From c6af13d334759c33c14b6fad4c676c6d1dbf9564 Mon Sep 17 00:00:00 2001 From: Heiner Kallweit Date: Fri, 1 May 2020 23:27:21 +0200 Subject: timer: add fsleep for flexible sleeping Sleeping for a certain amount of time requires use of different functions, depending on the time period. Documentation/timers/timers-howto.rst explains when to use which function, and also checkpatch checks for some potentially problematic cases. So let's create a helper that automatically chooses the appropriate sleep function -> fsleep(), for flexible sleeping If the delay is a constant, then the compiler should be able to ensure that the new helper doesn't create overhead. If the delay is not constant, then the new helper can save some code. Signed-off-by: Heiner Kallweit Signed-off-by: David S. Miller --- Documentation/timers/timers-howto.rst | 3 +++ include/linux/delay.h | 11 +++++++++++ 2 files changed, 14 insertions(+) diff --git a/Documentation/timers/timers-howto.rst b/Documentation/timers/timers-howto.rst index 7e3167bec2b1..afb0a43b8cdf 100644 --- a/Documentation/timers/timers-howto.rst +++ b/Documentation/timers/timers-howto.rst @@ -110,3 +110,6 @@ NON-ATOMIC CONTEXT: short, the difference is whether the sleep can be ended early by a signal. In general, just use msleep unless you know you have a need for the interruptible variant. + + FLEXIBLE SLEEPING (any delay, uninterruptible) + * Use fsleep diff --git a/include/linux/delay.h b/include/linux/delay.h index 8e6828094c1e..5e016a4029d9 100644 --- a/include/linux/delay.h +++ b/include/linux/delay.h @@ -65,4 +65,15 @@ static inline void ssleep(unsigned int seconds) 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) */ -- cgit v1.2.3-59-g8ed1b