[tip:x86/timers] s390/time: Add read_persistent_wall_and_boot_offset()

[tip-bot for Pavel Tatashin]

Commit-ID:  be2e0e4257678408b0ab00ea9e743b9094e393e8
Gitweb:     https://git.kernel.org/tip/be2e0e4257678408b0ab00ea9e743b9094e393e8
Author:     Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
AuthorDate: Thu, 19 Jul 2018 16:55:33 -0400
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Fri, 20 Jul 2018 00:02:40 +0200

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@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: steven.sistare@xxxxxxxxxx
Cc: daniel.m.jordan@xxxxxxxxxx
Cc: linux@xxxxxxxxxxxxxxx
Cc: heiko.carstens@xxxxxxxxxx
Cc: john.stultz@xxxxxxxxxx
Cc: sboyd@xxxxxxxxxxxxxx
Cc: hpa@xxxxxxxxx
Cc: douly.fnst@xxxxxxxxxxxxxx
Cc: peterz@xxxxxxxxxxxxx
Cc: prarit@xxxxxxxxxx
Cc: feng.tang@xxxxxxxxx
Cc: pmladek@xxxxxxxx
Cc: gnomes@xxxxxxxxxxxxxxxxxxx
Cc: linux-s390@xxxxxxxxxxxxxxx
Cc: boris.ostrovsky@xxxxxxxxxx
Cc: jgross@xxxxxxxx
Cc: pbonzini@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20180719205545.16512-15-pasha.tatashin@xxxxxxxxxx

---
 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];