linux-kernel - [PATCH 5.15 03/76] net: lan78xx: fix runtime PM count underflow on link stop

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Message-ID: <20240313164223.615640-4-sashal@kernel.org>
Date: Wed, 13 Mar 2024 12:41:10 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Oleksij Rempel <o.rempel@...gutronix.de>,
	Jiri Pirko <jiri@...dia.com>,
	"David S . Miller" <davem@...emloft.net>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 03/76] net: lan78xx: fix runtime PM count underflow on link stop

From: Oleksij Rempel <o.rempel@...gutronix.de>

[ Upstream commit 1eecc7ab82c42133b748e1895275942a054a7f67 ]

Current driver has some asymmetry in the runtime PM calls. On lan78xx_open()
it will call usb_autopm_get() and unconditionally usb_autopm_put(). And
on lan78xx_stop() it will call only usb_autopm_put(). So far, it was
working only because this driver do not activate autosuspend by default,
so it was visible only by warning "Runtime PM usage count underflow!".

Since, with current driver, we can't use runtime PM with active link,
execute lan78xx_open()->usb_autopm_put() only in error case. Otherwise,
keep ref counting high as long as interface is open.

Fixes: 55d7de9de6c3 ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet device driver")
Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
Reviewed-by: Jiri Pirko <jiri@...dia.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/usb/lan78xx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index c8b42892655a1..77cb30259dca7 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2960,7 +2960,8 @@ static int lan78xx_open(struct net_device *net)
 done:
 	mutex_unlock(&dev->dev_mutex);
 
-	usb_autopm_put_interface(dev->intf);
+	if (ret < 0)
+		usb_autopm_put_interface(dev->intf);
 
 	return ret;
 }
-- 
2.43.0