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author | Masahiro Yamada <yamada.masahiro@socionext.com> | 2016-12-28 00:36:02 +0900 |
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committer | Tom Rini <trini@konsulko.com> | 2017-01-14 16:46:30 -0500 |
commit | 21cdd133ca8b328fe790c85b1dc104fdc4992a71 (patch) | |
tree | af78391e095e5440dbd3231a00abcbe981ec2874 /include | |
parent | ff90af6c73883121358251bba66245ff4da3755c (diff) | |
download | u-boot-imx-21cdd133ca8b328fe790c85b1dc104fdc4992a71.zip u-boot-imx-21cdd133ca8b328fe790c85b1dc104fdc4992a71.tar.gz u-boot-imx-21cdd133ca8b328fe790c85b1dc104fdc4992a71.tar.bz2 |
time: import time_after, time_before and friends from Linux
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>
Diffstat (limited to 'include')
-rw-r--r-- | include/time.h | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/include/time.h b/include/time.h index 5ed021f..5746ad9 100644 --- a/include/time.h +++ b/include/time.h @@ -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 */ |