Re: [RFC v2 0/6] Managing cluser-level c-states with generic power domains

[Lina Iyer <lina.iyer@linaro.org>]

Hi Marc,

I am trying to apply this on top of Axel's patches on linux-next (after
fixing issues I saw with his v9), and running to issues applying your
patches. Could you rebase on top of his v10 (he said he would send to
the ML soon) ?

Thanks,
Lina

On Tue, Oct 06 2015 at 08:27 -0600, Marc Titinger wrote:
>v2:
> - rebase on Lina Iyer's latest series
> - remove unnecessary dependency on perf-state patches from Axel Haslam
>
>-----------------------
>
>Summary
>
>1) DESCRIPTION
>2) DEPENDENCIES
>3) URL
>------------------------
>
>
>1) DESCRIPTION
>
>
>	This patch set's underlying idea is that cluster-level c-states can be managed
>by the power domain, building upon Lina Iyers recent work on CPU-domain, and Axel Haslam's
>genpd multiple states. The power domain may contain CPU devices and non-CPU devices.
>
>Non-CPU Devices may expose latency constraints by registering intermediate power-states upon
>probing, for instance shallower states than the deepest cluster-off state. The generic
>power domain governor may chose a device retention state in place of the cluster-sleep
>state demanded by the menu governor, and call the platform specific handling to enter/leave
>that retention state.
>
>
>power-states
>-----------
>
>
>The proposed way how cluster-level c-states are declared as manageable by the
>power domain, rather than through the cpuidle-ops, relies on the introduction of
>"power-states", consistent with c-states. Here is an example of the DT bindings,
>the c-state CLUSTER_SLEEP_0 is exposed as a power-state in the compatible property:
>
>juno.dts:           idle-states {
>                        entry-method = "arm,psci";
>
>                        CPU_SLEEP_0: cpu-sleep-0 {
>                                compatible = "arm,idle-state";
>                                arm,psci-suspend-param = <0x0010000>;
>                                local-timer-stop;
>                                entry-latency-us = <100>;
>                                exit-latency-us = <250>;
>                                min-residency-us = <2000>;
>                        };
>
>                        CLUSTER_SLEEP_0: cluster-sleep-0 {
>                                compatible = "arm,power-state";
>                                arm,psci-suspend-param = <0x1010000>;
>                                local-timer-stop;
>                                entry-latency-us = <800>;
>                                exit-latency-us = <700>;
>                                min-residency-us = <2500>;
>                        };
>		}
>
>This will tell cpuidle runtime_put/get the CPU devices for this c-state. Eventually, the
>actual platform handlers may be called from the genpd platform ops (in place of cpuidle_ops).
>
>"drivers/cpuidle/cpuidle-arm.c":
>
>static const struct of_device_id arm_idle_state_match[] __initconst = {
>        {.compatible = "arm,idle-state",
>         .data = arm_enter_idle_state},
>        {.compatible = "arm,power-state",
>         .data = arm_enter_power_state},
>};
>
>
>In case of a power-state, arm_enter_power_state will only call pm_runtime_put/get_sync
>The power doamin will handle the power off, currently this patch set lacks the final
>call to the psci interface to have a fully fonctionnal setup
>(and there are some genpd_lock'ing issues if put/get actually suspend the CPU device.)
>
>Ultimately, we would like the Power Domain's simple governor to being able to chose
>the cluster power-state based on the c-states defered to it (power-states) and constraints
>added by the devices. Consequently, we need to "soak" those power-states into the
>power-domain intermediate states from Axel. Since power-states are declared and handled
>the same manner than c-states (idle-states in DT), these patches add a soaking used when
>attaching to a genpd, where power-states are parsed from the DT into the genpd states:
>
>
>"drivers/base/power/domain.c":
>
>static const struct of_device_id power_state_match[] = {
>        {.compatible = "arm,power-state",
>         },
>};
>
>int of_genpd_device_parse_states(struct device_node *np,
>                                 struct generic_pm_domain *genpd)
>
>debugfs addition
>---------------
>
>To easy debug, this patch set adds a seq-file names "states" to the pm_genpd debugfs:
>
>    cat /sys/kernel/debug/pm_genpd/*
>
>      Domain             State name        Enter (ns) / Exit (ns)
>    -------------------------------------------------------------
>    a53_pd               cluster-sleep-0      1500000 / 800000
>    a57_pd               cluster-sleep-0      1500000 / 800000
>
>And also a seq-file "timings", to help visualize the constrains of the non-CPU
>devices in a cluster PD.
>
>    Domain Devices, Timings in ns
>                       Stop/Start Save/Restore, Effective
>----------------------------------------------------  ---
>a57_pd
>    /cpus/cpu@0          800   /740    1320  /1720  ,0 (cached stop)
>    /cpus/cpu@1          800   /740    1420  /1780  ,0 (cached stop)
>    /D1                  660   /580    16560 /6080  ,2199420 (cached stop)
>
>
>Device power-states
>-------------------
>
>some devices, like L2 caches, may feature a shallower retention mode, between CPU_SLEEP_0
>and CLUSTER_SLEEP_0, in which mode the L2 memory is not powered off, leading to faster
>resume than CLUSTER_SLEEP_0.
>
>One way to handle device constrains and retention features in the power-domain, is to
>allow devices to register a new power-state (consistent with a c-state).
>
>idle-states:
>
>                        D1_RETENTION: d1-retention {
>                                compatible = "arm,power-state";
>                                /*leave the psci param, for demo/testing:
>                                * the psci cpuidle driver will not currently
>                                * understand that a c-state shall not have it's
>                                * table entry with a firmware command.
>                                * the actual .power_on/off would be registered
>                                * by the DECLARE macro for a given domain*/
>                                arm,psci-suspend-param = <0x1010000>;
>                                local-timer-stop;
>                                entry-latency-us = <800>;
>                                exit-latency-us = <200>;
>                                min-residency-us = <2500>;
>                        };
>
>
>        D1 {
>                compatible = "fake,fake-driver";
>                name = "D1";
>                constraint = <30000>;
>                power-domains = <&a53_pd>;
>		power-states =<&D1_RETENTION>;
>        };
>
>
>The genpd simple governor can now upon suspend of the last-man CPU chose a shallower
>retention state than CLUSTER_SLEEP_0.
>
>In order to achieve this, this patch set added the power-state parsing during the
>genpd_dev_pm_attach call. Multiple genpd states are now inserted in a sorted manner
>according to their depth: see pm_genpd_insert_state in "drivers/base/power/domain.c".
>
>
>
>2) DEPENDENCIES
>
>	This patch set applies over linux-4.2rc5 plus the following ordered dependencies:
>
> * Ulf Hansson:
>
>6637131 New          [V4] PM / Domains: Remove intermediate states from the power off sequence
>
> * Lina Iyer's patch series:
>
>7118981 Not Applicable [v2,1/7] PM / Domains: Allocate memory outside domain locks
>7118991 Not Applicable [v2,2/7] PM / Domains: Support IRQ safe PM domains
>7119001 Not Applicable [v2,3/7] drivers: cpu: Define CPU devices as IRQ safe
>7119011 Not Applicable [v2,4/7] PM / Domains: Introduce PM domains for CPUs/clusters
>7119021 Not Applicable [v2,5/7] ARM: cpuidle: Add runtime PM support for CPU idle
>7119031 Not Applicable [v2,6/7] ARM64: smp: Add runtime PM support for CPU hotplug
>7119041 Not Applicable [v2,7/7] ARM: smp: Add runtime PM support for CPU hotplug
>
> * John Medhurst:
>
>6303671 New          arm64: dts: Add idle-states for Juno
>
> * Axel Haslam:
>
>6301741 Not Applicable [v7,1/5] PM / Domains: prepare for multiple states
>6301751 Not Applicable [v7,2/5] PM / Domains: core changes for multiple states
>6301781 Not Applicable [v7,3/5] PM / Domains: make governor select deepest state
>6301771 Not Applicable [v7,4/5] ARM: imx6: pm: declare pm domain latency on power_state struct.
>6301761 Not Applicable [v7,5/5] PM / Domains: remove old power on/off latencies.
>
>2) URL
>
>playable from https://github.com/mtitinger/linux-pm.git
>
>by adding the "fake driver D1" and launching the test-dev-state.sh script.
>this will show the power domain suspending to an intermediate state, based on the
>device constraints.
>
>    domain                      status pstate     slaves
>           /device                                      runtime status
>-----------------------------------------------------------------------------------
>a53_pd                          on
>    /devices/system/cpu/cpu0                            active
>    /devices/system/cpu/cpu3                            suspended
>    /devices/system/cpu/cpu4                            suspended
>    /devices/system/cpu/cpu5                            suspended
>a57_pd                          d1-retention
>    /devices/system/cpu/cpu1                            suspended
>    /devices/system/cpu/cpu2                            suspended
>    /devices/platform/D1
>
>----------------------------------------------------------------------
>
>Marc Titinger (6):
>  arm64: Juno: declare generic power domains for both clusters.
>  PM / Domains: prepare for devices that might register a power state
>  PM / Domains: introduce power-states consistent with c-states.
>  PM / Domains: succeed & warn when attaching non-irqsafe devices to an
>    irq-safe domain.
>  arm: cpuidle: let genpd handle the cluster power transition with
>    'power-states'
>  PM / Domains: add debugfs 'states' and 'timings' seq files
>
> .../devicetree/bindings/arm/idle-states.txt        |  21 +-
> .../devicetree/bindings/power/power_domain.txt     |  29 ++
> arch/arm64/boot/dts/arm/juno.dts                   |  25 +-
> drivers/base/power/cpu-pd.c                        |   5 +
> drivers/base/power/domain.c                        | 415 +++++++++++++++------
> drivers/cpuidle/cpuidle-arm.c                      |  52 ++-
> include/linux/pm_domain.h                          |  21 +-
> 7 files changed, 437 insertions(+), 131 deletions(-)
>
>-- 
>1.9.1
>