On Thu, Oct 11, 2018 at 10:00:53AM -0600, Lina Iyer wrote:If we don't do this, then we leave a lot of power saving on the table,
The CPU PD does not power off the domain from Linux. That is done from
PSCI firmware (ATF). These patches are doing the part that Linux has do,
when powering off the CPUs, to achieve a low standby power consumption.
I don't understand why Linux *has do* this part as PSCI manages CPU PM.
Yes, it is a possibility and worth the chance taken. On an SoC, thereOn Thu, Oct 11 2018 at 05:20 -0600, Sudeep Holla wrote:
> On Thu, Oct 11, 2018 at 02:50:54AM +0530, Raju P.L.S.S.S.N wrote:
> > Use cpu hotplug callback mechanism to attach/dettach the cpu in
> > the cpu power domain. During cpu hotplug callback registration,
> > the starting callback is invoked on all online cpus. So there is
> > no need to attach from device probe.
> To be more explicit, NACK to this series(patches 4-8 to be more specific)
> unless you provide details on:
> 1. Why this is not in PSCI implementation ?
This is a linux activity and there is no provision in ATF or QC firmware
to do this activity. The task of physically powering down the domain,
still is a firmware decision and is done through PSCI platform
coordinated in the firmware.
Yes that was my understanding. So the addon question here is: if PSCI
decides to abort entering the idle state, the Linux doing the RPMH
request is of no use which can be prevented if done once PSCI f/w is
about to enter the state. I know it may be corner case, but we have
whole OSI mode based on such corner cases.
It may or may not, depending on which firmware you talk to. But consider> 2. If PSCI is used on this platform, how does it work/co-exist ?
Yes PSCI is used in this platform. ATF is the firmware and that supports
only Platform Coordinated. This SoC uses cpuidle and the regular PSCI
methods to power off the domain from the firmware. However, Linux has
responsibilities that it needs to complete before the power down can be
I understand the need to inform RPMH. So I take only reason to do that
in Linux is TF-A doesn't have any support to talk to RPMH ?
Now that we have some platform with PC, it's good to compare PC vs OSICan I take that you are okay with the OSI idea and this one, then :)
which we always lacked. Thanks for letting us know this platform is PC
What problem do you see with that? It would help if you could clarifyIsn't sharing ideas a key aspect of working with the community? ThisAh OK, so this platform will have flattened cpu-idle-states list ? That's
series just goes to say that the idea of CPU PM domains are useful,
whether PSCI uses it or not. If you still need clarifications, Raju and
I will be happy to set up a meeting and go over the idea.
absolutely fine. But what if we want to represent hierarchical PSCI based
PM domains and this power domain for some platform. That's the main
concern I raised. For me, the power-domains in DT introduced in this
is just to deal with RPMH though the actual work is done by PSCI.
That just doesn't look that good for me.