linux-kernel - Re: [PATCH v2 43/48] ARM: tegra: Add OPP tables and power domains to Tegra20 device-tree

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Message-ID: <e3ed3b17-b549-860b-1dc2-cb1d6eb3b90b@gmail.com>
Date:   Tue, 22 Dec 2020 22:24:33 +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 43/48] ARM: tegra: Add OPP tables and power domains to
 Tegra20 device-tree

22.12.2020 08:47, Viresh Kumar пишет:
> On 17-12-20, 21:06, Dmitry Osipenko wrote:
>> diff --git a/arch/arm/boot/dts/tegra20-peripherals-opp.dtsi b/arch/arm/boot/dts/tegra20-peripherals-opp.dtsi
>> index b84afecea154..7e015cdfbc55 100644
>> --- a/arch/arm/boot/dts/tegra20-peripherals-opp.dtsi
>> +++ b/arch/arm/boot/dts/tegra20-peripherals-opp.dtsi
>> @@ -1,6 +1,46 @@
>>  // SPDX-License-Identifier: GPL-2.0
>>  
>>  / {
>> +	core_opp_table: core-power-domain-opp-table {
>> +		compatible = "operating-points-v2";
>> +		opp-shared;
>> +
>> +		core_opp_950: opp@...000 {
>> +			opp-microvolt = <950000 950000 1300000>;
>> +			opp-level = <950000>;
>> +		};
> 
> I am not sure I fully understand this, why does it have both microvolt and level
> properties ?
> 

The level is used by everything related to GENPD, while voltage is used
by the domain driver.

I think it's cleaner to separate the level from voltage, even though
they are set to the same values, which is done purely for convenience.
The 0,1,2,3 levels are meaningless in the context of this power domain,
while voltages make total sense.