This patch adds a blacklist infrastructure to the TSC clocksource as
well as an entry for the 380XD Thinkpad. This allows us to manually add
systems (mainly older-laptops) where the TSC frequency is changed by the
BIOS without any notification to the OS.
The justification for using a blacklist instead of trying to detect the
problem is because the detectable symptoms are exactly the same as what
is observed when interrupts arrive too frequently (a semi-common issue
w/ broken PIT hardware), and the number of other older laptops with this
issue is likely small.
This patch resolves bugme bug #5868.
thanks
-john
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index cab2546..7e72219 100644
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -9,6 +9,7 @@
#include <linux/cpufreq.h>
#include <linux/jiffies.h>
#include <linux/init.h>
+#include <linux/dmi.h>
#include <asm/delay.h>
#include <asm/tsc.h>
@@ -359,6 +360,27 @@ static int tsc_update_callback(void)
return change;
}
+static int __init dmi_mark_tsc_unstable(struct dmi_system_id *d)
+{
+ printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
+ d->ident);
+ mark_tsc_unstable();
+ return 0;
+}
+
+/* List of systems that have known TSC problems */
+static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
+ {
+ .callback = dmi_mark_tsc_unstable,
+ .ident = "IBM Thinkpad 380XD",
+ .matches = {
+ DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
+ DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
+ },
+ },
+ {}
+};
+
/*
* Make an educated guess if the TSC is trustworthy and synchronized
* over all CPUs.
@@ -376,16 +398,21 @@ static __init int unsynchronized_tsc(voi
return num_possible_cpus() > 1;
}
-/* NUMAQ can't use TSC: */
static int __init init_tsc_clocksource(void)
{
- /* TSC initialization is done in arch/i386/kernel/tsc.c */
+
if (cpu_has_tsc && tsc_khz && !tsc_disable) {
- if (unsynchronized_tsc()) /* lower rating if unsynced */
+ /* check blacklist */
+ dmi_check_system(bad_tsc_dmi_table);
+
+ if (unsynchronized_tsc()) /* mark unstable if unsynced */
mark_tsc_unstable();
current_tsc_khz = tsc_khz;
clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
clocksource_tsc.shift);
+ /* lower the rating if we already know its unstable: */
+ if (check_tsc_unstable())
+ clocksource_tsc.rating = 50;
register_clocksource(&clocksource_tsc);
}
-
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