linux-kernel - Re: [PATCH net-next v6 5/8] net: phy: Immediately call adjust_link if only tx_lpi

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Date: Fri, 23 Feb 2024 14:17:59 +0100
From: Andrew Lunn <andrew@...n.ch>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>, Wei Fang <wei.fang@....com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	kernel@...gutronix.de, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, Shenwei Wang <shenwei.wang@....com>,
	Clark Wang <xiaoning.wang@....com>,
	NXP Linux Team <linux-imx@....com>
Subject: Re: [PATCH net-next v6 5/8] net: phy: Immediately call adjust_link
 if only tx_lpi_enabled changes

On Fri, Feb 23, 2024 at 10:38:20AM +0000, Russell King (Oracle) wrote:
> On Fri, Feb 23, 2024 at 10:44:22AM +0100, Oleksij Rempel wrote:
> > +static void phy_ethtool_set_eee_noneg(struct phy_device *phydev,
> > +				      struct ethtool_keee *data)
> > +{
> > +	if (phydev->eee_cfg.tx_lpi_enabled !=
> > +	    data->tx_lpi_enabled) {
> > +		eee_to_eeecfg(data, &phydev->eee_cfg);
> > +		phydev->enable_tx_lpi = eeecfg_mac_can_tx_lpi(&phydev->eee_cfg);
> > +		if (phydev->link)
> > +			phy_link_up(phydev);
> 
> I'm not convinced this is a good idea. Hasn't phylib previously had
> the guarantee that the link will go down between two link-up events?
> So calling phy_link_up() may result in either the MAC driver ignoring
> it, or modifying registers that are only supposed to be modified while
> the MAC side is down.

When auto-neg is used, we expect the link to go down and come back up
again.

Here we are dealing with the case that autoneg is not used. The MAC
needs informing somehow. If we want to preserve the down/up, we could
call phy_link_down() and then phy_link_up() back to back.

     Andrew