linux-kernel - Re: [PATCH v2 11/48] opp: Add dev_pm_opp_find_level

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Date:   Wed, 23 Dec 2020 23:37:47 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-media@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 11/48] opp: Add dev_pm_opp_find_level_ceil()

23.12.2020 07:19, Viresh Kumar пишет:
> On 22-12-20, 22:15, Dmitry Osipenko wrote:
>> 22.12.2020 09:42, Viresh Kumar пишет:
>>> On 17-12-20, 21:06, Dmitry Osipenko wrote:
>>>> Add a ceil version of the dev_pm_opp_find_level(). It's handy to have if
>>>> levels don't start from 0 in OPP table and zero usually means a minimal
>>>> level.
>>>>
>>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>>
>>> Why doesn't the exact version work for you here ?
>>>
>>
>> The exact version won't find OPP for level=0 if levels don't start with
>> 0, where 0 means that minimal level is desired.
> 
> Right, but why do you need to send 0 for your platform ?
> 

To put power domain into the lowest performance state when device is idling.

https://elixir.bootlin.com/linux/v5.10-rc2/source/drivers/opp/core.c#L897

https://elixir.bootlin.com/linux/v5.10-rc2/source/drivers/opp/core.c#L785

Also please see patch 32, tegra_clock_runtime_suspend().