netdev - RE: [EXT] Re: [PATCH v3 1/1] net: phylink: add phylink_set_mac

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Date:   Mon, 10 Oct 2022 14:54:24 +0000
From:   Shenwei Wang <shenwei.wang@....com>
To:     Russell King <linux@...linux.org.uk>
CC:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: RE: [EXT] Re: [PATCH v3 1/1] net: phylink: add phylink_set_mac_pm()
 helper



> -----Original Message-----
> From: Russell King <linux@...linux.org.uk>
> Sent: Saturday, October 8, 2022 2:28 AM
> To: Shenwei Wang <shenwei.wang@....com>
> Cc: Andrew Lunn <andrew@...n.ch>; Heiner Kallweit <hkallweit1@...il.com>;
> David S. Miller <davem@...emloft.net>; Eric Dumazet
> <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>; Paolo Abeni
> <pabeni@...hat.com>; netdev@...r.kernel.org; imx@...ts.linux.dev
> Subject: [EXT] Re: [PATCH v3 1/1] net: phylink: add phylink_set_mac_pm() helper
> 
> Caution: EXT Email
> 
> On Fri, Oct 07, 2022 at 10:42:46AM -0500, Shenwei Wang wrote:
> > +/**
> > + * phylink_set_mac_pm() - set phydev->mac_managed_pm to true
> > + * @pl: a pointer to a &struct phylink returned from phylink_create()
> > + *
> > + * Set the phydev->mac_managed_pm, which is under the phylink
> > +instance
> > + * specified by @pl, to true. This is to indicate that the MAC driver
> > +is
> > + * responsible for PHY PM.
> > + *
> > + * The function can be called in the end of net_device_ops ndo_open()
> > +method
> > + * or any place after phy is connected.
> 
> May I suggest a different wording:
> 
> "If the driver wishes to use this feature, this function should be called each time
> after the driver connects a PHY with phylink."
> 

Your wording is much better. Will use it in the next version.

> This makes it clear that after one of:
> 
> phylink_connect_phy()
> phylink_of_phy_connect()
> phylink_fwnode_phy_connect()
> 
> has been called, and the driver wants to call this function, the driver needs to
> call this every time just after the driver connects a PHY.
> 
> The alternative is that we store this information away when this function is
> called, and always update the phydev when one is connected.
> 
> There is also the question whether this should also be applied to PHYs on SFP
> modules or not. Should a network driver using mac managed PM, but also
> supports SFPs, and a copper SFP is plugged in with an accessible PHY, what
> should happen if the system goes into a low power state?
> 

In theory, the SFP should be covered by this patch too. Since the resume flow is
Controlled by the value of phydev->mac_managed_pm, it should work in the same
way after the phydev is linked to the SFP phy instance.

Regards,
Shenwei

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