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? > 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. Only drivers within the CPU itself need a notification. Note that both ARM drivers I modified did not have a register_cpu_notifier call. > Rafael > _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
