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Subject: Re: [PATCH v1 00/30] Introduce core voltage scaling for NVIDIA
 Tegra20/30 SoCs
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Alan Stern <stern@rowland.harvard.edu>,
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        Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
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        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Lee Jones <lee.jones@linaro.org>,
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        Rob Herring <robh+dt@kernel.org>,
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From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <1f644c22-991c-7d27-b147-f12489e7ed7d@gmail.com>
Date:   Fri, 13 Nov 2020 19:00:57 +0300
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13.11.2020 17:45, Ulf Hansson пишет:
> On Thu, 12 Nov 2020 at 23:14, Dmitry Osipenko <digetx@gmail.com> wrote:
>>
>> 12.11.2020 23:43, Thierry Reding пишет:
>>>> The difference in comparison to using voltage regulator directly is
>>>> minimal, basically the core-supply phandle is replaced is replaced with
>>>> a power-domain phandle in a device tree.
>>> These new power-domain handles would have to be added to devices that
>>> potentially already have a power-domain handle, right? Isn't that going
>>> to cause issues? I vaguely recall that we already have multiple power
>>> domains for the XUSB controller and we have to jump through extra hoops
>>> to make that work.
>>
>> I modeled the core PD as a parent of the PMC sub-domains, which
>> presumably is a correct way to represent the domains topology.
>>
>> https://gist.github.com/digetx/dfd92c7f7e0aa6cef20403c4298088d7
> 
> That could make sense, it seems.
> 
> Anyway, this made me realize that
> dev_pm_genpd_set_performance_state(dev) returns -EINVAL, in case the
> device's genpd doesn't have the ->set_performance_state() assigned.
> This may not be correct. Instead we should likely consider an empty
> callback as okay and continue to walk the topology upwards to the
> parent domain, etc.
> 
> Just wanted to point this out. I intend to post a patch as soon as I
> can for this.

Thank you, I was also going to make the same change, but haven't
bothered to do it so far. Please feel free to CC me on the patch.