linux-kernel - Re: "PM / wakeup: Show wakeup sources stats in sysfs" causes boot warnings

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Message-ID: <20190814084014.GB52127@atomide.com>
Date:   Wed, 14 Aug 2019 01:40:14 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Qian Cai <cai@....pw>, Tri Vo <trong@...roid.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rafael@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: "PM / wakeup: Show wakeup sources stats in sysfs" causes boot
 warnings

* Stephen Boyd <swboyd@...omium.org> [691231 23:00]:
> I also notice that device_set_wakeup_capable() has a check to see if the
> device is registered yet and it skips creating sysfs entries for the
> device if it isn't created in sysfs yet. Why? Just so it can be called
> before the device is created? I guess the same logic is handled by
> dpm_sysfs_add() if the device is registered after calling
> device_set_wakeup_*().

Hmm just guessing.. It's maybe because drivers can enable and disable
the wakeup capability at any point for example like driver/net drivers
do based on WOL etc?

> There's two approaches I see:
> 
> 	1) Do a similar check for device_set_wakeup_enable() and skip
> 	adding the wakeup class until dpm_sysfs_add().
> 
> 	2) Find each case where this happens and only call wakeup APIs
> 	on the device after the device is added.
> 
> I guess it's better to let devices have wakeup modified on them before
> they're registered with the device core?

I think we should at least initially handle case #1 above as multiple
places otherwise seem to break. Then maybe we could add a warning to
help fix all the #2 cases if needed?

Regards,

Tony