When a cpu goes to a deep idle state where its local timer is shutdown, it notifies the time framework to use the broadcast timer instead.
Unfortunately, the broadcast device could wake up any CPU, including an idle one which is not concerned by the wake up at all.
This implies, in the worst case, an idle CPU will wake up to send an IPI to another idle cpu.
This patch solves this by setting the irq affinity to the cpu concerned by the nearest timer event, by this way, the CPU which is wake up is guarantee to be the one concerned by the next event and we are safe with unnecessary wakeup for another idle CPU.
As the irq affinity is not supported by all the archs, a flag is needed to specify which clocksource can handle it.
Daniel Lezcano (3): time : pass broadcast parameter time : set broadcast irq affinity ARM: nomadik: add dynamic irq flag to the timer
Viresh Kumar (1): ARM: timer-sp: Set dynamic irq affinity
arch/arm/common/timer-sp.c | 3 ++- drivers/clocksource/nomadik-mtu.c | 3 ++- include/linux/clockchips.h | 1 + kernel/time/tick-broadcast.c | 40 +++++++++++++++++++++++++++++-------- 4 files changed, 37 insertions(+), 10 deletions(-)