Commit 27a5569d authored Jul 06, 2012 by Lorenzo Pieralisi Committed by Russell King Jul 09, 2012

ARM: 7444/1: kernel: add arch-timer C3STOP feature



When a CPU is shutdown its architected timer comparators registers are
lost. Within CPU idle, before processors enter shutdown they enter
clock events broadcast mode through the

clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, cpuid);

function where the local timers are emulated by a global always-on timer.
On CPU resume, the per-CPU tick device normal mode is restored by exiting
broadcast mode through

clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, cpuid);

In order for this mechanism to function, architected timers should add to
their feature C3STOP, which means that they are not able to function when the
CPU is in off-mode.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

parent a5203c4c

arch/arm/kernel/arch_timer.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -137,7 +137,7 @@ static int __cpuinit arch_timer_setup(struct clock_event_device *clk)
		/* Be safe... */
		arch_timer_disable();

		clk->features = CLOCK_EVT_FEAT_ONESHOT;
		clk->features = CLOCK_EVT_FEAT_ONESHOT \| CLOCK_EVT_FEAT_C3STOP;
		clk->name = "arch_sys_timer";
		clk->rating = 450;
		clk->set_mode = arch_timer_set_mode;