linux-kernel - Re: [PATCH v1 0/3] Add required-opps support to devfreq passive gov

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Date:   Mon, 24 Jun 2019 15:13:49 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, kernel-team@...roid.com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/3] Add required-opps support to devfreq passive gov

On 21-06-19, 17:34, Saravana Kannan wrote:
> The devfreq passive governor scales the frequency of a "child" device
> based on the current frequency of a "parent" device (not parent/child in
> the sense of device hierarchy). As of today, the passive governor
> requires one of the following to work correctly:
> 1. The parent and child device have the same number of frequencies
> 2. The child device driver passes a mapping function to translate from
>    parent frequency to child frequency.
> 
> When (1) is not true, (2) is the only option right now. But often times,
> all that is required is a simple mapping from parent's frequency to
> child's frequency.
> 
> Since OPPs already support pointing to other "required-opps", add
> support for using that to map from parent device frequency to child
> device frequency. That way, every child device driver doesn't have to
> implement a separate mapping function anytime (1) isn't true.

Can you please provide a real world example with DT code here so I
can understand it better ?

-- 
viresh