From: john stultz <johnstul@us.ibm.com>
It simply uses the TSC for delay_pmtmr much as delay_tsc does. The only
gotcha is that __delay will be affected by cpu-frequency changes (much as
the existing loop based delay) until I hook in the cpufreq notificaiton
into the ACPI PM timesource code.
---
arch/i386/kernel/timers/timer_pm.c | 27 +++++++++++----------------
1 files changed, 11 insertions(+), 16 deletions(-)
diff -puN arch/i386/kernel/timers/timer_pm.c~use-TSC-for-delay_pmtmr arch/i386/kernel/timers/timer_pm.c
--- 25/arch/i386/kernel/timers/timer_pm.c~use-TSC-for-delay_pmtmr 2004-01-23 17:47:39.000000000 -0800
+++ 25-akpm/arch/i386/kernel/timers/timer_pm.c 2004-01-23 17:47:39.000000000 -0800
@@ -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++) {
@@ -168,26 +172,17 @@ static unsigned long long monotonic_cloc
return ret;
}
-static void delay_pmtmr(unsigned long total_loops)
+static void delay_pmtmr(unsigned long loops)
{
- u32 then, now;
- unsigned long loops;
+ unsigned long bclock, now;
- do{
- if (total_loops > ACPI_PM_MASK)
- loops = ACPI_PM_MASK;
- else
- loops = total_loops;
- total_loops -= loops;
-
- then = read_pmtmr();
- do{
- now = read_pmtmr();
- } while (((now - then)&ACPI_PM_MASK) < loops);
- } while (total_loops);
+ rdtscl(bclock);
+ do {
+ rep_nop();
+ rdtscl(now);
+ } while ((now-bclock) < loops);
}
-
/*
* get the offset (in microseconds) from the last call to mark_offset()
* - Called holding a reader xtime_lock
_