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

["Russell King (Oracle)" <linux@armlinux.org.uk>]

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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