On Sat, Sep 10, 2016 at 3:31 PM, Lukas Wunner [off-list ref] wrote:

On Thu, Sep 08, 2016 at 11:28:33PM +0200, Rafael J. Wysocki wrote:

quoted

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.

You are right about the direct_complete thing, but the wakeup_path
thing is another matter.  It is about forwarding wakeup signals up the
hierarchy and I'd confine it to parents at least for the time being.

Thanks,
Rafael