On Wed, Jan 21, 2015 at 01:35:07PM +0000, Jisheng Zhang wrote: > Dear Sudeep, > > On Wed, 21 Jan 2015 05:21:39 -0800 > Jisheng Zhang <jszhang@xxxxxxxxxxx> wrote: > > > 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? > > Sorry for confusion. I mean > > If users explicitly hot-unplug other cores when system load is low to save > power, then at some point cpuidle want to suspend the cluster, how does the > distinguish this case with suspend the system to ram. Through the arm,psci-suspend-param DT property, ie PSCI CPU_SUSPEND power_state parameter. Did you read the patch :) ? > > In my private tree, I extend the PSCI spec to tell firmware we want to > > suspend the system. > > I extend the PSCI suspend function to help firmware distinguish suspend system > to ram and other suspend cores/clusters. See above. Thanks, Lorenzo -- 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
