ARM: sched_clock: allow init_sched_clock() to be called early

sched_clock is supposed to be initialized early - in the recently added
init_early platform hook.  However, in doing so we end up calling
mod_timer() before the timer lists are initialized, resulting in an
oops.

Split the initialization in two - the part which the platform calls
early which starts things off.  The addition of the timer can be
delayed until after we have more of the kernel initialized - when the
normal time sources are initialized.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/sched_clock.h

@@ -115,4 +115,6 @@ static inline void init_fixed_sched_clock(struct clock_data *cd,
 	}
 }
 
+extern void sched_clock_postinit(void);
+
 #endif

arch/arm/kernel/sched_clock.c

@@ -60,10 +60,15 @@ void __init init_sched_clock(struct clock_data *cd, void (*update)(void),
 	 * sets the initial epoch.
 	 */
 	sched_clock_timer.data = msecs_to_jiffies(w - (w / 10));
-	sched_clock_poll(sched_clock_timer.data);
+	update();
 
 	/*
 	 * Ensure that sched_clock() starts off at 0ns
 	 */
 	cd->epoch_ns = 0;
 }
+
+void __init sched_clock_postinit(void)
+{
+	sched_clock_poll(sched_clock_timer.data);
+}

arch/arm/kernel/time.c

@@ -29,6 +29,7 @@
 
 #include <asm/leds.h>
 #include <asm/thread_info.h>
+#include <asm/sched_clock.h>
 #include <asm/stacktrace.h>
 #include <asm/mach/arch.h>
 #include <asm/mach/time.h>
@@ -163,5 +164,8 @@ void __init time_init(void)
 {
 	system_timer = machine_desc->timer;
 	system_timer->init();
+#ifdef CONFIG_HAVE_SCHED_CLOCK
+	sched_clock_postinit();
+#endif
 }