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authorMasahiro Yamada <yamada.masahiro@socionext.com>2016-12-27 15:36:02 (GMT)
committerTom Rini <trini@konsulko.com>2017-01-14 21:46:30 (GMT)
commit21cdd133ca8b328fe790c85b1dc104fdc4992a71 (patch)
treeaf78391e095e5440dbd3231a00abcbe981ec2874 /include/time.h
parentff90af6c73883121358251bba66245ff4da3755c (diff)
downloadu-boot-fsl-qoriq-21cdd133ca8b328fe790c85b1dc104fdc4992a71.tar.xz
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/time.h')
-rw-r--r--include/time.h41
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 */