[PATCH 1/2] mfd: rtsx_usb: Fix runtime PM deadlock

[Roger Tseng <rogerable@realtek.com>]

sd_set_power_mode() in derived module drivers/mmc/host/rtsx_usb_sdmmc.c
acquires dev_mutex and then calls pm_runtime_get_sync() to make sure the
device is awake while initializing a newly inserted card. Once it is
called during suspending state and explicitly before rtsx_usb_suspend()
acquires the same dev_mutex, both routine deadlock and further hang the
driver because pm_runtime_get_sync() waits the pending PM operations.

Fix this by using an empty suspend method. mmc_core always turns the
LED off after a request is done and thus it is ok to remove the only
rtsx_usb_turn_off_led() here.

Cc: <stable@vger.kernel.org> # v3.16+
Fixes: 730876be2566 ("mfd: Add realtek USB card reader driver")
Signed-off-by: Roger Tseng <rogerable@realtek.com>
---
 drivers/mfd/rtsx_usb.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/drivers/mfd/rtsx_usb.c b/drivers/mfd/rtsx_usb.c
index dbdd0faeb6ce..076694126e5d 100644
--- a/drivers/mfd/rtsx_usb.c
+++ b/drivers/mfd/rtsx_usb.c
@@ -687,15 +687,6 @@ static int rtsx_usb_suspend(struct usb_interface *intf, pm_message_t message)
 	dev_dbg(&intf->dev, "%s called with pm message 0x%04x\n",
 			__func__, message.event);
 
-	/*
-	 * Call to make sure LED is off during suspend to save more power.
-	 * It is NOT a permanent state and could be turned on anytime later.
-	 * Thus no need to call turn_on when resunming.
-	 */
-	mutex_lock(&ucr->dev_mutex);
-	rtsx_usb_turn_off_led(ucr);
-	mutex_unlock(&ucr->dev_mutex);
-
 	return 0;
 }
 
-- 
2.1.3