linux-kernel - RE: [PATCH net-next 3/3] net: fec: reset phy on resume after power-up

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Date:   Thu, 16 Dec 2021 04:52:39 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Francesco Dolcini <francesco.dolcini@...adex.com>,
        Andrew Lunn <andrew@...n.ch>,
        "Russell King (Oracle)" <linux@...linux.org.uk>
CC:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Philippe Schenker <philippe.schenker@...adex.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next 3/3] net: fec: reset phy on resume after power-up


> -----Original Message-----
> From: Francesco Dolcini <francesco.dolcini@...adex.com>
> Sent: 2021年12月15日 19:02
> To: Andrew Lunn <andrew@...n.ch>; Russell King (Oracle)
> <linux@...linux.org.uk>; Joakim Zhang <qiangqing.zhang@....com>
> Cc: Russell King (Oracle) <linux@...linux.org.uk>; Francesco Dolcini
> <francesco.dolcini@...adex.com>; Philippe Schenker
> <philippe.schenker@...adex.com>; netdev@...r.kernel.org; Joakim Zhang
> <qiangqing.zhang@....com>; David S . Miller <davem@...emloft.net>;
> Heiner Kallweit <hkallweit1@...il.com>; Jakub Kicinski <kuba@...nel.org>;
> Fabio Estevam <festevam@...il.com>; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH net-next 3/3] net: fec: reset phy on resume after
> power-up
> 
[...]

> On Wed, Dec 15, 2021 at 10:25:14AM +0000, Joakim Zhang wrote:
> > As I mentioned before, both mac and phylib have not taken PHY reset
> > into consideration during system suspend/resume scenario. As Andrew
> > suggested, you could move this into phy driver suspend function, this
> > is a corner case. One point I don't understand, why do you reject to
> > assert reset signal during system suspended?
> See my answer to Andrew above, in short asserting the reset without
> disabling the regulator will create a regression on the power consumption.

As I can see, when system suspended, PHY is totally powered down, since you disable the 
regulator. At this situation, if you assert reset signal, you mean it will increase the power
consumption? PHY is totally powered down, why assert reset signal still affect PHY? 
 
Best Regards,
Joakim Zhang