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 09:53:06 -0800
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>,
 Andrew Lunn <andrew@...n.ch>
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>, 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 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.
-- 
Florian

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