On PowerPC, when CPUs enter deep idle states, their local timers are switched off. The responsibility of waking them up at their next timer event, needs to be handed over to an external device. On PowerPC, we do not have an external device equivalent to HPET, which is currently done on architectures like x86. Instead we assign the local timer of one of the CPUs to do this job.
This patchset is an attempt to make use of the existing timer broadcast framework in the kernel to meet the above requirement, except that the tick broadcast device is the local timer of the boot CPU. This patch series is ported ontop of 3.11-rc1 + the cpuidle driver backend for powernv posted by Deepthi Dharwar recently. The current design and implementation supports the ONESHOT tick mode. It does not yet support the PERIODIC tick mode. This patch is tested with NOHZ_FULL off. Patch[1/5], Patch[2/5]: optimize the broadcast mechanism on ppc. Patch[3/5]: Introduces the core of the timer offload framework on powerpc. Patch[4/5]: The cpu doing the broadcast should not go into tickless idle. Patch[5/5]: Add a deep idle state to the cpuidle state table on powernv. Patch[5/5] is the patch that ultimately makes use of the timer offload framework that the patches Patch[1/5] to Patch[4/5] build. This patch series is being resent to clarify certain ambiguity in the patch descriptions from the previous post. Discussion around this: https://lkml.org/lkml/2013/7/25/754 --- Preeti U Murthy (3): cpuidle/ppc: Add timer offload framework to support deep idle states cpuidle/ppc: CPU goes tickless if there are no arch-specific constraints cpuidle/ppc: Add longnap state to the idle states on powernv Srivatsa S. Bhat (2): powerpc: Free up the IPI message slot of ipi call function (PPC_MSG_CALL_FUNC) powerpc: Implement broadcast timer interrupt as an IPI message arch/powerpc/include/asm/smp.h | 3 + arch/powerpc/include/asm/time.h | 3 + arch/powerpc/kernel/smp.c | 23 ++++-- arch/powerpc/kernel/time.c | 86 +++++++++++++++++++++++ arch/powerpc/platforms/cell/interrupt.c | 2 - arch/powerpc/platforms/powernv/Kconfig | 1 arch/powerpc/platforms/powernv/processor_idle.c | 48 +++++++++++++ arch/powerpc/platforms/ps3/smp.c | 2 - kernel/time/tick-sched.c | 7 ++ 9 files changed, 163 insertions(+), 12 deletions(-) _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
