[RFC/PATCH v3 00/13] PM QoS: add a per-device latency constraints class

[jean.pihet@newoldbits.com]

From: Jean Pihet <j-pihet@ti.com>

This patch set is in an RFC state, for review and comments.

High level implementation:

1. Add a new PM QoS class for device wake-up constraints (PM_QOS_DEV_LATENCY).
. Define a pm_qos_constraints struct for the storage of the constraints list
and associated values (target_value, default_value, type ...).
. Update the pm_qos_object struct with the information related to a PM QoS
class: ptr to constraints list, notifer ptr, name ...
. Each PM QoS class statically declare objects for pm_qos_object and
pm_qos_constraints. The only exception is the devices constraints, cf. below.
. The device constraints class is statically declaring a pm_qos_object. The
pm_qos_constraints are per-device and so are embedded into the device struct.

The new class is available from kernel drivers and shall be made available
to user space through a per-device sysfs entry. User space API to come as a 
subsequent patch.

2. Added a notification of device insertion/removal from the device PM framework
to PM QoS.
This allows to init/de-init the per-device constraints list upon device insertion
and removal.
RFC state for comments and review, lightly tested

3. Make the pm_qos_add_request API more generic by using a
struct pm_qos_parameters parameter. This allows easy extension in the future.

4. Upon a change of the aggregated constraint value in the PM_QOS_DEV_LATENCY class
a notification chain mechanism is used to take action on the system.
This is the proposed way to have PM QoS and the platform dependant code to
interact with each other, cf. 5 below.
The notification mechanism now passes the constraint request struct ptr in
order for the notifier callback to have access to the full set of constraint
data, e.g. the struct device ptr.

5. cpuidle interaction with the OMAP3 cpuidle handler
Since cpuidle is a CPU centric framework it decides the MPU next power state
based on the MPU exit_latency and target_residency figures.
    
The rest of the power domains get their next power state programmed from
the PM_QOS_DEV_LATENCY class of the PM QoS framework, via the device
wake-up latency constraints callback to the OMAP_PM_CONSTRAINTS framework.

Note: the exit_latency and target_residency figures of the MPU include the MPU
itself and the peripherals needed for the MPU to execute instructions (e.g.
main memory, caches, IRQ controller, MMU etc).
Some of those peripherals can belong to other power domains than the MPU
subsystem and so the corresponding latencies must be included in those figures.

6. Update the pm_qos_add_request callers to the generic API

7. Misc fixes to improve code readability:
. rename of the PM QoS implementation file from pm_qos_params.[ch] to pm_qos.[ch]
. rename of fields names (request, list, constraints, class),
. simplification of the in-kernel PM QoS API implementation. The main logic part
is now implemented in the update_target function.

Questions:
1. per-device user-space API: since sysfs does not provide open/close
callbacks it is not possible to support multiple and simultaneous users of
the per-device sysfs entry. A user-space constraints aggregation application is
needed in case of multiple constraints for a device. Is this the way to go?

On-going developments, patches in preparation:
1. add a user-space API for the devices constratins PM QoS, using a sysfs entry
   per device
2. write Documentation for the new PM QoS class, once the RFC is agreed on
3. validate the constraints framework on OMAP4 HW (done on OMAP3)
4. refine the power domains wake-up latency and the cpuidle figures

Based on the master branch of the linux-omap git tree (3.0.0-rc7). Compile
tested using OMAP and x86 generic defconfigs.
Lightly tested on OMAP3 Beagleboard (ES2.x).


Changelog:

v3:
. Complete PM QoS re-design after the comments on MLs
. Patch set split up for improved readability and easier maintenance

v2:
. Rework after comments on the mailing lists
. Added a notification of device insertion/removal from the device PM framework
. Validated on OMAP3 HW

v1:
. Initial implementation


Jean Pihet (12):
  PM: QoS: rename pm_qos_params files to pm_qos
  PM: add a per-device wake-up latency constraints plist
  PM: QoS: extend the in-kernel API with per-device latency constraints
  PM: QoS: implement the per-device latency constraints
  PM: QoS: support the dynamic insertion and removal of devices
  OMAP PM: create a PM layer plugin for per-device constraints
  OMAP PM: early init of the pwrdms states
  OMAP2+: powerdomain: control power domains next state
  OMAP3: powerdomain data: add wake-up latency figures
  OMAP2+: omap_hwmod: manage the wake-up latency constraints
  OMAP: PM CONSTRAINTS: implement the devices wake-up latency
    constraints
  OMAP2+: cpuidle only influences the MPU state

Vishwanath BS (1):
  OMAP4: powerdomain data: add wake-up latency figures

 arch/arm/mach-msm/clock.c                    |    2 +-
 arch/arm/mach-omap2/cpuidle34xx.c            |   42 +--
 arch/arm/mach-omap2/omap_hwmod.c             |   26 ++-
 arch/arm/mach-omap2/pm.h                     |   17 +-
 arch/arm/mach-omap2/pm34xx.c                 |    2 +-
 arch/arm/mach-omap2/pm44xx.c                 |    2 +-
 arch/arm/mach-omap2/powerdomain.c            |  190 +++++++++
 arch/arm/mach-omap2/powerdomain.h            |   33 ++-
 arch/arm/mach-omap2/powerdomains3xxx_data.c  |   77 ++++
 arch/arm/mach-omap2/powerdomains44xx_data.c  |   84 ++++
 arch/arm/plat-omap/Kconfig                   |    7 +
 arch/arm/plat-omap/Makefile                  |    1 +
 arch/arm/plat-omap/i2c.c                     |   20 -
 arch/arm/plat-omap/include/plat/omap-pm.h    |  128 ------
 arch/arm/plat-omap/include/plat/omap_hwmod.h |    2 +
 arch/arm/plat-omap/omap-pm-constraints.c     |  344 ++++++++++++++++
 arch/arm/plat-omap/omap-pm-noop.c            |   89 ----
 drivers/acpi/processor_idle.c                |    2 +-
 drivers/base/power/main.c                    |    4 +
 drivers/cpuidle/cpuidle.c                    |    2 +-
 drivers/cpuidle/governors/ladder.c           |    2 +-
 drivers/cpuidle/governors/menu.c             |    2 +-
 drivers/i2c/busses/i2c-omap.c                |   35 +-
 drivers/media/video/via-camera.c             |    9 +-
 drivers/net/e1000e/netdev.c                  |   11 +-
 drivers/net/wireless/ipw2x00/ipw2100.c       |   10 +-
 drivers/staging/msm/lcdc.c                   |    2 +-
 drivers/staging/msm/tvenc.c                  |    2 +-
 include/linux/netdevice.h                    |    4 +-
 include/linux/pm.h                           |    4 +
 include/linux/pm_qos.h                       |   68 ++++
 include/linux/pm_qos_params.h                |   38 --
 include/sound/pcm.h                          |    4 +-
 kernel/Makefile                              |    2 +-
 kernel/pm_qos.c                              |  557 ++++++++++++++++++++++++++
 kernel/pm_qos_params.c                       |  481 ----------------------
 net/mac80211/main.c                          |    2 +-
 net/mac80211/mlme.c                          |    2 +-
 net/mac80211/scan.c                          |    2 +-
 sound/core/pcm_native.c                      |   10 +-
 40 files changed, 1487 insertions(+), 834 deletions(-)
 create mode 100644 arch/arm/plat-omap/omap-pm-constraints.c
 create mode 100644 include/linux/pm_qos.h
 delete mode 100644 include/linux/pm_qos_params.h
 create mode 100644 kernel/pm_qos.c
 delete mode 100644 kernel/pm_qos_params.c

-- 
1.7.2.5