[Resend RFC PATCH 0/5] cpuidle/ppc: Timer offload framework to support deep idle states

Preeti U Murthy preeti at linux.vnet.ibm.com
Fri Jul 26 15:13:54 EST 2013

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

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:


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(-)

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