Hi Ulf, I will suggest some wording changes not of which are not compulsory and left to you to pick up or drop. On 28/12/17 14:40, Ulf Hansson wrote: > From: Lina Iyer <lina.iyer@xxxxxxxxxx> > > Update DT bindings to represent hierarchical CPU and CPU domain idle states > for PSCI. Also update the PSCI examples to clearly show how flattened and > hierarchical idle states can be represented in DT. > > Signed-off-by: Lina Iyer <lina.iyer@xxxxxxxxxx> > Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx> > --- > > Changes in v2: > - Addressed comments from Rob. > - Updated some labels in the examples to get more consistency. > > For your information, I have picked up the work from Lina Iyer around the so > called CPU cluster idling series [1,2] and I working on new versions. However, > I decided to post the updates to the PSCI DT bindings first, as they will be > needed to be agreed upon before further changes can be done to the PSCI firmware > driver. > > Note, these bindings have been discussed over and over again, at LKML, but > especially also at various Linux conferences, like LPC and Linaro Connect. We > finally came to a conclusion and the changes we agreed upon, should be reflected > in this update. > > Of course, it's a while ago since the latest discussions, but hopefully people > don't have too hard time to remember. > > Kind regards > Uffe > > [1] > https://www.spinics.net/lists/arm-kernel/msg566200.html > > [2] > https://lwn.net/Articles/716300/ > > --- > Documentation/devicetree/bindings/arm/psci.txt | 152 +++++++++++++++++++++++++ > 1 file changed, 152 insertions(+) > > diff --git a/Documentation/devicetree/bindings/arm/psci.txt b/Documentation/devicetree/bindings/arm/psci.txt > index a2c4f1d..8a09bd2 100644 > --- a/Documentation/devicetree/bindings/arm/psci.txt > +++ b/Documentation/devicetree/bindings/arm/psci.txt > @@ -105,7 +105,159 @@ Case 3: PSCI v0.2 and PSCI v0.1. > ... > }; > > +PSCI v1.0 onwards, supports OS-Initiated mode for powering off CPUs and CPU > +clusters from the firmware. Since we are trying to avoid usage of "clusters"(as it's not architecturally defined, but I know it's too late as it widely used everywhere). Also this binding is not just OSI specific, it can be used for Platform Co-ordinated also so let's not specify them at all. How about: "ARM systems can have multiple cores sometimes in hierarchical arrangement. This often, but not always, maps directly to the processor power topology of the system. Individual nodes in a topology have their own specific power states and can be better represented in DT hierarchically" > For such topologies the PSCI firmware driver acts PSCI firmware can be represented as a pseudo power controller ? > +as pseudo-controller, which may be specified in the psci DT node. The > +definitions of the CPU and the CPU cluster topology, must conform to the domain > +idle state specification [3]. I assume it should be "..definitions of the idle states for CPU and the CPU topology" above, otherwise they should conform to topology binding :) rather than domain idle state bindings. > The domain idle states themselves, must be > +compatible with the defined 'domain-idle-state' binding [1], and also need to > +specify the arm,psci-suspend-param property for each idle state. > + > +DT allows representing CPU and CPU cluster idle states in two different ways - > + > +The flattened model as given in Example 1, lists CPU's idle states followed by > +the domain idle state that the CPUs may choose. This is the general practice > +followed in PSCI firmwares that support Platform Coordinated mode. I would rather drop the above statement or specify in Example 2 that it can be used for both OSI and PC. > Note that > +the idle states are all compatible with "arm,idle-state". > + > +Example 2 represents the hierarchical model of CPU and domain idle states. > +CPUs define their domain provider in their DT node. The domain controls the > +power to the CPU and possibly other h/w blocks that would be powered off when > +the CPU is powered off. The CPU's idle states may therefore be considered as > +the domain's idle states and have the compatible "arm,idle-state". Such domains > +may be embedded within another domain that represents common h/w blocks between > +these CPUs viz. the cluster. The idle states of the cluster would be > +represented as the domain's idle states. In order to use OS-Initiated mode of > +PSCI in the firmware, the hierarchical representation must be used. > + Can we avoid using poweroff as it's one of the idle states and not the only one ? Other than that, the examples look good to me. -- Regards, Sudeep -- 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
