Hi!
> > Unfortunately, when my toshiba changes speed, it changes speed of
> > cycle counter, too :-(. That sounds like show stopper.
>
> Thats a gift not a show stopper. Just check the rdtsc change between each
> timer tick looks believeable. Timer ticks might get delayed but if you start
> to get an excessive numbers of ticks per n cycles of the tsc you know your
> CPU slowed down
Detecting this is easy (and actually works): [It does not recalculate
bogomips just now. Should we really recalculate them or just scale
them according to the tsc?]
But... That is wrong solution. We already ran for at least one tick
with wrong bogomips. If by chance some flaky device is used for that
one-tick period, we already lost the game...
Pavel
--- clean/arch/i386/kernel/time.c Sun Oct 10 11:22:47 1999
+++ linux/arch/i386/kernel/time.c Sun Oct 31 23:17:28 1999
@@ -429,6 +466,27 @@
*/
write_lock(&xtime_lock);
+ if (use_tsc) {
+ long off = do_gettimeoffset();
+ static int faster = 0, slower = 0;
+ if (off > (1100000/HZ))
+ faster++;
+ else
+ faster = 0;
+
+ if (off < (900000/HZ))
+ slower++;
+ else
+ slower = 0;
+
+ if ((faster > 10) || (slower > 10)) {
+ printk( KERN_ERR "TSC is %s than it should be! ", (faster >
+10) ? "faster" : "slower" );
+ big_calibrate_tsc();
+ faster = 0;
+ slower = 0;
+ }
+ }
+
if (use_tsc)
{
/*
@@ -547,7 +605,7 @@
#define CALIBRATE_LATCH (5 * LATCH)
#define CALIBRATE_TIME (5 * 1000020/HZ)
-static unsigned long __init calibrate_tsc(void)
+static unsigned long calibrate_tsc(void)
{
/* Set the Gate high, disable speaker */
outb((inb(0x61) & ~0x02) | 0x01, 0x61);
@@ -612,11 +670,39 @@
return 0;
}
+void big_calibrate_tsc(void)
+{
+ if (boot_cpu_data.x86_capability & X86_FEATURE_TSC) {
+ unsigned long tsc_quotient = calibrate_tsc();
+ if (tsc_quotient) {
+ fast_gettimeoffset_quotient = tsc_quotient;
+ use_tsc = 1;
+#ifndef do_gettimeoffset
+ do_gettimeoffset = do_fast_gettimeoffset;
+#endif
+ do_get_fast_time = do_gettimeofday;
+
+ /* report CPU clock rate in Hz.
+ * The formula is (10^6 * 2^32) / (2^32 * 1 / (clocks/us)) =
+ * clock/second. Our precision is about 100 ppm.
+ */
+ { unsigned long eax=0, edx=1000000;
+ __asm__("divl %2"
+ :"=a" (cpu_hz), "=d" (edx)
+ :"r" (tsc_quotient),
+ "0" (eax), "1" (edx));
+ printk("Detected %ld Hz processor.\n", cpu_hz);
+ }
+ }
+ }
+}
+
void __init time_init(void)
{
xtime.tv_sec = get_cmos_time();
xtime.tv_usec = 0;
+
/*
* If we have APM enabled or the CPU clock speed is variable
* (CPU stops clock on HLT or slows clock to save power)
@@ -644,29 +730,7 @@
dodgy_tsc();
- if (boot_cpu_data.x86_capability & X86_FEATURE_TSC) {
- unsigned long tsc_quotient = calibrate_tsc();
- if (tsc_quotient) {
- fast_gettimeoffset_quotient = tsc_quotient;
- use_tsc = 1;
-#ifndef do_gettimeoffset
- do_gettimeoffset = do_fast_gettimeoffset;
-#endif
- do_get_fast_time = do_gettimeofday;
-
- /* report CPU clock rate in Hz.
- * The formula is (10^6 * 2^32) / (2^32 * 1 / (clocks/us)) =
- * clock/second. Our precision is about 100 ppm.
- */
- { unsigned long eax=0, edx=1000000;
- __asm__("divl %2"
- :"=a" (cpu_hz), "=d" (edx)
- :"r" (tsc_quotient),
- "0" (eax), "1" (edx));
- printk("Detected %ld Hz processor.\n", cpu_hz);
- }
- }
- }
+ big_calibrate_tsc();
#ifdef CONFIG_VISWS
printk("Starting Cobalt Timer system clock\n");
@@ -686,3 +750,4 @@
setup_irq(0, &irq0);
#endif
}
+
--
I'm really [EMAIL PROTECTED] Look at http://195.113.31.123/~pavel. Pavel
Hi! I'm a .signature virus! Copy me into your ~/.signature, please!
