diff --git a/include/linux/timex.h b/include/linux/timex.h
index 5745c90c88005..fbbe34226044a 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -62,6 +62,8 @@
 #include <linux/types.h>
 #include <linux/param.h>
 
+extern unsigned long random_get_entropy_fallback(void);
+
 #include <asm/timex.h>
 
 #ifndef random_get_entropy
@@ -74,8 +76,14 @@
  *
  * By default we use get_cycles() for this purpose, but individual
  * architectures may override this in their asm/timex.h header file.
+ * If a given arch does not have get_cycles(), then we fallback to
+ * using random_get_entropy_fallback().
  */
+#ifdef get_cycles
 #define random_get_entropy()	((unsigned long)get_cycles())
+#else
+#define random_get_entropy()	random_get_entropy_fallback()
+#endif
 #endif
 
 /*
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index dcdcb85121e40..7fd7c6d3f74a2 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2380,6 +2380,14 @@ static int timekeeping_validate_timex(const struct __kernel_timex *txc)
 	return 0;
 }
 
+/**
+ * random_read_entropy_fallback - Returns the raw clock source value,
+ * used by random.c for platforms with no valid random_get_entropy().
+ */
+unsigned long random_get_entropy_fallback(void)
+{
+	return tk_clock_read(&tk_core.timekeeper.tkr_mono);
+}
 
 /**
  * do_adjtimex() - Accessor function to NTP __do_adjtimex function