linux-kernel - [PATCH 4.9 02/59] time: Introduce jiffies64_to

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Date:   Mon,  8 Oct 2018 20:31:09 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Frederic Weisbecker <fweisbec@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Ingo Molnar <mingo@...nel.org>,
        Ivan Delalande <colona@...sta.com>
Subject: [PATCH 4.9 02/59] time: Introduce jiffies64_to_nsecs()

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Frederic Weisbecker <fweisbec@...il.com>

commit 07e5f5e353aaa61696c8353d87050994a0c4648a upstream.

This will be needed for the cputime_t to nsec conversion.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Stanislaw Gruszka <sgruszka@...hat.com>
Cc: Wanpeng Li <wanpeng.li@...mail.com>
Link: http://lkml.kernel.org/r/1485832191-26889-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Ivan Delalande <colona@...sta.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 include/linux/jiffies.h  |    2 ++
 kernel/time/time.c       |   10 ++++++++++
 kernel/time/timeconst.bc |    6 ++++++
 3 files changed, 18 insertions(+)

--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -292,6 +292,8 @@ static inline u64 jiffies_to_nsecs(const
 	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)
 /*
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -704,6 +704,16 @@ 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
  *
--- 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"