1 files changed, 40 insertions, 0 deletions
diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c
index 437dda64fd7a..edc4afc080fa 100644
--- a/arch/mips/kernel/csrc-r4k.c
+++ b/arch/mips/kernel/csrc-r4k.c
@@ -6,6 +6,7 @@
  * Copyright (C) 2007 by Ralf Baechle
  */
 #include <linux/clocksource.h>
+#include <linux/cpufreq.h>
 #include <linux/init.h>
 #include <linux/sched_clock.h>
 
@@ -65,6 +66,45 @@ static bool rdhwr_count_usable(void)
 	return false;
 }
 
+#ifdef CONFIG_CPU_FREQ
+
+static bool __read_mostly r4k_clock_unstable;
+
+static void r4k_clocksource_unstable(char *reason)
+{
+	if (r4k_clock_unstable)
+		return;
+
+	r4k_clock_unstable = true;
+
+	pr_info("R4K timer is unstable due to %s\n", reason);
+
+	clocksource_mark_unstable(&clocksource_mips);
+}
+
+static int r4k_cpufreq_callback(struct notifier_block *nb,
+				unsigned long val, void *data)
+{
+	if (val == CPUFREQ_POSTCHANGE)
+		r4k_clocksource_unstable("CPU frequency change");
+
+	return 0;
+}
+
+static struct notifier_block r4k_cpufreq_notifier = {
+	.notifier_call  = r4k_cpufreq_callback,
+};
+
+static int __init r4k_register_cpufreq_notifier(void)
+{
+	return cpufreq_register_notifier(&r4k_cpufreq_notifier,
+					 CPUFREQ_TRANSITION_NOTIFIER);
+
+}
+core_initcall(r4k_register_cpufreq_notifier);
+
+#endif /* !CONFIG_CPU_FREQ */
+
 int __init init_r4k_clocksource(void)
 {
 	if (!cpu_has_counter || !mips_hpt_frequency)