lkml.org 
[lkml]   [2012]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC][PATCH v3 1/3] runtime interpreted power sequences
    On 07/30/2012 09:44 AM, Rob Herring wrote:
    > On 07/27/2012 07:05 AM, Alexandre Courbot wrote:
    >> Some device drivers (panel backlights especially) need to follow precise
    >> sequences for powering on and off, involving gpios, regulators, PWMs
    >> with a precise powering order and delays to respect between each steps.
    >> These sequences are board-specific, and do not belong to a particular
    >> driver - therefore they have been performed by board-specific hook
    >> functions to far.
    >>
    >> With the advent of the device tree and of ARM kernels that are not
    >> board-tied, we cannot rely on these board-specific hooks anymore but
    >> need a way to implement these sequences in a portable manner. This patch
    >> introduces a simple interpreter that can execute such power sequences
    >> encoded either as platform data or within the device tree.
    >>
    >
    > Why not? We'll always have some amount of board code. The key is to
    > limit parts that are just data. I'm not sure this is something that
    > should be in devicetree.
    >
    > Perhaps what is needed is a better way to hook into the driver like
    > notifiers?

    I would answer that by asking the reverse question - why should we have
    to put some data in DT, and some data into board files still?

    I'd certainly argue that the sequence of which GPIOs/regulators/PWMs to
    manipulate is just data.

    To be honest, if we're going to have to put some parts of a board's
    configuration into board files anyway, then the entirety of DT seems
    useless; I'd far rather see all the configuration in one cohesive place
    than arbitrarily split into two/n different locations - that would make
    everything harder to maintain.


    \
     
     \ /
      Last update: 2012-07-31 01:01    [from the cache]
    ©2003-2011 Jasper Spaans