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

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Date:   Mon, 31 Aug 2020 16:34:08 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
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

On 31-08-20, 12:54, Dmitry Osipenko wrote:
> 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.

How exactly do you know what voltage belongs to a particular OPP ?

		opp@...000000 {
			clock-latency-ns = <400000>;
			opp-supported-hw = <0x0F 0x0003>;
			opp-hz = /bits/ 64 <216000000>;
			opp-microvolt-fast-process0 = <750000 750000 1125000>;
			opp-microvolt-slow-process0 = <750000 850000 1125000>;

		};

		opp@...000000 {
			clock-latency-ns = <400000>;
			opp-supported-hw = <0x0F 0x0003>;
			opp-hz = /bits/ 64 <312000000>;
			opp-microvolt-fast-process0 = <750000 750000 1125000>;
			opp-microvolt-slow-process0 = <750000 850000 1125000>;
		};

You can make any combinations of such names that come from speedo,
process, or something else. If you can get this done as a fixed
formula then it is workable.

-- 
viresh