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

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Message-ID: <Zdot-Mqw1z4ZEo8v@pengutronix.de>
Date: Sat, 24 Feb 2024 18:57:12 +0100
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Florian Fainelli <florian.fainelli@...adcom.com>
Cc: "Russell King (Oracle)" <linux@...linux.org.uk>,
	Andrew Lunn <andrew@...n.ch>, 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>, 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 09:53:06AM -0800, Florian Fainelli wrote:
> On 2/23/24 05:26, Russell King (Oracle) wrote:
> > 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.
> 
> That sounds like a good approach to me. The additional callback also helps
> figure out which drivers use the API and it should be simpler to audit for
> changes in the future, too.

At this point I need help to understand how to proceed.
What exactly do you have in mind? Some description like following would
be helpful:
Add callback with name phy_link_set_eee(), which should be executed in
function bla/blup..

Regards,
Oleksij
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