From: john stultz <johnstul@us.ibm.com>
This patch replaces the loop based delay_pmtmr with a TSC based
delay_pmtmr, which resolves a number of issues caused by the loop based
delay. Unsynced TSCs as well frequency changing TSCs will effect the
length of __delay(), but it seems this method works best.
---
25-akpm/arch/i386/kernel/timers/timer_pm.c | 24 ++++++++++++------------
1 files changed, 12 insertions(+), 12 deletions(-)
diff -puN arch/i386/kernel/timers/timer_pm.c~use-TSC-for-delay_pmtmr-2 arch/i386/kernel/timers/timer_pm.c
--- 25/arch/i386/kernel/timers/timer_pm.c~use-TSC-for-delay_pmtmr-2 Wed Jan 28 16:28:20 2004
+++ 25-akpm/arch/i386/kernel/timers/timer_pm.c Wed Jan 28 16:28:20 2004
@@ -68,6 +68,10 @@ static int init_pmtmr(char* override)
if (!pmtmr_ioport)
return -ENODEV;
+ /* we use the TSC for delay_pmtmr, so make sure it exists */
+ if (!cpu_has_tsc)
+ return -ENODEV;
+
/* "verify" this timing source */
value1 = read_pmtmr();
for (i = 0; i < 10000; i++) {
@@ -168,20 +172,16 @@ static unsigned long long monotonic_cloc
return ret;
}
-/*
- * copied from delay_pit
- */
static void delay_pmtmr(unsigned long loops)
{
- int d0;
- __asm__ __volatile__(
- "\tjmp 1f\n"
- ".align 16\n"
- "1:\tjmp 2f\n"
- ".align 16\n"
- "2:\tdecl %0\n\tjns 2b"
- :"=&a" (d0)
- :"0" (loops));
+ unsigned long bclock, now;
+
+ rdtscl(bclock);
+ do
+ {
+ rep_nop();
+ rdtscl(now);
+ } while ((now-bclock) < loops);
}
_