--- zzzz-none-000/linux-4.4.60/include/linux/delay.h	2017-04-08 07:53:53.000000000 +0000
+++ hawkeye-5590-729/linux-4.4.60/include/linux/delay.h	2022-03-30 14:21:53.000000000 +0000
@@ -52,4 +52,15 @@
 	msleep(seconds * 1000);
 }
 
+/* see Documentation/timers/timers-howto.rst for the thresholds */
+static inline void fsleep(unsigned long usecs)
+{
+	if (usecs <= 10)
+		udelay(usecs);
+	else if (usecs <= 20000)
+		usleep_range(usecs, 2 * usecs);
+	else
+		msleep(DIV_ROUND_UP(usecs, 1000));
+}
+
 #endif /* defined(_LINUX_DELAY_H) */