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SubjectRe: [PATCH v10 00/27] PM / Domains: Support hierarchical CPU arrangement (PSCI/ARM)
Rafael, Sudeep, Lorenzo, Mark,

On Thu, 29 Nov 2018 at 18:47, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> Over the years this series have been iterated and discussed at various Linux
> conferences and LKML. In this new v10, a quite significant amount of changes
> have been made to address comments from v8 and v9. A summary is available
> below, although let's start with a brand new clarification of the motivation
> behind this series.
>
> For ARM64/ARM based platforms CPUs are often arranged in a hierarchical manner.
> From a CPU idle state perspective, this means some states may be shared among a
> group of CPUs (aka CPU cluster).
>
> To deal with idle management of a group of CPUs, sometimes the kernel needs to
> be involved to manage the last-man standing algorithm, simply because it can't
> rely solely on power management FWs to deal with this. Depending on the
> platform, of course.
>
> There are a couple of typical scenarios for when the kernel needs to be in
> control, dealing with synchronization of when the last CPU in a cluster is about
> to enter a deep idle state.
>
> 1)
> The kernel needs to carry out so called last-man activities before the
> CPU cluster can enter a deep idle state. This may for example involve to
> configure external logics for wakeups, as the GIC may no longer be functional
> once a deep cluster idle state have been entered. Likewise, these operations
> may need to be restored, when the first CPU wakes up.
>
> 2)
> Other more generic I/O devices, such as an MMC controller for example, may be a
> part of the same power domain as the CPU cluster, due to a shared power-rail.
> For these scenarios, when the MMC controller is in use dealing with an MMC
> request, a deeper idle state of the CPU cluster may needs to be temporarily
> disabled. This is needed to retain the MMC controller in a functional state,
> else it may loose its register-context in the middle of serving a request.
>
> In this series, we are extending the generic PM domain (aka genpd) to be used
> for also CPU devices. Hence the goal is to re-use much of its current code to
> help us manage the last-man standing synchronization. Moreover, as we already
> use genpd to model power domains for generic I/O devices, both 1) and 2) can be
> address with its help.
>
> Moreover, to address these problems for ARM64 DT based platforms, we are
> deploying support for genpd and runtime PM to the PSCI FW driver - and finally
> we make some updates to two ARM64 DTBs, as to deploy the new PSCI CPU topology
> layout.
>
> The series has been tested on the QCOM 410c dragonboard and the Hisilicon Hikey
> board. You may also find the code at:
>
> git.linaro.org/people/ulf.hansson/linux-pm.git next

It's soon been three weeks since I posted this and I would really
appreciate some feedback.

Rafael, I need your feedback on patch 1->4.

Mark, Sudeep, Lorenzo, please have a look at the PSCI related changes.

When it comes to the the cpuidle related changes, I have pinged Daniel
offlist - and he is preparing some responses.

Kind regards
Uffe


>
> Kind regards
> Ulf Hansson
>
>
> Changes in v10:
> - Quite significant changes have been to the PSCI driver deployment. According
> to an agreement with Lorenzo, the hierarchical CPU layout for PSCI should be
> orthogonal to whether the PSCI FW supports OSI or not. This has been taken
> care of in this version.
> - Drop the generic attach/detach helpers of CPUs to genpd, instead make that
> related code internal to PSCI, for now.
> - Fix "BUG: sleeping for invalid context" for hotplug, as reported by Raju.
> - Addressed various comments from version 8 and 9.
> - Clarified changelogs and re-wrote the cover-letter to better explain the
> motivations behind these changes.
>
> Changes in v9:
> - Collect only a subset from the changes in v8.
> - Patch 3 is new, documenting existing genpd flags. Future wise, this means
> when a new genpd flag is invented, we must also properly document it.
> - No changes have been made to the patches picked from v8.
> - Dropped the text from v8 cover-letter[1], to avoid confusion. When posting v10
> (or whatever the next version containing the rest becomes), I am going re-write
> the cover-letter to clarify, more exactly, the problems this series intends to
> solve. The earlier text was simply too vague.
>
> [1]
> https://lwn.net/Articles/758091/
>
> Changes in v8:
> - Added some tags for reviews and acks.
> - Cleanup timer patch (patch6) according to comments from Rafael.
> - Rebased series on top of v4.18rc1 - it applied cleanly, except for patch 5.
> - While adopting patch 5 to new genpd changes, I took the opportunity to
> improve the new function description a bit.
> - Corrected malformed SPDX-License-Identifier in patch20.
>
> Changes in v7:
> - Addressed comments concerning the PSCI changes from Mark Rutland, which moves
> the psci firmware driver to a new firmware subdir and change to force PSCI PC
> mode during boot to cope with kexec'ed booted kernels.
> - Added some maintainers in cc for the timer/nohz patches.
> - Minor update to the new genpd governor, taking into account the state's
> poweroff latency while validating the sleep duration time.
> - Addressed a problem pointed out by Geert Uytterhoeven, around calling
> pm_runtime_get|put() for CPUs that has not been attached to a CPU PM domain.
> - Re-based on Linus' latest master.
>
>
> Lina Iyer (5):
> timer: Export next wakeup time of a CPU
> dt: psci: Update DT bindings to support hierarchical PSCI states
> cpuidle: dt: Support hierarchical CPU idle states
> drivers: firmware: psci: Support hierarchical CPU idle states
> arm64: dts: Convert to the hierarchical CPU topology layout for
> MSM8916
>
> Ulf Hansson (22):
> PM / Domains: Add generic data pointer to genpd_power_state struct
> PM / Domains: Add support for CPU devices to genpd
> PM / Domains: Add genpd governor for CPUs
> of: base: Add of_get_cpu_state_node() to get idle states for a CPU
> node
> ARM/ARM64: cpuidle: Let back-end init ops take the driver as input
> drivers: firmware: psci: Move psci to separate directory
> MAINTAINERS: Update files for PSCI
> drivers: firmware: psci: Split psci_dt_cpu_init_idle()
> drivers: firmware: psci: Simplify state node parsing
> drivers: firmware: psci: Simplify error path of psci_dt_init()
> drivers: firmware: psci: Announce support for OS initiated suspend
> mode
> drivers: firmware: psci: Prepare to use OS initiated suspend mode
> drivers: firmware: psci: Prepare to support PM domains
> drivers: firmware: psci: Add support for PM domains using genpd
> drivers: firmware: psci: Add hierarchical domain idle states converter
> drivers: firmware: psci: Introduce psci_dt_topology_init()
> drivers: firmware: psci: Add a helper to attach a CPU to its PM domain
> drivers: firmware: psci: Attach the CPU's device to its PM domain
> drivers: firmware: psci: Manage runtime PM in the idle path for CPUs
> drivers: firmware: psci: Support CPU hotplug for the hierarchical
> model
> arm64: kernel: Respect the hierarchical CPU topology in DT for PSCI
> arm64: dts: hikey: Convert to the hierarchical CPU topology layout
>
> .../devicetree/bindings/arm/psci.txt | 166 ++++++++
> MAINTAINERS | 2 +-
> arch/arm/include/asm/cpuidle.h | 4 +-
> arch/arm/kernel/cpuidle.c | 5 +-
> arch/arm64/boot/dts/hisilicon/hi6220.dtsi | 87 +++-
> arch/arm64/boot/dts/qcom/msm8916.dtsi | 57 ++-
> arch/arm64/include/asm/cpu_ops.h | 4 +-
> arch/arm64/include/asm/cpuidle.h | 6 +-
> arch/arm64/kernel/cpuidle.c | 6 +-
> arch/arm64/kernel/setup.c | 3 +
> drivers/base/power/domain.c | 74 +++-
> drivers/base/power/domain_governor.c | 61 ++-
> drivers/cpuidle/cpuidle-arm.c | 2 +-
> drivers/cpuidle/dt_idle_states.c | 5 +-
> drivers/firmware/Kconfig | 15 +-
> drivers/firmware/Makefile | 3 +-
> drivers/firmware/psci/Kconfig | 13 +
> drivers/firmware/psci/Makefile | 4 +
> drivers/firmware/{ => psci}/psci.c | 240 ++++++++---
> drivers/firmware/psci/psci.h | 23 ++
> drivers/firmware/{ => psci}/psci_checker.c | 0
> drivers/firmware/psci/psci_pm_domain.c | 389 ++++++++++++++++++
> drivers/of/base.c | 35 ++
> drivers/soc/qcom/spm.c | 3 +-
> include/linux/of.h | 8 +
> include/linux/pm_domain.h | 19 +-
> include/linux/psci.h | 6 +-
> include/linux/tick.h | 8 +
> include/uapi/linux/psci.h | 5 +
> kernel/time/tick-sched.c | 13 +
> 30 files changed, 1163 insertions(+), 103 deletions(-)
> create mode 100644 drivers/firmware/psci/Kconfig
> create mode 100644 drivers/firmware/psci/Makefile
> rename drivers/firmware/{ => psci}/psci.c (76%)
> create mode 100644 drivers/firmware/psci/psci.h
> rename drivers/firmware/{ => psci}/psci_checker.c (100%)
> create mode 100644 drivers/firmware/psci/psci_pm_domain.c
>
> --
> 2.17.1
>

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