linux-kernel - Re: [RFC/RFT][PATCH v2 3/7] PM / sleep: Make async suspend/resume of devices use device links

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Date:   Sat, 10 Sep 2016 15:31:45 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM list <linux-pm@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Mark Brown <broonie@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "Luis R. Rodriguez" <mcgrof@...e.com>
Subject: Re: [RFC/RFT][PATCH v2 3/7] PM / sleep: Make async suspend/resume of
 devices use device links

On Thu, Sep 08, 2016 at 11:28:33PM +0200, Rafael J. Wysocki wrote:
> Make the device suspend/resume part of the core system
> suspend/resume code use device links to ensure that supplier
> and consumer devices will be suspended and resumed in the right
> order in case of async suspend/resume.
> 
> The idea, roughly, is to use dpm_wait() to wait for all consumers
> before a supplier device suspend and to wait for all suppliers
> before a consumer device resume.

For devices with a parent/child relationship, if the child does not
utilize direct_complete, the parent is not allowed to utilize it
either and is runtime resumed upon system sleep.

Don't we need the same for supplier/consumer relationships?

The code enforcing this is in __device_suspend() and looks like this:

	if (parent) {
		spin_lock_irq(&parent->power.lock);

		dev->parent->power.direct_complete = false;
		if (dev->power.wakeup_path
		    && !dev->parent->power.ignore_children)
			dev->parent->power.wakeup_path = true;

		spin_unlock_irq(&parent->power.lock);
	}

I guess we need to iterate over the suppliers here and execute
the block for each of them.

Thanks,

Lukas