On Monday, June 13, 2011, Colin Cross wrote: > On Mon, Jun 13, 2011 at 11:37 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > > On Monday, June 13, 2011, Colin Cross wrote: > >> This patch set tries to address Russell's concerns with platform > >> pm code calling into the driver for every block in the Cortex A9s > >> during idle, hotplug, and suspend. The first patch adds cpu pm > >> notifiers that can be called by platform code, the second uses > >> the notifier to save and restore the GIC state, and the third > >> saves the VFP state. > >> > >> The notifiers are used for two types of events, CPU PM events and > >> CPU complex PM events. CPU PM events are used to save and restore > >> per-cpu context when a single CPU is preparing to enter or has > >> just exited a low power state. For example, the VFP saves the > >> last thread context, and the GIC saves banked CPU registers. > >> > >> CPU complex events are used after all the CPUs in a power domain > >> have been prepared for the low power state. The GIC uses these > >> events to save global register state. > >> > >> Platforms that call the cpu_pm APIs must select > >> CONFIG_ARCH_USES_CPU_PM > >> > >> L2 cache is not covered by this patch set, as the determination > >> of when the L2 is reset and when it is retained is > >> platform-specific, and most of the APIs necessary are already > >> present. > >> > >> arch/arm/Kconfig | 7 ++ > >> arch/arm/common/gic.c | 212 +++++++++++++++++++++++++++++++++++++++++ > >> arch/arm/include/asm/cpu_pm.h | 54 +++++++++++ > >> arch/arm/kernel/Makefile | 1 + > >> arch/arm/kernel/cpu_pm.c | 181 +++++++++++++++++++++++++++++++++++ > > > > Is there any reason why this has to be ARM-specific? There are other > > architectures where this kind of feature might make sense (SH and > > powerpc at least). > > Nothing other than there are currently no adaptations for any drivers > besides ARM, but I can move it somewhere outside ARM. Any suggestions > where? Well, there is kernel/cpu.c. It contains mostly CPU hotplug and PM code at the moment, so it looks like a good place. > > Besides, is there any overlap between this feature and the CPU hotplug > > notifiers? > > I don't think so - the hotplug notifiers are used when a CPU is being > removed from the system, so no saving and restoring is necessary - the > CPU will be rebooted from scratch. They are used by systems outside > the CPU that need to know that a CPU no longer exists. > > CPU PM notifiers are used when a CPU is going through reset in a way > that should be transparent to most of the system. Do I guess correctly that you mean cpuidle? Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
