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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Tue, 12 Jan 2021 14:30:39 +0100
Message-ID: <CAPDyKFrj-8WwK1U7KJaCiWkt2bsohgoEnqhQ4sgwjZzZfX2iMA@mail.gmail.com>
Subject: Re: [PATCH v2 29/48] soc/tegra: pmc: Link domains to the parent Core domain
To:     Dmitry Osipenko <digetx@gmail.com>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Kevin Hilman <khilman@kernel.org>,
        Peter De Schrijver <pdeschrijver@nvidia.com>,
        Viresh Kumar <vireshk@kernel.org>,
        Stephen Boyd <sboyd@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-tegra <linux-tegra@vger.kernel.org>
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- trimmed cc-list

On Thu, 17 Dec 2020 at 19:07, Dmitry Osipenko <digetx@gmail.com> wrote:
>
> The Core domain is a parent of PMC power domains, hence PMC domains
> should be set up as a sub-domains of the parent (Core) domain if
> "power-domains" phandle presents in a device-tree node of PMC domain.
>
> This allows to propagate GENPD performance changes to the parent Core
> domain if performance change is applied to PMC domain.
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/soc/tegra/pmc.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
> index 4f96dc7745c4..1a659d1c06d7 100644
> --- a/drivers/soc/tegra/pmc.c
> +++ b/drivers/soc/tegra/pmc.c
> @@ -1236,6 +1236,7 @@ static int tegra_powergate_add(struct tegra_pmc *pmc, struct device_node *np)
>  static int tegra_powergate_init(struct tegra_pmc *pmc,
>                                 struct device_node *parent)
>  {
> +       struct of_phandle_args child_args, parent_args;
>         struct device_node *np, *child;
>         int err = 0;
>
> @@ -1249,6 +1250,24 @@ static int tegra_powergate_init(struct tegra_pmc *pmc,
>                         of_node_put(child);
>                         break;
>                 }
> +
> +               if (of_parse_phandle_with_args(child, "power-domains",
> +                                              "#power-domain-cells",
> +                                              0, &parent_args))
> +                       continue;
> +
> +               child_args.np = child;
> +               child_args.args_count = 0;
> +
> +               err = of_genpd_add_subdomain(&parent_args, &child_args);
> +               of_node_put(parent_args.np);
> +               if (err) {
> +                       if (err == -ENOENT)
> +                               err = -EPROBE_DEFER;

Okay. So this special error treatment is needed because
of_genpd_add_subdomain may return -ENOENT, in case the providers for
the parent-domain and child-domain haven't been registered yet.

I suggest we move this into of_genpd_add_subdomain() instead, thus
letting it return -EPROBE_DEFER when there are parent/child nodes
specified in DT, but the providers are lacking.

> +
> +                       of_node_put(child);
> +                       break;
> +               }
>         }
>
>         of_node_put(np);
> --
> 2.29.2
>

Kind regards
Uffe