[S390] add read_persistent_clock

Add a read_persistent_clock function that does not just return 0.
Since timekeeping_init calls the function before time_init has been
called move reset_tod_clock to early.c to make sure that the TOD
clock is running when read_persistent_clock is invoked.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index d4e1e5b..cf09948 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -38,6 +38,21 @@ static unsigned long machine_flags;
 
 static void __init setup_boot_command_line(void);
 
+/*
+ * Get the TOD clock running.
+ */
+static void __init reset_tod_clock(void)
+{
+	u64 time;
+
+	if (store_clock(&time) == 0)
+		return;
+	/* TOD clock not running. Set the clock to Unix Epoch. */
+	if (set_clock(TOD_UNIX_EPOCH) != 0 || store_clock(&time) != 0)
+		disabled_wait(0);
+
+	sched_clock_base_cc = TOD_UNIX_EPOCH;
+}
 
 #ifdef CONFIG_SHARED_KERNEL
 int __init savesys_ipl_nss(char *cmd, const int cmdlen);
@@ -372,6 +387,7 @@ static void __init setup_boot_command_line(void)
  */
 void __init startup_init(void)
 {
+	reset_tod_clock();
 	ipl_save_parameters();
 	rescue_initrd();
 	clear_bss_section();