v4.19.13 snapshot.
diff --git a/kernel/time/timekeeping_internal.h b/kernel/time/timekeeping_internal.h
new file mode 100644
index 0000000..bcbb52d
--- /dev/null
+++ b/kernel/time/timekeeping_internal.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TIMEKEEPING_INTERNAL_H
+#define _TIMEKEEPING_INTERNAL_H
+/*
+ * timekeeping debug functions
+ */
+#include <linux/clocksource.h>
+#include <linux/time.h>
+
+#ifdef CONFIG_DEBUG_FS
+extern void tk_debug_account_sleep_time(const struct timespec64 *t);
+#else
+#define tk_debug_account_sleep_time(x)
+#endif
+
+#ifdef CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE
+static inline u64 clocksource_delta(u64 now, u64 last, u64 mask)
+{
+ u64 ret = (now - last) & mask;
+
+ /*
+ * Prevent time going backwards by checking the MSB of mask in
+ * the result. If set, return 0.
+ */
+ return ret & ~(mask >> 1) ? 0 : ret;
+}
+#else
+static inline u64 clocksource_delta(u64 now, u64 last, u64 mask)
+{
+ return (now - last) & mask;
+}
+#endif
+
+#endif /* _TIMEKEEPING_INTERNAL_H */