netdev - Re: [PATCH] net: phy: at803x: Improve hibernation support on start up

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Message-ID: <ZNSpEbDVFe5MdyqD@shell.armlinux.org.uk>
Date: Thu, 10 Aug 2023 10:08:33 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Wei Fang <wei.fang@....com>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>, Marek Vasut <marex@...x.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Lunn <andrew@...n.ch>, Eric Dumazet <edumazet@...gle.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
	Stephen Boyd <sboyd@...nel.org>,
	Michael Turquette <mturquette@...libre.com>
Subject: Re: [PATCH] net: phy: at803x: Improve hibernation support on start up

On Thu, Aug 10, 2023 at 03:28:13AM +0000, Wei Fang wrote:
> > > Furthermore,
> > > we would expect the hibernation mode is enabled when the ethernet
> > > interface is brought up but the cable is not plugged, that is to say,
> > > we only need the PHY to provide the clock for a while to make the MAC
> > reset successfully.
> > 
> > Means, if external clock is not provided, MAC is not fully functional.
> > Correct?
> > 
> The MAC will failed to do software reset if the PHY input clocks are not
> present.

Yes, that's well known to me - it's been brought up before with stmmac
and phylink. I said earlier in this thread about this.

> > For example, if stmmac_open() fails without external clock, will
> > stmmac_release() work properly?
> Actually, I don't know much about stmmac driver and the dwmac IP,
> Because I'm not responsible for this IP on NXP i.MX platform. But I
> have a look at the code of stmmac_release(), I think stmmac_release()
> will work properly, because it invokes phylink_stop() and phylink_disconnect_phy()
> first which will disable the clock from PHY.

When tearing down a network device, there should be no reason to call
phylink_stop() - unregistering the netdev will take the network device
down, and thus call the .ndo_stop method if the device was up. .ndo_stop
should already be calling phylink_stop().

I just don't get why driver authors don't check things like this...

-- 
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