linux-kernel - Re: [PATCH v13 02/35] soc/tegra: Add devm_tegra_core_dev_init_opp_table

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Date:   Fri, 1 Oct 2021 14:50:25 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>,
        Viresh Kumar <vireshk@...nel.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        Peter Chen <peter.chen@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Nishanth Menon <nm@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Michael Turquette <mturquette@...libre.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        linux-staging@...ts.linux.dev, linux-pwm@...r.kernel.org,
        linux-mmc <linux-mmc@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        DTML <devicetree@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Richard Weinberger <richard@....at>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Lucas Stach <dev@...xeye.de>, Stefan Agner <stefan@...er.ch>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        David Heidelberg <david@...t.cz>
Subject: Re: [PATCH v13 02/35] soc/tegra: Add devm_tegra_core_dev_init_opp_table_common()

On Mon, 27 Sept 2021 at 00:42, Dmitry Osipenko <digetx@...il.com> wrote:
>
> Only couple drivers need to get the -ENODEV error code and majority of
> drivers need to explicitly initialize the performance state. Add new
> common helper which sets up OPP table for these drivers.
>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  include/soc/tegra/common.h | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/include/soc/tegra/common.h b/include/soc/tegra/common.h
> index af41ad80ec21..5b4a042f60fb 100644
> --- a/include/soc/tegra/common.h
> +++ b/include/soc/tegra/common.h
> @@ -39,4 +39,28 @@ devm_tegra_core_dev_init_opp_table(struct device *dev,
>  }
>  #endif
>
> +/*
> + * This function should be invoked with the enabled runtime PM of the device
> + * in order to initialize performance state properly. Most of Tegra devices
> + * are assumed to be suspended at a probe time and GENPD require RPM to be
> + * enabled to set up the rpm-resume state, otherwise device is active and
> + * performance state is applied immediately. Note that it will initialize
> + * OPP bandwidth if it's wired in a device-tree for this device, which is
> + * undesirable for a suspended device.
> + */
> +static inline int
> +devm_tegra_core_dev_init_opp_table_common(struct device *dev)
> +{
> +       struct tegra_core_opp_params opp_params = {};
> +       int err;
> +
> +       opp_params.init_state = true;
> +
> +       err = devm_tegra_core_dev_init_opp_table(dev, &opp_params);
> +       if (err != -ENODEV)
> +               return err;
> +
> +       return 0;
> +}

Just want to share a few thoughts around these functions.

So, I assume it's fine to call
devm_tegra_core_dev_init_opp_table_common() or
devm_tegra_core_dev_init_opp_table() from consumer drivers during
->probe(), as long as those drivers are tegra specific, which I assume
all are in the series!?

My point is, a cross SoC consumer driver that needs to initiate OPP
tables can get rather messy, if it would need to make one specific
function call per SoC.

That said, I hope we can tackle this as a separate/future problem, so
the series can get merged as is.

> +
>  #endif /* __SOC_TEGRA_COMMON_H__ */
> --
> 2.32.0
>

Kind regards
Uffe