linux-kernel - [PATCH v14 15/25] s390/time: add read_persistent_wall_and_boot

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Date:   Tue, 17 Jul 2018 22:22:01 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        linux@...linux.org.uk, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, john.stultz@...aro.org,
        sboyd@...eaurora.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
        douly.fnst@...fujitsu.com, peterz@...radead.org, prarit@...hat.com,
        feng.tang@...el.com, pmladek@...e.com, gnomes@...rguk.ukuu.org.uk,
        linux-s390@...r.kernel.org, pasha.tatashin@...cle.com,
        boris.ostrovsky@...cle.com, jgross@...e.com, pbonzini@...hat.com
Subject: [PATCH v14 15/25] s390/time: add read_persistent_wall_and_boot_offset()

read_persistent_wall_and_boot_offset() will replace read_boot_clock64()
because on some architectures it is more convenient to read both sources
as one may depend on the other. For s390, implementation is the same
as read_boot_clock64() but also calling and returning value of
read_persistent_clock64()

Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
Reviewed-by: Martin Schwidefsky <schwidefsky@...ibm.com>
---
 arch/s390/kernel/time.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index cf561160ea88..d1f5447d5687 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -221,6 +221,24 @@ void read_persistent_clock64(struct timespec64 *ts)
 	ext_to_timespec64(clk, ts);
 }
 
+void __init read_persistent_wall_and_boot_offset(struct timespec64 *wall_time,
+						 struct timespec64 *boot_offset)
+{
+	unsigned char clk[STORE_CLOCK_EXT_SIZE];
+	struct timespec64 boot_time;
+	__u64 delta;
+
+	delta = initial_leap_seconds + TOD_UNIX_EPOCH;
+	memcpy(clk, tod_clock_base, STORE_CLOCK_EXT_SIZE);
+	*(__u64 *)&clk[1] -= delta;
+	if (*(__u64 *)&clk[1] > delta)
+		clk[0]--;
+	ext_to_timespec64(clk, &boot_time);
+
+	read_persistent_clock64(wall_time);
+	*boot_offset = timespec64_sub(*wall_time, boot_time);
+}
+
 void read_boot_clock64(struct timespec64 *ts)
 {
 	unsigned char clk[STORE_CLOCK_EXT_SIZE];
-- 
2.18.0