clocksource: Cleanup clocksource selection

If a non high-resolution clocksource is first set as override clock
and then registered it becomes active even if the system is in one-shot
mode. Move the override check from sysfs_override_clocksource to the
clocksource selection. That fixes the bug and simplifies the code. The
check in clocksource_register for double registration of the same
clocksource is removed without replacement.

To find the initial clocksource a new weak function in jiffies.c is
defined that returns the jiffies clocksource. The architecture code
can then override the weak function with a more suitable clocksource,
e.g. the TOD clock on s390.

[ tglx: Folded in a fix from John Stultz ]

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134808.388024160@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index c3f6c30816e3..5404a8456909 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -61,7 +61,6 @@ struct clocksource clocksource_jiffies = {
 	.read		= jiffies_read,
 	.mask		= 0xffffffff, /*32bits*/
 	.mult		= NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */
-	.mult_orig	= NSEC_PER_JIFFY << JIFFIES_SHIFT,
 	.shift		= JIFFIES_SHIFT,
 };
 
@@ -71,3 +70,8 @@ static int __init init_jiffies_clocksource(void)
 }
 
 core_initcall(init_jiffies_clocksource);
+
+struct clocksource * __init __weak clocksource_default_clock(void)
+{
+	return &clocksource_jiffies;
+}