From a55d48174cfd1a5bc184159513f48dcbbe409c83 Mon Sep 17 00:00:00 2001 From: Shinya Kuribayashi Date: Thu, 5 Jun 2008 22:29:00 +0900 Subject: [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 --- lib_mips/time.c | 31 +++++++++++++++++++++++++------ 1 file changed, 25 insertions(+), 6 deletions(-) (limited to 'lib_mips') diff --git a/lib_mips/time.c b/lib_mips/time.c index fe365303b..1e9278996 100644 --- a/lib_mips/time.c +++ b/lib_mips/time.c @@ -24,31 +24,50 @@ #include #include +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) { - write_c0_compare(0); - write_c0_count(0); + /* 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) { - write_c0_count(0); + timestamp = 0; + write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY); } ulong get_timer(ulong base) { - return read_c0_count() - 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) { - write_c0_count(t); + timestamp = t; + write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY); } void udelay(unsigned long usec) @@ -66,7 +85,7 @@ void udelay(unsigned long usec) */ unsigned long long get_ticks(void) { - return read_c0_count(); + return get_timer(0); } /* -- cgit v1.2.3