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authorShinya Kuribayashi <skuribay@ruby.dti.ne.jp>2008-06-05 22:29:00 +0900
committerShinya Kuribayashi <skuribay@ruby.dti.ne.jp>2008-06-05 22:29:00 +0900
commita55d48174cfd1a5bc184159513f48dcbbe409c83 (patch)
tree9d55affb405aea800e9f2a5c423805cf2370c824 /lib_mips
parent199e4f657c8af42efe3fb3ba1d1104eb6bb28c25 (diff)
[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>
Diffstat (limited to 'lib_mips')
-rw-r--r--lib_mips/time.c31
1 files changed, 25 insertions, 6 deletions
diff --git a/lib_mips/time.c b/lib_mips/time.c
index fe365303b4d..1e9278996e5 100644
--- a/lib_mips/time.c
+++ b/lib_mips/time.c
@@ -24,31 +24,50 @@
#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)
{
- 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);
}
/*