linux-kernel - Re: [PATCH v8 01/34] opp: Add dev_pm_opp

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Date:   Wed, 18 Aug 2021 18:55:22 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        Peter Chen <peter.chen@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Richard Weinberger <richard@....at>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Lucas Stach <dev@...xeye.de>, Stefan Agner <stefan@...er.ch>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        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-spi@...r.kernel.org,
        linux-pwm@...r.kernel.org, linux-mtd@...ts.infradead.org,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        DTML <devicetree@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v8 01/34] opp: Add dev_pm_opp_sync() helper

18.08.2021 12:41, Ulf Hansson пишет:
> On Wed, 18 Aug 2021 at 11:14, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>>
>> On 18-08-21, 10:29, Ulf Hansson wrote:
>>> Me and Dmitry discussed adding a new genpd callback for this. I agreed
>>> that it seems like a reasonable thing to add, if he insists.

Either way gives the equal result. The new callback allows to remove the
boilerplate dev_pm_opp_set_rate(clk_get_rate() code from the rpm-resume
of consumer devices, that's it.

>>> The intent was to invoke the new callback from __genpd_dev_pm_attach()
>>> when the device has been attached to its genpd. This allows the
>>> callback, to invoke clk_get_rate() and then dev_pm_opp_set_rate(), to
>>> update the vote according to the current state of the HW.
>>
>> I wouldn't call dev_pm_opp_set_rate() from there, since it means
>> configure and enable (both) for different resources, clk, regulator,
>> genpd, etc..
> 
> Right, good point!
> 
> dev_pm_opp_set_rate() is best called from consumer drivers, as they
> need to be in control.
>> What we need here is just configure. So something like this then:
The intent wasn't to use dev_pm_opp_set_rate() from
__genpd_dev_pm_attach(), but to set genpd->rpm_pstate in accordance to
the h/w configuration.

On Tegra we have a chain of PDs and it's not trivial to convert the
device's OPP into pstate because only the parent domain can translate
the required OPP.

Viresh, please take a look at what I did in [1]. Maybe it could be done
in another way.

[1]
https://patchwork.ozlabs.org/project/linux-tegra/patch/20210701232728.23591-3-digetx@gmail.com/