at91: warn if irqs are enabled in set_next_event

Thomas claims that irqs are disabled when set_next_event is called.  But
David and Remy claim they saw irqs being enabled here.  As both sides
don't seem to have time to investigate here, start with a warning that
might trigger if the problem still exists.
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-By: NDavid Brownell <dbrownell@users.sourceforge.net>
Cc: Bill Gatliff <bgat@billgatliff.com>
Acked-By: NRemy Bohmer <linux@bohmer.net>
Cc: Thomas Gleixner <tglx@linutronix.de>

arch/arm/mach-at91/at91rm9200_time.c

@@ -141,6 +141,15 @@ clkevt32k_next_event(unsigned long delta, struct clock_event_device *dev)
 	/* Use "raw" primitives so we behave correctly on RT kernels. */
 	raw_local_irq_save(flags);
 
+	/*
+	 * According to Thomas Gleixner irqs are already disabled here.  Simply
+	 * removing raw_local_irq_save above (and the matching
+	 * raw_local_irq_restore) was not accepted.  See
+	 * http://thread.gmane.org/gmane.linux.ports.arm.kernel/41174
+	 * So for now (2008-11-20) just warn once if irqs were not disabled ...
+	 */
+	WARN_ON_ONCE(!raw_irqs_disabled_flags(flags));
+
 	/* The alarm IRQ uses absolute time (now+delta), not the relative
 	 * time (delta) in our calling convention.  Like all clockevents
 	 * using such "match" hardware, we have a race to defend against.