linux-kernel - Re: [PATCH net v1 1/1] net: lan78xx: fix runtime PM count underflow on link stop

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Date: Wed, 28 Feb 2024 14:18:02 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Woojung Huh <woojung.huh@...rochip.com>, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net v1 1/1] net: lan78xx: fix runtime PM count underflow
 on link stop

Wed, Feb 28, 2024 at 01:45:17PM CET, o.rempel@...gutronix.de wrote:
>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>