Re: [PATCH v4 0/3] DEVFREQ, DVFS framework for non-CPU devices

[Kevin Hilman <khilman@ti.com>]

MyungJoo Ham <myungjoo.ham@samsung.com> writes:

> On Wed, Aug 3, 2011 at 7:02 AM, Kevin Hilman <khilman@ti.com> wrote:

[...]

>> Maybe I'm not understanding the usage of it fully, but that seems like
>> hard-coding policy into the framework that might not be appropriate.
>> For example, what if there are other devices with constraints such that
>> they cannot currently scale frequency/voltage?
>>
>> Mabye MyungJoo can explain in more detail the usecases for tickle?
>
> Tickle is not for QoS between devices. It is for faster reaction to
> (human) user inputs at DVFS side where waiting for DVFS's reaction
> takes too much time and reducing polling interval costs too much. 

This is exactly what quality of service (QoS) is about.

The user (whether it's a human user input or another device) has low
quality and expects higher quality.  It wants to request better quality,
so it needs a way to request it.   

The proposed "tickle" approach proposed here is simply a "request max
frequency for duration X" QoS request.

Kevin