linux-kernel - Re: [PATCH] PCMCIA / PM: Combine system resume callbacks

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Message-ID: <20180220213839.GA12082@light.dominikbrodowski.net>
Date:   Tue, 20 Feb 2018 22:38:39 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCMCIA / PM: Combine system resume callbacks

On Tue, Feb 20, 2018 at 12:47:27PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> There is a problem with PCMCIA system resume callbacks with respect
> to suspend-to-idle in which the ->suspend_noirq() callback may be
> invoked after the ->resume_noirq() one without resuming the system
> entirely in some cases.  This doesn't work for PCMCIA because of
> the lack of symmetry between its system suspend and system resume
> "noirq" callbacks.
> 
> The system resume handling in PCMCIA is split between
> socket_early_resume() and socket_late_resume() which are called in
> different phases of system resume and both need to run for
> socket_suspend() (invoked by the system suspend "noirq" callback)
> to work.  Specifically, socket_suspend() returns an error when
> called after socket_early_resume() without socket_late_resume(),
> so if the suspend-to-idle core detects a spurious wakeup event and
> attempts to put the system back to sleep, that is aborted by the
> error coming from socket_suspend().
> 
> This design doesn't follow the power management documentation
> stating that the "noirq" resume callback is expected to reverse
> the changes made by the "noirq" suspend one.  Moreover, I don't see
> a reason for splitting the PCMCIA socket system resume handling this
> way

Unless I am mistaken, this split was introduced by commit
9905d1b411946 . So we should take into account the reasons stated
in that commit message.

Thanks,
	Dominik