linux-kernel - Re: [RFC PATCH v1 6/6] soc/tegra: regulators: Add regulators coupler for Tegra30

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Date:   Wed, 8 May 2019 16:27:42 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1 6/6] soc/tegra: regulators: Add regulators coupler
 for Tegra30

08.05.2019 10:58, Mark Brown пишет:
> On Sun, Apr 14, 2019 at 08:59:39PM +0300, Dmitry Osipenko wrote:
>> Add regulators coupler for Tegra30 SoC's that performs voltage balancing
>> of a coupled regulators and thus provides voltage scaling functionality.
> 
> Same here, what are the requirements this is implementing?
> 

There are two coupled regulators: CPU and CORE.

Constraints:

1) The max-spread voltage is 300mV.

2) CORE voltage must be higher than the CPU by at least N mV, where N
varies depending on the CPU voltage.

3) There is a constraint on the maximum CORE voltage depending on
hardware model/revision (cpu_speedo_id) where a higher voltages
apparently may cause physical damage, so it's better to hardcode the
limitation in the code rather than to rely on a board's device-tree
description. This constraint is quite vaguely defined in the downstream
kernel, I'm not really sure if it's solely about the hardware safety.