lkml.org 
[lkml]   [2015]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Subject[RFC 0/7] Managing cluser-level c-states with generic power domains
Date
-----------------------

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:

6945201 New [1/9] PM / Domains: Allocate memory outside domain locks
6945221 New [2/9] PM / Domains: Remove dev->driver check for runtime PM
6945231 New [3/9] PM / Domains: Support IRQ safe PM domains
6945211 New [4/9] kernel/cpu_pm: fix cpu_cluster_pm_exit comment
6945251 New [5/9] ARM: common: Introduce PM domains for CPUs/clusters
6945281 New [6/9] ARM: domain: Add platform handlers for CPU PM domains
6945261 New [7/9] ARM: cpuidle: Add runtime PM support for CPU idle
6945241 New [8/9] ARM64: smp: Add runtime PM support for CPU hotplug
6945271 New [9/9] ARM: smp: Add runtime PM support for CPU hotplug

* John Medhurst:

6303671 New arm64: dts: Add idle-states for Juno

* Axel Haslam:

7b4eda6 ARM: imx6: pm: declare pm domain latency on power_state struct.
e65789a PM / Domains: make governor select deepest state
8b22b90 PM / Domains: core changes for multiple states
84af098 PM / Domains: prepare for multiple states

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 (7):
arm64: pm/domains: try mutualize CPU domains init between arm/arm64
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/arm/common/domains.c | 9 +-
arch/arm64/Kconfig | 1 +
arch/arm64/boot/dts/arm/juno.dts | 25 +-
arch/arm64/include/asm/arm-pd.h | 1 +
arch/arm64/kernel/Makefile | 6 +
arch/arm64/kernel/domains.c | 1 +
drivers/base/power/domain.c | 418 +++++++++++++++------
drivers/cpuidle/cpuidle-arm.c | 50 ++-
include/linux/pm_domain.h | 21 +-
11 files changed, 452 insertions(+), 130 deletions(-)
create mode 120000 arch/arm64/include/asm/arm-pd.h
create mode 120000 arch/arm64/kernel/domains.c

--
1.9.1



\
 
 \ /
  Last update: 2015-09-25 15:21    [W:0.139 / U:10.512 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site