[tip:sched/core] time: Introduce jiffies64_to_nsecs()

[tip-bot for Frederic Weisbecker]

Commit-ID:  07e5f5e353aaa61696c8353d87050994a0c4648a
Gitweb:     http://git.kernel.org/tip/07e5f5e353aaa61696c8353d87050994a0c4648a
Author:     Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Tue, 31 Jan 2017 04:09:17 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 1 Feb 2017 09:13:45 +0100

time: Introduce jiffies64_to_nsecs()

This will be needed for the cputime_t to nsec conversion.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Cc: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1485832191-26889-2-git-send-email-fweisbec@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 include/linux/jiffies.h  |  2 ++
 kernel/time/time.c       | 10 ++++++++++
 kernel/time/timeconst.bc |  6 ++++++
 3 files changed, 18 insertions(+)

diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index 589d14e..624215c 100644
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -293,6 +293,8 @@ static inline u64 jiffies_to_nsecs(const unsigned long j)
 	return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC;
 }
 
+extern u64 jiffies64_to_nsecs(u64 j);
+
 extern unsigned long __msecs_to_jiffies(const unsigned int m);
 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
 /*
diff --git a/kernel/time/time.c b/kernel/time/time.c
index a3a9a8a..25bdd25 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -702,6 +702,16 @@ u64 nsec_to_clock_t(u64 x)
 #endif
 }
 
+u64 jiffies64_to_nsecs(u64 j)
+{
+#if !(NSEC_PER_SEC % HZ)
+	return (NSEC_PER_SEC / HZ) * j;
+# else
+	return div_u64(j * HZ_TO_NSEC_NUM, HZ_TO_NSEC_DEN);
+#endif
+}
+EXPORT_SYMBOL(jiffies64_to_nsecs);
+
 /**
  * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
  *
diff --git a/kernel/time/timeconst.bc b/kernel/time/timeconst.bc
index c486889..f83bbb8 100644
--- a/kernel/time/timeconst.bc
+++ b/kernel/time/timeconst.bc
@@ -98,6 +98,12 @@ define timeconst(hz) {
 		print "#define HZ_TO_USEC_DEN\t\t", hz/cd, "\n"
 		print "#define USEC_TO_HZ_NUM\t\t", hz/cd, "\n"
 		print "#define USEC_TO_HZ_DEN\t\t", 1000000/cd, "\n"
+
+		cd=gcd(hz,1000000000)
+		print "#define HZ_TO_NSEC_NUM\t\t", 1000000000/cd, "\n"
+		print "#define HZ_TO_NSEC_DEN\t\t", hz/cd, "\n"
+		print "#define NSEC_TO_HZ_NUM\t\t", hz/cd, "\n"
+		print "#define NSEC_TO_HZ_DEN\t\t", 1000000000/cd, "\n"
 		print "\n"
 
 		print "#endif /* KERNEL_TIMECONST_H */\n"