It seems we have rather unsolvable problems with udelay() on
notebooks. This patch at least detects change of rdtsc speed, which is
sign of bogomips problems that might came later. [In future, we might
want to switch udelay() to use rdtsc, instead of bogomips. It should
be more accurate. If you want I can write such patch.] Yes and this
should fix gettimeofday to be monotonic on notebooks. So it is worth
applying after all.
Pavel
--- clean/arch/i386/kernel/time.c Sun Oct 10 11:22:47 1999
+++ linux/arch/i386/kernel/time.c Tue Nov 2 13:42:09 1999
@@ -144,7 +144,7 @@
* comp.protocols.time.ntp!
*/
-static unsigned long do_slow_gettimeoffset(void)
+static unsigned long do_read_hwtimer(void)
{
int count;
@@ -208,7 +209,7 @@
count -= 256;
#else
- printk("do_slow_gettimeoffset(): hardware timer problem?\n");
+ printk("do_read_hwtimer(): hardware timer problem?\n");
#endif
}
}
@@ -216,6 +217,12 @@
jiffies_p = jiffies_t;
count_p = count;
+ return count;
+}
+
+unsigned long do_slow_gettimeoffset(void)
+{
+ unsigned long count = do_read_hwtimer();
count = ((LATCH-1) - count) * TICK_SIZE;
count = (count + LATCH/2) / LATCH;
@@ -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 > 100) || (slower > 100)) {
+ 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");
-- I'm really pavel@ucw.cz. Look at http://195.113.31.123/~pavel. Pavel Hi! I'm a .signature virus! Copy me into your ~/.signature, please!- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/