Mirrors/u-boot
2
0
Fork 0
mirror of https://github.com/AsahiLinux/u-boot synced 2024-11-10 15:14:43 +00:00
Code Issues Projects Releases Packages Wiki Activity

time: import time_after, time_before and friends from Linux

Browse source 
It is not safe to compare timer values directly.

On 32-bit systems, for example, timer_get_us() wraps around every
72 min. (2 ^ 32 / 1000000 =~ 4295 sec =~ 72 min).  Depending on
the get_ticks() implementation, it may wrap more frequently.
The 72 min might be possible on the use of U-Boot.

Let's borrow time_after, time_before, and friends to solve the
wrap-around problem.

These macros were copied from include/linux/jiffies.h of Linux 4.9.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Masahiro Yamada 2016-12-28 00:36:02 +09:00 committed by Tom Rini
parent ff90af6c73
commit 21cdd133ca
1 changed files with 41 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

41
include/time.h
View file

@ -5,6 +5,8 @@
#ifndef _TIME_H
#define _TIME_H
#include <linux/typecheck.h>
unsigned long get_timer(unsigned long base);
/*
@ -13,4 +15,43 @@ unsigned long get_timer(unsigned long base);
*/
unsigned long timer_get_us(void);
/*
* These inlines deal with timer wrapping correctly. You are
* strongly encouraged to use them
* 1. Because people otherwise forget
* 2. Because if the timer wrap changes in future you won't have to
* alter your driver code.
*
* time_after(a,b) returns true if the time a is after time b.
*
* Do this with "<0" and ">=0" to only test the sign of the result. A
* good compiler would generate better code (and a really good compiler
* wouldn't care). Gcc is currently neither.
*/
#define time_after(a,b) \
(typecheck(unsigned long, a) && \
typecheck(unsigned long, b) && \
((long)((b) - (a)) < 0))
#define time_before(a,b) time_after(b,a)
#define time_after_eq(a,b) \
(typecheck(unsigned long, a) && \
typecheck(unsigned long, b) && \
((long)((a) - (b)) >= 0))
#define time_before_eq(a,b) time_after_eq(b,a)
/*
* Calculate whether a is in the range of [b, c].
*/
#define time_in_range(a,b,c) \
(time_after_eq(a,b) && \
time_before_eq(a,c))
/*
* Calculate whether a is in the range of [b, c).
*/
#define time_in_range_open(a,b,c) \
(time_after_eq(a,b) && \
time_before(a,c))
#endif /* _TIME_H */