linux-kernel - Re: [PATCH net-next] net: fec: add pm runtime force suspend and resume support

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Message-ID: <YxdcPJNgM+txE+8A@lunn.ch>
Date:   Tue, 6 Sep 2022 16:42:04 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     wei.fang@....com
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: fec: add pm runtime force suspend and
 resume support

On Tue, Sep 06, 2022 at 04:39:23PM +0800, wei.fang@....com wrote:
> From: Wei Fang <wei.fang@....com>
> 
> Force mii bus into runtime pm suspend state during device suspends,
> since phydev state is already PHY_HALTED, and there is no need to
> access mii bus during device suspend state. Then force mii bus into
> runtime pm resume state when device resumes.

Have you tested this with an Ethernet switch hanging off the MDIO bus?
It has a life cycle of its own, and i'm not sure it is guaranteed that
the switch is suspended before the FEC. That is why the MDIO
read/write functions have there own runtime PM calls, they can be used
when the interface itself is down.

     Andrew