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

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Message-ID: <ab874e0c-903a-fc3b-d33b-54a7a9f0e109@gmail.com>
Date:   Fri, 1 Oct 2021 22:15:29 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        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()

01.10.2021 15:50, Ulf Hansson пишет:
> 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!?

That is correct, all drivers are tegra-specific in this series. External
devices are attached to the internal SoC devices and this series is
about the SoC power management.

> 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.

Yes, as we already have seen, it's not an easy problem to make PD core
to handle it in a generic way. If there will be a similar demand from
other SoCs, then we may try to solve that problem again.