linux-kernel - [PATCH] sdio: fix suspend/resume regression

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Date:	Wed, 13 Oct 2010 09:31:56 +0200
From:	Ohad Ben-Cohen <ohad@...ery.com>
To:	<linux-mmc@...r.kernel.org>
Cc:	Sven Neumann <s.neumann@...mfeld.com>, Chris Ball <cjb@...top.org>,
	Nicolas Pitre <nico@...xnic.net>,
	<libertas-dev@...ts.infradead.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Daniel Mack <daniel@...aq.de>,
	Colin Cross <ccross@...roid.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	Ohad Ben-Cohen <ohad@...ery.com>, <stable@...nel.org>
Subject: [PATCH] sdio: fix suspend/resume regression

Fix SDIO suspend/resume regression introduced by
4c2ef25fe0b847d2ae818f74758ddb0be1c27d8e "mmc: fix all hangs related to
mmc/sd card insert/removal during suspend/resume":

[ 5647.295953] PM: Syncing filesystems ... done.
[ 5647.318792] Freezing user space processes ... (elapsed 0.01 seconds) done.
[ 5647.337048] Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done.
[ 5647.356915] Suspending console(s) (use no_console_suspend to debug)
[ 5647.366651] pm_op(): platform_pm_suspend+0x0/0x5c returns -38
[ 5647.366671] PM: Device pxa2xx-mci.0 failed to suspend: error -38
[ 5647.367082] PM: Some devices failed to suspend

4c2ef25fe0b847d2ae818f74758ddb0be1c27d8e moved the card removal/insertion
mechanism out of MMC's suspend/resume path and into pm notifiers
(mmc_pm_notify), and that broke SDIO's expectation that mmc_suspend_host()
will remove the card, and squash the error, in case -ENOSYS is returned
from the bus suspend handler (mmc_sdio_suspend() in this case).

mmc_sdio_suspend() is using this whenever at least one of the card's SDIO
function drivers does not have suspend/resume handlers - in that case
it is agreed to force removal of the entire card.

This patch fixes this regression by trivially bringing back that part of
mmc_suspend_host(), which was removed by 4c2ef25fe0b847d2ae818f74758ddb0be1c27d8e.

Reported-and-tested-by: Sven Neumann <s.neumann@...mfeld.com>
Signed-off-by: Ohad Ben-Cohen <ohad@...ery.com>
Cc: Maxim Levitsky <maximlevitsky@...il.com>
Cc: <stable@...nel.org>
--

It may still be desired to further clean this area up by using the card
removal mechanism in mmc_pm_notify() for SDIO as well.

To use mmc_pm_notify's card-removal code also for SDIO, we need it
to check if all the SDIO functions have suspend handlers. That
would probably make us add a new bus_ops handler (something like
host->bus_ops->remove_card_on_suspend ?).

It's starting to get a bit complicated though, and I'm not sure it
would make the code a lot more readable.

In addition, this would still not work for drivers like libertas sdio,
which do have a suspend handler, but sometimes let it return -ENOSYS,
expecting mmc_suspend_host() to remove the card and squash the error.
For those cases, we still need the old card-removal logic in mmc_suspend_host().

This brings up a question whether libertas_sdio really needs this
functionality; When MMC_PM_KEEP_POWER is not needed, can't it just return 0
(and as a result the card will be powered down, but not removed) ?

Until we have an agreement on this, I suggest we at least fix the
regression with this patch.

Thanks Sven Neumann for reporting and testing the issue and this patch.

 drivers/mmc/core/core.c |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index c94565d..515ff39 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1682,6 +1682,19 @@ int mmc_suspend_host(struct mmc_host *host)
 	if (host->bus_ops && !host->bus_dead) {
 		if (host->bus_ops->suspend)
 			err = host->bus_ops->suspend(host);
+		if (err == -ENOSYS || !host->bus_ops->resume) {
+			/*
+			 * We simply "remove" the card in this case.
+			 * It will be redetected on resume.
+			 */
+			if (host->bus_ops->remove)
+				host->bus_ops->remove(host);
+			mmc_claim_host(host);
+			mmc_detach_bus(host);
+			mmc_release_host(host);
+			host->pm_flags = 0;
+			err = 0;
+		}
 	}
 	mmc_bus_put(host);

-- 
1.7.0.4

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