Re: [PATCH v6 0/7] PM QoS: add a per-device latency constraints framework

Hi,

On Wednesday, August 17, 2011, jean.pihet@newoldbits.com wrote:

From: Jean Pihet <redacted>

High level implementation:

1. Preparation of the PM QoS for the addition of a device PM QoS constraints
   framework:
  . rename and move of the PM QoS implementation files to kernel/power/qos.c
    and include/linux/pm_qos.h
  . rename of API parameters and internal fields names
  . Move around the PM QoS misc devices management code for better readability
  . re-organize the internal data structs
  . generalize and export the constraints management core code

2. Implementation of the per-device PM QoS constraints:
  . create drivers/base/power/qos.c for the implementation
  . create a device PM QoS API, which calls the PM QoS constraints management
    core code
  . the per-device latency constraints data strctures are stored in the device
    dev_pm_info struct
  . the device PM code calls the init and destroy of the per-device constraints
    data struct in order to support the dynamic insertion and removal of the
    devices in the system.
  . to minimize the data usage by the per-device constraints, the data struct
    is only allocated at the first call to dev_pm_qos_add_request. The data
    is later free'd when the device is removed from the system
  . per-device notification callbacks can be registered and called upon a
    change to the aggregated constraint value
  . a global mutex protects the constraints users from the data being
    allocated and free'd.

3. add a global notification mechanism for the device constraints
  . add a global notification chain that gets called upon changes to the
    aggregated constraint value for any device.
  . the notification callbacks are passing the full constraint request data
    in order for the callees to have access to it. The current use is for the
    platform low-level code to access the target device of the constraint


Questions:
1. the user space API is still under discussions on linux-omap and linux-pm MLs,
   cf. [1]. The idea is to add a user-space API for the devices constratins
   PM QoS, using a sysfs entry per device

[1] http://marc.info/?l=linux-omap&m=131232344503327&w=2

ToDo:
1. write Documentation for the new PM QoS class, once the code is agreed on
2. submit patches for the OMAP low level code to control the power domains
   states from the device constraints, using a global notification callback

   
Based on the master branch of the linux-omap git tree (3.1.0-rc1). Compile
tested using OMAP and x86 generic defconfigs.

Tested on OMAP3 Beagleboard (ES2.x).
Need testing on platforms other than OMAP, because of the impact on the
device insertion/removal in device_pm_add/remove

OK

If that were my code, I'd probably change a couple of things more, but
it looks good enough to me to take as is.  I'm going to push this patchset
for 3.2.

Thanks a lot for your hard work on it,
Rafael