linux-kernel - Re: [PATCH] PCMCIA / PM: Avoid noirq suspend aborts during suspend-to-idle

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Message-ID: <20180222164532.GA15359@light.dominikbrodowski.net>
Date:   Thu, 22 Feb 2018 17:45:32 +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: Avoid noirq suspend aborts during
 suspend-to-idle

On Wed, Feb 21, 2018 at 01:24:16PM +0100, Rafael J. Wysocki wrote:
> Avoid that by using a new socket state flag, SOCKET_IN_RESUME,
> to indicate that socket_early_resume() has already run for the
> socket in which case socket_suspend() will do minimum handling
> and return 0.

That looks to be *too* minimal: For example, yenta_socket does some
socket set-up in ->init(), which is called by socket_early_resume().
That needs to be undone by ->suspend(). What about this variant
(untested, not even compile-tested)?

Oh, and
	a) does this need -stable tags, and
	b) do you want to push it yourself, or should it go through the
	   PCMCIA tree?

Thanks,
	Dominik

---
From: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Date: Wed, 21 Feb 2018 13:24:16 +0100
Subject: [PATCH] PCMCIA / PM: Avoid noirq suspend aborts during
 suspend-to-idle

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().

Avoid that by using a new socket state flag, SOCKET_IN_RESUME,
to indicate that socket_early_resume() has already run for the
socket in which case socket_suspend() will do minimum handling
and return 0.

This change has been tested on my venerable Toshiba Portege R500
(which is where the problem has been discovered in the first place),
but admittedly I have no PCMCIA cards to test along with the socket
itself.

Fixes: 33e4f80ee69b (ACPI / PM: Ignore spurious SCI wakeups from suspend-to-idle)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
[linux@...inikbrodowski.net: follow same codepaths for both suspend variants; call ->suspend()]
Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>

diff --git a/drivers/pcmcia/cs.c b/drivers/pcmcia/cs.c
index c3b615c94b4b..513b2d4d5b20 100644
--- a/drivers/pcmcia/cs.c
+++ b/drivers/pcmcia/cs.c
@@ -452,17 +452,20 @@ static int socket_insert(struct pcmcia_socket *skt)

 static int socket_suspend(struct pcmcia_socket *skt)
 {
-	if (skt->state & SOCKET_SUSPEND)
+	if ((skt->state & SOCKET_SUSPEND) && !(skt->state & SOCKET_IN_RESUME))
 		return -EBUSY;

 	mutex_lock(&skt->ops_mutex);
-	skt->suspended_state = skt->state;
+	/* store state on first suspend, but not after spurious wakeups */
+	if !(skt->state & SOCKET_IN_RESUME)
+		skt->suspended_state = skt->state;

 	skt->socket = dead_socket;
 	skt->ops->set_socket(skt, &skt->socket);
 	if (skt->ops->suspend)
 		skt->ops->suspend(skt);
 	skt->state |= SOCKET_SUSPEND;
+	skt->state &= ~(SOCKET_IN_RESUME);
 	mutex_unlock(&skt->ops_mutex);
 	return 0;
 }
@@ -475,6 +478,7 @@ static int socket_early_resume(struct pcmcia_socket *skt)
 	skt->ops->set_socket(skt, &skt->socket);
 	if (skt->state & SOCKET_PRESENT)
 		skt->resume_status = socket_setup(skt, resume_delay);
+	skt->state |= SOCKET_IN_RESUME;
 	mutex_unlock(&skt->ops_mutex);
 	return 0;
 }
@@ -484,7 +488,7 @@ static int socket_late_resume(struct pcmcia_socket *skt)
 	int ret = 0;

 	mutex_lock(&skt->ops_mutex);
-	skt->state &= ~SOCKET_SUSPEND;
+	skt->state &= ~(SOCKET_SUSPEND | SOCKET_IN_RESUME);
 	mutex_unlock(&skt->ops_mutex);

 	if (!(skt->state & SOCKET_PRESENT)) {
diff --git a/drivers/pcmcia/cs_internal.h b/drivers/pcmcia/cs_internal.h
index 6765beadea95..03ec43802909 100644
--- a/drivers/pcmcia/cs_internal.h
+++ b/drivers/pcmcia/cs_internal.h
@@ -70,6 +70,7 @@ struct pccard_resource_ops {
 /* Flags in socket state */
 #define SOCKET_PRESENT		0x0008
 #define SOCKET_INUSE		0x0010
+#define SOCKET_IN_RESUME	0x0040
 #define SOCKET_SUSPEND		0x0080
 #define SOCKET_WIN_REQ(i)	(0x0100<<(i))
 #define SOCKET_CARDBUS		0x8000