/*
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* timer without interrupts
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*/
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int timer_init(void)
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{
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/* Set up the timer for the first expiration. */
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timestamp = 0;
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write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY);
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return 0;
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}
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void reset_timer(void)
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{
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timestamp = 0;
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write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY);
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}
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ulong get_timer(ulong base)
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{
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unsigned int count;
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unsigned int expirelo = read_c0_compare();
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/* Check to see if we have missed any timestamps. */
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count = read_c0_count();
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while ((count - expirelo) < 0x7fffffff) {
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expirelo += CYCLES_PER_JIFFY;
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timestamp++;
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}
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write_c0_compare(expirelo);
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return (timestamp - base);
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}
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void set_timer(ulong t)
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{
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timestamp = t;
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write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY);
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}
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void udelay(unsigned long usec)
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{
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unsigned int tmo;
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tmo = read_c0_count() + (usec * (CFG_MIPS_TIMER_FREQ / 1000000));
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while ((tmo - read_c0_count()) < 0x7fffffff)
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/*NOP*/;
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}
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/*
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* This function is derived from PowerPC code (read timebase as long long).
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* On MIPS it just returns the timer value.
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*/
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unsigned long long get_ticks(void)
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{
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return get_timer(0);
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}
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/*
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* This function is derived from PowerPC code (timebase clock frequency).
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* On MIPS it returns the number of timer ticks per second.
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*/
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ulong get_tbclk(void)
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{
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return CFG_HZ;
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}
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