On PowerPC, when CPUs enter certain deep idle states, the local timers stop and the time base could go out of sync with the rest of the cores in the system.
This patchset adds support to wake up CPUs in such idle states by broadcasting IPIs to them at their next timer events. We refer to these IPIs as the tick broadcast IPIs in this patchset to refer to this context. The patchset also includes resyncing of time base with the rest of the cores in the system as soon as the CPUs wake up from deep idle states. "Fast-Sleep" is a deep idle state on Power8 in which the above mentioned challenges exist. With the required support for deep idle states thus in place, the patchset adds Fast-Sleep into cpuidle. Fast-Sleep can yield us significantly more power savings than the idle states that we have in cpuidle so far. This patchset is based on mainline-3.13-rc1 and the cpuidle driver for power posted by Deepthi Dharwar: https://lkml.org/lkml/2013/11/11/29 Changes in V4: 1. Add Fast Sleep CPU idle state on PowerNV. 2. Add the required context management for Fast Sleep and the call to OPAL to synchronize time base after wakeup from fast sleep. 4. Add parsing of CPU idle states from the device tree to populate the cpuidle state table. 5. Rename ambiguous functions in the code around waking up of CPUs from fast sleep. 6. Fixed a bug in re-programming of the hrtimer that is queued to wakeup the CPUs in fast sleep and modified Changelogs. 7. Added the ARCH_HAS_TICK_BROADCAST option. This signifies that we have a arch specific function to perform broadcast. Changes in V3: http://thread.gmane.org/gmane.linux.power-management.general/38113 1. Fix the way in which a broadcast ipi is handled on the idling cpus. Timer handling on a broadcast ipi is being done now without missing out any timer stats generation. 2. Fix a bug in the programming of the hrtimer meant to do broadcast. Program it to trigger at the earlier of a "broadcast period", and the next wakeup event. By introducing the "broadcast period" as the maximum period after which the broadcast hrtimer can fire, we ensure that we do not miss wakeups in corner cases. 3. On hotplug of a broadcast cpu, trigger the hrtimer meant to do broadcast to fire immediately on the new broadcast cpu. This will ensure we do not miss doing a broadcast pending in the nearest future. 4. Change the type of allocation from GFP_KERNEL to GFP_NOWAIT while initializing bc_hrtimer since we are in an atomic context and cannot sleep. 5. Use the broadcast ipi to wakeup the newly nominated broadcast cpu on hotplug of the old instead of smp_call_function_single(). This is because we are interrupt disabled at this point and should not be using smp_call_function_single or its children in this context to send an ipi. 6. Move GENERIC_CLOCKEVENTS_BROADCAST to arch/powerpc/Kconfig. 7. Fix coding style issues. Changes in V2: https://lkml.org/lkml/2013/8/14/239 1. Dynamically pick a broadcast CPU, instead of having a dedicated one. 2. Remove the constraint of having to disable tickless idle on the broadcast CPU by queueing a hrtimer dedicated to do broadcast. V1 posting: https://lkml.org/lkml/2013/7/25/740. 1. Added the infrastructure to wakeup CPUs in deep idle states in which the local timers stop. --- Preeti U Murthy (5): cpuidle/ppc: Split timer_interrupt() into timer handling and interrupt handling routines cpuidle/ppc: Add basic infrastructure to enable the broadcast framework on ppc cpuidle/powernv: Add "Fast-Sleep" CPU idle state cpuidle/ppc: Nominate new broadcast cpu on hotplug of the old cpuidle/powernv: Parse device tree to setup idle states Srivatsa S. Bhat (2): powerpc: Free up the slot of PPC_MSG_CALL_FUNC_SINGLE IPI message powerpc: Implement tick broadcast IPI as a fixed IPI message Vaidyanathan Srinivasan (2): powernv/cpuidle: Add context management for Fast Sleep powermgt: Add OPAL call to resync timebase on wakeup arch/powerpc/Kconfig | 2 arch/powerpc/include/asm/opal.h | 2 arch/powerpc/include/asm/processor.h | 1 arch/powerpc/include/asm/smp.h | 2 arch/powerpc/include/asm/time.h | 4 arch/powerpc/kernel/exceptions-64s.S | 10 + arch/powerpc/kernel/idle_power7.S | 90 +++++++-- arch/powerpc/kernel/smp.c | 23 ++ arch/powerpc/kernel/time.c | 137 ++++++++++---- arch/powerpc/platforms/cell/interrupt.c | 2 arch/powerpc/platforms/powernv/opal-wrappers.S | 1 arch/powerpc/platforms/ps3/smp.c | 2 drivers/cpuidle/cpuidle-powerpc-book3s.c | 241 +++++++++++++++++++++++- 13 files changed, 443 insertions(+), 74 deletions(-) -- _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
