linux-kernel - Re: [PATCH V2 09/13] OPP: Assert clk

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Message-ID: <20220706063946.pmtkwiyfzxx5ka7h@vireshk-i7>
Date:   Wed, 6 Jul 2022 12:09:46 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 09/13] OPP: Assert clk_count == 1 for single clk
 helpers

On 05-07-22, 19:21, Krzysztof Kozlowski wrote:
> Where is the safety problem with multiple-clocks case?

All these APIs, which I have added the assert to now, are designed
with a single clk/freq in mind. They simply take a clock frequency
value as input and do something based on it. It only works fine with
single clk case, as more information is required for multiple clock
case, a freq value isn't sufficient here. In order to avoid abuse or
accidental use of the wrong API, these WARNs were required.

> And how users of PM OPP API are supposed to iterate/find OPPs they
> want if the API now throws WARN?

We need to provide new APIs for that, as I mentioned in the cover
letter and the other mail I sent you yesterday.

Specifically, if we want to have OPP finder API based on freq value,
then it needs to either have index + freq as input, or an array of
frequencies (one for each clk) as input.

Though I am not sure what you would need at the moment, as you can
also use opp-level for OPPs as they match UFS gears, that was my
understanding from earlier discussion.

-- 
viresh