netdev - RE: [PATCH net-next 0/9] net: add phylink managed EEE support

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Message-ID: <06dc01db68c8$f5853fa0$e08fbee0$@trustnetic.com>
Date: Fri, 17 Jan 2025 18:17:05 +0800
From: Jiawen Wu <jiawenwu@...stnetic.com>
To: "'Russell King \(Oracle\)'" <linux@...linux.org.uk>
Cc: "'Andrew Lunn'" <andrew@...n.ch>,
	"'Heiner Kallweit'" <hkallweit1@...il.com>,
	<mengyuanlou@...-swift.com>,
	"'Alexandre Torgue'" <alexandre.torgue@...s.st.com>,
	"'Andrew Lunn'" <andrew+netdev@...n.ch>,
	"'Bryan Whitehead'" <bryan.whitehead@...rochip.com>,
	"'David S. Miller'" <davem@...emloft.net>,
	"'Eric Dumazet'" <edumazet@...gle.com>,
	"'Jakub Kicinski'" <kuba@...nel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	"'Marcin Wojtas'" <marcin.s.wojtas@...il.com>,
	"'Maxime Coquelin'" <mcoquelin.stm32@...il.com>,
	<netdev@...r.kernel.org>,
	"'Paolo Abeni'" <pabeni@...hat.com>,
	<UNGLinuxDriver@...rochip.com>
Subject: RE: [PATCH net-next 0/9] net: add phylink managed EEE support

> > Since merging these patches, phylink_connect_phy() can no longer be
> > invoked correctly in ngbe_open(). The error is returned from the function
> > phy_eee_rx_clock_stop(). Since EEE is not supported on our NGBE hardware.
> 
> That would mean phy_modify_mmd() is failing, but the question is why
> that is. Please investigate. Thanks.

Yes, phy_modify_mmd() returns -EOPNOTSUPP. Since .read/write_mmd are
implemented in the PHY driver, but it's not supported to read/write the
register field (devnum=MDIO_MMD_PCS, regnum= MDIO_CTRL1).

So the error occurs on  __phy_read_mmd():
	if (phydev->drv && phydev->drv->read_mmd)
		return phydev->drv->read_mmd(phydev, devad, regnum);