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

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Date:   Wed, 18 Aug 2021 18:42:08 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Jonathan Hunter <jonathanh@...dia.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        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@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-pm@...r.kernel.org, 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@...r.kernel.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v8 07/34] clk: tegra: Support runtime PM and power domain

On Wed, Aug 18, 2021 at 06:05:21PM +0300, Dmitry Osipenko wrote:
> 18.08.2021 17:07, Thierry Reding пишет:
> > On Tue, Aug 17, 2021 at 04:27:27AM +0300, Dmitry Osipenko wrote:
> > [...]
> >> +struct clk *tegra_clk_register(struct clk_hw *hw)
> >> +{
> >> +	struct platform_device *pdev;
> >> +	struct device *dev = NULL;
> >> +	struct device_node *np;
> >> +	const char *dev_name;
> >> +
> >> +	np = tegra_clk_get_of_node(hw);
> >> +
> >> +	if (!of_device_is_available(np))
> >> +		goto put_node;
> >> +
> >> +	dev_name = kasprintf(GFP_KERNEL, "tegra_clk_%s", hw->init->name);
> >> +	if (!dev_name)
> >> +		goto put_node;
> >> +
> >> +	pdev = of_platform_device_create(np, dev_name, NULL);
> >> +	if (!pdev) {
> >> +		pr_err("%s: failed to create device for %pOF\n", __func__, np);
> >> +		kfree(dev_name);
> >> +		goto put_node;
> >> +	}
> >> +
> >> +	dev = &pdev->dev;
> >> +	pm_runtime_enable(dev);
> >> +put_node:
> >> +	of_node_put(np);
> >> +
> >> +	return clk_register(dev, hw);
> >> +}
> > 
> > This looks wrong. Why do we need struct platform_device objects for each
> > of these clocks? That's going to be a massive amount of platform devices
> > and they will completely mess up sysfs.
> 
> RPM works with a device. It's not a massive amount of devices, it's one
> device for T20 and four devices for T30.

I'm still not sure I understand why we need to call RPM functions on a
clock. And even if they are few, it seems wrong to make these platform
devices.

Perhaps they can be simple struct device:s instead? Ideally they would
also be parented to the CAR so that they appear in the right place in
the sysfs hierarchy.

Thierry

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