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Date: Fri, 23 Feb 2024 13:26:18 +0000
From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Oleksij Rempel <o.rempel@pengutronix.de>, Wei Fang <wei.fang@nxp.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	Florian Fainelli <florian.fainelli@broadcom.com>,
	kernel@pengutronix.de, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, Shenwei Wang <shenwei.wang@nxp.com>,
	Clark Wang <xiaoning.wang@nxp.com>,
	NXP Linux Team <linux-imx@nxp.com>
Subject: Re: [PATCH net-next v6 5/8] net: phy: Immediately call adjust_link
 if only tx_lpi_enabled changes
Message-ID: <Zdic+ua5LnWxjLPn@shell.armlinux.org.uk>
References: <20240223094425.691209-1-o.rempel@pengutronix.de>
 <20240223094425.691209-6-o.rempel@pengutronix.de>
 <Zdh1nMWZDynP/AMc@shell.armlinux.org.uk>
 <84e1368d-ec6a-48af-945b-509528c45dff@lunn.ch>
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Sender: Russell King (Oracle) <linux@armlinux.org.uk>

On Fri, Feb 23, 2024 at 02:17:59PM +0100, Andrew Lunn wrote:
> 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.

Would it be better to have a separate callback for EEE state (as I
mentioned in another comment on this series?) That would be better
for future SmartEEE support.

-- 
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