Dear Sudeep, On Wed, 21 Jan 2015 03:35:54 -0800 Sudeep Holla <sudeep.holla@xxxxxxx> wrote: > ARM based platforms implement unique ways to enter system suspend > (i.e. Suspend to RAM). The mechanism and the parameters defining the > system state vary on a per-platform basis forcing the OS to handle it > in very platform specific way. > > Since ARM 32-bit systems had machine specific code, no attempts to > standardize are being made as it provides easy way to implement suspend > operations in a platform specific manner. However, this approach not > only makes maintainance more difficult as the number of platforms > supported increases but also not feasible for ARM64. > > This DT binding aims at standardizing the system suspend for ARM > platforms. ARM64 platforms mandates entry-method property in DT for > this system suspend node. > > On system implementing PSCI as an enable-method to enter system suspend, > the PSCI CPU suspend method is used on versions upto v0.2 and requires > the power_state parameter to be passed to the PSCI CPU suspend function. > > This parameter is platform specific, therefore must be provided by > firmware to the OS in order to enable proper call sequence. > > This ARM system suspend DT bindings rely on a property > (i.e. arm,psci-suspend-param) in the PSCI DT bindings that describes > how the PSCI CPU suspend power_state parameter should be defined in DT. > > Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx> > --- > Documentation/devicetree/bindings/arm/psci.txt | 11 +++ > .../devicetree/bindings/arm/system-suspend.txt | 93 > ++++++++++++++++++++++ 2 files changed, 104 insertions(+) > create mode 100644 Documentation/devicetree/bindings/arm/system-suspend.txt > > diff --git a/Documentation/devicetree/bindings/arm/psci.txt > b/Documentation/devicetree/bindings/arm/psci.txt index > 5aa40ede0e99..bd3977a2a333 100644 --- > a/Documentation/devicetree/bindings/arm/psci.txt +++ > b/Documentation/devicetree/bindings/arm/psci.txt @@ -61,6 +61,14 @@ Device > tree nodes that require usage of PSCI CPU_SUSPEND function (ie idle > Definition: power_state parameter to pass to the PSCI suspend call. > > +PSCI v0.2 and earlier versions don't have explicit operation for system > +suspend. However, one can implement system suspend using CPU_SUSPEND by > +ensuring every other core except the one executing the CPU_SUSPEND call > +has called into PSCI through a CPU_OFF call. If users explicitly hot-unplug other cores when system load is low to save power, then we want to suspend at some point, how does the firmware know this case? In my private tree, I extend the PSCI spec to tell firmware we want to suspend the system. Thanks, Jisheng -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
