[PATCH] clocksource: Add verification (watchdog) helper

The TSC needs to be verified against another clocksource.  Instead of using
hardwired assumptions of available hardware, provide a generic verification
mechanism.  The verification uses the best available clocksource and handles
the usability for high resolution timers / dynticks of the clocksource which
needs to be verified.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 4 insertions, 49 deletions

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index 4ea31c327d1f..458b3aad3eb3 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -18,6 +18,10 @@ config GENERIC_TIME
         bool
         default y
 
+config CLOCKSOURCE_WATCHDOG
+        bool
+        default y
+
 config LOCKDEP_SUPPORT
         bool
         default y
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index b4b2be21d1c7..22931d24027c 100644
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -344,49 +344,6 @@ static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
          {}
 };
 
-#define TSC_FREQ_CHECK_INTERVAL (10*MSEC_PER_SEC) /* 10sec in MS */
-static struct timer_list verify_tsc_freq_timer;
-
-/* XXX - Probably should add locking */
-static void verify_tsc_freq(unsigned long unused)
-{
-        static u64 last_tsc;
-        static unsigned long last_jiffies;
-
-        u64 now_tsc, interval_tsc;
-        unsigned long now_jiffies, interval_jiffies;
-
-
-        if (check_tsc_unstable())
-                return;
-
-        rdtscll(now_tsc);
-        now_jiffies = jiffies;
-
-        if (!last_jiffies) {
-                goto out;
-        }
-
-        interval_jiffies = now_jiffies - last_jiffies;
-        interval_tsc = now_tsc - last_tsc;
-        interval_tsc *= HZ;
-        do_div(interval_tsc, cpu_khz*1000);
-
-        if (interval_tsc < (interval_jiffies * 3 / 4)) {
-                printk("TSC appears to be running slowly. "
-                        "Marking it as unstable\n");
-                mark_tsc_unstable();
-                return;
-        }
-
-out:
-        last_tsc = now_tsc;
-        last_jiffies = now_jiffies;
-        /* set us up to go off on the next interval: */
-        mod_timer(&verify_tsc_freq_timer,
-                jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL));
-}
-
 /*
  * Make an educated guess if the TSC is trustworthy and synchronized
  * over all CPUs.
@@ -424,12 +381,6 @@ static int __init init_tsc_clocksource(void)
                         clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
                 }
 
-                init_timer(&verify_tsc_freq_timer);
-                verify_tsc_freq_timer.function = verify_tsc_freq;
-                verify_tsc_freq_timer.expires =
-                        jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL);
-                add_timer(&verify_tsc_freq_timer);
-
                 return clocksource_register(&clocksource_tsc);
         }