linux-kernel - Re: [PATCH 3/3] ARM: tegra: Pass multiple versions in opp-supported-hw property

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Message-ID: <cbfa012b-8f50-e460-972c-c51fa52bb858@gmail.com>
Date:   Mon, 31 Aug 2020 12:54:19 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>,
        Stephan Gerhold <stephan@...hold.net>,
        devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] ARM: tegra: Pass multiple versions in
 opp-supported-hw property

31.08.2020 11:41, Viresh Kumar пишет:
> On 31-08-20, 10:54, Dmitry Osipenko wrote:
>> 31.08.2020 07:39, Viresh Kumar пишет:
>> ...
>>>>> Dmitry, I think there is further scope of simplifying stuff here by
>>>>> using the opp-microvolt-<name> property and corresponding
>>>>> dev_pm_opp_set_prop_name() call.
>>>
>>> Any inputs on this Dmitry ?
>>
>> Could you please give an example?
> 
> There are many users of it in the kernel. grep for "opp-microvolt-" in
> the DT files and you will see.
> 
> The use of this property is to specific multiple microvolt properties
> to the same frequency without a need to create separate nodes for them
> all. The right microvolt property will be selected based on the call
> made to dev_pm_opp_set_prop_name(), search for that too in kernel.
> 

It's not clear to me how it could be applicable to the Tegra CPU OPP
because Tegra depends on a combination of SPEEDO + PROCESS versions.

It's not like all voltages are the same for all OPPs that have the same
PROCESS ID, otherwise it indeed would be nice to have
"opp-microvolt-process0", but unfortunately this variant is not suitable
for Tegra because some freqs have different voltages using the same
PROCESS ID and the same applies to the SPEEDO ID.