linux-kernel - Re: [PATCH v8 07/34] clk: tegra: Support runtime PM and power domain

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Date:   Sat, 21 Aug 2021 20:45:54 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>
Cc:     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 07/34] clk: tegra: Support runtime PM and power domain

20.08.2021 16:08, Ulf Hansson пишет:
...
>> I suppose if there's really no good way of doing this other than
>> providing a struct device, then so be it. I think the cleaned up sysfs
>> shown in the summary above looks much better than what the original
>> would've looked like.
>>
>> Perhaps an additional tweak to that would be to not create platform
>> devices. Instead, just create struct device. Those really have
>> everything you need (.of_node, and can be used with RPM and GENPD). As I
>> mentioned earlier, platform device implies a CPU-memory-mapped bus,
>> which this clearly isn't. It's kind of a separate "bus" if you want, so
>> just using struct device directly seems more appropriate.
> 
> Just a heads up. If you don't use a platform device or have a driver
> associated with it for probing, you need to manage the attachment to
> genpd yourself. That means calling one of the dev_pm_domain_attach*()
> APIs, but that's perfectly fine, ofcourse.
> 
>>
>> We did something similar for XUSB pads, see drivers/phy/tegra/xusb.[ch]
>> for an example of how that was done. I think you can do something
>> similar here.

We need a platform device because we have a platform device driver that
must be bound to the device, otherwise PMC driver state won't be synced
since it it's synced after all drivers of devices that reference PMC
node in DT are probed.