diff --git a/include/net/tcp.h b/include/net/tcp.h
index b4dc93d..4b45be5 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -700,11 +700,14 @@
 
 void tcp_send_window_probe(struct sock *sk);
 
-/* TCP timestamps are only 32-bits, this causes a slight
- * complication on 64-bit systems since we store a snapshot
- * of jiffies in the buffer control blocks below.  We decided
- * to use only the low 32-bits of jiffies and hide the ugly
- * casts with the following macro.
+/* TCP uses 32bit jiffies to save some space.
+ * Note that this is different from tcp_time_stamp, which
+ * historically has been the same until linux-4.13.
+ */
+#define tcp_jiffies32 ((u32)jiffies)
+
+/* Generator for TCP TS option (RFC 7323)
+ * Currently tied to 'jiffies' but will soon be driven by 1 ms clock.
  */
 #define tcp_time_stamp		((__u32)(jiffies))